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1

Rf cavity primer for cyclic proton accelerators  

SciTech Connect

The purpose of this note is to describe the electrical and mechanical properites of particle accelerator rf cavities in a manner which will be useful to physics and engineering graduates entering the accelerator field. The discussion will be limited to proton (or antiproton) synchrotron accelerators or storage rings operating roughly in the range of 20 to 200 MHz. The very high gradient, fixed frequency UHF or microwave devices appropriate for electron machines and the somewhat lower frequency and broader bandwidth devices required for heavy ion accelerators are discussed extensively in other papers in this series. While it is common pratice to employ field calculation programs such as SUPERFISH, URMEL, or MAFIA as design aids in the development of rf cavities, we attempt here to elucidate various of the design parameters commonly dealt with in proton machines through the use of simple standing wave coaxial resonator expressions. In so doing, we treat only standing wave structures. Although low-impedance, moderately broad pass-band travelling wave accelerating systems are used in the CERN SPS, such systems are more commonly found in linacs, and they have not been used widely in large cyclic accelerators. Two appendices providing useful supporting material regarding relativistic particle dynamics and synchrotron motion in cyclic accelerators are added to supplement the text.

Griffin, J.E.

1988-04-01

2

ELECTRON INJECTION INTO CYCLIC ACCELERATOR USING  

E-print Network

it is necessary to create the gas cloud with proper parameters. the characteristic accelerating gradient is 318.1 mm and =1 m 0.01 ab2 Injection without kicker directly into the vacuum chamber Ax == #12;Beam loss. 5 Expansion of Mg gas 1 ­ evaporating light, 2 -Mg target, 3 ­ Mg cloud is the radius of the gas

3

Limiting electron beam current for cyclic induction acceleration in a constant guide field  

SciTech Connect

Theoretical relations are derived for the limiting beam current in a cyclic induction accelerator (CIA) with a constant guide field. The calculations are in agreement with the available experimental data. It is shown that the limiting average beam current in a CIA is of the order of 100 microamperes, i.e., the level attained in microtrons and linear accelerators. The CIA may find industrial applications.

Kanunnikov, V.N.

1982-09-01

4

Cyclic AMP accelerates calcium waves in pancreatic acinar cells.  

PubMed

Cytosolic Ca(2+) (Ca(i)(2+)) flux within the pancreatic acinar cell is important both physiologically and pathologically. We examined the role of cAMP in shaping the apical-to-basal Ca(2+) wave generated by the Ca(2+)-activating agonist carbachol. We hypothesized that cAMP modulates intra-acinar Ca(2+) channel opening by affecting either cAMP-dependent protein kinase (PKA) or exchange protein directly activated by cAMP (Epac). Isolated pancreatic acinar cells from rats were stimulated with carbachol (1 muM) with or without vasoactive intestinal polypeptide (VIP) or 8-bromo-cAMP (8-Br-cAMP), and then Ca(i)(2+) was monitored by confocal laser-scanning microscopy. The apical-to-basal carbachol (1 muM)-stimulated Ca(2+) wave was 8.63 +/- 0.68 microm/s; it increased to 19.66 +/- 2.22 microm/s (*P < 0.0005) with VIP (100 nM), and similar increases were observed with 8-Br-cAMP (100 microM). The Ca(2+) rise time after carbachol stimulation was reduced in both regions but to a greater degree in the basal. Lag time and maximal Ca(2+) elevation were not significantly affected by cAMP. The effect of cAMP on Ca(2+) waves also did not appear to depend on extracellular Ca(2+). However, the ryanodine receptor (RyR) inhibitor dantrolene (100 microM) reduced the cAMP-enhancement of wave speed. It was also reduced by the PKA inhibitor PKI (1 microM). 8-(4-chloro-phenylthio)-2'-O-Me-cAMP, a specific agonist of Epac, caused a similar increase as 8-Br-cAMP or VIP. These data suggest that cAMP accelerates the speed of the Ca(2+) wave in pancreatic acinar cells. A likely target of this modulation is the RyR, and these effects are mediated independently by PKA and Epac pathways. PMID:18388188

Shah, Ahsan U; Grant, Wayne M; Latif, Sahibzada U; Mannan, Zahir M; Park, Alexander J; Husain, Sohail Z

2008-06-01

5

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

PubMed

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

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

2015-01-16

6

Cyclic Vomiting Syndrome Association  

MedlinePLUS

... Wilson CVS Media Links Relevant Organizations Research Anxiety Risk in Youth with Cyclic Vomiting Syndrome: Threat Perception, Coping and Physiological Reactivity Participate in Research Studies ...

7

Finite element forced vibration analysis of rotating cyclic structures  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

8

Affordable Cyclic Voltammetry  

ERIC Educational Resources Information Center

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

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

2009-01-01

9

Cyclic control stick  

DOEpatents

A cyclic control stick of the type used in helicopters for reducing the safety hazards associated with such a mechanism in the event of a crewman being thrown violently into contact with the cyclic control stick resulting from a crash or the like. The cyclic control stick is configured to break away upon the exertion of an impact force which exceeds a predetermined value and/or is exerted for more than a momentary time duration. The cyclic control stick is also configured to be adjustable so as to locate the grip thereof as far away from the crewman as possible for safety reasons without comprising the comfort of the crewman or the use of the control stick, and a crushable pad is provided on the top of the grip for impact energy absorbing purposes.

Whitaker, Charles N. (2834 S. Extension Rd., No. 2024, Mesa, AZ 85202); Zimmermann, Richard E. (425 E. Greenway, Tempe, AZ 85282)

1989-01-01

10

Cyclic testing of meniscal sutures.  

PubMed

Suturing the meniscus has become a standard procedure for repairable tears. Studies investigating the outcome of meniscal sutures report a considerable rate of failures. Regarding the indications, which have been extended to the avascular zones, and regarding some accelerated rehabilitation protocols, the need for further in vitro investigations has become obvious. The aim of this study was to compare different meniscal suture types (vertical and horizontal mattress sutures) and materials (absorbable monofilament PDS 2-0, and nonabsorbable braided Ethibond 2-0 [Ethicon, Somerville, NJ]) under standard and cyclic loading conditions. Testing was performed on medial porcine menisci. In group A, specimens were tested to failure at a cross-head speed of 50 mm/minute. In group B, cyclic testing (100 cycles) was performed first within different load intervals (5 to 20 N and 5 to 40 N). Finally, the specimens were loaded until failure. In both groups, the failure loads were recorded and the failure modes were analyzed. In group A, there was no difference between suture type or suture material, with a mean failure load of 60 N. The failure modes were significantly different for vertical (100% suture failure) and horizontal sutures (50% suture failure) (P <.0001). In group B, 13% of the sutures failed under cyclic loading (7 with 40-N load, 1 with 20-N load). The gap of the sutured tear that appeared within the first load cycles was broader in horizontal sutures (P <.001). During the first cycles, the thread cut through the meniscus tissue and disappeared from the surface (partial tissue failure). There was no difference according to suture material. The ultimate failure loads after cyclic loading did not differ from the values of group A. These results show that meniscal sutures may fail under repetitive loading conditions and that a gap appears between the meniscal margins within the first loading cycles irrespective of the suture type and suture material used. The appearance of the gap and suture disappearance on the meniscal surface because of partial tissue failures (which were more pronounced in the horizontal sutures) confirmed the superior resistance of meniscal tissue to vertical sutures. PMID:10882446

Seil, R; Rupp, S; Kohn, D M

2000-01-01

11

The cyclic reduction algorithm  

NASA Astrophysics Data System (ADS)

Cyclic reduction is an algorithm invented by G.H. Golub and R. W. Hockney in the mid 1960s for solving linear systems related to the finite differences discretization of the Poisson equation over a rectangle. Among the algorithms of Gene Golub, it is one of the most versatile and powerful ever created. Recently, it has been applied to solve different problems from different applicative areas. In this paper we survey the main features of cyclic reduction, relate it to properties of analytic functions, recall its extension to solving more general finite and infinite linear systems, and different kinds of nonlinear matrix equations, including algebraic Riccati equations, with applications to Markov chains, queueing models and transport theory. Some new results concerning the convergence properties of cyclic reduction and its applicability are proved under very weak assumptions. New formulae for overcoming breakdown are provided.

Bini, Dario; Meini, Beatrice

2009-05-01

12

Flow in cyclic cosmology  

NASA Astrophysics Data System (ADS)

In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as ekpyrotic and cyclic models. We show that the inflationary flow equations are invariant under the duality and therefore apply equally well to inflation or to cyclic cosmology. We construct a self-consistent small-parameter approximation dual to the slow-roll approximation in inflation, and calculate the power spectrum of perturbations in this limit. We also recover the matter-dominated contracting solution of Wands, and the recently proposed adiabatic ekpyrosis solution.

Kinney, William H.; Dizgah, Azadeh Moradinezhad

2010-10-01

13

Flow in cyclic cosmology  

SciTech Connect

In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as ekpyrotic and cyclic models. We show that the inflationary flow equations are invariant under the duality and therefore apply equally well to inflation or to cyclic cosmology. We construct a self-consistent small-parameter approximation dual to the slow-roll approximation in inflation, and calculate the power spectrum of perturbations in this limit. We also recover the matter-dominated contracting solution of Wands, and the recently proposed adiabatic ekpyrosis solution.

Kinney, William H.; Dizgah, Azadeh Moradinezhad [Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260-1500 (United States)

2010-10-15

14

Cyclic membrane separation process  

DOEpatents

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.

Nemser, Stuart M.

2005-05-03

15

Cyclic membrane separation process  

SciTech Connect

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.

Bowser, John

2004-04-13

16

Guanosine 3',5'-cyclic monophosphate and the in vitro physiology of frog photoreceptor membranes  

Microsoft Academic Search

A B S T R A C T Frog rod outer segments freshly detached from dark-adapted reti- nas contain approximately 1-2 molecules of guanosine 3',5'-cyclic monophosphate (cyclic GMP) for every 100 molecules of visual pigment present. This cyclic GMP decays to 5'-GMP, and the conversion is accelerated upon illumination of the outer segments. Bleaching one rhodopsin molecule can lead to

MICHAEL L. WOODRUFF; DERIC BOWNDS; STEVEN H. GREEN; JERRY L. MORRISEY; ALEXANDRA SHEDLOVSKY

1977-01-01

17

Forced vibration analysis of rotating cyclic structures in NASTRAN  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

18

Virtual screening using combinatorial cyclic Peptide libraries reveals protein interfaces readily targetable by cyclic peptides.  

PubMed

Protein-protein and protein-peptide interactions are responsible for the vast majority of biological functions in vivo, but targeting these interactions with small molecules has historically been difficult. What is required are efficient combined computational and experimental screening methods to choose among a number of potential protein interfaces worthy of targeting lead macrocyclic compounds for further investigation. To achieve this, we have generated combinatorial 3D virtual libraries of short disulfide-bonded peptides and compared them to pharmacophore models of important protein-protein and protein-peptide structures, including short linear motifs (SLiMs), protein-binding peptides, and turn structures at protein-protein interfaces, built from 3D models available in the Protein Data Bank. We prepared a total of 372 reference pharmacophores, which were matched against 108,659 multiconformer cyclic peptides. After normalization to exclude nonspecific cyclic peptides, the top hits notably are enriched for mimetics of turn structures, including a turn at the interaction surface of human ? thrombin, and also feature several protein-binding peptides. The top cyclic peptide hits also cover the critical "hot spot" interaction sites predicted from the interaction crystal structure. We have validated our method by testing cyclic peptides predicted to inhibit thrombin, a key protein in the blood coagulation pathway of important therapeutic interest, identifying a cyclic peptide inhibitor with lead-like activity. We conclude that protein interfaces most readily targetable by cyclic peptides and related macrocyclic drugs may be identified computationally among a set of candidate interfaces, accelerating the choice of interfaces against which lead compounds may be screened. PMID:25668361

Duffy, Fergal J; O'Donovan, Darragh; Devocelle, Marc; Moran, Niamh; O'Connell, David J; Shields, Denis C

2015-03-23

19

The Cyclic Model Simplified  

E-print Network

The Cyclic Model attempts to resolve the homogeneity, isotropy, and flatness problems and generate a nearly scale-invariant spectrum of fluctuations during a period of slow contraction that precedes a bounce to an expanding phase. Here we describe at a conceptual level the recent developments that have greatly simplified our understanding of the contraction phase and the Cyclic Model overall. The answers to many past questions and criticisms are now understood. In particular, we show that the contraction phase has equation of state w>1 and that contraction with w>1 has a surprisingly similar properties to inflation with w < -1/3. At one stroke, this shows how the model is different from inflation and why it may work just as well as inflation in resolving cosmological problems.

Paul J. Steinhardt; Neil Turok

2004-04-24

20

Turnaround in Cyclic Cosmology  

SciTech Connect

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.

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

2007-02-16

21

Iontophoresis of cyclic AMP.  

PubMed Central

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

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

1975-01-01

22

Cyclic generalized projection MRI.  

PubMed

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

Sarty, Gordon E

2015-04-01

23

GAF Domains: Cyclic Nucleotides Come Full Circle  

NSDL National Science Digital Library

Cyclic nucleotides are ubiquitous signaling molecules that are present in life forms ranging from bacteria to yeast to humans. In higher eukaryotes, conserved molecular machinery processes signals through both cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP). Hurley describes how one widespread cyclic nucleotide recognition module, the GAF (cyclic GMP, adenylyl cyclase, FhlA) domain, formerly thought to bind only cyclic GMP, has now been found to bind cyclic AMP as well. Recent structural analysis of a cyclic GMP-binding GAF domain shows how conserved elements among the cyclic nucleotide-binding subgroup of GAF domains recognize the common chemical moieties in the two compounds.

James H. Hurley (National Institutes of Health; Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases REV)

2003-01-07

24

Method of controlling cyclic variation in engine combustion  

DOEpatents

Cyclic variation in combustion of a lean burning engine is reduced by detecting an engine combustion event output such as torsional acceleration in a cylinder (i) at a combustion event (k), using the detected acceleration to predict a target acceleration for the cylinder at the next combustion event (k+1), modifying the target output by a correction term that is inversely proportional to the average phase of the combustion event output of cylinder (i) and calculating a control output such as fuel pulse width or spark timing necessary to achieve the target acceleration for cylinder (i) at combustion event (k+1) based on anti-correlation with the detected acceleration and spill-over effects from fueling. 27 figs.

Davis, L.I. Jr.; Daw, C.S.; Feldkamp, L.A.; Hoard, J.W.; Yuan, F.; Connolly, F.T.

1999-07-13

25

Linear Accelerators  

SciTech Connect

In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

Sidorin, Anatoly [Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna (Russian Federation)

2010-01-05

26

Cyclic Bonds in Branched Polymers  

E-print Network

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.

Kazumi Suematsu

2015-02-19

27

CYCLIC AMP, CYCLIC GMP, AND GLUCOCORTICOIDS AS POTENTIAL METABOLIC REGULATORS OF EPIDERMAL PROLIFERATION AND DIFFERENTIATION  

Microsoft Academic Search

The two cyclic nucleotides, cyclic AMP and cyclic GMP, appear to be central to the metabolic regulation of cell proliferation and differentiation in various cells. Moreover, in many systems glucocorticoids appear to act in concert with or parallel to cyclic AMP. The available evidence suggests that these three molecular species cyclic AMP, cyclic GMP, and glucocorticoids may be

John J. Voorhees; Cynthia L. Marcelo; Elizabeth A. Duell

1975-01-01

28

NASTRAN forced vibration analysis of rotating cyclic structures  

NASA Technical Reports Server (NTRS)

Theoretical aspects of a new capability developed and implemented in NASTRAN level 17.7 to analyze forced vibration of a cyclic structure rotating about its axis of symmetry are presented. Fans, propellers, and bladed shrouded discs of turbomachines are some examples of such structures. The capability includes the effects of Coriolis and centripetal accelerations on the rotating structure which can be loaded with: (1) directly applied loads moving with the structure and (2) inertial loas due to the translational acceleration of the axis of rotation (''base' acceleration). Steady-state sinusoidal or general periodic loads are specified to represent: (1) the physical loads on various segments of the complete structure, or (2) the circumferential harmonic components of the loads in (1). The cyclic symmetry feature of the rotating structure is used in deriving and solving the equations of forced motion. Consequently, only one of the cyclic sectors is modelled and analyzed using finite elements, yielding substantial savings in the analysis cost. Results, however, are obtained for the entire structure. A tuned twelve bladed disc example is used to demonstrate the various features of the capability.

Elchuri, V.; Smith, G. C. C.; Gallo, A. M.

1983-01-01

29

Can Accelerators Accelerate Learning?  

NASA Astrophysics Data System (ADS)

The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

2009-03-01

30

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

Microsoft Academic Search

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

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

1993-01-01

31

Cyclic AMP in prokaryotes.  

PubMed Central

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

Botsford, J L; Harman, J G

1992-01-01

32

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

PubMed Central

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

Flitney, F W; Singh, J

1980-01-01

33

Cyclic vomiting syndrome: treatment options.  

PubMed

Cyclic vomiting syndrome is a disorder characterized by recurrent episodes of severe nausea and vomiting separated by symptom-free periods. Our aims were to review treatments of adult cyclic vomiting syndrome as well as to identify areas for further clinical research and the unanswered questions in this field. We conducted a PubMed search using such keywords as "cyclic vomiting syndrome," "nausea," "vomiting," "treatment," "trigger factors" and "tricyclic antidepressants" and combined this information with the knowledge and clinical research from the authors. Available data show that in adult cyclic vomiting syndrome, there is an impressive and sustained response to high-dose tricyclic antidepressants. In up to 13% who are regarded as poor responders to tricyclic antidepressants, a predictable profile can be identified related to coexisting psychological disorders, marijuana use, poorly controlled migraine headache or chronic narcotic use. Cyclic vomiting syndrome in adults is being an increasingly recognized entity. Tricyclic antidepressants are the main treatment for controlling symptoms. Eliminating and addressing trigger factors are an essential part of management. PMID:24862509

Hejazi, Reza A; McCallum, Richard W

2014-08-01

34

Android Acceleration  

NSDL National Science Digital Library

Students prepare for the associated activity in which they investigate acceleration by collecting acceleration vs. time data using the accelerometer of a sliding Android device. Based on the experimental set-up for the activity, students form hypotheses about the acceleration of the device. Students will investigate how the force on the device changes according to Newton's Second Law. Different types of acceleration, including average, instantaneous and constant acceleration, are introduced. Acceleration and force is described mathematically and in terms of processes and applications.

2014-09-18

35

Experimental Study of Shock-accelerated Liquid  

E-print Network

Experimental Study of Shock-accelerated Liquid Layers for IFE Reactors Mark Anderson, Phongsan University of Wisconsin-Madison #12;actors High density energy pu compresses the fuel Very strong shock wav propagates outward Cyclic process Liquid wall absorb the and protect the chamber w #12;Motivation #12

36

Future accelerators (?)  

SciTech Connect

I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

John Womersley

2003-08-21

37

Electrostatic accelerators  

E-print Network

The principle of electrostatic accelerators is presented. We consider Cockcroft? Walton, Van de Graaff and Tandem Van de Graaff accelerators. We resume high voltage generators such as cascade generators, Van de Graaff band generators, Pelletron generators, Laddertron generators and Dynamitron generators. The speci c features of accelerating tubes, ion optics and methods of voltage stabilization are described. We discuss the characteristic beam properties and the variety of possible beams. We sketch possible applications and the progress in the development of electrostatic accelerators.

Hinterberger, F

2006-01-01

38

Non-cyclic graph of a group  

Microsoft Academic Search

We associate a graph $\\\\Gamma_G$ to a non locally cyclic group $G$ (called the non-cyclic graph of $G$) as follows: take $G\\\\backslash Cyc(G)$ as vertex set, where $Cyc(G)=\\\\{x\\\\in G | \\\\left \\\\text{is cyclic for all} y\\\\in G\\\\}$, and join two vertices if they do not generate a cyclic subgroup. We study the properties of this graph and we establish some

Alireza Abdollahi; A. Mohammadi Hassanabadi

2007-01-01

39

Key issues in cyclic plastic deformation: Experimentation  

Microsoft Academic Search

Cyclic plastic deformation phenomena include the Bauschinger effect, cyclic hardening\\/softening, strain range effect, loading history memory, ratcheting, mean stress dependent hardening, mean stress relaxation and non-proportional hardening. In this work, different cyclic plastic deformation responses of piping materials (SA333 CMn steel and 304LN stainless steel) are experimentally explored. Cyclic hardening\\/softening is depends upon loading types (i.e. stress\\/strain controlled), previous loading

Surajit Kumar Paul; S. Sivaprasad; S. Dhar; S. Tarafder

2011-01-01

40

40 CFR 721.2120 - Cyclic amide.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Cyclic amide. 721.2120 Section 721.2120...Specific Chemical Substances 721.2120 Cyclic amide. (a) Chemical substance and...The chemical substance identified as a cyclic amide (PMN P-92-131) is...

2010-07-01

41

Photodissociation Spectra of Cyclic and Non-Cyclic Nucleotides  

NASA Astrophysics Data System (ADS)

We have studied the UV photodepletion and photofragment action spectra of deprotonated adenosine monophosphate and guanosine monophosphate as well as their cyclic analogs. We observe the same anionic fragments as in earlier experiments on collision-induced dissociation of deoxyribonucleotides, although their relative intensities are quite different, especially with respect to the abundance of the deprotonated base anions. The suppression and amplification of spectral features provides information about the threshold energies for the active fragment channels.

Kaufman, Sydney H.; Marcum, Jesse C.; Weber, J. Mathias

2010-06-01

42

Supramolecular nesting of cyclic polymers  

NASA Astrophysics Data System (ADS)

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 CC 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.

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

2015-04-01

43

High-Intensity Proton Accelerator  

SciTech Connect

Analysis is presented for an eight-cavity proton cyclotron accelerator that could have advantages as compared with other accelerators because of its potentially high acceleration gradient. The high gradient is possible since protons orbit in a sequence of TE111 rotating mode cavities of equally diminishing frequencies with path lengths during acceleration that greatly exceed the cavity lengths. As the cavities operate at sequential harmonics of a basic repetition frequency, phase synchronism can be maintained over a relatively wide injection phase window without undue beam emittance growth. It is shown that use of radial vanes can allow cavity designs with significantly smaller radii, as compared with simple cylindrical cavities. Preliminary beam transport studies show that acceptable extraction and focusing of a proton beam after cyclic motion in this accelerator should be possible. Progress is also reported on design and tests of a four-cavity electron counterpart accelerator for experiments to study effects on beam quality arising from variations injection phase window width. This device is powered by four 500-MW pulsed amplifiers at 1500, 1800, 2100, and 2400 MHz that provide phase synchronous outputs, since they are driven from a with harmonics derived from a phase-locked 300 MHz source.

Jay L. Hirshfield

2011-12-27

44

Protein misfolding cyclic amplification of infectious prions  

PubMed Central

Prions are proteinaceous infectious agents responsible for the transmission of prion diseases. The lack of a procedure for cultivating prions in the laboratory has been a major limitation to the study of the unorthodox nature of this infectious agent and the molecular mechanism by which the normal prion protein (PrPC) is converted into the abnormal isoform (PrPSc). Protein misfolding cyclic amplification (PMCA ), described in detail in this protocol, is a simple, fast and efficient methodology to mimic prion replication in the test tube. PMCA involves incubating materials containing minute amounts of infectious prions with an excess of PrPC and boosting the conversion by cycles of sonication to fragment the converting units, thereby leading to accelerated prion replication. PMCA is able to detect the equivalent of a single molecule of infectious PrPSc and propagate prions that maintain high infectivity, strain properties and species specificity. A single PMCA assay takes little more than 3 d to replicate a large amount of prions, which could take years in an in vivo situation. Since its invention 10 years ago, PMCA has helped to answer fundamental questions about this intriguing infectious agent and has been broadly applied in research areas that include the food industry, blood bank safety and human and veterinary disease diagnosis. PMID:22743831

Morales, Rodrigo; Duran-Aniotz, Claudia; Diaz-Espinoza, Rodrigo; Camacho, Manuel V; Soto, Claudio

2014-01-01

45

Advances in targeting cyclic nucleotide phosphodiesterases  

PubMed Central

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

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

2014-01-01

46

Podcast: Acceleration  

NSDL National Science Digital Library

The Podcast: Acceleration is a segment of the Force and Motion Short Course. The podcast is 2 minutes 13 seconds in duration. Presented by science experts and NSTA staff, the NSTA Online Short Courses are professional development opportunities de

2009-07-06

47

Modular arithmetic weight and cyclic shifting.  

NASA Technical Reports Server (NTRS)

This note shows that the modular arithmetic weight of an integer is invariant to the cyclic shifts of its radix-2 form. This result leads to a reduced search for the minimum weight codeword in a cyclic AN-code as well as to a better understanding of previous work.

Hartman, W. F.

1972-01-01

48

Similarity Cyclic DNA Codes over Rings  

Microsoft Academic Search

In this paper we construct a special type of cyclic codes called cyclic DNA codes over the ring R = {0, 1, u, u + 1} where u2 = 1. These codes are important in the subject of biomolecular computation and DNA computing. We apply a more suitable measure (the similarity measure) than the Hamming distance measure on the set

Irfan Siap; T. Abualrub; A. Ghrayeb

2008-01-01

49

Cyclic Universe la string theory  

E-print Network

We shall present a model of the "cyclic universe" that can be constructed only by assuming a minimal set of properties of string theory. We clarify our viewpoint of the cyclic universe and show some attempts to mateliarize the idea as field theoretical manner.

Yoshinobu Habara; Hikaru Kawai; Masao Ninomiya

2005-04-12

50

Ants, Crickets and Frogs in Cyclic Pursuit  

Microsoft Academic Search

. We consider a deterministic continuous pursuit, in which n ants chase each otherin cyclic order and with preassigned, varying speeds. We also consider two discrete analogs, inwhich crickets or frogs are engaged in cyclic pursuit with constant and equal speeds. We examinethe possible evolutions of these pursuits as time goes to infinity: collision, limit points, equilibriumstates and periodic motion.IntroductionImagine

A. m. Bruckstein; N. Cohen; A. Efrat

1991-01-01

51

Cell reorientation under cyclic stretching  

E-print Network

Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations -- cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell's passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity.

Ariel Livne; Eran Bouchbinder; Benjamin Geiger

2014-12-01

52

Cell reorientation under cyclic stretching  

PubMed Central

Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cells passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity. PMID:24875391

Livne, Ariel; Bouchbinder, Eran; Geiger, Benjamin

2014-01-01

53

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... 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and...chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

2010-07-01

54

Accelerator-induced transients in Accelerator Driven Subcritical Reactors  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

55

A high-current racetrack induction accelerator  

SciTech Connect

In this paper, the energy and system scaling laws of the Racetrack Induction Accelerator are determined and its operating principles are discussed. This device is a cyclic accelerator that is capable of multi-kiloamp operation. Long pulse induction linac technology is used to obtain short acceleration times. The accelerator consists of a long-pulse linear induction module and a racetrack beam transport system. For detailed studies of the particle dynamics in a racetrack, a numerical model is required to integrate the fully-relativistic single-particle equations of motion in an externally applied magnetic field. The numerical model is a compromise between the need for a large rotational transform and the need for a reasonable volume within the separatrix.

Mondelli, A.; Roberson, C.W.

1983-08-01

56

Cyclic hypervalent iodine reagents and iron catalysts: the winning team for late-stage c?h azidation.  

PubMed

1+1=3: By combining the exceptional reactivities of cyclic hypervalent iodine reagents and iron catalysts, Sharma and Hartwig achieved the azidation of C?H bonds with unprecedented efficiency and selectivity. The late-stage introduction of azides into complex bioactive molecules will greatly facilitate the synthesis of analogues and accelerate the discovery of new chemical entities. PMID:25825000

Vita, Maria Victoria; Waser, Jerome

2015-04-27

57

Non-cyclic graph of a group  

E-print Network

We associate a graph $\\Gamma_G$ to a non locally cyclic group $G$ (called the non-cyclic graph of $G$) as follows: take $G\\backslash Cyc(G)$ as vertex set, where $Cyc(G)=\\{x\\in G | \\left \\text{is cyclic for all} y\\in G\\}$, and join two vertices if they do not generate a cyclic subgroup. We study the properties of this graph and we establish some graph theoretical properties (such as regularity) of this graph in terms of the group ones. We prove that the clique number of $\\Gamma_G$ is finite if and only if $\\Gamma_G$ has no infinite clique. We prove that if $G$ is a finite nilpotent group and $H$ is a group with $\\Gamma_G\\cong\\Gamma_H$ and $|Cyc(G)|=|Cyc(H)|=1$, then $H$ is a finite nilpotent group. We give some examples of groups $G$ whose non-cyclic graphs are ``unique'', i.e., if $\\Gamma_G\\cong \\Gamma_H$ for some group $H$, then $G\\cong H$. In view of these examples, we conjecture that every finite non-abelian simple group has a unique non-cyclic graph. Also we give some examples of finite non-cyclic groups...

Abdollahi, Alireza

2007-01-01

58

Plasma accelerator  

DOEpatents

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.

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

2002-01-01

59

Particle acceleration  

NASA Technical Reports Server (NTRS)

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.

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

60

Accelerated Achievement  

ERIC Educational Resources Information Center

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

Ford, William J.

2010-01-01

61

Cyclic block filtered multitone modulation  

NASA Astrophysics Data System (ADS)

A filter bank modulation transceiver is presented. The idea is to obtain good sub-channel frequency confinement as it is done by the family of exponentially modulated filter banks that is typically referred to as filtered multitone (FMT) modulation. However, differently from conventional FMT, the linear convolutions are replaced with circular convolutions. Since transmission occurs in blocks, the scheme is referred to as cyclic block FMT (CB-FMT). This paper focuses on the principles, design, and implementation of CB-FMT. In particular, it is shown that an efficient realization of both the transmitter and the receiver is possible in the frequency domain (FD), and it is based on the concatenation of an inner discrete Fourier transform (DFT) and a bank of outer DFTs. Such an implementation suggests a simple sub-channel FD equalizer. The overall required implementation complexity is lower than in FMT. Furthermore, the orthogonal filter bank design is simplified. The sub-channel frequency confinement in CB-FMT yields compact power spectrum and lower peak-to-average power ratio than in OFDM. Furthermore, the FD equalization allows the exploitation of the transmission medium time and frequency diversity; thus, it potentially yields lower symbol error rate and higher achievable rate in time-variant frequency-selective fading.

Tonello, Andrea M.; Girotto, Mauro

2014-12-01

62

Parallel architectures for computing cyclic convolutions  

NASA Technical Reports Server (NTRS)

In the paper two parallel architectural structures are developed to compute one-dimensional cyclic convolutions. The first structure is based on the Chinese remainder theorem and Kung's pipelined array. The second structure is a direct mapping from the mathematical definition of a cyclic convolution to a computational architecture. To compute a d-point cyclic convolution the first structure needs d/2 inner product cells, while the second structure and Kung's linear array require d cells. However, to compute a cyclic convolution, the second structure requires less time than both the first structure and Kung's linear array. Another application of the second structure is to multiply a Toeplitz matrix by a vector. A table is listed to compare these two structures and Kung's linear array. Both structures are simple and regular and are therefore suitable for VLSI implementation.

Yeh, C.-S.; Reed, I. S.; Truong, T. K.

1983-01-01

63

Cyclical dynamics of airline industry earnings  

E-print Network

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 ...

Pierson, Kawika

64

Compact accelerator  

DOEpatents

A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Los Alamos, NM)

2007-02-06

65

Comment on "Turnaround in Cyclic Cosmology"  

E-print Network

We comment on a recent paper by L. Baum and P. H. Frampton [Phys. Rev. Lett. 98, 071301 (2007)] where it was argued that the entropy problem can be resolved in a peculiar cyclic universe model through a deflation mechanism (i.e., the universe is fragmented into many disconnected causal patches at the turnaround). We point out that in this cyclic model the Hubble length will become infinity at the turnaround, thus the deflation scenario is not valid.

Xin Zhang

2008-04-02

66

Antimicrobial cyclic peptides for plant disease control.  

PubMed

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

Lee, Dong Wan; Kim, Beom Seok

2015-03-01

67

The evolution of Momordica cyclic peptides.  

PubMed

Cyclic proteins have evolved for millions of years across all kingdoms of life to confer structural stability over their acyclic counterparts while maintaining intrinsic functional properties. Here, we show that cyclic miniproteins (or peptides) from Momordica (Cucurbitaceae) seeds evolved in species that diverged from an African ancestor around 19 Ma. The ability to achieve head-to-tail cyclization of Momordica cyclic peptides appears to have been acquired through a series of mutations in their acyclic precursor coding sequences following recent and independent gene expansion event(s). Evolutionary analysis of Momordica cyclic peptides reveals sites that are under selection, highlighting residues that are presumably constrained for maintaining their function as potent trypsin inhibitors. Molecular dynamics of Momordica cyclic peptides in complex with trypsin reveals site-specific residues involved in target binding. In a broader context, this study provides a basis for selecting Momordica species to further investigate the biosynthesis of the cyclic peptides and for constructing libraries that may be screened against evolutionarily related serine proteases implicated in human diseases. PMID:25376175

Mahatmanto, Tunjung; Mylne, Joshua S; Poth, Aaron G; Swedberg, Joakim E; Kaas, Quentin; Schaefer, Hanno; Craik, David J

2015-02-01

68

Antimicrobial Cyclic Peptides for Plant Disease Control  

PubMed Central

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

Lee, Dong Wan; Kim, Beom Seok

2015-01-01

69

Non-cyclic graph associated with a group  

Microsoft Academic Search

We associate a graph $\\\\mathcal{C}_G$ to a non locally cyclic group $G$ (called the non-cyclic graph of $G$) as follows: take $G\\\\backslash Cyc(G)$ as vertex set, where $Cyc(G)=\\\\{x\\\\in G | \\\\text{is cyclic for all} y\\\\in G\\\\}$ is called the cyclicizer of $G$, and join two vertices if they do not generate a cyclic subgroup. For a simple graph $\\\\Gamma$, $w(\\\\Gamma)$

Alireza Abdollahi; A. Mohammadi Hassanabadi

2008-01-01

70

Analytical tools in accelerator physics  

SciTech Connect

This paper is a sub-set of my lectures presented in the Accelerator Physics course (USPAS, Santa Rosa, California, January 14-25, 2008). It is based on my notes I wrote during period from 1976 to 1979 in Novosibirsk. Only few copies (in Russian) were distributed to my colleagues in Novosibirsk Institute of Nuclear Physics. The goal of these notes is a complete description starting from the arbitrary reference orbit, explicit expressions for 4-potential and accelerator Hamiltonian and finishing with parameterization with action and angle variables. To a large degree follow logic developed in Theory of Cyclic Particle Accelerators by A.A.Kolmensky and A.N.Lebedev [Kolomensky], but going beyond the book in a number of directions. One of unusual feature is these notes use of matrix function and Sylvester formula for calculating matrices of arbitrary elements. Teaching the USPAS course motivated me to translate significant part of my notes into the English. I also included some introductory materials following Classical Theory of Fields by L.D. Landau and E.M. Liftsitz [Landau]. A large number of short notes covering various techniques are placed in the Appendices.

Litvinenko, V.N.

2010-09-01

71

Accelerators and the Accelerator Community  

SciTech Connect

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.

Malamud, Ernest; Sessler, Andrew

2008-06-01

72

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

PubMed

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

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

1981-01-01

73

Measuring Cyclic Error in Laser Heterodyne Interferometers  

NASA Technical Reports Server (NTRS)

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-

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

2010-01-01

74

Impact accelerations  

NASA Technical Reports Server (NTRS)

The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

Vongierke, H. E.; Brinkley, J. W.

1975-01-01

75

Ring accelerators  

SciTech Connect

We present two-dimensional simulations in (r-z) and r-theta) cylinderical geometries of imploding-liner-driven accelerators of rings of charged particles. We address issues of azimuthal and longitudinal stability of the rings. We discuss self-trapping designs in which beam injection and extraction is aided by means of external cusp fields. Our simulations are done with the 2-1/2-D particle-in-cell plasma simulation code CLINER, which combines collisionless, electromagnetic PIC capabilities with a quasi-MHD finite element package.

Gisler, G.; Faehl, R.

1983-01-01

76

Construction of nonbinary cyclic, quasi-cyclic and regular LDPC codes: a finite geometry approach  

Microsoft Academic Search

This paper presents five methods for constructing nonbinary LDPC codes based on finite geometries. These meth- ods result in five classes of nonbinary LDPC codes, one class of cyclic LDPC codes, three classes of quasi-cyclic LDPC codes and one class of structured regular LDPC codes. Experimental results show that constructed codes in these classes decoded with iterative decoding based on

Lingqi Zeng; Lan Lan; Ying Yu Tai; Bo Zhou; Shu Lin; Khaled A. S. Abdel-ghaffar

2008-01-01

77

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

78

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

79

Cyclic phosphate-linked oligosaccharides: synthesis and conformational behavior of novel cyclic oligosaccharide analogues.  

PubMed

CyPLOS (cyclic phosphate-linked oligosaccharides), that is, novel cyclic oligosaccharide surrogates, consisting of two, three, and four phenyl-beta-D-glucopyranoside units, 4,6-linked through stable phosphodiester bonds, were prepared by a straightforward and efficient solid-phase protocol. The assembly of the linear precursors was achieved by standard phosphoramidite chemistry on an automated DNA synthesizer, using a suitably protected 4-phosphoramidite derivative of D-glucose as the building block. For the crucial cyclization step a phosphotriester methodology was exploited, followed by a mild basic treatment releasing the desired cyclic molecules in solution in a highly pure form. The cyclic dimer and trimer were also independently prepared by classical solution synthesis, basically following the same approach. The solution structural preferences of the cyclic dimer and trimer, obtained by detailed NMR analysis, are also reported. PMID:16626119

Di Fabio, Giovanni; Randazzo, Antonio; D'Onofrio, Jennifer; Ausn, Cristina; Pedroso, Enrique; Grandas, Anna; De Napoli, Lorenzo; Montesarchio, Daniela

2006-04-28

80

Visualization of cyclic nucleotide dynamics in neurons  

PubMed Central

The second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) transduce many neuromodulatory signals from hormones and neurotransmitters into specific functional outputs. Their production, degradation and signaling are spatiotemporally regulated to achieve high specificity in signal transduction. The development of genetically encodable fluorescent biosensors has provided researchers with useful tools to study these versatile second messengers and their downstream effectors with unparalleled spatial and temporal resolution in cultured cells and living animals. In this review, we introduce the general design of these fluorescent biosensors and describe several of them in more detail. Then we discuss a few examples of using cyclic nucleotide fluorescent biosensors to study regulation of neuronal function and finish with a discussion of advances in the field. Although there has been significant progress made in understanding how the specific signaling of cyclic nucleotide second messengers is achieved, the mechanistic details in complex cell types like neurons are only just beginning to surface. Current and future fluorescent protein reporters will be essential to elucidate the role of cyclic nucleotide signaling dynamics in the functions of individual neurons and their networks. PMID:25538560

Gorshkov, Kirill; Zhang, Jin

2014-01-01

81

Aircraft control by propeller cyclic blades  

NASA Technical Reports Server (NTRS)

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.

Deyoung, J.

1979-01-01

82

Cyclic depsipeptides as potential cancer therapeutics.  

PubMed

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

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

2015-03-01

83

Further studies on cyclic erythropoiesis in mice  

SciTech Connect

When young adult female W/Wv mice are given 0.5 micro+Ci /sup 89/Sr/g body weight intravenously, their hematocrit values oscillate from nadirs of 26% to zeniths of 42% with a periodicity of 16 days. The response of the W/Wv mouse to an assortment of radioactive and hematologic stresses have been examined in an effort to understand better the pathophysiology of cyclic erythropoiesis. When the dose of /sup 89/Sr is increased, the amplitude of cycling increases as nadirs are lowered, but periodicity is unchanged. When the dose of /sup 89/Sr is lowered to 0.3 microCi or less, cyclic erythropoiesis of substantial amplitude is observed only after five or six microoscillations. A single hematopoietic insult of 80 rad x-irradiation coupled with phlebotomy produces a transient form of cyclic erythropoiesis, namely, a series of dampened oscillations prior to recovery. Finally, we report that Wv/Wv mice exhibit a form of cyclic erythropoiesis in response to 0.5 microCi /sup 89/Sr/g body weight, in which the hematocrit values of successive nadirs gradually increase, and stabilize at about 100 days. /sup 89/Sr does not induce cyclic erythropoiesis in the +/+, W/+, or W/v/+ mice, the Hertwig strain of anemic mice, or in normal BDF1 mice.

Gibson, C.M.; Gurney, C.W.; Simmons, E.L.; Gaston, E.O.

1985-10-01

84

Biosynthesis of the endogenous cyclic adenosine monophosphate (AMP) antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), from prostaglandin E and activated inositol polyphosphate in rat liver plasma membranes  

Microsoft Academic Search

The endogenous cyclic adenosine monophosphate (AMP) antagonist, cyclic PIP, has been identified as a prostaglandylinositol cyclic phosphate. It inhibits protein kinase A 100% and activates protein serine phosphatase about sevenfold. It is biosynthesized by an enzyme of the plasma membrane when the assay mixture contains adenosine triphosphate (ATP), Mg 2+, prostaglandin E and a novel inositol polyphosphate, which cannot be

H. K. Wasner; M. Lemann; M. Conrad; H. Amini; E. Psarakis; A. Mir-Mohammad-Sadegh

1996-01-01

85

Biosynthesis of the endogenous cyclic adenosine monophosphate (AMP) antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), from prostaglandin E and activated inositol polyphosphate in rat liver plasma membranes  

Microsoft Academic Search

The endogenous cyclic adenosine monophosphate (AMP) antagonist, cyclic PIP, has been identified as a prostaglandylinositol cyclic phosphate. It inhibits protein kinase A 100% and activates protein serine phosphatase about sevenfold. It is biosynthesized by an enzyme of the plasma membrane when the assay mixture contains adenosine triphosphate (ATP), Mg2+, prostaglandin E and a novel inositol polyphosphate, which cannot be substituted

H. K. Wasner; M. Lemann; M. Conrad; H. Amini; E. Psarakis; A. Mir-Mohammad-Sadegh

1996-01-01

86

Evaluation of homogeneous electrocatalysts by cyclic voltammetry.  

PubMed

The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (?), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed. PMID:25247280

Rountree, Eric S; McCarthy, Brian D; Eisenhart, Thomas T; Dempsey, Jillian L

2014-10-01

87

Progress on plasma accelerators  

SciTech Connect

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.

Chen, P.

1986-05-01

88

Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.  

ERIC Educational Resources Information Center

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

Wilkinson, Bruce H.

1982-01-01

89

Thermodynamic approach in cyclical testing of materials  

Microsoft Academic Search

loped sufficiently because of imperfections of the apparatus employed. The emergence of much improved instruments in recent years for contactless temperature measurements (imaging infrared sensors, radiometers) has made it possible to turn to this problem. This paper shows that when a specimen (component) is subjected to cyclical loading in stages, the change in its surface temperature enables us to determine

G. A. Kurilenko

1989-01-01

90

Phase Regulation of Decentralized Cyclic Robotic Systems  

Microsoft Academic Search

We address the problem of coupling cyclic robotic tasks to produce a specified coordinated behavior. Such coordination tasks are common in robotics, appearing in applications like walking, hopping, run- ning, juggling and factory automation. In this paper we introduce a general methodology for designing controllers for such settings. We introduce a class of dynamical systems defined over n-dimensional tori (the

Eric Klavins; Daniel E. Koditschek

2002-01-01

91

The equations of Conformal Cyclic Cosmology  

NASA Astrophysics Data System (ADS)

I review the equations of Conformal Cyclic Cosmology given by Penrose (Cycles of time: an extraordinary new view of the universe. Bodley Head, London, 2010). Motivated by the example of FRW cosmologies, I suggest a slight modification to Penrose's prescription and show how this works out for Class A Bianchi cosmologies, and in general.

Tod, Paul

2015-03-01

92

A Numerical Simulation of Cyclic Mesocyclogenesis  

Microsoft Academic Search

A three-dimensional nonhydrostatic numerical model, the Advanced Regional Prediction System, is used to study the process of cyclic mesocyclogenesis in a classic supercell thunderstorm. During the 4-h simulation, the storm's mesocyclone undergoes two distinct occlusions, with the beginning of a third indicated at the end of the simulation. The occlusion process exhibits a period of approximately 60 min and is

Edwin J. Adlerman; Kelvin K. Droegemeier; Robert Davies-Jones

1999-01-01

93

Sequential Steam: An Engineered Cyclic Steaming Method  

Microsoft Academic Search

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.

Jeff Jones; Gary Cawthon

1990-01-01

94

Cyclic and circadian variations in cardiovascular events  

Microsoft Academic Search

The incidence of many biologic phenomena displays a reproducible and cyclic variation. Cardiovascular disease, the most common cause of death in the United States and other developed countries, also has an intrinsic variation in events. These events are more common in winter, at the beginning of each month, on Mondays (in working people), and during the early morning hours of

William J. Elliott

2001-01-01

95

Ants, Crickets and Frogs in Cyclic Pursuit  

E-print Network

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 with synchronized crickets that jump together every unit of time. Here the relative complexity of the problem

Efrat, Alon

96

Rhodium-catalyzed dehydrogenative borylation of cyclic alkenes  

E-print Network

A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. SuzukiMiyaura ...

Kondoh, Azusa

97

21 CFR 862.1230 - Cyclic AMP test system.  

Code of Federal Regulations, 2010 CFR

...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...

2010-04-01

98

21 CFR 862.1230 - Cyclic AMP test system.  

Code of Federal Regulations, 2013 CFR

...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...

2013-04-01

99

21 CFR 862.1230 - Cyclic AMP test system.  

Code of Federal Regulations, 2014 CFR

...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...

2014-04-01

100

21 CFR 862.1230 - Cyclic AMP test system.  

Code of Federal Regulations, 2012 CFR

...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...

2012-04-01

101

21 CFR 862.1230 - Cyclic AMP test system.  

Code of Federal Regulations, 2011 CFR

...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...

2011-04-01

102

for sequence accelerators  

E-print Network

Wynn's -algorithm for sequence accelerators using high precision arithmetic Rachel Baumann University of Arizona Wynn's -algorithm for sequence accelerators using high precision arithmetic Rachel Baumann University of Arizona April 17, 2012 #12;Wynn's -algorithm for sequence accelerators using high

Zakharov, Vladimir

103

Cyclic stress analysis of ceramic coated gas turbine seals  

NASA Technical Reports Server (NTRS)

Through the use of the Finite Element Method, the cyclic thermomechanical response of ceramic coated gas turbine parts is considered. The analysis includes temperature dependent elastic-plastic-creep material properties and cyclic thermal loads. To demonstrate the cyclic thermomechanical response, a ceramic coated outer gas path seal is studied. The analysis will estimate the significant residual stress field created by the cyclic thermal loads.

Padovan, Joe; Dougherty, Dan; Hendricks, Bob

1985-01-01

104

The time characteristics of cyclic service in Profibus  

Microsoft Academic Search

In Profibus master stations poll data from slave stations using the cyclic service CSRD (Cyclic Send and Request Data with Reply). Because the polling-interval determines the data sampling interval, it is important for the Profibus user to be able to know the maximum polling-interval of a cyclic service. We develop a formula for determining the maximum polling-interval of a cyclic

M. Li; L. Stoeckli

1996-01-01

105

Chemical Accelerators The phrase "chemical accelerators"  

E-print Network

that there is a wealth of important chemistry occurring only at higher energies (of the order of the strength of chemicalMeetings Chemical Accelerators The phrase "chemical accelerators" is scarcely older than for one or two dozen people grew to include nearly a hundred. Chemical accelerators is a name sug- gested

Zare, Richard N.

106

Glycine receptor in hippocampal neurons as a target for action of extracellular cyclic nucleotides.  

PubMed

Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are well known intracellular second messengers. At present study, we describe the effects of extracellularly applied cAMP and cGMP on glycine-induced chloride currents (I(Gly)) in isolated rat hippocampal pyramidal neurons. 50 or 500 ?M glycine was applied for 600 ms with 1 min intervals. cAMP and cGMP were co-applied with glycine. We found that both cAMP and cGMP rapidly, reversibly and in a dose-dependent manner accelerated the I(Gly) desensitization. The effect was more prominent on I(Gly) induced by 500 ?M than by 50 ?M glycine. Dose-response curves were constructed in the 0.1-100,000 nM range of cAMP and cGMP concentrations. They demonstrate that threshold concentration of both compounds was about 1 nM and maximal effect was manifested at 100 nM. When cAMP and cGMP were added to the recording pipette, their extracellular application caused the effects similar to those obtained with normal intracellular medium. The effects of cyclic nucleotides remained unchanged in the presence of the antagonist of adenosine receptors in extracellular solution, and the agonist of adenosine receptors did not mimic the effect of cyclic nucleotides. The changes in the decay kinetics were equally pronounced at negative and positive membrane potentials. When co-administered 1 nM cAMP and 1 nM cGMP caused a weaker effect than either of the compounds alone which suggests a negative interaction between binding sites for cAMP and cGMP. This work describes a novel mode of action of cyclic nucleotides, namely, the modulation of GlyRs functions from extracellular side. PMID:24373992

Bukanova, Julia V; Solntseva, Elena I; Kondratenko, Rodion V; Skrebitsky, Vladimir G

2014-02-21

107

Is the Class of Cyclic Codes Asymptotically Good?  

E-print Network

Is the Class of Cyclic Codes Asymptotically Good? Conchita Mart??�nez­P??erez Departamento de Matem whether the class of cyclic codes is asymptotically good. By an old result of Lin and Weldon, long BCH that there are asymptotically good sequences of binary cyclic codes in which all lengths are prime numbers provided there is any

Willems, Wolfgang

108

Synthesis of cyclic sulfones by ring-closing metathesis.  

PubMed

A general and highly efficient synthesis of cyclic sulfones based on ring-closing metathesis has been developed. The synthetic utility of the resulting cyclic sulfones was demonstrated by their participation in stereoselective Diels-Alder reactions and transformation to cyclic dienes by the Ramberg-Bcklund reaction. PMID:11820896

Yao, Qingwei

2002-02-01

109

Structural requirements for the biosynthesis of backbone cyclic peptide libraries  

E-print Network

Structural requirements for the biosynthesis of backbone cyclic peptide libraries Charles P. Scott to biosynthesis of backbone cyclic peptide libraries that combines the strengths of synthetic and genetic methods is very promiscuous with respect to peptide substrate composition, and can generate cyclic products

Ahmad, Sajjad

110

Stiffness degradation of natural fine grained soils during cyclic loading  

Microsoft Academic Search

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

D. V. Okur; A. Ansal

2007-01-01

111

High-Multiplicity Cyclic Job Shop Scheduling Tracy Kimbrel  

E-print Network

on a specific machine. Here we consider what we term the High-Multiplicity Cyclic Job Shop Scheduling ProblemHigh-Multiplicity Cyclic Job Shop Scheduling Tracy Kimbrel IBM T. J. Watson Research Center P consider the High-Multiplicity Cyclic Job Shop Scheduling Problem, in which we are given a set of identical

Atkinson, Katie

112

Theoretical Estimation to the Cyclic Strength Coefficient and the Cyclic StrainHardening Exponent for Metallic Materials: Preliminary Study  

Microsoft Academic Search

The ultimate purpose of the present article is to theoretically estimate the cyclic strength coefficient and the cyclic strain-hardening\\u000a exponent. For this purpose, the performance parameters of 22 alloys were examined and equations that relate the cyclic strength\\u000a coefficient and the cyclic strain-hardening exponent to the monotonic tensile ones were developed. Then, by using formulas\\u000a that express the strength coefficient

Zhongping Zhang; Yanjiang Qiao; Qiang Sun; Chunwang Li; Jing Li

2009-01-01

113

Cyclic GMP/cyclic GMP-dependent protein kinase system prevents excitotoxicity in an immortalized oligodendroglial cell line.  

PubMed

Previously, we have demonstrated that excitotoxicity of oligodendrocyte-like cells (OLC), differentiated from immortalized rat O-2A progenitor cells (CG-4 cells), is prevented by cyclic AMP-elevating agents. We now report that some agents that elevate cyclic GMP prevent OLC excitotoxicity. Kainate-induced injury was prevented by cyclic GMP analogues (8-bromo-cyclic GMP and dibutyryl cyclic GMP), a guanylate cyclase activator [atrial natriuretic peptide (ANP)], and phosphodiesterase inhibitors [3-isobutyl-1-methylxanthine (IBMX), ibudilast, propentofylline, and rolipram]. When both forskolin and 8-bromo-cyclic GMP were added, kainate-induced injury was additively prevented. There was a strong positive correlation between suppression of kainate-induced Ca2+ influx and prevention of injury by these chemicals. The measurement of intracellular cyclic AMP and cyclic GMP by radioimmunoassay demonstrated the following: an increase of cyclic GMP with treatment with 8-bromo-cyclic GMP, dibutyryl cyclic GMP, and ANP; an increase of cyclic AMP with treatment with ibudilast and rolipram; and an increase of both cyclic AMP and cyclic GMP with treatment with IBMX and propentofylline. Kainate-induced Ca2+ influx was decreased by 8-(4-chlorophenylthiol)-guanosine-3',5'-monophosphate, an activator of cyclic GMP-dependent protein kinase (PKG), or okadaic acid, an inhibitor of protein phosphatases 1 and 2A. RT-PCR and westem blotting of OLC demonstrated transcription of PKG II gene and translation of PKG Ibeta mRNA, but no translation of PKG Ialpha mRNA. Therefore, we concluded that the cyclic GMP/PKG system prevents OLC excitotoxicity. PMID:10646514

Yoshioka, A; Yamaya, Y; Saiki, S; Kanemoto, M; Hirose, G; Pleasure, D

2000-02-01

114

Cyclic nucleotide metabolism in pineal homogenates.  

PubMed

Adenylate cyclase (AC) in pineal particulate fractions from rabbit, rat, cow, and the vole Microtus montanus was stimulated by L-norepinephrine (NE) and L-isoproterenol (ISO). NE stimulation of rabbit and bovine pineal AC was biphasic, with a plateau between 0.01 microM and 1.0 microM and additional stimulation by NE above 1.0 microM. Stimulation by different ISO concentrations gave a typical hyperbolic curve, and optimal stimulation by ISO exceeded that by NE. Melatonin decreased ISO and NE stimulation of AC 10-20%. Although, alpha-adrenergic agonists increase beta-agonist-mediated adenosine-3',5'-cyclic monophosphate (cyclic AMP) accumulation in intact pinealocytes, similar amplification of AC stimulation was not seen with broken-cell preparations. Most (60-70%) pineal guanylate cyclase (GC) was recovered in supernatant fractions after centrifugation of homogenates at 110,000 x g; this soluble GC was unaffected by potential agonists. Low concentrations (0.01-1 nM) of NE, ISO, and phenylephrine (PE) stimulated GC in impure and purified membrane fractions, but each inhibited at concentrations above 10 microM. All concentrations of ISO and NE inhibited GC in the presence of the alpha-agonist PE. Melatonin alone did not affect particulate GC, but L-ISO stimulation was not seen in the presence of equivalent concentrations of melatonin. The in vitro data are consistent with both alpha- and beta-receptor regulation of cyclic nucleotide metabolism in pinealocytes. Endogenous NE may differentially regulate cyclic AMP and guanosine-3',5'-cyclic monophosphate (cyclic GMP) in pineal; low NE concentrations that stimulate GC have only a slight effect on AC, but higher NE concentrations that inhibit GC maximally stimulate AC. Particulate GC and AC also were resolved by equilibrium centrifugation, to give several discrete peaks of enzyme activity. The results support the existence of several forms of AC and GC, which have different responses to adrenergic agonists. PMID:2905388

Sweat, F W; Carmack, C F; Jewell, L S

1988-01-01

115

Cyclic nucleotide signalling in kidney fibrosis.  

PubMed

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

Schinner, Elisabeth; Wetzl, Veronika; Schlossmann, Jens

2015-01-01

116

Cyclic ethers adsorbed on Ru(001)  

NASA Astrophysics Data System (ADS)

The three cyclic ethers 1,3-dioxane. 1,4-dioxane and 1,3,5-trioxane all exhibit multiple desorption states from Ru(001) between 200 and 310 K, in addition to the multilayer and metastable states at lower temperature. Most distinctive are the two low-temperature ?-states. which are similar in shape, position, and relative population for all three compounds. This suggests that these states are associated with configurations which are accessible to all three molecules. The data also indicate that there is some molecular decomposition to gaseous CO and H 2. 1,4-Dioxane yields the largest amounts of these decomposition products, suggesting that this molecule is most susceptible to surface-catalyzed decomposition. The desorption data for the three cyclic ethers are grossly similar to each other, and also to the straight-chain diethers which we have previously studied.

Walczak, M. M.; Thiel, P. A.

1990-11-01

117

Cyclic Oxidation Modeling and Life Prediction  

NASA Technical Reports Server (NTRS)

The cyclic oxidation process can be described as an iterative scale growth and spallation sequence by a number of similar models. Model input variable include oxide scale type and growth parameters, spalling geometry, spall constant, and cycle duration. Outputs include net weight change, the amounts of retained and spalled oxide, the total oxygen and metal consumed, and the terminal rates of weight loss and metal consumption. All models and their variations produce a number of similar characteristic features. In general, spalling and material consumption increase to a steady state rate, at which point the retained scale approaches a constant and the rate of weight loss becomes linear. For one model, this regularity was demonstrated as dimensionless, universal expressions, obtained by normalizing the variables by critical performance factors. These insights were enabled through the use of the COSP for Windows cyclic oxidation spalling program.

Smialek, James L.

2004-01-01

118

Failure mechanism models for cyclic fatigue  

NASA Astrophysics Data System (ADS)

This tutorial illustrates design situations where mechanical fatigue under cyclic loading, of one or more components, can compromise system performance. In this failure mechanism, damage accumulates with each load cycle, thereby causing a physical wearout failure mechanism. Phenomenological continuum length-scale models, based on micromechanical considerations, are presented to predict the onset (or initiation) of fatigue cracking in ductile materials. Fatigue-crack propagation is modeled with continuum fracture-mechanics principles. The number of load cycles required to cause failure is predicted based on these models. Approaches for modeling creep-fatigue interactions are briefly discussed. Analytic physics-of-failure methods and examples are presented for designing against wearout failure due to cyclic fatigue. These models can be implemented in an engineering design environment. The associated stress analysis requires numerical finite-element techniques in many cases. The associated material property characterization techniques have matured since the 1950s and are specified in engineering handbooks.

Dasgupta, Abhijit

1993-12-01

119

Cyclic nucleotide signalling in kidney fibrosis  

PubMed Central

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

Schinner, Elisabeth; Wetzl, Veronika; Schlossmann, Jens

2015-01-01

120

Differential diagnosis of cyclic vomiting syndrome.  

PubMed

Vomiting is a nonspecific symptom and cyclic vomiting is a symptom complex that may result from a disorder of any major organ system. Children with cyclic vomiting syndrome (CVS) need careful review and investigation at their earliest presentations to exclude potentially lethal abnormalities such as intestinal volvulus, metabolic disorders, and neurologic space-occupying lesions. The range of abnormalities that may present with features consistent with CVS includes gastrointestinal obstructive, inflammatory and motility abnormalities, pancreatic disease, metabolic disease (particularly the amino acid-opathies, organic acidurias, fatty acid oxidation defects, and acute intermittent porphyria), renal disease, epilepsy, migraine, and psychiatric disorders. Careful history taking will usually provide clues to these uncommon problems, but all children should undergo baseline assessment of gastrointestinal morphology and screening tests for renal and metabolic disease. PMID:8708860

Forbes, D

1995-01-01

121

Acceleration without Horizons  

E-print Network

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} velocity or, equivalently, by an acceleration parameter and terminal velocity.

Doria, Alaric

2015-01-01

122

Acceleration without Horizons  

E-print Network

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} velocity or, equivalently, by an acceleration parameter and terminal velocity.

Alaric Doria; Gerardo Munoz

2015-02-18

123

Laser driven ion accelerator  

DOEpatents

A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

Tajima, Toshiki

2005-06-14

124

Induction linear accelerators  

Microsoft Academic Search

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very

Daniel Birx

1992-01-01

125

Laser driven ion accelerator  

DOEpatents

A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

Tajima, Toshiki

2006-04-18

126

Non-cyclic graph associated with a group  

E-print Network

We associate a graph $\\mathcal{C}_G$ to a non locally cyclic group $G$ (called the non-cyclic graph of $G$) as follows: take $G\\backslash Cyc(G)$ as vertex set, where $Cyc(G)=\\{x\\in G | \\text{is cyclic for all} y\\in G\\}$ is called the cyclicizer of $G$, and join two vertices if they do not generate a cyclic subgroup. For a simple graph $\\Gamma$, $w(\\Gamma)$ denotes the clique number of $\\Gamma$, which is the maximum size (if it exists) of a complete subgraph of $\\Gamma$. In this paper we characterize groups whose non-cyclic graphs have clique numbers at most 4. We prove that a non-cyclic group $G$ is solvable whenever $w(\\mathcal{C}_G)<31$ and the equality for a non-solvable group $G$ holds if and only if $G/Cyc(G)\\cong A_5$ or $S_5$.

Abdollahi, Alireza

2008-01-01

127

Cyclical Asymmetries in Unemployment Rates: International Evidence  

Microsoft Academic Search

This paper investigates to what extent the observed nonlinearities in the unemployment rates of six major developed economies\\u000a are the response to cyclical asymmetries. Two classes of models are compared: strict smooth transition autoregressions and\\u000a models where the transition variable is GDP growth, which is considered a more direct indicator of the business cycle. The\\u000a empirical evidence points out that

Jos Ramn Cancelo

2007-01-01

128

Star-shaped cyclic-twinning nanowires  

Microsoft Academic Search

We report the discovery of a new class of nanowires with a star-shaped cross section. Unlike most nanowires, it shows a prominent regular reentrant surface profile. The electron diffraction and electron energy loss spectroscopy analyses indicate that the nanowire is composed of superhard boron suboxide (B6O). The fivefold symmetry of the star-shaped nanowire could be understood as a cyclic twinning

Jun Jiang; Minghe Cao; Yuekui Sun; Peiwen Wu; Jun Yuan

2006-01-01

129

A diffusion-based cyclic particle extractor  

Microsoft Academic Search

A cyclic particle extractor based on particle diffusion is presented. The extraction realized by the device features simplicity,\\u000a programmability, and low cost. Although conventional particle separation based on diffusion can be spontaneously realized\\u000a without any active inputs, the extraction efficiency decreases as the size difference between particles decreases or if the\\u000a diffusion length is insufficient. In this article, a primary

Han-Sheng ChuangStephen; Stephen C. Jacobson; Steven T. Wereley

2010-01-01

130

High-affinity Cyclic Peptide Matriptase Inhibitors*  

PubMed Central

The type II transmembrane serine protease matriptase is a key activator of multiple signaling pathways associated with cell proliferation and modification of the extracellular matrix. Deregulated matriptase activity correlates with a number of diseases, including cancer and hence highly selective matriptase inhibitors may have therapeutic potential. The plant-derived cyclic peptide, sunflower trypsin inhibitor-1 (SFTI-1), is a promising drug scaffold with potent matriptase inhibitory activity. In the current study we have analyzed the structure-activity relationships of SFTI-1 and Momordica cochinchinensis trypsin inhibitor-II (MCoTI-II), a structurally divergent trypsin inhibitor from Momordica cochinchinensis that also contains a cyclic backbone. We show that MCoTI-II is a significantly more potent matriptase inhibitor than SFTI-1 and that all alanine mutants of both peptides, generated using positional scanning mutagenesis, have decreased trypsin affinity, whereas several mutations either maintain or result in enhanced matriptase inhibitory activity. These intriguing results were used to design one of the most potent matriptase inhibitors known to date with a 290 pm equilibrium dissociation constant, and provide the first indication on how to modulate affinity for matriptase over trypsin in cyclic peptides. This information might be useful for the design of more selective and therapeutically relevant inhibitors of matriptase. PMID:23548907

Quimbar, Pedro; Malik, Uru; Sommerhoff, Christian P.; Kaas, Quentin; Chan, Lai Y.; Huang, Yen-Hua; Grundhuber, Maresa; Dunse, Kerry; Craik, David J.; Anderson, Marilyn A.; Daly, Norelle L.

2013-01-01

131

The structure of adsorbed cyclic chains.  

PubMed

In order to determine the structure of polymer films formed of cyclic chains (rings) we developed and studied a simple coarse-grained model. Our main goal was to check how the percolation and jamming thresholds in such a system were related to the thresholds obtained for linear flexible chains system, i.e., how the geometry of objects influenced both thresholds. All atomic details were suppressed and polymers were represented as a sequence of identical beads and the chains were embedded to a square lattice (a strictly 2D model). The system was athermal and the excluded volume was the only potential introduced. A random sequential adsorption algorithm was chosen to determine the properties of a polymer monolayer. It was shown that the percolation threshold of cyclic chains was considerably higher than those of linear flexible chains while the jamming thresholds for both chain architectures are very similar. The shape of adsorbed cyclic chains was found to be more prolate when compared to average single chain. PMID:25701088

Kuriata, Aleksander; Sikorski, Andrzej

2015-03-01

132

Cyclic dominance in evolutionary games: a review.  

PubMed

Rock is wrapped by paper, paper is cut by scissors and scissors are crushed by rock. This simple game is popular among children and adults to decide on trivial disputes that have no obvious winner, but cyclic dominance is also at the heart of predator-prey interactions, the mating strategy of side-blotched lizards, the overgrowth of marine sessile organisms and competition in microbial populations. Cyclical interactions also emerge spontaneously in evolutionary games entailing volunteering, reward, punishment, and in fact are common when the competing strategies are three or more, regardless of the particularities of the game. Here, we review recent advances on the rock-paper-scissors (RPS) and related evolutionary games, focusing, in particular, on pattern formation, the impact of mobility and the spontaneous emergence of cyclic dominance. We also review mean-field and zero-dimensional RPS models and the application of the complex Ginzburg-Landau equation, and we highlight the importance and usefulness of statistical physics for the successful study of large-scale ecological systems. Directions for future research, related, for example, to dynamical effects of coevolutionary rules and invasion reversals owing to multi-point interactions, are also outlined. PMID:25232048

Szolnoki, Attila; Mobilia, Mauro; Jiang, Luo-Luo; Szczesny, Bartosz; Rucklidge, Alastair M; Perc, Matja

2014-11-01

133

Status of the Fatigue Studies on the CLIC Accelerating Structures  

E-print Network

The need for high accelerating gradients for the future multi-TeV e+e- Compact Linear Collider (CLIC) imposes considerable constraints on the materials of the accelerating structures. The surfaces exposed to high pulsed RF (Radio Frequency) currents are subject to cyclic thermal stresses which are expected to induce surface break up by fatigue. Since no fatigue data exists in the literature up to very large numbers of cycles and for the particular stress pattern present in RF cavities, a comprehensive study of copper alloys in this parameter range has been initiated. Fatigue data for selected copper alloys in different states are presented

Calatroni, S; Neupert, H; Wuensch, Walter; CERN. Geneva

2006-01-01

134

Universal Responses of Cyclic-Oxidation Models Studied  

NASA Technical Reports Server (NTRS)

Oxidation is an important degradation process for materials operating in the high-temperature air or oxygen environments typical of jet turbine or rocket engines. Reaction of the combustion gases with the component material forms surface layer scales during these oxidative exposures. Typically, the instantaneous rate of reaction is inversely proportional to the existing scale thickness, giving rise to parabolic kinetics. However, more realistic applications entail periodic startup and shutdown. Some scale spallation may occur upon cooling, resulting in loss of the protective diffusion barrier provided by a fully intact scale. Upon reheating, the component will experience accelerated oxidation due to this spallation. Cyclic-oxidation testing has, therefore, been a mainstay of characterization and performance ranking for high-temperature materials. Models simulate this process by calculating how a scale spalls upon cooling and regrows upon heating (refs. 1 to 3). Recently released NASA software (COSP for Windows) allows researchers to specify a uniform layer or discrete segments of spallation (ref. 4). Families of model curves exhibit consistent regularity and trends with input parameters, and characteristic features have been empirically described in terms of these parameters. Although much insight has been gained from experimental and model curves, no equation has been derived that can describe this behavior explicitly as functions of the key oxidation parameters.

Smialek, James L.

2003-01-01

135

Cyclic transition to turbulence in rigid abdominal aortic aneurysm models  

NASA Astrophysics Data System (ADS)

The hydrodynamic stability of cyclic flows inside rigid abdominal aortic aneurysm (AAA) models was investigated. Rectified sine waveforms were used to simulate aortic flow conditions (Re mean=1600-2100 and ?=7.2-12.2). Depending on the bulge geometry ( D/ d and L/ d ratios), AAA flows can be broadly classified into three regimes, namely types A, B and C, respectively. While type A has no vortex formation, type B and C have distinctive laminar vortical structures that are very different from one another. The type of flow regimes would also determine where and when the transition to turbulence would occur and the portion of the cycle at which the flow remains turbulent in the bulge. The stability characteristics of types B and C are obtained from the linear stability analysis performed on the unsteady velocity profiles measured at different phases of a cycle. Based on the linear stability analyses, instability is found to initiate in the bulge for types B and C through the formation of vortical structures. Instability grows progressively during the acceleration phase and transition to turbulence in the bulge occurs shortly after the commencement of the deceleration phase in all cases investigated. The mechanisms of transition to turbulence for types B and C are discussed. Although transition to turbulence appears in all the cases investigated here, fully laminar flows in types B and C are predicted to exist by the linear stability theory under extreme flow conditions. Finally, the in vivo biological implications of the in vitro results were discussed.

Yip, T. H.; Yu, S. C. M.

2001-08-01

136

A Mechanochemical Model of Cell Reorientation on Substrates under Cyclic Stretch  

PubMed Central

We report a theoretical study on the cyclic stretch-induced reorientation of spindle-shaped cells. Specifically, by taking into account the evolution of sub-cellular structures like the contractile stress fibers and adhesive receptor-ligand clusters, we develop a mechanochemical model to describe the dynamics of cell realignment in response to cyclically stretched substrates. Our main hypothesis is that cells tend to orient in the direction where the formation of stress fibers is energetically most favorable. We show that, when subjected to cyclic stretch, the final alignment of cells reflects the competition between the elevated force within stress fibers that accelerates their disassembly and the disruption of cell-substrate adhesion as well, and an effectively increased substrate rigidity that promotes more stable focal adhesions. Our model predictions are consistent with various observations like the substrate rigidity dependent formation of stable adhesions and the stretching frequency, as well as stretching amplitude, dependence of cell realignment. This theory also provides a simple explanation on the regulation of protein Rho in the formation of stretch-induced stress fibers in cells. PMID:23762444

Qian, Jin; Liu, Haipei; Lin, Yuan; Chen, Weiqiu; Gao, Huajian

2013-01-01

137

A mechanochemical model of cell reorientation on substrates under cyclic stretch.  

PubMed

We report a theoretical study on the cyclic stretch-induced reorientation of spindle-shaped cells. Specifically, by taking into account the evolution of sub-cellular structures like the contractile stress fibers and adhesive receptor-ligand clusters, we develop a mechanochemical model to describe the dynamics of cell realignment in response to cyclically stretched substrates. Our main hypothesis is that cells tend to orient in the direction where the formation of stress fibers is energetically most favorable. We show that, when subjected to cyclic stretch, the final alignment of cells reflects the competition between the elevated force within stress fibers that accelerates their disassembly and the disruption of cell-substrate adhesion as well, and an effectively increased substrate rigidity that promotes more stable focal adhesions. Our model predictions are consistent with various observations like the substrate rigidity dependent formation of stable adhesions and the stretching frequency, as well as stretching amplitude, dependence of cell realignment. This theory also provides a simple explanation on the regulation of protein Rho in the formation of stretch-induced stress fibers in cells. PMID:23762444

Qian, Jin; Liu, Haipei; Lin, Yuan; Chen, Weiqiu; Gao, Huajian

2013-01-01

138

Long-Term Cyclic Oxidation Behavior of Wrought Commercial Alloys at High Temperatures  

SciTech Connect

The oxidation resistance of a high-temperature alloy is dependent upon sustaining the formation of a protective scale, which is strongly related to the alloying composition and the oxidation condition. The protective oxide scale only provides a finite period of oxidation resistance owing to its eventual breakdown, which is especially accelerated under thermal cycling conditions. This current study focuses on the long-term cyclic oxidation behavior of a number of commercial wrought alloys. The alloys studied were Fe- and Ni-based, containing different levels of minor elements, such as Si, Al, Mn, and Ti. Oxidation testing was conducted at 1000 and 1100 C in still air under both isothermal and thermal cycling conditions (1-day and 7-days). The specific aspects studied were the oxidation behavior of chromia-forming alloys that are used extensively in industry. The current study analyzed the effects of alloying elements, especially the effect of minor element Si, on cyclic oxidation resistance. The behavior of oxide scale growth, scale spallation, subsurface changes, and chromium interdiffusion in the alloy were analyzed in detail. A novel model was developed in the current study to predict the life-time during cyclic oxidation by simulating oxidation kinetics and chromium interdiffusion in the subsurface of chromia-forming alloys.

Bingtao Li

2003-08-05

139

Uptake of Cyclic AMP by Natural Populations of Marine Bacteria  

PubMed Central

The major objective of this study was to describe the mechanism(s) of cyclic AMP uptake by natural populations of marine bacteria. A second objective was to determine whether this uptake could contribute to the intracellular regulatory pool of cyclic AMP. Using high-specific-activity 32P-labeled cyclic AMP, we found several high-affinity uptake systems. The highest-affinity system had a half-saturation constant of <10 pM. This system was extremely specific for cyclic nucleotides, particularly cyclic AMP. It appeared to meet the criteria for active transport. Uptake of cyclic AMP over a wide concentration range (up to 2 ?M) showed multiphasic kinetics, with half-saturation constants of 1 nM and greater. These lower-affinity systems were much less specific for cyclic nucleotides. Although much of the labeled cyclic AMP taken up by the high-affinity systems was metabolized, some remained as intact cyclic AMP within the cells during 1 h of incubation. This suggests that at least some of the bacteria use cyclic AMP dissolved in seawater to augment their intracellular pools. PMID:16345995

Ammerman, James W.; Azam, Farooq

1982-01-01

140

Cyclic AMP Receptor Protein-Aequorin Molecular Switch for Cyclic AMP  

PubMed Central

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

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

2011-01-01

141

Accelerated cleanup risk reduction  

SciTech Connect

There is no proven technology for remediating contaminant plume source regions in a heterogeneous subsurface. This project is an interdisciplinary effort to develop the requisite new technologies so that will be rapidly accepted by the remediation community. Our technology focus is hydrous pyrolysis/oxidation (HPO) which is a novel in situ thermal technique. We have expanded this core technology to leverage the action of steam injection and place an in situ microbial filter downstream to intercept and destroy the accelerated movement of contaminated groundwater. Most contaminant plume source regions, including the chlorinated solvent plume at LLNL, are in subsurface media characterized by a wide range in hydraulic conductivity. At LLNL, the main conduits for contaminant transport are buried stream channels composed of gravels and sands; these have a hydraulic conductivity in the range of 10{sup -1} to 10{sup -2} cm/s. Clay and silt units with a hydraulic conductivity of 10{sup -1} to 10{sup -6} cm/s bound these buried channels; these are barriers to groundwater movement and contain the highest contaminant concentrations in the source region. New remediation technologies are required because the current ones preferentially access the high conductivity units. HPO is an innovative process for the in situ destruction of contaminants in the entire subsurface. It operates by the injection of steam. We have demonstrated in laboratory experiments that many contaminants rapidly oxidize to harmless compounds at temperatures easily achieved by injecting steam, provided sufficient dissolved oxygen is present. One important challenge in a heterogeneous source region is getting heat, contaminants, and an oxidizing agent in the same place at the same time. We have used the NUFT computer program to simulate the cyclic injection of steam into a contaminated aquifer for design of a field demonstration. We used an 8 hour, steam/oxygen injection cycle followed by a 56 hour relaxation period in which the well was `capped`. Our results show the formation of an inclined gas phase during injection and a fast collapse of the steam zone within an hour of terminating steam injection. The majority of destruction occurs during the collapse phase, when contaminant laden water is drawn back towards the well. Little to no noncondensible gasses are created in this process, removing any possibility of sparging processes interfering with contaminant destruction. Our models suggest that the thermal region should be as hot and as large as possible. To have HPO accepted, we need to demonstrate the in situ destruction of contaminants. This requires the ability to inexpensively sample at depth and under high temperatures. We proved the ability to implies monitoring points at depths exceeding 150 feet in highly heterogeneous soils by use of cone penetrometry. In addition, an extractive system has been developed for sampling fluids and measuring their chemistry under the range of extreme conditions expected. We conducted a collaborative field test of HPO at a Superfund site in southern California where the contaminant is mainly creosote and pentachlorophenol. Field results confirm the destruction of contaminants by HPO, validate our field design from simulations, demonstrate that accurate field measurements of the critical fluid parameters can be obtained using existing monitoring wells (and minimal capital cost) and yield reliable cost estimates for future commercial application. We also tested the in situ microbial filter technology as a means to intercept and destroy the accelerated flow of contaminants caused by the injection of steam. A series of laboratory and field tests revealed that the selected bacterial species effectively degrades trichloroethene in LLNL Groundwater and under LLNL site conditions. In addition, it was demonstrated that the bacteria effectively attach to the LLNL subsurface media. An in-well treatability study indicated that the bacteria initially degrade greater than 99% of the contaminant, to concentrations less than regulatory limit

Knapp, R.B.; Aines, R.M.; Blake, R.G.; Copeland, A.B.; Newmark, R.L.; Tompson, A.F.B.

1998-02-01

142

Universal Behavior of a Cyclic Oxidation Model  

NASA Technical Reports Server (NTRS)

A mathematical model has been generated to represent the iterative, discrete growth and spallation processes associated with cyclic oxidation. Parabolic growth kinetics (k(sub p)) over and a constant spall area (F(sub A)) were assumed, with spalling occurring interfacially at the thickest regions of the scale. Although most models require numerical techniques, the regularity and simplicity of this progression permitted an approximation by algebraic expressions. Normalization could now be performed to reflect all parametric effects, and a universal cyclic oxidation response was generated: W(sub u) = 1/2 {3J(sub u)(sup 1/2)+ J(sub u)(sup 3/2)} where W, is weight change normalized by the maximum and J(sub u) is the cycle number normalized by the number to reach maximum. Similarly, the total amount of metal consumed was represented by a single normalized curve. The factor [(S(sub c)-l)(raised dot)sqrt(F(sub A)k(sub p)DELTAt)] was identified as a general figure of merit, where S(sub c) is the mass ratio of oxide to oxygen and DELTAt is the cycle duration. A cyclic oxidation failure map was constructed, in normalized k(sub p)-F(sub A) space, as defined by the locus of points corresponding to a critical amount of metal consumption in a given time. All three constructions describe behavior for every value of growth rate, spall fraction, and cycle duration by means of single curves, but with two branches corresponding to the times before and after steady state is achieved.

Smialek, James L.

2003-01-01

143

Cyclical konzo epidemics and climate variability.  

PubMed

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] Ann Neurol 2015;77:371-380. PMID:25523348

Oluwole, Olusegun Steven A

2015-03-01

144

Model for Cyclically Astable Third Sound Resonance  

SciTech Connect

Third sound in a circular resonator is capable of rich behavior due to the coincidence of several characteristics: a high quality factor; the capability for wave-induced circulation changes; vortex pinning on the substrate; and the Doppler shifting of modes. One dimensional models for each of these components have previously been used to reproduce highly nonlinear third sound CW lineshapes using a steady-state approximation. We now include oscillator transients to account for cyclical amplitude modulations of third sound recently observed under conditions of a drive force where both the amplitude and frequency are fixed.

Ellis, F. M.; Carbone, Ian; Dang, Hoan [Department of Physics, Wesleyan Unversity, Middletown, CT 06459 (United States)

2006-09-07

145

Entropy production of cyclic population dynamics  

E-print Network

Entropy serves as a central observable in equilibrium thermodynamics. However, many biological and ecological systems operate far from thermal equilibrium. Here we show that entropy production can characterize the behavior of such nonequilibrium systems. To this end we calculate the entropy production for a population model that displays nonequilibrium behavior resulting from cyclic competition. At a critical point the dynamics exhibits a transition from large, limit-cycle like oscillations to small, erratic oscillations. We show that the entropy production peaks very close to the critical point and tends to zero upon deviating from it. We further provide analytical methods for computing the entropy production which agree excellently with numerical simulations.

Andrae, Benjamin; Reichenbach, Tobias; Frey, Erwin

2010-01-01

146

Characterization of cyclic peptides containing disulfide bonds.  

PubMed

Unlike linear peptides, analysis of cyclic peptides containing disulfide bonds is not straightforward and demands indirect methods to achieve a rigorous proof of structure. Three peptides that belong to this category, p-Cl-Phe-DPDPE, DPDPE, and CTOP, were analyzed and the results are presented in this paper. The great potential of two dimensional NMR and ESI tandem mass spectrometry was harnessed during the course of peptide characterizations. A new RP-HPLC method for the analysis of trifluoroacetic acid is also presented. It is robust, simple, and efficient compared to the currently available methods. PMID:25778927

Johnson, Mindy; Liu, Mingtao; Struble, Elaine; Hettiarachchi, Kanthi

2015-05-10

147

Star-shaped cyclic-twinning nanowires  

NASA Astrophysics Data System (ADS)

We report the discovery of a new class of nanowires with a star-shaped cross section. Unlike most nanowires, it shows a prominent regular reentrant surface profile. The electron diffraction and electron energy loss spectroscopy analyses indicate that the nanowire is composed of superhard boron suboxide (B6O). The fivefold symmetry of the star-shaped nanowire could be understood as a cyclic twinning structure. The crystallographic analysis further suggested that it could be a common occurrence in boron-rich compounds. Star-shaped nanowires with regular reentrant surfaces are attractive for applications in nanotechnology.

Jiang, Jun; Cao, Minghe; Sun, Yuekui; Wu, Peiwen; Yuan, Jun

2006-04-01

148

Tutorial on cyclic potentiodynamic polarization technique  

SciTech Connect

The cyclic potentiodynamic polarization technique provides a reasonable, rapid method for qualitatively predicting the propensity of an alloy to suffer localized corrosion in the form of pitting and crevice corrosion. Better and more accurate techniques are available for estimating general corrosion rates. This paper outlines the features that have been found useful for interpreting the polarization scan along with an example of how such an interpretation might be made. The paper follows with a discussion of some of the effects that uncompensated solution resistance, inappropriate scan rate, and improper point of scan reversal can have on the polarization scan features and how these effects might influence the interpretation.

Silverman, D.C. [Solutia Inc., St. Louis, MO (United States)

1998-12-31

149

Synthesis of cyclic oligonucleotides by a modified phosphotriester approach.  

PubMed Central

Evidence will be presented to show that the allyl group is suitable for the protection of a 3'-terminal phosphodiester function. The latter will be demonstrated by the synthesis, via a phosphotriester approach, of two cyclic tetraribonucleotides [r(AAAA) and r(UAMe2UAMe2)], two cyclic hexadeoxyribonucleotides [d(CGCGCG) and d(TAAAAA)] and a cyclic octadeoxyribonucleotide [d(CGTGCGTG)]. PMID:3380690

de Vroom, E; Broxterman, H J; Sliedregt, L A; van der Marel, G A; van Boom, J H

1988-01-01

150

Interpretation of tandem mass spectra obtained from cyclic nonribosomal peptides.  

PubMed

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

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

151

Ageing effect on cyclic plasticity of a tempered martensitic steel  

Microsoft Academic Search

Specific isothermal cyclic deformation tests were carried out on a tempered martensitic steel 55NiCrMoV7 at four hardness levels in the temperature range 20600C. The cyclic stress response generally shows an initial exponential softening for the first few cycles, followed by a gradual softening without saturation. The influences of initial hardness obtained after tempering, temperature, strain rate and ageing on cyclic

Z. Zhang; D. Delagnes; G. Bernhart

2007-01-01

152

Acceleration of Gravity 1  

NSDL National Science Digital Library

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

Michael Horton

2009-05-30

153

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 ...

154

Dependence of the Excitability of Pituitary Cells on Cyclic Nucleotides  

PubMed Central

Cyclic 3?,5?-adenosine monophosphate and cyclic 3?,5?-guanosine monophosphate are intracellular (second) messengers that are produced from the nucleotide triphosphates by a family of enzymes consisting of adenylyl and guanylyl cyclases. These enzymes are involved in a broad array of signal transduction pathways mediated by the cyclic nucleotide monophosphates and their kinases, which control multiple aspects of cell function through the phosphorylation of protein substrates. Here, we review the findings and working hypotheses on the role of the cyclic nucleotides and their kinases in the control of electrical activity of the endocrine pituitary cells and the plasma membrane channels involved in this process. PMID:22564128

Stojilkovic, Stanko S.; Kretschmannova, Karla; Tomic, Melanija; Stratakis, Constantine A.

2012-01-01

155

Cyclic Process as a Tool for Considering Evolution  

NASA Astrophysics Data System (ADS)

Evolution is the process. The primary question is which tools we use to consider the process. In this work, basing on the original results of investigation of the intrinsic bistability in quantum systems, the concept of the cyclic process is developed for qualitative and quantitative consideration of processes as following: Everything that happens is the process of changing; the process is the cyclic process of ``... -> seed -> plant -> seed ->...'' type; the cyclic process is formed by two complement phase transitions of ``seed -> plant'' and ``plant -> seed'' type; the cyclic process is the manifestation of self-consistent interaction of interdependent two-state system, environment, and radiation, so that the whole Universe is involved in each process; the cyclic process can be described qualitatively and quantitatively by a real cubic equation with four generalized dimensionless real parameters, provided that one of the parameters undertakes cyclic change of its value and all four parameters belong to limited interdependent intervals to maintain cyclic process. Using the cyclic process approach as a powerful tool a variety of issues is considered. Preference of evolution, extinction, adaptation, and relation between microscopic structure and macroscopic behavior of the system are addressed. Seeing the evolution is the most transcending seeing of existence. The cyclic process approach is suggested to be a corner stone for scientific approach to seeing evolution.

Bondarenko, Victor

2009-03-01

156

Cyclic Nucleotide Concentrations in Relation to Renal Growth and Hypertrophy  

PubMed Central

In rats no consistent change in the concentration of cyclic GMP or cyclic AMP concentration was found in the renal cortex between 2 hours and seven days after unilateral nephrectomy. In regenerating liver tissue, between 2 hours and seven days after removal of one-third of the liver, there were no consistent changes in cyclic GMP concentrations, but cyclic AMP concentrations were higher than in controls. During postnatal growth, no consistent changes occurred in the cyclic GMP concentration of the spleen, the testes, the kidney cortex, the renal papilla, the liver or the ventricle between two and sixty days after birth. Cyclic AMP concentration on the other hand, in all these tissues with the exception of the spleen, was depressed between the twenty-first and fortieth day after birth, i.e., at a period of rapid growth. In the spleen, the concentration of cyclic AMP increased continuously from the second to the fifth day after birth. During renal parenchymal hyperplasia induced by a large intravenous dose of folic acid two days before sacrifice, the concentration of cyclic GMP in renal cortical tissue increased consistently. A model is proposed to explain the different patterns of changes in the cyclic nucleotide concentrations found. PMID:216165

Solomon, Sidney; Wise, Phyllis M.; Sanborn, Carolyn; Ratner, Albert

1978-01-01

157

Transresonant Electron Acceleration  

Microsoft Academic Search

ttelliwell and Bell have suggested synchronous acceleration of electrons by electromagnetic waves in the whistler range in the geomagnetic field. The acceleration of trapped electrons by electromagnetic waves is here generalized to include nonsynchronous or transresonant acceleration. It is shown that whistlers will scatter the electron velocity, by an amount inversely proportional to the square root of the time rate

E. N. Parker; Enrico Fermi

1961-01-01

158

Angular Acceleration without Torque?  

ERIC Educational Resources Information Center

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.

Kaufman, Richard D.

2012-01-01

159

Acceleration: It's Elementary  

ERIC Educational Resources Information Center

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

Willis, Mariam

2012-01-01

160

Force, mass and acceleration  

Microsoft Academic Search

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

Phil Dalrymple; Richard Griffiths

2005-01-01

161

Direction of Acceleration  

NSDL National Science Digital Library

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.

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

162

Far field acceleration  

SciTech Connect

Far fields are propagating electromagnetic waves far from their source, boundary surfaces, and free charges. The general principles governing the acceleration of charged particles by far fields are reviewed. A survey of proposed field configurations is given. The two most important schemes, Inverse Cerenkov acceleration and Inverse free electron laser acceleration, are discussed in detail.

Fernow, R.C.

1995-07-01

163

Theoretical Studies of Some HEDM Species: Cyclic O4, Cyclic O3 and Cubane  

NASA Technical Reports Server (NTRS)

Calculations have been carried out for the HEDM species (cyclic O4, cyclic O3, and cubane) using CASSCF/derivative and CASSCF/ICCI methods. Cyclic O4 is of interest both as a potential HEDM species and because of its possible role in the ozone deficit problem in atmospheric chemistry. We have studied the pathway for decomposition from the D(2d) minimum and also have found the approximate location of the singlet triplet crossing. The barrier to decomposition is found to be about 9 kcal/mol and is not limited by the singlet triplet crossing. For cyclic O3 we have focused on the crossings between the lowest five surfaces (X(1)A(1), s(1)A(1), (1)A(2), (1)B(1), and (1)B(2)) to provide some insight into ways to form cyclic O3 photochemically. The crossing region between the X(1)A(1) and 2(1)A(1) surfaces is in agreement with the work of Xantheas et al. The calculations show that vertical excitation from the ground state to the (1)A(2) state leads to a crossing with the (1)A(1) manifold near the crossing region of the X(1)A(1) and 2(1)A(1) surfaces. We have studied the decomposition pathways for cubane to benzene plus acetylene and to cyclooctatetraene. We have also studied the ground and excited states for the photochemical ring closure step. The state which closes to cubane can be described as a double triplet pi to pi* excitation with respect to the ground state. Thus, this state has only a small oscillator strength with respect to the ground state. However, there is a singlet pi to pi* state at nearly the same energy and excitation to this state followed by intersystem crossing could lead to the triplet pi to pi* state.

Walch, Stephen P.; Langhoff, Steve R. (Technical Monitor)

1996-01-01

164

Superplastic deformation induced by cyclic hydrogen charging  

SciTech Connect

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.

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

165

[Cyclic psychosis associated with the menstrual cycle].  

PubMed

Cyclic psychosis associated with the menstrual cycle is an uncommon disorder, not included under the accepted definitions of functional psychoses. We present three female adolescents who developed an acute psychosis a few days before menstruation, which resolved completely upon bleeding or several days later, only to reappear in the same form in subsequent cycles. The clinical presentation was not in line with that of the typical functional psychoses. An extensive medical work-up did not show any significant disturbances, with the exception of anovulatory cycles in one youngster. Psychotropic treatment had no effect on the course of the psychosis. Treatment with progesterone in the second half of the cycle in one case, and with a combined progesterone/estrogen contraceptive agent in another, resulted in full recovery within several cycles. The third girl showed a spontaneous remission within four cycles. Remission continued in all cases after discontinuation of the hormonal treatment, and with no need to reintroduce any psychotropic agent, for a period of 2-4 years. We discuss several possible etiologic mechanisms for cyclic psychosis associated with the menstrual cycle, including it being a cycloid non-specific affective disorder, and its association with a temporary functional hypothalamic-pituitary dysfunction, and with anovulation. We also discuss the role of psychotropic and hormonal treatment in this disorder. PMID:12908384

Stein, D; Blumenshon, R; Hanukoglu, A; Witztum, E

2003-07-01

166

Cyclical components of local rainfall data  

NASA Astrophysics Data System (ADS)

This paper reports on the use of a comparatively simple statistical methodology to study local short time series rainfall data. The objective is to help in agricultural planning, by diminishing the risks associated with some uncertainties affecting this business activity.The analysis starts by assuming a model of unobservable components, trend, cycle, seasonal and irregular, that is well known in many areas of application. When series are in the realm of business and economics, the statistical methods popularized by the US Census Bureau US National Bureau of Economic Research are used for seasonal and cyclical estimation, respectively. The flexibility of these methods makes them good candidates to be applied in the meteorological context, and this is done in this paper for a selection of monthly rainfall time series.Use of the results to help in analysing and forecasting cyclical components is emphasized. The results are interesting. An agricultural entrepreneur, or a group of them located in a single geographical region, will profit by systematically collecting information (monthly in our work) about rainfall, and adopting the scheme of analysis described in this paper.

Mentz, R. P.; D'Urso, M. A.; Jarma, N. M.; Mentz, G. B.

2000-02-01

167

Regulation of Cyclic Nucleotide Concentrations in Photoreceptors: An ATP-Dependent Stimulation of Cyclic Nucleotide Phosphodiesterase by Light  

Microsoft Academic Search

Regulation of cyclic nucleotide concentrations in rod outer segments (Rana pipiens) has been further examined. The present studies show that illumination markedly diminishes the concentration of cyclic nucleotides in suspensions of photoreceptor membranes, but the locus of regulation is cyclic nucleotide phosphodiesterase (EC 3.1.4.c) (light-stimulated) and not adenylate cyclase. There is a marked disproportionality between bleaching of rhodopsin and stimulation

Naomasa Miki; James J. Keirns; Frederick R. Marcus; Jenny Freeman; Mark W. Bitensky

1973-01-01

168

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

169

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

NASA Technical Reports Server (NTRS)

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. Performance and operating characteristics were nearly constant throughout the test except for a change in the accelerator back-streaming limit. Findings 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 have been substantiated, and attainable improvements in propellant utilization efficiency should significantly reduce accelerator erosion.

Nakanishi, S.

1976-01-01

170

Virtual Accelerator for Accelerator Optics Improvement  

SciTech Connect

Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and coupling reduction to improve PEP-II luminosity.

Yan, Y.T.; Cai, Y.; Decker, F-J.; Ecklund, S.; Irwin, J.; Seeman, J.; Sillivan, M.; Turner, J.; Wienands, U.; /SLAC

2005-09-30

171

High brightness electron accelerator  

DOEpatents

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.

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

1994-01-01

172

Acceleration in astrophysics  

SciTech Connect

The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.

Colgate, S.A.

1993-12-31

173

An introduction to acceleration mechanisms  

SciTech Connect

This paper discusses the acceleration of charged particles by electromagnetic fields, i.e., by fields that are produced by the motion of other charged particles driven by some power source. The mechanisms that are discussed include: Ponderamotive Forces, Acceleration, Plasma Beat Wave Acceleration, Inverse Free Electron Laser Acceleration, Inverse Cerenkov Acceleration, Gravity Acceleration, 2D Linac Acceleration and Conventional Iris Loaded Linac Structure Acceleration. (LSP)

Palmer, R.B.

1987-05-01

174

Performance of relay cyclic delay diversity in multicarrier system  

Microsoft Academic Search

In this paper, the performance of a cooperative relaying scheme with cyclic delay diversity (CDD) for an orthogonal frequency division multiplexing (OFDM) system is investigated. The system under consideration consists of multiple single-antenna terminals acting as relays and cooperating to provide spatial diversity. Cyclic shift is introduced at each relay and thus increase the frequency selectivity of relay channels. To

Nur Abdul Razak; Fatin Said; A. Hamid Aghvami

2009-01-01

175

Emergence of cyclic competitions in spatial ecosystems Marcus Frean  

E-print Network

between species is often governed by the competitive exclusion principle (Gause 1934), particularlyEmergence of cyclic competitions in spatial ecosystems Marcus Frean School of Mathematics ABSTRACT This paper considers ways in which cyclic competitions between species might emerge from other

Frean, Marcus

176

Card-cyclic-to-random shuffling with Johan Jonasson  

E-print Network

Card-cyclic-to-random shuffling with relabeling Johan Jonasson March 11, 2014 Abstract The card-cyclic-to-random shuffle is the card shuffle where the n cards are labeled 1, . . . , n according to their starting positions. Then the cards are mixed by first picking card 1 from the deck and reinserting it at a uniformly

Jonasson, Johan

177

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. ...

178

DIRECTED CYCLIC HAMILTONIAN CYCLE SYSTEMS OF THE COMPLETE SYMMETRIC DIGRAPH  

E-print Network

DIRECTED CYCLIC HAMILTONIAN CYCLE SYSTEMS OF THE COMPLETE SYMMETRIC DIGRAPH HEATHER JORDON AND JOY symmetric digraph, K n, exist if and only if n 2 (mod 4) and n = 2p with p prime and 1. We also show that directed cyclic hamiltonian cycle systems of the complete symmetric digraph minus a set of n/2 vertex

Morris, Joy

179

Variation potential influence on photosynthetic cyclic electron flow in pea  

PubMed Central

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

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

2015-01-01

180

On blocks with cyclic defect group and their head orders.  

E-print Network

such a block is determined by its planar embedded Brauer tree. Applying the radical idealiser process the head] gives a rather explicit description of blocks with cyclic defect group B = ZpG of p-adic group rings with cyclic defect group of group rings over discrete valuation rings. The fact that blocks of group rings

Nebe, Gabriele

181

CYCLIC VECTORS IN KORENBLUM TYPE SPACES ABDELOUAHAB HANINE  

E-print Network

the technique of premeasures, introduced by Korenblum in the 1970-s, to give a characterization of cyclic(z) := exp - 1 2 2 0 ei + z ei - z dµ(), z D, is cyclic in A2 (D) if and only if its associated positive

Paris-Sud XI, Université de

182

Response of saturated sands to cyclic shear at earthquake amplitudes  

Microsoft Academic Search

Both quasi-static and resonant cyclic shear tests were performed on hollow cylindrical specimens of saturated sands at various densities and confining stresses. Shear moduli measured at nondestructive amplitudes were shown to be independent of frequency for the range of 0.1 Hz to 50 Hz. Application of cyclic shear at larger amplitudess caused effective stress to decrease and failure. The number

V. P. Drnevich; J. P. Jent

1975-01-01

183

Synthesis of cyclic guanidines via Pd-catalyzed alkene carboamination.  

PubMed

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

Zavesky, Blane P; Babij, Nicholas R; Fritz, Jonathan A; Wolfe, John P

2013-11-01

184

NBER WORKING PAPER SERIES THE CHANGING CYCLICAL BEHAVIOR  

E-print Network

about .lX. The analysis makes use of two methods to study the changing cyclical behavior of inflation trend in cyclical wage and price flexibility have recently appeared. The studies use different analytic, surprisingly little formal analysis has been made of long--term changes In the curve's parameters. Both

185

Mathematical Modeling of Stress Fiber Reorganization Induced by Cyclic Stretch  

E-print Network

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...

Hsu, Hui-Ju

2010-01-14

186

Technology evaluation of man-rated acceleration test equipment for vestibular research  

NASA Technical Reports Server (NTRS)

The considerations for eliminating acceleration noise cues in horizontal, linear, cyclic-motion sleds intended for both ground and shuttle-flight applications are addressed. the principal concerns are the acceleration transients associated with change in direction-of-motion for the carriage. The study presents a design limit for acceleration cues or transients based upon published measurements for thresholds of human perception to linear cyclic motion. The sources and levels for motion transients are presented based upon measurements obtained from existing sled systems. The approaches to a noise-free system recommends the use of air bearings for the carriage support and moving-coil linear induction motors operating at low frequency as the drive system. Metal belts running on air bearing pulleys provide an alternate approach to the driving system. The appendix presents a discussion of alternate testing techniques intended to provide preliminary type data by means of pendulums, linear motion devices and commercial air bearing tables.

Taback, I.; Kenimer, R. L.; Butterfield, A. J.

1983-01-01

187

Statistical cyclicity of the supercontinent cycle  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

188

The Cyclic Universe: An Informal Introduction  

E-print Network

The Cyclic Model is a radical, new cosmological scenario which proposes that the Universe undergoes an endless sequence of epochs which begin with a `big bang' and end in a `big crunch.' When the Universe bounces from contraction to re-expansion, the temperature and density remain finite. The model does not include a period of rapid inflation, yet it reproduces all of the successful predictions of standard big bang and inflationary cosmology. We point out numerous novel elements that have not been used previously which may open the door to further alternative cosmologies. Although the model is motivated by M-theory, branes and extra-dimensions, here we show that the scenario can be described almost entirely in terms of conventional 4d field theory and 4d cosmology.

Paul J. Steinhardt; Neil Turok

2002-04-29

189

Optical properties of cyclic olefin copolymers  

NASA Astrophysics Data System (ADS)

The optical properties of a cyclic olefin copolymer, TopasTM, made by Celanese AG, are presented. This class of materials is attractive on account of their high use temperature, excellent optical transmission, low birefringence, and low moisture uptake. These materials are compared with other commonly used thermoplastics, namely, polycarbonate and polymethyl methacrylate. Finally, TopasTM is compared with a number of other optical polymers being studied for optical waveguiding applications. It is found that at 830 nm TopasTM has low losses (less than 0.5 dB/cm), so that it may be useful for datacom applications. At the telecommunication wavelength of 1550 nm the losses are in the range of 0.7 dB/cm.

Khanarian, Garo

2001-06-01

190

Compensation for the variable cyclic error in homodyne laser interferometers.  

PubMed

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

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

2015-01-01

191

Which Digraphs with Ring Structure are Essentially Cyclic?  

E-print Network

We say that a digraph is essentially cyclic if its Laplacian spectrum is not completely real. The essential cyclicity implies the presence of directed cycles, but not vice versa. The problem of characterizing essential cyclicity in terms of graph topology is difficult and yet unsolved. Its solution is important for some applications of graph theory, including that in decentralized control. In the present paper, this problem is solved with respect to the class of digraphs with ring structure, which models some typical communication networks. It is shown that the digraphs in this class are essentially cyclic, except for certain specified digraphs. The main technical tool we employ is the Chebyshev polynomials of the second kind. We also consider the problem of essential cyclicity for weighted digraphs and enumerate the spanning trees in some digraphs with ring structure.

Agaev, Rafig

2009-01-01

192

Cyclic phosphatidic acid relieves osteoarthritis symptoms  

PubMed Central

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 42days) 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

2014-01-01

193

Globally synchronized oscillations in complex cyclic games  

NASA Astrophysics Data System (ADS)

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. Ltz et al. [J. Theor. Biol. 317, 286 (2013), 10.1016/j.jtbi.2012.10.024] 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.

Rulquin, Charlotte; Arenzon, Jeferson J.

2014-03-01

194

Cyclic-AMP and bacterial cyclic-AMP receptor proteins revisited: adaptation for different ecological niches?  

PubMed Central

Escherichia coli cyclic-AMP receptor protein (CRP) represents one of the paradigms of bacterial gene regulation. Yet despite decades of intensive study, new information continues to emerge that prompts reassessment of this classic regulatory system. Moreover, in recent years CRPs from several other bacterial species have been characterized, allowing the general applicability of the CRP paradigm to be tested. Here the properties of the E. coli, Mycobacterium tuberculosis and Pseudomonas putida CRPs are considered in the context of the ecological niches occupied by these bacteria. It appears that the cyclic-AMP-CRP regulatory system has been adapted to respond to distinct external and internal inputs across a broad sensitivity range that is, at least in part, determined by bacterial lifestyles. PMID:24509484

Green, Jeffrey; Stapleton, Melanie R; Smith, Laura J; Artymiuk, Peter J; Kahramanoglou, Christina; Hunt, Debbie M; Buxton, Roger S

2014-01-01

195

Cyclic-AMP and bacterial cyclic-AMP receptor proteins revisited: adaptation for different ecological niches.  

PubMed

Escherichia coli cyclic-AMP receptor protein (CRP) represents one of the paradigms of bacterial gene regulation. Yet despite decades of intensive study, new information continues to emerge that prompts reassessment of this classic regulatory system. Moreover, in recent years CRPs from several other bacterial species have been characterized, allowing the general applicability of the CRP paradigm to be tested. Here the properties of the E. coli, Mycobacterium tuberculosis and Pseudomonas putida CRPs are considered in the context of the ecological niches occupied by these bacteria. It appears that the cyclic-AMP-CRP regulatory system has been adapted to respond to distinct external and internal inputs across a broad sensitivity range that is, at least in part, determined by bacterial lifestyles. PMID:24509484

Green, Jeffrey; Stapleton, Melanie R; Smith, Laura J; Artymiuk, Peter J; Kahramanoglou, Christina; Hunt, Debbie M; Buxton, Roger S

2014-04-01

196

Linking numbers in rational homology 3-spheres, cyclic branched covers and infinite cyclic covers  

Microsoft Academic Search

We study the linking numbers in a rational homology 3-sphere and in the infinite cyclic cover of the complement of a knot. They take values in $\\\\Bbb Q$ and in ${Q}({\\\\Bbb Z}[t,t^{-1}])$ respectively, where ${Q}({\\\\Bbb Z}[t,t^{-1}])$ denotes the quotient field of ${\\\\Bbb Z}[t,t^{-1}]$. It is known that the modulo-$\\\\Bbb Z$ linking number in the rational homology 3-sphere is determined by

Jozef H. Przytycki; Akira Yasuhara

2001-01-01

197

Leaky Fermi accelerators  

E-print Network

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 sufficiently long time. The heat production is found to depend strongly on the type of the Fermi accelerator. An ergodic accelerator, i.e. one which has a single ergodic component, produces a weaker energy flow than a multi-component accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multi-component case the energy flow may be significantly increased by shrinking the hole size.

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

2015-01-01

198

Leaky Fermi accelerators  

E-print Network

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 sufficiently long time. The heat production is found to depend strongly on the type of the Fermi accelerator. An ergodic accelerator, i.e. one which has a single ergodic component, produces a weaker energy flow than a multi-component accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multi-component case the energy flow may be significantly increased by shrinking the hole size.

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

2015-04-03

199

THE DIELECTRIC WALL ACCELERATOR  

SciTech Connect

The Dielectric Wall Accelerator (DWA), a class of induction accelerators, employs a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge to mass ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.

Caporaso, G J; Chen, Y; Sampayan, S E

2009-08-17

200

Optically pulsed electron accelerator  

DOEpatents

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.

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

1985-05-20

201

Optically pulsed electron accelerator  

DOEpatents

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 radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

Fraser, John S. (Los Alamos, NM); Sheffield, Richard L. (Los Alamos, NM)

1987-01-01

202

Android Acceleration Application  

NSDL National Science Digital Library

In the first of two sequential lessons, students create mobile apps that collect data from an Android device's accelerometer and then store that data to a database. This lesson provides practice with MIT's App Inventor software and culminates with students writing their own apps for measuring acceleration. In the second lesson, students are given an app for an Android device, which measures acceleration. They investigate acceleration by collecting acceleration vs. time data using the accelerometer of a sliding Android device. Then they use the data to create velocity vs. time graphs and approximate the maximum velocity of the device.

IMPART RET Program, College of Information Science & Technology,

203

Particle acceleration in flares  

NASA Technical Reports Server (NTRS)

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.

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

204

Accelerators and Nobel Laureates  

NSDL National Science Digital Library

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.

Kullander, Sven

205

Charged particle accelerator grating  

DOEpatents

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.

Palmer, Robert B. (Shoreham, NY)

1986-01-01

206

Accelerator-based BNCT.  

PubMed

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

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

207

Accelerating Research with  

E-print Network

Accelerating Academic Research with Cloud Computing Published: September 2014 For the latest, maintained, and updated by expert staff. Worries about data loss from disasters (natural disasters, flooding

Bernstein, Phil

208

Cyclic AMP-dependent protein kinase activity in Trypanosoma cruzi.  

PubMed Central

A cyclic AMP-dependent protein kinase activity from epimastigote forms of Trypanosoma cruzi was characterized. Cytosolic extracts were chromatographed on DEAE-cellulose columns, giving two peaks of kinase activity, which were eluted at 0.15 M- and 0.32 M-NaCl respectively. The second activity peak was stimulated by nanomolar concentrations of cyclic AMP. In addition, a cyclic AMP-binding protein co-eluted with the second kinase activity peak. Cyclic AMP-dependent protein kinase activity was further purified by gel filtration, affinity chromatography on histone-agarose and cyclic AMP-agarose, as well as by chromatography on CM-Sephadex. The enzyme ('holoenzyme') could be partially dissociated into two different components: 'catalytic' and 'regulatory'. The 'regulatory' component had specific binding for cyclic AMP, and it inhibited phosphotransferase activity of the homologous 'catalytic component' or of the 'catalytic subunit' from bovine heart. Cyclic AMP reversed these inhibitions. A 'holoenzyme preparation' was phosphorylated in the absence of exogenous phosphate acceptor and analysed by polyacrylamide-gel electrophoresis. A 56 kDa band was phosphorylated. The same preparation was analysed by Western blotting, by using polyclonal antibodies to the regulatory subunits of protein kinases type I or II. Both antibodies reacted with the 56 kDa band. Images Fig. 7. Fig. 8. PMID:2848508

Ulloa, R M; Mesri, E; Esteva, M; Torres, H N; Tllez-In, M T

1988-01-01

209

Long-term cyclic strain downregulates endothelial Nox4.  

PubMed

Endothelial cells in vivo are constantly exposed to mechanical forces such as cyclic strain. In endothelial cells, Nox4-containing NAD(P)H oxidase complexes have been identified as major sources of superoxide anion (.O(2)(-)) formation. In this study, we analyzed the effect of cyclic strain on endothelial ROS formation by electron paramagnetic resonance spectroscopy, cytochrome c assay, and dihydroethidium fluorescence, on NO formation by Griess reaction and on gene expression by RT-PCR and Western blot. Primary cultures of human umbilical vein endothelial cells were exposed to 2-18% cyclic strain for up to 24 h using the Flexercell system. Long-term application of 5-12% cyclic strain downregulated Nox4 expression and ROS formation in a time-dependent manner. Downregulation of Nox4 was further confirmed by promoter analysis using dual-luciferase assay. Cu/Zn SOD, MnSOD, and catalase expression was decreased after application of chronic 12% cyclic strain. In contrast, endothelial NO formation and eNOS were increased by cyclic strain. Strain-dependent Nox4 downregulation was abolished by eNOS inhibition with L-NAME. In conclusion, physiological levels of cyclic strain downregulate Nox4 expression and superoxide anion formation. This novel mechanism might contribute to a vasoprotective balance between NO and superoxide anions in response to physiological mechanical stimulation of endothelial cells. PMID:19309265

Goettsch, Claudia; Goettsch, Winfried; Arsov, Alexander; Hofbauer, Lorenz C; Bornstein, Stefan R; Morawietz, Henning

2009-10-01

210

Phorbol esters modulate cyclic AMP accumulation in porcine thyroid cells  

SciTech Connect

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.

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

1988-01-01

211

Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams  

SciTech Connect

Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

Siemann, R.H.; /SLAC

2011-10-24

212

Cyclic AMP-elevating agents prevent oligodendroglial excitotoxicity.  

PubMed

Previously, we have demonstrated that cells of the oligodendroglial lineage express non-NMDA glutamate receptor genes and are damaged by kainate-induced Ca2+ influx via non-NMDA glutamate receptor channels, representing oligodendroglial excitotoxicity. We find in the present study that agents that elevate intracellular cyclic AMP prevent oligodendroglial excitotoxicity. After oligodendrocyte-like cells, differentiated from the CG-4 cell line established from rat oligodendrocyte type-2 astrocyte progenitor cells, were exposed to 2 mM kainate for 24 h, cell death was evaluated by measuring activity of lactate dehydrogenase released into the culture medium. Released lactate dehydrogenase increased about threefold when exposed to 2 mM kainate. Kainate-induced cell death was prevented by one of the following agents: adenylate cyclase activator (forskolin), cyclic AMP analogues (dibutyryl cyclic AMP and 8-bromo-cyclic AMP), and cyclic AMP phosphodiesterase inhibitors (3-isobutyl-1-methylxanthine, pentoxifylline, propentofylline, and ibudilast). Simultaneous addition of both forskolin and phosphodiesterase inhibitors prevented the kainate-induced cell death in an additive manner. A remarkable increase in Ca2+ influx (approximately 5.5-fold) also was induced by kainate. The cyclic AMP-elevating agents caused a partial suppression of the kainate-induced increase in Ca2+ influx, leading to a less prominent response of intracellular Ca2+ concentration to kainate. The suppressing effect of forskolin on the kainate-induced Ca2+ influx was partially reversed by H-89, an inhibitor of cyclic AMP-dependent protein kinase. In contrast to this, okadaic acid, an inhibitor of protein phosphatases 1 and 2A, brought about a decrease in the kainate-induced Ca2+ influx. We therefore concluded that cyclic AMP-elevating agents prevented oligodendroglial excitotoxicity by cyclic AMP-dependent protein kinase-dependent protein phosphorylation, resulting in decreased kainate-induced Ca2+ influx. PMID:9603206

Yoshioka, A; Shimizu, Y; Hirose, G; Kitasato, H; Pleasure, D

1998-06-01

213

Microscale acceleration history discriminators  

DOEpatents

A new class of micromechanical acceleration history discriminators is claimed. These discriminators allow the precise differentiation of a wide range of acceleration-time histories, thereby allowing adaptive events to be triggered in response to the severity (or lack thereof) of an external environment. Such devices have applications in airbag activation, and other safety and surety applications.

Polosky, Marc A. (Albuquerque, NM); Plummer, David W. (Albuquerque, NM)

2002-01-01

214

Accelerators Beyond The Tevatron?  

SciTech Connect

Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?

Lach, Joseph; /Fermilab

2010-07-01

215

Ion Cyclotron Resonance Accelerator  

Microsoft Academic Search

The Ion Cyclotron Resonance Accelerator (ICRA) is based on the operating principles of cyclotrons and gyrotrons, and should provide beam suitable for the production of radioisotopes for positron emission tomography (PET) or neutrons at a fraction of the cost of present day cyclotrons and linacs. The concept extends cyclotron resonance acceleration to ions by using a superconducting solenoid and a

T. L. Grimm; C. T. Ramsell; R. C. York

1997-01-01

216

KEK digital accelerator  

NASA Astrophysics Data System (ADS)

The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA) is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.

Iwashita, T.; Adachi, T.; Takayama, K.; Leo, K. W.; Arai, T.; Arakida, Y.; Hashimoto, M.; Kadokura, E.; Kawai, M.; Kawakubo, T.; Kubo, Tomio; Koyama, K.; Nakanishi, H.; Okazaki, K.; Okamura, K.; Someya, H.; Takagi, A.; Tokuchi, A.; Wake, M.

2011-07-01

217

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.

218

Induction linear accelerators  

NASA Astrophysics Data System (ADS)

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

Birx, Daniel

1992-03-01

219

Accelerators (4/5)  

ScienceCinema

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.

None

2011-10-06

220

Accelerators (3/5)  

ScienceCinema

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.

None

2011-10-06

221

Accelerators (5/5)  

ScienceCinema

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.

None

2011-10-06

222

NEW ACCELERATION METHODS  

Microsoft Academic Search

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

Sessler

1984-01-01

223

ACCELERATOR RESEARCH STUDIES  

SciTech Connect

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

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

2004-01-23

224

Acceleration in astrophysics  

Microsoft Academic Search

The origin of cosmic rays and applicable laboratory experiments are discussed. The principle problems of shock acceleration for the production of cosmic rays in the context of astrophysical conditions are found to be: (1) The presumed unique explanation of the power law spectrum is shown instead to be expected as a universal property of all accelerators with high loss; (2)

Stirling A Colgate

1994-01-01

225

Scaling FFAG accelerator for muon acceleration  

SciTech Connect

Recent developments in scaling fixed field alternating gradient (FFAG) accelerators have opened new ways for lattice design, with straight sections, and insertions like dispersion suppressors. Such principles and matching issues are detailed in this paper. An application of these new concepts is presented to overcome problems in the PRISM project.

Lagrange, JB.; Planche, T. [Graduate School of Engineering, Kyoto University Katsura, Nishikyo-ku Kyoto, 615-8530 (Japan); Mori, Y. [Kyoto University Research Reactor Institute, Department of Nuclear Science and Engineering, 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka, 590-0494 (Japan)

2011-10-06

226

Dynamic effects of predators on cyclic voles: field experimentation and model extrapolation.  

PubMed Central

Mechanisms generating the well-known 3-5 year cyclic fluctuations in densities of northern small rodents (voles and lemmings) have remained an ecological puzzle for decades. The hypothesis that these fluctuations are caused by delayed density-dependent impacts of predators was tested by replicated field experimentation in western Finland. We reduced densities of all main mammalian and avian predators through a 3 year vole cycle and compared vole abundances between four reduction and four control areas (each 2.5-3 km(2)). The reduction of predator densities increased the autumn density of voles fourfold in the low phase, accelerated the increase twofold, increased the autumn density of voles twofold in the peak phase, and retarded the initiation of decline of the vole cycle. Extrapolating these experimental results to their expected long-term dynamic effects through a demographic model produces changes from regular multiannual cycles to annual fluctuations with declining densities of specialist predators. This supports the findings of the field experiment and is in agreement with the predation hypothesis. We conclude that predators may indeed generate the cyclic population fluctuations of voles observed in northern Europe. PMID:12028754

Korpimki, Erkki; Norrdahl, Kai; Klemola, Tero; Pettersen, Terje; Stenseth, Nils Chr

2002-01-01

227

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

SciTech Connect

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.

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

2010-09-15

228

Cyclical vomiting syndrome: Recognition, assessment and management  

PubMed Central

Cyclical vomiting syndrome (CVS) is a functional, debilitating disorder of childhood frequently leading to hospitalization. Affected children usually experience a stereotypical pattern of vomiting though it may vary between different individuals. The vomiting is intense often bilious, and accompanied by disabling nausea. Identifiable precipitating factors for CVS include psychosocial stressors, infections, lack of sleep and occasionally even food triggers. Often, it may be difficult to distinguish episodes of CVS from other causes of acute abdomen and altered consciousness. Thus, the diagnosis of CVS remains largely one of exclusion. Investigations routinely done during the work-up of a child with suspected CVS include both blood and imaging modalities. Plasma lactate, ammonia, amino acid and acylcarnitine profiles as well as urine organic acid profile are indicated to exclude inborn errors of metabolism. The treatment remains challenging and targeted at prevention or shortening of the attacks and can be considered as abortive, supportive and prophylactic. Use of non-pharmacological therapy is also part of the management of CVS. The prognosis of CVS is variable. More insight into the pathogenesis of this disorder as well as role of non-pharmacological therapy is needed. PMID:25254185

Tan, Michelle LN; Liwanag, Maria Janelle; Quak, Seng Hock

2014-01-01

229

Steady state oxygen reduction and cyclic voltammetry.  

PubMed

The catalytic activity of Pt and Pt3Ni for the oxygen reduction reaction is investigated by applying a Sabatier model based on density functional calculations. We investigate the role of adsorbed OH on the activity, by comparing cyclic voltammetry obtained from theory with previously published experimental results with and without molecular oxygen present. We find that the simple Sabatier model predicts both the potential dependence of the OH coverage and the measured current densities seen in experiments, and that it offers an understanding of the oxygen reduction reaction (ORR) at the atomic level. To investigate kinetic effects we develop a simple kinetic model for ORR. Whereas kinetic corrections only matter close to the volcano top, an interesting outcome of the kinetic model is a first order dependence on the oxygen pressure. Importantly, the conclusion obtained from the simple Sabatier model still persists: an intermediate binding of OH corresponds to the highest catalytic activity, i.e. Pt is limited by a too strong OH binding and Pt3Ni is limited by a too weak OH binding. PMID:19213325

Rossmeisl, Jan; Karlberg, Gustav S; Jaramillo, Thomas; Nrskov, Jens K

2008-01-01

230

Effect of Cyclic Deformation on Magnetorheological Elastomers  

NASA Astrophysics Data System (ADS)

Fatigue properties of magnetorheological elastomer (MRE) samples were investigated based on cis-polybutadiene rubber by using a fatigue test machine. Three MRE samples with iron particles mass fraction of 60%, 70%, and 80% were fabricated, and their properties dependence of three strain amplitudes (50%, 75%, and 100%) were measured. The absolute magnetorheological (MR) effect, storage modulus, and loss modulus of MRE samples after fatigue were evaluated by a modified dynamic mechanical analyzer. The results revealed that MR effect, storage modulus, and loss modulus of MREs containing 80% iron particles depended strongly on the strain amplitudes and the number of cycles, while storage modulus and loss modulus of MREs containing 70% iron particles also depended on the strain amplitudes and the number of cycles but not as strongly as sample which contains 80% iron particles, but the properties of MREs containing 60% iron particles after cyclic deformation were almost independent of the fatigued conditions. In order to investigate the fatigue mechanism of MREs, the sample was carried out with a quasi-static tensile testing and its surface morphology during testing was observed in situ by scanning electron microscopy.

Zhang, Wei; Gong, Xing-long; Sun, Tao-lin; Fan, Yan-ceng; Jiang, Wan-quan

2010-04-01

231

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

PubMed

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 O? (as an electron acceptor) is essential and H?O (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 H?O (or H?) 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

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

2013-01-01

232

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

PubMed Central

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

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

2013-01-01

233

The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading  

NASA Astrophysics Data System (ADS)

Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending ( R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation.

Qian, Zhongyuan; Chumbley, Scott; Karakulak, Tugce; Johnson, Eric

2013-07-01

234

Gramicidin S: Relationship of Cyclic Structure to Antibiotic Activity  

Microsoft Academic Search

GRAMICIDIN S is a polypeptide antibiotic elaborated by a strain of Bacillus brevis1. Its postulated structure, well substantiated by experimental results2, is that of a cyclic decapeptide of the following nature3:

Bernard F. Erlanger; Louise Goode

1954-01-01

235

Tonal interaction in Kinande : cyclicity, opacity, and morphosyntactic structure  

E-print Network

This dissertation develops a constraint-based analysis of opaque tonal interactions in Kinande verb forms and, based on this analysis, argues for a phonological architecture that incorporates both cyclic evaluation and ...

Jones, Patrick Jackson

2014-01-01

236

Microwave-assisted synthesis of cyclic phosphopeptide on solid support.  

PubMed

Phosphopeptides are important tools for studying intracellular signal transduction events in vitro and in vivo and are also potential drugs due to their direct competition with phosphoprotein recognition elements. Cyclization has been demonstrated to improve peptide selectivity, metabolic stability, and bioavailability. However, cyclic phosphopeptide synthesis may not be straightforward due to the sterically hindered phosphorylated side-chain amino acid derivatives. One option to overcome this hurdle is to use microwave-assisted synthesis, which has been shown to increase efficiency and reduce synthesis time. Herein, a detailed protocol is provided for synthesizing cyclic phosphopeptides using automated microwave. The overall synthesis duration was reduced and yields increased compared with a manual conventional method. This method provides a general, fast and facile way to synthesize cyclic peptides, demonstrating the synthesis of cyclic phosphorylated peptides which are known to be among the most challenging to produce. PMID:25042903

Qvit, Nir

2015-03-01

237

Cyclic AMP Signaling: A Molecular Determinant of Peripheral Nerve Regeneration  

PubMed Central

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

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

2014-01-01

238

Metabolically regulated cyclical contractures in microinjected Spirostomum : A pharmacological study  

Microsoft Academic Search

Summary Spirostomum was treated extracellularly and intracellularly with a range of metabolites to investigate the intracellular regulation of cyclic calcium movements. The results indicate, close links between calcium movements and mitochondrial metabolism.

S. Dikstein; R. B. Hawkes

1976-01-01

239

Cohomological Constructions of Regular Cyclic Coverings of the Platonic Maps  

Microsoft Academic Search

In we described the regular maps and hypermaps which are cyclic coverings of the Platonic maps, branched over the face centers, vertices or midpoints of edges. Here we determine cochains by which these coverings can be explicitly constructed.

David B. Surowski; Gareth A. Jones

2000-01-01

240

Pro-cyclical mortality across socioeconomic groups and health status.  

PubMed

Using variation across geographic regions, a number of studies from the U.S. and other developed countries have found more deaths in economic upturns and less deaths in economic downturns. We use data from regions in Norway for 1977-2008 and find the same pro-cyclical patterns. Using individual-level register data for the identical population, we find that disadvantaged socioeconomic groups are not hit harder by pro-cyclical mortality than advantaged groups. We also find that other indicators of deteriorated health (than death), like becoming disabled, are pro-cyclical. Overall, our analysis suggests that pro-cyclical mortality is rather related to deaths of people already in deteriorated health than to people of low socioeconomic status. PMID:25205610

Haaland, Venke Furre; Telle, Kjetil

2015-01-01

241

Continuous versus Cyclic Progesterone Exposure Differentially Regulates Hippocampal Gene Expression  

E-print Network

homeostasis (peroxiredoxin 5; Prdx5), insulin signaling (insulin-like growth factor I; Igf1), and cholesterol whereas a cyclic combined regimen, which is more physiological, could be an effective strategy to maintain

Brinton, Roberta Diaz

242

Virtual Character Behavior Architecture using Cyclic Richard Zhao  

E-print Network

Virtual Character Behavior Architecture using Cyclic Scheduling Richard Zhao Department Tiered Behavior Architecture model for controlling the behaviors of virtual characters. For local scenes, techniques such as Behavior Capture with Hidden Markov Models, which has been evaluated by user studies

Szafron, Duane

243

Atomistic mechanisms of cyclic hardening in metallic glass  

E-print Network

Molecular dynamics with an embedded-atom method potential is used to simulate the nanoindentation of Cu[subscript 63.5]Zr[subscript 36.5] metallic glasses. In particular, the effects of cyclic loading within the nominal ...

Deng, Chuang

244

The Cyclical Relationship Approach in Teaching Basic Accounting Principles.  

ERIC Educational Resources Information Center

Shows how teachers can provide a more meaningful presentation of various accounting principles by illustrating them through a cyclical relationship approach. Thus, the students see the entire accounting relationship as a result of doing business. (CT)

Golen, Steven

1981-01-01

245

The Role of Opportunistic Migration in Cyclic Games  

PubMed Central

We study cyclic evolutionary games in a spatial diluted grid environment in which agents strategically interact locally but can also opportunistically move to other positions within a given migration radius. We find that opportunistic migration can inverse the cyclic prevalence between the strategies when the frequency of random imitation is large enough compared to the payoff-driven imitation. At the transition the average size of the patterns diverges and this threatens diversity of strategies. PMID:24892660

Buesser, Pierre; Tomassini, Marco

2014-01-01

246

CRACK PROPAGATION IN PZT DCB SPECIMENS UNDER CYCLIC ELECTRIC LOADING  

Microsoft Academic Search

Crack propagation in ferroelectric materials under cyclic electric and combined electro-mechanical loading has been studied by several research groups. In most experiments however, Vickers-indented surface cracks and not through-thickness cracks were used. We studied crack propagation under cyclic electric loading in a commercial, soft ferroelectric lead-zirconate-titanate material. The samples were 40mm x 5mm x 1.5mm in dimension, poled in the

I. Westram; J. Rdel

247

Phantom energy accretion onto black holes in a cyclic universe  

SciTech Connect

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.

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

2008-09-15

248

The role of opportunistic migration in cyclic games.  

PubMed

We study cyclic evolutionary games in a spatial diluted grid environment in which agents strategically interact locally but can also opportunistically move to other positions within a given migration radius. We find that opportunistic migration can inverse the cyclic prevalence between the strategies when the frequency of random imitation is large enough compared to the payoff-driven imitation. At the transition the average size of the patterns diverges and this threatens diversity of strategies. PMID:24892660

Buesser, Pierre; Tomassini, Marco

2014-01-01

249

Modulation of Synapse Formation by Cyclic Adenosine Monophosphate  

Microsoft Academic Search

Synapses between neuroblastoma-hybrid cells and myotubes exhibit a high degree of plasticity. Increase of cyclic adenosine monophosphate (AMP) levels of the hybrid cells for several days results in the appearance of functional voltagesensitive Ca2+ channels, which are required for evoked secretion of acetylcholine. The results show that cyclic AMP regulates synaptogenesis by regulating the expression of voltage-sensitive Ca2+ channels, and

M. Nirenberg; S. Wilson; H. Higashida; A. Rotter; K. Krueger; N. Busis; R. Ray; J. G. Kenimer; M. Adler

1983-01-01

250

A Reduced Order Cyclic Method for Computation of Limit Cycles  

Microsoft Academic Search

A reduced order cyclic method was developed to compute limit-cycle oscillations for large, nonlinear, multidisciplinary systems of equations. Method efficacy was demonstrated for two simplified models: a typical-section airfoil with nonlinear structural coupling and a nonlinear panel in high-speed flow. The cyclic method was verified to maintain second-order temporal accuracy, yield converged limit cycles in about 10 Newton iterates, and

P. S. Beran; D. J. Lucia

2005-01-01

251

Spectroscopic Investigations of Selected Cyclic and Bicyclic Molecules  

E-print Network

SPECTROSCOPIC INVESTIGATIONS OF SELECTED CYCLIC AND BICYCLIC MOLECULES A Dissertation by KATHLEEN RAE MCCANN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of DOCTOR OF PHILOSOPHY August 2009 Major Subject: Chemistry SPECTROSCOPIC INVESTIGATIONS OF SELECTED CYCLIC AND BICYCLIC MOLECULES A Dissertation by KATHLEEN RAE MCCANN Submitted to the Office of Graduate Studies...

McCann, Kathleen Rae

2010-10-12

252

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics  

PubMed Central

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 deprotectioncyclization 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

Koopmanschap, Gijs; Ruijter, Eelco

2014-01-01

253

Cyclic Diguanylate Regulates Vibrio cholerae Virulence Gene Expression  

Microsoft Academic Search

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

Anna D. Tischler; Andrew Camilli

2005-01-01

254

A computer program for cyclic plasticity and structural fatigue analysis  

NASA Technical Reports Server (NTRS)

A computerized tool for the analysis of time independent cyclic plasticity structural response, life to crack initiation prediction, and crack growth rate prediction for metallic materials is described. Three analytical items are combined: the finite element method with its associated numerical techniques for idealization of the structural component, cyclic plasticity models for idealization of the material behavior, and damage accumulation criteria for the fatigue failure.

Kalev, I.

1980-01-01

255

Shock front nonstationarity and ion acceleration in supercritical perpendicular shocks  

NASA Astrophysics Data System (ADS)

Previous particle-in-cell simulations have evidenced that quasiperpendicular shocks are nonstationary and suffer a self-reformation on gyro scale of the incoming ions due to the accumulation of reflected ions. In this paper, by separating the incoming ions into reflected and directly transmitted parts, we investigate the detailed mechanisms of ion acceleration in a nonstationary perpendicular shock. Test particle simulations are performed where the shock profiles are issued from self-consistent one-dimensional full particle-in-cell simulations. Both shell and Maxwellian incoming ion distributions are used. In both cases, most energetic particles correspond to reflected ions, and the associated acceleration mechanisms include both shock drift acceleration (SDA) and shock surfing acceleration (SSA). Two types of results are obtained. First, if we fix the shock profiles at different times within a self-reformation cycle, the mechanisms of particle acceleration are different at different profiles. SDA process appears as the dominant acceleration mechanism when the width of the ramp is broad (and overshoot amplitude is low) whereas both SDA and SSA contribute as the width of the ramp is narrow (and overshoot amplitude is high). For the different shock profiles concerned herein, SDA process is more efficient (higher resulting ion energy gain) than the SSA process. Second, in order to investigate ion acceleration in self-reforming shocks, not only the ramp but also the variations of the whole shock front need to be included. In the continuously time-evolving shock, SDA remains a dominant acceleration mechanism whereas SSA mechanism becomes more and more important with the increase of the initial particle energy. The percentage of reflected ions cyclically varies in time with a period equal to the self reformation cycle, which is in agreement with previous full particle simulations. The reflected ions not only come from the distribution wings of the incoming ions but also from the core part, in contrast with previous results based on stationary shocks.

Yang, Z. W.; Lu, Q. M.; Lembge, B.; Wang, S.

2009-03-01

256

Large electrostatic accelerators  

SciTech Connect

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.

Jones, C.M.

1984-01-01

257

Space Acceleration Measurement Systems  

NASA Technical Reports Server (NTRS)

The Space Acceleration Measurement Systems (SAMS) Project develops and deploys the measurement systems for the Acceleration Measurement Program (AMP). At this time there are two types of measurement systems available, quasi-steady and vibratory. Orbital Acceleration Research Experiment (OARE) and Microgravity Acceleration Measurement System (MAMS) are the current quasi-steady systems available. OARE has flown numerous times supporting STS missions. MAMS has been delivered to Kennedy Space Center (KSC) for its deployment on the International Space Station (ISS). Vibratory measurements have been made and will be made by the Space Acceleration Measurement System (SAMS-I) Generation I, Space Acceleration Measurement System Generation II (SAMS-II), and Space Acceleration Measurement System Free Flyer or Generation III (SAMS-FF). SAMS-I supported 21 STS missions and has been retired. SAMS-II will be delivered to KSC to support ISS-6A launch (currently April 19, 2001). SAMS-FF has replaced SAMS-I in support of STS missions and has been deployed on sounding rockets, the KC-135 and ground facilities. SAMS-FF hardware shall be deployed on ISS in the future to provide a more compact solution.

Foster, William

2000-01-01

258

Gallium and Indium Complexes for Ring-Opening Polymerization of Cyclic Ethers, Esters and Carbonates  

E-print Network

1 Gallium and Indium Complexes for Ring-Opening Polymerization of Cyclic Ethers, Esters for the ROP of cyclic ethers 2.2. Gallium complexes for the ROP of cyclic esters and carbonates 3. Indium-based Initiators/catalysts for ROP of cyclic esters 3.1. Synthesis of well-defined indium-based complexes for ROP

Paris-Sud XI, Université de

259

Determination of nonlinear energy toughness values for cyclic loading applications  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

260

The Two Sides of Opioids in Cyclical Vomiting Syndrome  

PubMed Central

Background: Cyclical vomiting syndrome is increasingly recognized in adults, with recent reports suggesting coalescing attacks in one third of the patients. We hypothesized that the common need for opioid treatment may contribute to coalescing attacks through development of opioid dependence and withdrawal, triggering cyclical vomiting syndrome. Aim: This study was to review iatrogenic opioid dependence as the potential cause for triggering cyclical vomiting syndrome. Materials and Methods: A retrospective review was performed to identify patients treated for cyclical vomiting syndrome by a single physician between Jan and December of 2010. Demographic data, clinical presentation, treatment, cumulative opioid prescription during hospitalizations and emergency room visits and days of inpatient stay were abstracted from the chart. Results: Forty-one patients (mean age 37.5.6 2.6 years; 66% female) were seen within this timeframe. In eleven patients (27%) with ongoing opioid use, the initial cyclical illness had progressed and eventually coalesced. A cohort of 23 patients was followed for at least 6 months (12.3 1.7 months). The best single predictor of repeat hospitalizations was the cumulative opioid dosage. Conclusion: Continued use of opioid therapy is a poor prognostic marker of cyclical vomiting syndrome and may contribute to disease coalescence, with dependence and withdrawal triggering recurrent episodes. PMID:24741549

Saligram, Shreyas; Bielefeldt, Klaus

2014-01-01

261

Amps particle accelerator definition study  

NASA Technical Reports Server (NTRS)

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.

Sellen, J. M., Jr.

1975-01-01

262

Cyclical Regolith Processes on Hydrous Asteroids  

NASA Astrophysics Data System (ADS)

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

Zolensky, M. E.

1995-09-01

263

Entropic Accelerating Universe  

E-print Network

To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann-Lemaitre equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on the horizon surface screen. We consider an additional quantitative approach inspired by surface terms in general relativity and show that this leads to the entropic accelerating universe.

Damien A. Easson; Paul H. Frampton; George F. Smoot

2010-10-24

264

Entropic accelerating universe  

NASA Astrophysics Data System (ADS)

To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann-Lematre equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on the horizon surface screen. We consider an additional quantitative approach inspired by surface terms in general relativity and show that this leads to the entropic accelerating universe.

Easson, Damien A.; Frampton, Paul H.; Smoot, George F.

2011-01-01

265

Accelerator Production of Radionuclides  

NASA Astrophysics Data System (ADS)

While many radioactive isotopes in use today are found in nature, many more are artificially produced by irradiating target materials with nuclear particles. Two different technologies can provide the energetic particles needed: nuclear reactors, which produce a flux of neutrons, and particle accelerators, which produce a flux of charged particles. This chapter will deal with the important aspects of the production of radionuclides with accelerators, along with some details on their applications, commercially-available accelerator systems used for this purpose, and the size of the equipment business.

Schlyer, David J.; Ruth, Thomas J.

2012-06-01

266

The MESA accelerator  

SciTech Connect

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.

Aulenbacher, Kurt [Institut fr Kernphysik, Johannnes-Gutenberg-Universitt Mainz (Germany)

2013-11-07

267

Cilengitide - Exceptional pseudopolymorphism of a cyclic pentapeptide.  

PubMed

Cilengitide (Cil) represents a cyclic pentapeptide, cyclo-(Arg-Gly-Asp-D-Phe-N-MeVal). Existence of an anhydrate form (A1) and a tetrahydrate form Cil1(H2O)4 has been observed. Surprisingly the anhydrate form proved to be more stable in aqueous environment compared to the tetrahydrate form. Assessment of thermodynamic stability has been carried out by competitive slurry experiments as well as by investigation of thermodynamic solubility. The lower solubility of the anhydrate form A1 can be explained by the hydrogen bonding motifs within the crystal structures. The tetrahydrate form Cil1(H2O)4 represents a special manifestation of a class of non-stoichiometric water-alcohol solvates Cil1(H2O)x(alcohol)y where methanol and ethanol can substitute water molecules in the crystal lattice of the tetrahydrate form leading to the hydrate-solvate systems Cil1(H2O)x(methanol)y named S1 and Cil1(H2O)x(ethanol)y named S2 with x?4, y?1 and y?2-0.5x. The non-stoichiometric water alcohol solvates exhibit a higher solubility compared to the anhydrate form but convert rapidly to the anhydrate form in aqueous environments. Accordingly, the better soluble non-stoichiometric water alcohol solvates cannot be obtained by crystallization from aqueous media. However slurries or crystallization from solvent mixtures containing methanol and ethanol represent a means to obtain the highly soluble pseudo-polymorphs S1 and S2 and to circumvent formation of the low soluble anhydrate form A1. PMID:25681628

Saal, C; Lange, M; Kuehn, C; Untenecker, H; Jonczyk, A; Petersen, S; Scholz, G; Buback, V; Dotzauer, M; Bauer, H; Foerster, J; Schumacher, J; Metz, A; Schmidt, M; Seemann, K

2015-04-25

268

A New Interstellar Cyclic Molecule, Ethylene Oxide  

NASA Astrophysics Data System (ADS)

Ethylene oxide (c-C2H4O) is only the fourth known ring molecule identified in the interstellar medium, detected in the Galactic Center cloud SgrB2(N) by Dickens et al. (1997). It is the higher energy isomer of both the more familiar interstellar species acetaldehyde (CH3CHO) and the as yet undetected molecule vinyl alcohol (CH2CHOH). Dickens et al. (1997) reported a c-C2H4O molecular column density about an order of magnitude less than that reported for CH3CHO in SgrB2(N). This is a factor of 200 larger than the predictions of the new standard gas phase chemistry model of Lee, Bettens, and Herbst (1996), suggesting that the formation of c-C2H4O may be related to molecular formation on interstellar grains. We present observations of the c-C2H4O to CH3CHO abundance ratio in 5 additional molecular clouds. The data were taken in October 1997 with the Swedish-European Submillimeter Telescope in Chile. The confirmation of ethylene oxide in molecular clouds provides an appealing scenario for the first link in the chain of reactions leading to the origin of life, since it has been suggested as a possible pathway to the formation of the related cyclic molecule oxiranecarbonitrile (c-C3H3NO; cf., Dickens et al. 1996), a precursor to the synthesis of sugar phosphates which comprise the backbone of our molecular genetic structure. References: Dickens, J.E., Irvine, W.M., Ohishi, M., Ikeda, M., Ishikawa, S., Nummelin, A., and Hjalmarson, A. 1997, Astrophys. J., 489 (in press). Dickens, J.E. et al. 1996, Orig. Life Evol. Biosphere, 26, 97. Lee, H.-H., Bettens, R.P.A., and Herbst, E. 1996, Astron. Astrophys. Supp., 119, 111.

Dickens, J. E.; Irvine, W. M.; Ohishi, M.; Ikeda, M.; Ishikawa, S.; Nummelin, A.; Hjalmarson, A.

1997-12-01

269

Highly Efficient Protein Misfolding Cyclic Amplification  

PubMed Central

Protein misfolding cyclic amplification (PMCA) provides faithful replication of mammalian prions in vitro and has numerous applications in prion research. However, the low efficiency of conversion of PrPC into PrPSc in PMCA limits the applicability of PMCA for many uses including structural studies of infectious prions. It also implies that only a small sub-fraction of PrPC may be available for conversion. Here we show that the yield, rate, and robustness of prion conversion and the sensitivity of prion detection are significantly improved by a simple modification of the PMCA format. Conducting PMCA reactions in the presence of Teflon beads (PMCAb) increased the conversion of PrPC into PrPSc from ?10% to up to 100%. In PMCAb, a single 24-hour round consistently amplified PrPSc by 600-700-fold. Furthermore, the sensitivity of prion detection in one round (24 hours) increased by 2-3 orders of magnitude. Using serial PMCAb, a 1012-fold dilution of scrapie brain material could be amplified to the level detectible by Western blotting in 3 rounds (72 hours). The improvements in amplification efficiency were observed for the commonly used hamster 263K strain and for the synthetic strain SSLOW that otherwise amplifies poorly in PMCA. The increase in the amplification efficiency did not come at the expense of prion replication specificity. The current study demonstrates that poor conversion efficiencies observed previously have not been due to the scarcity of a sub-fraction of PrPC susceptible to conversion nor due to limited concentrations of essential cellular cofactors required for conversion. The new PMCAb format offers immediate practical benefits and opens new avenues for developing fast ultrasensitive assays and for producing abundant quantities of PrPSc in vitro. PMID:21347353

Ostapchenko, Valeriy G.; Savtchenk, Regina; Alexeeva, Irina; Rohwer, Robert G.; Baskakov, Ilia V.

2011-01-01

270

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

NASA Technical Reports Server (NTRS)

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.

Nakanishi, S.

1976-01-01

271

Plastic deformation behavior and dislocation structure in Ti{sub 3}Al single crystals cyclically deforming by prism slip  

SciTech Connect

The effect of prism slip on cyclic hardening and deformation substructure in Ti{sub 3}Al single crystals cyclically deformed was examined. Fatigue tests were carried out in a symmetrical tension/compression mode at a fixed total strain amplitude ({Delta}{epsilon}) of {+-}0.2% to {+-}0.4% at room temperature. As {Delta}{epsilon} and the number of cycles increased, the stress amplitude rose depending on crystal orientation. The cyclic hardening was more accelerated for specimens deformed by double prism slips than for those deformed by single prism slip. At the saturated stage, the edge dipoles and/or multipoles gathered at a localized region and formed bundles with a high residual stress field in specimens deforming by double prism slips, while a high density of dislocations existed the bundled structure did not develop under operation of single prism slip. The peculiar structure containing bundles was called saturated bundled structure (SBS). The formation process of the SBS and the role of the bundled structure on the plastic behavior are described.

Nakano, T.; Ogawa, B.; Koizumi, Y.; Umakoshi, Y. [Osaka Univ. (Japan)] [Osaka Univ. (Japan)

1998-07-24

272

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

PubMed Central

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 mechanismsinduction of cyclic nucleotide synthesis, inhibition of cyclic nucleotide degradation, or activation of cyclic nucleotide receptorsis 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

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

2014-01-01

273

The Characteristics of Cyclical and Non-Cyclical Mastalgia: A Prospective Study using a Modified McGill Pain Questionnaire  

Microsoft Academic Search

Breast pain (mastalgia) is a common condition (usually classified as cyclical or non-cyclical) the characteristics of which have never been studied using a standardized pain instrument. We have modified the short form of the McGill Pain Questionnaire (SF-MPQ) for the measurement of mastalgia, and have administered it to 271 women with breast pain and without breast cancer. The mean pain-rating

Seema A. Khan; A. Vania Apkarian

2002-01-01

274

Effects of glucagon and insulin on the cyclic AMP binding capacity of hepatocyte cyclic AMP-dependent protein kinase  

Microsoft Academic Search

Extracts obtained from rat hepatocytes incubated with saline, glucagon or insulin were electrophoresed on polyacrylamide gels and then assayed for cyclic (3H)AMP binding capacity. Analysis of the binding patterns demonstrated that glucagon dissociated a holoenzyme of cyclic AMP-dependent protein kinase in a dose-dependent manner. The increase in free regulatory subunits and, hence, in free catalytic subunits explains the activation of

Carlos J. Ciudad; Jordi Vila; M. Angels Mor; Joan J. Guinovart

1987-01-01

275

The Importance of Calcium Ions for the Regulation of Guanosine 3':5'-cyclic Monophosphate Levels  

Microsoft Academic Search

Guanosine 3':5'-cyclic monosphosphate (cyclic GMP) levels in the ductus deferens of the rat were increased 2- to 3-fold by acetylcholine (10-1000 mu M) or by 125 mM KCl, while adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels were not changed. After incubation for 30 min in the absence of Ca++, cyclic GMP control levels were decreased by 85% and were not affected

G. Schultz; J. G. Hardman; K. Schultz; C. E. Baird; E. W. Sutherland

1973-01-01

276

TESLA superconducting accelerating structures  

NASA Astrophysics Data System (ADS)

Superconducting standing wave structures have been used for charged particle acceleration for almost 40 years. A brief introduction to this application with examples, test procedures and recently achieved results are discussed in this paper.

Sekutowicz, J.

2007-08-01

277

Learning about Accelerated Learning.  

ERIC Educational Resources Information Center

When accelerated learning programs succeed, they do so in part because they invoke and integrate skills and basic information, theoretical understanding, and natural knowledge. The trainer must blend these elements appropriately. (JOW)

Caine, Geoffrey; Caine, Renate Nummela

1989-01-01

278

Accelerator on a Chip  

SciTech Connect

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)

England, Joel

2014-06-30

279

Accelerator on a Chip  

ScienceCinema

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)

England, Joel

2014-07-16

280

Non-accelerator experiments  

SciTech Connect

This report discusses several topics which can be investigated without the use of accelerators. Topics covered are: (1) proton decay, (2) atmospheric neutrinos, (3) neutrino detection, (4) muons from Cygnus X-3, and (5) the double-beta decay.

Goldhaber, M.

1986-01-01

281

An active particle accelerator  

SciTech Connect

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.

Goldman, T.

1991-01-01

282

Breakthrough: Fermilab Accelerator Technology  

SciTech Connect

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.

None

2012-04-23

283

Breakthrough: Fermilab Accelerator Technology  

ScienceCinema

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.

None

2014-08-12

284

Rolamite acceleration sensor  

DOEpatents

A rolamite acceleration sensor is described which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently. 6 figures.

Abbin, J.P.; Briner, C.F.; Martin, S.B.

1993-12-21

285

Uniformly accelerated black holes  

Microsoft Academic Search

The static and stationary C-metric are revisited in a generic framework and\\u000atheir interpretations studied in some detail. Specially those with two event\\u000ahorizons, one for the black hole and another for the acceleration. We found\\u000athat: i) The spacetime of an accelerated static black hole is plagued by either\\u000aconical singularities or lack of smoothness and compactness of the

Patricio S. Letelierand; Samuel R. Oliveira

2001-01-01

286

Rolamite acceleration sensor  

DOEpatents

A rolamite acceleration sensor which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently.

Abbin, Joseph P. (Albuquerque, NM); Briner, Clifton F. (Albuquerque, NM); Martin, Samuel B. (Albuquerque, NM)

1993-01-01

287

CEBAF accelerator achievements  

SciTech Connect

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.

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

2011-06-01

288

Laser electron accelerator  

Microsoft Academic Search

An intense electromagnetic pulse can create weak plasma oscillations through the action of the nonlinear ponderomotive force. Electrons trapped in the wake can be accelerated to high energy. Existing glass lasers of power density 10 to the 18th W\\/sq cm shone on plasmas of densities 10 to the 18th\\/cu cm can yield gigaelectronvolts of electron energy per centimeter of acceleration

T. Tajima; J. M. Dawson

1979-01-01

289

A Material Model for the Cyclic Behavior of Nitinol  

NASA Astrophysics Data System (ADS)

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 Systmes 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.

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

2011-07-01

290

Sources of Water to Wells for Transient Cyclic Systems  

USGS Publications Warehouse

Many state agencies are currently (1995) developing wellhead protection programs. The thrust of some of these programs is to protect water supplies by determining the areas contributing recharge to water-supply wells and by specifying regulations to minimize the opportunity for contamination of the recharge water by activities at the land surface. The area contributing recharge to a discharging well is the surface area at the water table through which the water flowing to the well entered the ground-water system. In the analyses of ground-water flow systems, steady-state average conditions are commonly used to simplify the problem and make a solution tractable. However, recharge is usually cyclic in nature, with seasonal cycles and longer term climatic cycles. The effect of these cyclic stresses on the area contributing recharge to wells is quantitatively analyzed for a hypothetical alluvial valley aquifer system that is representative of a large class of ground-water systems that are extensively developed for water supply. The analysis shows that, in many cases, these cyclic changes in the recharge rates do not significantly affect the location and size of the areas contributing recharge to wells. The ratio of the mean travel time to the length of the cyclic stress period appears to be an indicator of whether the transient effects of the cyclic stress must be explicitly represented in the analysis of contributing areas to wells. For the cases examined, if the ratio of the mean travel time to the period of the cyclic stress was much greater than one, then the transient area contributing recharge to wells was similar to the area calculated using an average steady-state condition. However, cyclic stresses on systems with ratios less than one do have an effect on the location and size of the areas contributing recharge to wells.

Reilly, T.E.; Pollock, D.W.

1996-01-01

291

US LHC Accelerator Research Program  

E-print Network

US LHC Accelerator Research Program Instrumentation Collaboration Meeting John Marriner May 9, 2003 #12;2/14/03 US LARP Instrumentation Collaboration Mtg 2 US LARP LARP = LHC Accelerator Research Program LARP is an outgrowth of the US LHC Accelerator Project The US LHC Accelerator Project built

Large Hadron Collider Program

292

Plasma-based accelerator structures  

SciTech Connect

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.

Schroeder, Carl B.

1999-12-01

293

Accelerator-based Neutron Sources  

Microsoft Academic Search

Since the earliest experiments defining the properties of the neutron, accelerators have played an important role in providing neutrons for research and applications. For many years, neutrons produced at accelerator facilities have complemented capabilities available from reactor-based sources. Now, with the declining availability of reactor facilities, upgrades of existing accelerator facilities and proposed new, more powerful accelerator-based sources will be

James B. Ball

1997-01-01

294

Synthesis of cyclic Py-Im polyamide libraries.  

PubMed

Cyclic Py-Im polyamides containing two GABA turn units exhibit enhanced DNA binding affinity, but extensive studies of their biological properties have been hindered due to synthetic inaccessibility. A facile modular approach toward cyclic polyamides has been developed via microwave-assisted solid-phase synthesis of hairpin amino acid oligomer intermediates followed by macrocyclization. A focused library of cyclic polyamides 1-7 targeted to the androgen response element (ARE) and the estrogen response element (ERE) were synthesized in 12-17% overall yield. The Fmoc protection strategy also allows for selective modifications on the GABA turn units that have been shown to improve cellular uptake properties. The DNA binding affinities of a library of cyclic polyamides were measured by DNA thermal denaturation assays and compared to the corresponding hairpin polyamides. Fluorescein-labeled cyclic polyamides have been synthesized and imaged via confocal microscopy in A549 and T47D cell lines. The IC(50) values of compounds 1-7 and 9-11 were determined, revealing remarkably varying levels of cytotoxicity. PMID:23106218

Li, Benjamin C; Montgomery, David C; Puckett, James W; Dervan, Peter B

2013-01-01

295

Synthesis of Cyclic Py-Im Polyamide Libraries  

PubMed Central

Cyclic Py-Im polyamides containing two GABA turn units exhibit enhanced DNA binding affinity, but extensive studies of their biological properties have been hindered due to synthetic inaccessibility. A facile modular approach toward cyclic polyamides has been developed via microwave-assisted solid-phase synthesis of hairpin amino acid oligomer intermediates followed by macrocyclization. A focused library of cyclic polyamides 17 targeted to the androgen response element (ARE) and the estrogen response element (ERE) were synthesized in 1217% overall yield. The Fmoc protection strategy also allows for selective modifications on the GABA turn units that have been shown to improve cellular uptake properties. The DNA binding affinities of a library of cyclic polyamides were measured by DNA thermal denaturation assays and compared to the corresponding hairpin polyamides. Fluorescein-labeled cyclic polyamides have been synthesized and imaged via confocal microscopy in A549 and T47D cell lines. The IC50 values of compounds 17 and 911 were determined, revealing remarkably varying levels of cytotoxicity. PMID:23106218

2012-01-01

296

Temperature Dependent Cyclic Deformation Mechanisms in Haynes 188 Superalloy  

NASA Technical Reports Server (NTRS)

The cyclic deformation behavior of a wrought cobalt-base superalloy, Haynes 188, has been investigated over a range of temperatures between 25 and 1000 C under isothermal and in-phase thermomechanical fatigue (TMF) conditions. Constant mechanical strain rates (epsilon-dot) of 10(exp -3)/s and 10(exp -4)/s were examined with a fully reversed strain range of 0.8%. Particular attention was given to the effects of dynamic strain aging (DSA) on the stress-strain response and low cycle fatigue life. A correlation between cyclic deformation behavior and microstructural substructure was made through detailed transmission electron microscopy. Although DSA was found to occur over a wide temperature range between approximately 300 and 750 C the microstructural characteristics and the deformation mechanisms responsible for DSA varied considerably and were dependent upon temperature. In general, the operation of DSA processes led to a maximum of the cyclic stress amplitude at 650 C and was accompanied by pronounced planar slip, relatively high dislocation density, and the generation of stacking faults. DSA was evidenced through a combination of phenomena, including serrated yielding, an inverse dependence of the maximum cyclic hardening with epsilon-dot, and an instantaneous inverse epsilon-dot sensitivity verified by specialized epsilon-dot -change tests. The TMF cyclic hardening behavior of the alloy appeared to be dictated by the substructural changes occuring at the maximum temperature in the TMF cycle.

Rao, K. Bhanu Sankara; Castelli, Michael G.; Allen, Gorden P.; Ellis, John R.

1995-01-01

297

Low severity coal liquefaction promoted by cyclic olefins  

SciTech Connect

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.

Curtis, C.W.

1992-01-01

298

Laser acceleration with open waveguides  

SciTech Connect

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.

Xie, Ming

1999-03-01

299

Studies of accelerated compact toruses  

SciTech Connect

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.

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

1983-01-04

300

Dielectric laser accelerators  

NASA Astrophysics Data System (ADS)

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.

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

301

Low Severity Coal Liquefaction Promoted by Cyclic Olefins  

SciTech Connect

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.

Christine W. Curtis

1998-04-09

302

Cyclic Tetrapyrrole Sulfonation, Metals, and Oligomerization in Antiprion Activity?  

PubMed Central

Cyclic tetrapyrroles are among the most potent compounds with activity against transmissible spongiform encephalopathies (TSEs; or prion diseases). Here the effects of differential sulfonation and metal binding to cyclic tetrapyrroles were investigated. Their potencies in inhibiting disease-associated protease-resistant prion protein were compared in several types of TSE-infected cell cultures. In addition, prophylactic antiscrapie activities were determined in scrapie-infected mice. The activity of phthalocyanine was relatively insensitive to the number of peripheral sulfonate groups but varied with the type of metal bound at the center of the molecule. The tendency of the various phthalocyanine sulfonates to oligomerize (i.e., stack) correlated with anti-TSE activity. Notably, aluminum(III) phthalocyanine tetrasulfonate was both the poorest anti-TSE compound and the least prone to oligomerization in aqueous media. Similar comparisons of iron- and manganese-bound porphyrin sulfonates confirmed that stacking ability correlates with anti-TSE activity among cyclic tetrapyrroles. PMID:17709470

Caughey, Winslow S.; Priola, Suzette A.; Kocisko, David A.; Raymond, Lynne D.; Ward, Anne; Caughey, Byron

2007-01-01

303

The SU(3) Algebra in a Cyclic Basis  

E-print Network

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.

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

2014-07-31

304

Application Of Shakedown Analysis To Cyclic Creep Damage Limits  

SciTech Connect

Shakedown analysis may be used to provide a conservative estimate of local rupture and hence cyclic creep damage for use in a creep-fatigue assessment. The shakedown analysis is based on an elastic-perfectly plastic material with a temperature-dependent pseudo yield stress defined to guarantee that a shakedown solution exists which does not exceed rupture stress and temperature for a defined life. The ratio of design life to the estimated maximum cyclic life is the shakedown creep damage. The methodology does not require stress classification and is also applicable to cycles over the full range of temperature above and below the creep regime. Full cyclic creep and damage analysis is the alternative when shakedown analysis appears to be excessively conservative.

Carter, Peter [Stress Engineering Services Inc.] [Stress Engineering Services Inc.; Jetter, Robert I [Consultant] [Consultant; Sham, Sam [ORNL] [ORNL

2012-01-01

305

Development of a viscoelastic continuum damage model for cyclic loading  

NASA Astrophysics Data System (ADS)

A previously developed spectrum model for linear viscoelastic behavior of solids is used to describe the rate-dependent damage growth of a time dependent material under cyclic loading. Through the use of the iterative solution of a special Volterra integral equation, the cyclic strain history is described. The spectrum-based model is generalized for any strain rate and any uniaxial load history to formulate the damage function. Damage evolution in the body is described through the use of a rate-type evolution law which uses a pseudo strain to express the viscoelastic constitutive equation with damage. The resulting damage function is used to formulate a residual strength model. The methodology presented is demonstrated by comparing the peak values of the computed cyclic strain history as well as the residual strength model predictions to the experimental data of a polymer matrix composite.

Sullivan, R. W.

2008-12-01

306

Chaos in Accelerators  

SciTech Connect

Chaos is a general phenomenon in nonlinear dynamical systems. Accelerators--storage rings in particular--in which particles are stored for 10{sup 10} revolutions constitute a particularly intricate nonlinear dynamical system. (In comparison, the earth has revolved around the sun for only 10{sup 9} turns.) Storage rings therefore provide an ideal testing ground for chaos physics. In fact, it is the chaos phenomenon that imposes one of the key design criteria for these accelerators. One might arguably say that the demise of the Superconducting Super Collider project originated from a misjudgement in its chaos analysis at one point along its design path, leading to its first substantial cost escalation. This talk gives an elementary introduction to the study of chaos in accelerators.

Chao, Alex

1999-05-11

307

Accelerator Technology Program  

NASA Astrophysics Data System (ADS)

Highlights of major projects in the Accelerator Technology Division of the Los Alamos National Laboratory are presented. The first section deals with the Fusion Materials Irradiation Test Facility's 2-MeV accelerator on which tests began in May, as scheduled. Then, activities are reported on beam dynamics, inertial fusion, structure development, the racetrack microtron, the CERN high-energy physics experiment NA-12, and LAMPF II. The Proton Storage Ring is discussed next, with emphasis on the computer control system, diagnostics interfacing, and theoretical support. Other sections summarize progress on a portable radiographic linac, developments on the klystron code, and on permanent magnets. Activities of the Theory and Simulation Group are outlined next, followed by discussion of the oscillator experiment and the energy-recovery experiment in the free electron laser project. The last section reports on the accelerator test stand.

Jameson, R. A.

1984-07-01

308

High intensity hadron accelerators  

SciTech Connect

This rapporteur report consists mainly of two parts. Part I is an abridged review of the status of all High Intensity Hadron Accelerator projects in the world in semi-tabulated form for quick reference and comparison. Part II is a brief discussion of the salient features of the different technologies involved. The discussion is based mainly on my personal experiences and opinions, tempered, I hope, by the discussions I participated in in the various parallel sessions of the workshop. In addition, appended at the end is my evaluation and expression of the merits of high intensity hadron accelerators as research facilities for nuclear and particle physics.

Teng, L.C.

1989-05-01

309

Accelerated molecular dynamics methods  

SciTech Connect

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.

Perez, Danny [Los Alamos National Laboratory

2011-01-04

310

Acceleration of metal plates  

NASA Astrophysics Data System (ADS)

High-explosive charges were used to accelerate stainless steel plates to velocities of 6 to 7 km/s. A two-stage system was used in which the first stage is a plane-wave detonating system that accelerates the plate down a short barrel. The second stage consists of a hollow cylindrical charge through which the moving plate passes. After an adjustable delay this charge is detonated on the outer circumference of the entry side of the charge. Flash radiographs and witness plates show no breakup in the first stage but bowing and frequent breakup in the second stage.

Marsh, S. P.; McQueen, R. G.; Tan, T. H.

1989-08-01

311

Photocathodes in accelerator applications  

SciTech Connect

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.

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

1987-01-01

312

An accelerator technology legacy  

SciTech Connect

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.

Heighway, E.A.

1994-11-01

313

Accelerating cosmologies from compactification.  

PubMed

A solution of the (4+n)-dimensional vacuum Einstein equations is found for which spacetime is compactified on an n-dimensional compact hyperbolic manifold (n> or =2) of time-varying volume to a flat four-dimensional Friedmann-Lemaitre-Robertson-Walker cosmology undergoing a period of accelerated expansion in the Einstein conformal frame. This shows that the "no-go" theorem forbidding acceleration in "standard" (time-independent) compactifications of string or M theory does not apply to "cosmological" (time-dependent) hyperbolic compactifications. PMID:12935064

Townsend, Paul K; Wohlfarth, Mattias N R

2003-08-01

314

US LHC Accelerator Project  

NSDL National Science Digital Library

As the US part of the Large Hadron Collider Program, US LHC "consists of efforts of Brookhaven National Laboratory (BNL), Fermi National Accelerator Laboratory (FNAL), and Lawrence Berkeley National Laboratory (LBNL) to support the construction of the LHC at CERN." This Web site provides visitors with links to each of the three participating laboratories as well as information on recent papers, reports, and other materials related to the project. While a bit dated, there is also a press release covering the production of the highest energy producing superconducting accelerator in the world; it utilizes over 6,000 superconducting magnets.

315

Interfacing to accelerator instrumentation  

SciTech Connect

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.

Shea, T.J.

1995-12-31

316

Cyclic Nucleotides Converge on Brown Adipose Tissue Differentiation  

NSDL National Science Digital Library

Brown adipose tissue (BAT) is rich in mitochondria and can uncouple oxidative phosphorylation to produce heat as a by-product of fatty acid metabolism. This thermogenic effect helps to maintain body temperature and also plays a critical role in energy homeostasis and the regulation of body weight. Both cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) contribute to the intracellular regulation of mitochondrial biogenesis and the differentiation of BAT. New evidence has defined the essential role of the cGMP-dependent protein kinase I in a pathway that modulates the RhoA-ROCK pathway and insulin receptor signaling to elicit BAT differentiation and stimulate thermogenesis.

Paul S. Amieux (University of Washington; Department of Pharmacology REV)

2010-01-12

317

Bounce and cyclic cosmology in extended nonlinear massive gravity  

SciTech Connect

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 Stckelberg-scalar function, or with a suitably chosen Stckelberg-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.

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

318

Polymerization of the cyclic pyrophosphates of nucleosides and their analogues  

NASA Technical Reports Server (NTRS)

When 2-prime-deoxythymidine 3-prime, 5-prime-cyclic diphosphate, or the cyclic pyrophosphates of the acyclic nucleoside analogs II and IV are heated to 65-85 C in the presence of imidazole, oligomers with lengths up to 20-30 are formed in excellent yield. This reaction provides a useful source of oligomers for use as templates in aqueous condensation reactions. In the absence of evidence to the contrary, it is assumed that the oligomers are atactic. The potential significance of this reaction in prebiotic chemistry is discussed.

Tohidi, Mahrokh; Orgel, Leslie E.

1990-01-01

319

Performance of tubular members under cyclic axial loads  

SciTech Connect

In this paper the behavior of pin-ended tubular steel members under cyclic axial loads is studied by using Finite Element Method (FEM) considering both geometrical and material non-linearities. The factors considered in this study are the cyclic loading characteristics (displacement amplitude and mean displacement), geometrical parameters (diameter-to-thickness ratio D/t and normalized slenderness ratio {lambda}) and inelastic characteristics of the material. The results of numerical analysis are closely examined with respect to both ultimate strength and energy dissipation capacity.

Shaker, R.E.; Murakawa, Hidekazu; Ueda, Yukio [Osaka Univ. (Japan)

1995-12-31

320

Monotonic and cyclic fatigue properties of automotive aluminum alloys  

SciTech Connect

Monotonic and strain-controlled fatigue tests were conducted on 2014-T6, 6061-T6 and 7175-T73 hand-forgings, 5052-H32 and 6061-T6 sheet, and a 1983/84 production Chevrolet Corvette upper-control-arm-pivot shaft (UCAPS) cold-forged from 5454-H12 and 6061-T4 rolled rod (the 6061 UCAPS was artificially-aged to the -T6 temper, after forging). Various monotonic and cyclic fatigue stress-strain material properties are presented. The responses of the various alloys and product-forms in terms of cyclic hardening or softening are described.

Wong, W.A.

1984-01-01

321

Multilayer cyclic C6 structures intercalated with metal atoms  

NASA Astrophysics Data System (ADS)

A new type of tubular inorganic metal-carbon sandwich molecule based on cyclic C6 is proposed. These consist of multiple layers of cyclic C6 with intercalated metal atoms. Structures and electronic properties of these molecules have been calculated using first-principles density functional techniques. We have evaluated all metals in the first six periods of the periodic table, except for the lanthanides, as possible components of such molecules. Our calculations show high bond energy and small energy gaps in many of these structures. We suggest that the high structural stability and high conductivity in these sandwich compounds make them very promising for use in nanoelectronic applications.

Kuzmin, Stanislav; Duley, Walter W.

2011-02-01

322

Calmodulin-stimulated cyclic nucleotide phosphodiesterase from Neurospora crassa.  

PubMed

Cyclic nucleotide phosphodiesterase has been partially purified by calmodulin-Sepharose affinity chromatography from a soluble extract of Neurospora crassa. The phosphodiesterase activity remained bound to the affinity column even in the presence of 6 M urea and could only be eluted by calcium chelation. The enzyme exhibits cAMP and cGMP phosphodiesterase activities. Both activities can be enhanced by calmodulin in a Ca2+-dependent manner. Stimulation of cyclic nucleotide phosphodiesterase by calmodulin can be inhibited by calmodulin antagonists such as pimozide, trifluoperazine and chlorpromazine. PMID:6305427

Ortega Perez, R; Van Tuinen, D; Marm, D; Turian, G

1983-07-01

323

Ion sources for accelerators  

Microsoft Academic Search

A survey of different types of ion sources used for accelerator applications is given. Typical problems like the source life time, or the special need for technical solutions for specific elements will demonstrate the advantage of each type of ion source. In any case reliability is a main topic. Besides the plasma generation of the desired element, beam formation and

P. Spdtke; J. Bossler; H. Emig; K. D Leible; C. Mhle; H. Schulte; K. Tinschert

1998-01-01

324

Radioisotope Dating with Accelerators.  

ERIC Educational Resources Information Center

Explains a new method of detecting radioactive isotopes by counting their accelerated ions rather than the atoms that decay during the counting period. This method increases the sensitivity by several orders of magnitude, and allows one to find the ages of much older and smaller samples. (GA)

Muller, Richard A.

1979-01-01

325

Accelerating incomplete feature selection  

Microsoft Academic Search

Feature selection from incomplete data aims to retain the discriminatory power of original features in rough set theory. Many feature selection algorithms are computationally time-consuming. To overcome this drawback, we introduce a theoretic framework based on rough set theory, called positive approximation, which can be used to accelerate a heuristic process of feature selection from incomplete data. Based on the

Yuhua Qian; Jiye Liang; Wei Wei

2009-01-01

326

Prospects for Accelerator Technology  

NASA Astrophysics Data System (ADS)

Accelerator technology today is a greater than US$5 billion per annum business. Development of higher-performance technology with improved reliability that delivers reduced system size and life cycle cost is expected to significantly increase the total accelerator technology market and open up new application sales. Potential future directions are identified and pitfalls in new market penetration are considered. Both of the present big market segments, medical radiation therapy units and semiconductor ion implanters, are approaching the "maturity" phase of their product cycles, where incremental development rather than paradigm shifts is the norm, but they should continue to dominate commercial sales for some time. It is anticipated that large discovery-science accelerators will continue to provide a specialty market beset by the unpredictable cycles resulting from the scale of the projects themselves, coupled with external political and economic drivers. Although fraught with differing market entry difficulties, the security and environmental markets, together with new, as yet unrealized, industrial material processing applications, are expected to provide the bulk of future commercial accelerator technology growth.

Todd, Alan

2011-02-01

327

Compact plasma accelerator device  

Microsoft Academic Search

A compact plasma accelerator concept based on plasma production at a magnetic cusp was designed and fabricated. Plume and discharge characteristics of the device were documented using a Faraday probe and a retarding potential analyzer. The discharge current variations with increasing discharge voltage were nonlinear with the discharge current increasing rapidly with voltage. The device demonstrated the capability of generating

John E. Foster

2002-01-01

328

Improving the transparency of a rehabilitation robot by exploiting the cyclic behaviour of walking.  

PubMed

To promote active participation of neurological patients during robotic gait training, controllers, such as "assist as needed" or "cooperative control", are suggested. Apart from providing support, these controllers also require that the robot should be capable of resembling natural, unsupported, walking. This means that they should have a transparent mode, where the interaction forces between the human and the robot are minimal. Traditional feedback-control algorithms do not exploit the cyclic nature of walking to improve the transparency of the robot. The purpose of this study was to improve the transparent mode of robotic devices, by developing two controllers that use the rhythmic behavior of gait. Both controllers use adaptive frequency oscillators and kernel-based non-linear filters. Kernelbased non-linear filters can be used to estimate signals and their time derivatives, as a function of the gait phase. The first controller learns the motor angle, associated with a certain joint angle pattern, and acts as a feed-forward controller to improve the torque tracking (including the zero-torque mode). The second controller learns the state of the mechanical system and compensates for the dynamical effects (e.g. the acceleration of robot masses). Both controllers have been tested separately and in combination on a small subject population. Using the feedforward controller resulted in an improved torque tracking of at least 52 percent at the hip joint, and 61 percent at the knee joint. When both controllers were active simultaneously, the interaction power between the robot and the human leg was reduced by at least 40 percent at the thigh, and 43 percent at the shank. These results indicate that: if a robotic task is cyclic, the torque tracking and transparency can be improved by exploiting the predictions of adaptive frequency oscillator and kernel-based nonlinear filters. PMID:24187212

van Dijk, W; van der Kooij, H; Koopman, B; van Asseldonk, E H F; van der Kooij, H

2013-06-01

329

Synergistic degradation of dentin by cyclic stress and buffer agitation.  

PubMed

Secondary caries and non-carious lesions develop in regions of stress concentrations and oral fluid movement. The objective of this study was to evaluate the influence of cyclic stress and fluid movement on material loss and subsurface degradation of dentin within an acidic environment. Rectangular specimens of radicular dentin were prepared from caries-free unrestored 3rd molars. Two groups were subjected to cyclic cantilever loading within a lactic acid solution (pH=5) to achieve compressive stresses on the inner (pulpal) or outer sides of the specimens. Two additional groups were evaluated in the same solution, one subjected to movement only (no stress) and the second held stagnant (control: no stress or movement). Exterior material loss profiles and subsurface degradation were quantified on the two sides of the specimens. Results showed that under cyclic stress material loss was significantly greater (p?0.0005) on the pulpal side than on the outer side and significantly greater (p?0.05) under compression than tension. However, movement only caused significantly greater material loss (p?0.0005) than cyclic stress. Subsurface degradation was greatest at the location of highest stress, but was not influenced by stress state or movement. PMID:25637823

Orrego, Santiago; Romberg, Elaine; Arola, Dwayne

2015-04-01

330

Performance of Randomized Cyclic Delay Code Encoded by Convolutional Coding  

Microsoft Academic Search

We study distributed cooperative communication systems in which a single source transmits its information with the help of multiple relays to a destination. Specifically, we consider decode and forward relay networks based on orthogonal frequency division multiplexing (OFDM). Most previous work needs a priori information for antenna allocation to obtain cooperative diversity advantages. A randomized cyclic delay code does not

Seungwon Choi; Dong-jo Park

2008-01-01

331

Gravity Dual for Cyclic Renormalization Group Flow without Conformal Invariance  

E-print Network

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.

Yu Nakayama

2011-07-21

332

Cyclical modulation of human ventricular repolarization by respiration  

PubMed Central

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 026 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

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

2012-01-01

333

Ratchetting of porcine skin under uniaxial cyclic loading.  

PubMed

Skin soft tissue (e.g., porcine skin) was tested in vitro under uniaxial cyclic loading, and its biomechanical responses were investigated to realize some basic properties which are very significant in assessing the fatigue life of skin soft tissue. The results show that a cyclic accumulation of peak and valley strain, which can be terminologically called as ratchetting in terms of material science of metals, occurs in the porcine skin during cyclic tension-unloading, tension-tension and compression-unloading tests. Observed ratchetting of porcine skin depends on load level and loading orientation greatly and also presents remarkable rate dependence due to the viscosity of skin soft tissue. The ratchetting is much more remarkable during the test at lower loading rate than that at higher loading rate. Moreover, some basic properties of porcine skin were also investigated by monotonic tension, compression and creep tests in order to address the ratchetting more comprehensively. Finally, collagen fiber bundles in the porcine skin and their variation during monotonic and cyclic tension tests were observed microscopically in term of standard iron-hematoxylin staining method. The observations are useful to realize the micro-mechanism of ratchetting deformation. PMID:21316638

Kang, Guozheng; Wu, Xinfeng

2011-04-01

334

MODELING CYCLIC WAVES OF CIRCULATING T CELLS IN AUTOIMMUNE DIABETES  

E-print Network

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

Mahaffy, Joseph M.

335

Serinocyclins A and B, Cyclic Heptapeptides from Metarhizium anisopliae  

Technology Transfer Automated Retrieval System (TEKTRAN)

Two new cyclic heptapeptides, serinocyclins A (1) and B (2), were isolated from conidia of the entomopathogenic fungus Metarhizium anisopliae. Structures were elucidated by a combination of mass spectrometric, NMR, and X-ray diffraction techniques. Serinocyclin A (1) contains three serine units, a...

336

Title: How does cyclic electron flow alleviate photoinhibition in Arabidopsis?  

Microsoft Academic Search

Word and character Counts: The number,of words in the abstract: 217 words; the total number,of characters in the paper: 39932. Abbreviations Footnote: CEF, cyclic electron flow; NPQ, non-photochemical Plant Physiology Preview. Published on December 31, 2008, as DOI:10.1104\\/pp.108.134122 Copyright 2008 by the American Society of Plant Biologists

Shunichi Takahashi; Sara E Milward; Da-Yong Fan; Wah Soon Chow; Murray R

2008-01-01

337

Methods and systems for the formation of cyclic carbonates  

DOEpatents

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.

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

2014-12-30

338

Scheduling for Multi-modal Cyclic Transport Systems  

Microsoft Academic Search

This paper concerns the domain of the multimodal transportation systems composed of buses, trains, trams and subways lines and focuses on the scheduling problems encountered in these systems. Transportation Network Infrastructure (TNI) can be modeled as a network of lines providing cyclic routes for particular kinds of stream-like moving transportation means. Lines are connected by common shared change stations. Depending

Grzegorz Bocewicz; Zbigniew Banaszak

2012-01-01

339

Ideal homomorphic secret sharing schemes over cyclic groups  

Microsoft Academic Search

For a cyclic groupG and an access structureA, the sufficient and necessary condition under whichA isG-ideal homomorphic is given by using the fine-representation of the corresponding matroid over the ring$$\\\\mathbb{Z}_m $$. Furthermore, the clasification ofG-ideal homomorphic graphic access structures is shown.

Mulan Liu; Zhanfei Zhou

1998-01-01

340

Radical reaction of trinitromethane derivatives with cyclic ethers  

Microsoft Academic Search

The photolysis of solutions of C(NO2)4, IC(NO2)3 and CH(NO2)3 in tetrahydrofuran and tetrahydropyran at 20 leads to the formation of the correspondinga-trinitromethyl derivatives of cyclic ethers. Data were obtained in support of a radical nonchain reaction mechanism.

I. A. Leenson; G. B. Sergeev; O. P. Shitov; S. L. Ioffe; V. A. Tartakovskii

1973-01-01

341

Micromechanical Analysis of Geosynthetic-Soil Interaction Under Cyclic Loading  

E-print Network

Micromechanical Analysis of Geosynthetic-Soil Interaction under Cyclic Loading By Anil Bhandari B.E., Tribhuvan University, Nepal, 2003 M.E., Asian Institute of Technology, Thailand, 2006 Submitted to graduate degree program... ____________________ Committee members Dr. Anil Misra ____________________ Dr. Robert L. Parsons ____________________ Dr. Steven D. Schrock ____________________ Dr. W. Lynn Watney Date defended: ________ i The Dissertation Committee for Anil Bhandari certifies...

Bhandari, Anil

2010-05-28

342

Fmoc-based synthesis of disulfide-rich cyclic peptides.  

PubMed

Disulfide-rich cyclic peptides have exciting potential as leads or frameworks in drug discovery; however, their use is faced with some synthetic challenges, mainly associated with construction of the circular backbone and formation of the correct disulfides. Here we describe a simple and efficient Fmoc solid-phase peptide synthesis (SPPS)-based method for synthesizing disulfide-rich cyclic peptides. This approach involves SPPS on 2-chlorotrityl resin, cyclization of the partially protected peptide in solution, cleavage of the side-chain protecting groups, and oxidization of cysteines to yield the desired product. We illustrate this method with the synthesis of peptides from three different classes of cyclic cystine knot motif-containing cyclotides: Mbius (M), trypsin inhibitor (T), and bracelet (B). We show that the method is broadly applicable to peptide engineering, illustrated by the synthesis of two mutants and three grafted analogues of kalata B1. The method reduces the use of highly caustic and toxic reagents and is better suited for high-throughput synthesis than previously reported methods for producing disulfide-rich cyclic peptides, thus offering great potential to facilitate pharmaceutical optimization of these scaffolds. PMID:24918986

Cheneval, Olivier; Schroeder, Christina I; Durek, Thomas; Walsh, Phillip; Huang, Yen-Hua; Liras, Spiros; Price, David A; Craik, David J

2014-06-20

343

Cyclic Expression of Lhx2 Regulates Hair Formation  

Microsoft Academic Search

Hair is important for thermoregulation, physical protection, sensory activity, seasonal camouflage, and social interactions. Hair is generated in hair follicles (HFs) and, following morphogenesis, HFs undergo cyclic phases of active growth (anagen), regression (catagen), and inactivity (telogen) throughout life. The transcriptional regulation of this process is not well understood. We show that the transcription factor Lhx2 is expressed in cells

Gunilla Trnqvist; Anna Sandberg; Anna-Carin Hgglund; Leif Carlsson

2010-01-01

344

Behavior of Nonplastic Silty Soils under Cyclic Loading  

PubMed Central

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

Ural, Nazile; Gunduz, Zeki

2014-01-01

345

Bargaining theory, inflation, and cyclical strike activity in manufacturing  

Microsoft Academic Search

This paper presents a theoretical and empirical analysis of cyclical movements in strike activity. The first part of the paper develops a bargaining model that demonstrates the crucial role of limited information as a cause of strikes. This model is believed to be an improvement over others because it allows for maximizing behavior on the part of both the union

Bruce E. Kaufman

1981-01-01

346

Homogeneous charge engines -- Basis of cyclic variations. Final report  

Microsoft Academic Search

The objectives of the Grant required investigations of cyclic variations in a homogeneous-charge engine initially with gas combustion and the air from ranging from near quiescent to the incorporation of swirl and tumble by valve inserts. Later experiments were performed with unleaded gasoline. The measurements included local velocity and cylinder pressure through the four strokes of a single-cylinder engine, under

Whitelaw

1997-01-01

347

Activation mechanism of rod outer segment cyclic GMP phosphodiesterase  

SciTech Connect

The physiological regulation of light-activated cyclic GMP phosphodiesterase in rod outer segments has been shown to depend upon a heat-stable inhibitor and upon the reversal of its effect by a specific GTP/GTP-binding protein complex.

Yamazaki, A.; Stein, P.J.; Chernoff, N.; Bitensky, M.W.

1983-07-10

348

Parametric analysis of a passive cyclic control device for helicopters  

NASA Technical Reports Server (NTRS)

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.

Kumagai, H.

1984-01-01

349

Multigrid and cyclic reduction applied to the Helmholtz equation  

NASA Technical Reports Server (NTRS)

We consider the Helmholtz equation with a discontinuous complex parameter and inhomogeneous Dirichlet boundary conditions in a rectangular domain. A variant of the direct method of cyclic reduction (CR) is employed to facilitate the design of improved multigrid (MG) components, resulting in the method of CR-MG. We demonstrate the improved convergence properties of this method.

Brackenridge, Kenneth

1993-01-01

350

Cyclic calculations and life estimation in thermomechanical fatigue  

E-print Network

Cyclic calculations and life estimation in thermomechanical fatigue F. Azzouz1, G. Cailletaud1, J thermomechanical loading, (2) in a short review of an advanced fatigue model which can reproduce the Woehler curve, associated with high mean stresses. One of the difficulties of the inelastic analysis of the component

Paris-Sud XI, Universit de

351

Technical Report No. 494 Using Cyclic Genetic Algorithms  

E-print Network

for a small hexapod robot are generated by a cyclic genetic algorithm. From these automata a Xilinx net list the communication network of an experimental robot colony. This recon guration of the hexapod's nervous system the control modules| realized as Xilinx xc030pc44 devices|for multiple robot agents are synthe- sized and down

Portland State University

352

The Cyclic Theory of the Universe Paul J. Steinhardt  

E-print Network

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

Millis, Andrew

353

How turbulence regulates biodiversity in systems with cyclic competition  

NASA Astrophysics Data System (ADS)

Cyclic, nonhierarchical interactions among biological species represent a general mechanism by which ecosystems are able to maintain high levels of biodiversity. However, species coexistence is often possible only in spatially extended systems with a limited range of dispersal, whereas in well-mixed environments models for cyclic competition often lead to a loss of biodiversity. Here we consider the dispersal of biological species in a fluid environment, where mixing is achieved by a combination of advection and diffusion. In particular, we perform a detailed numerical analysis of a model composed of turbulent advection, diffusive transport, and cyclic interactions among biological species in two spatial dimensions and discuss the circumstances under which biodiversity is maintained when external environmental conditions, such as resource supply, are uniform in space. Cyclic interactions are represented by a model with three competitors, resembling the children's game of rock-paper-scissors, whereas the flow field is obtained from a direct numerical simulation of two-dimensional turbulence with hyperviscosity. It is shown that the space-averaged dynamics undergoes bifurcations as the relative strengths of advection and diffusion compared to biological interactions are varied.

Groelj, Daniel; Jenko, Frank; Frey, Erwin

2015-03-01

354

Cyclic pulse coding for fast BOTDA fiber sensors.  

PubMed

A cyclic pulse coding technique is proposed and experimentally demonstrated for fast implementation of long-range Brillouin optical time-domain analysis (BOTDA). The proposed technique allows for accurate temperature and strain measurements with meter-scale spatial resolution over kilometers of standard single-mode fiber, with subsecond measurement times. PMID:23903168

Taki, M; Muanenda, Y; Oton, C J; Nannipieri, T; Signorini, A; Di Pasquale, F

2013-08-01

355

Cyclic mechanical property degradation during fatigue loading of cortical bone  

Microsoft Academic Search

Fatigue damage accumulation has been demonstrated in living bone and postulated as a stimulus to the bone modeling and remodeling response. Mechanical property degradation is one manifestation of fatigue damage accumulation. This study examines changes in secant modulus and cyclic energy dissipation behavior during axial load-controlled fatigue loading of cortical bone specimens. The findings suggest that secant modulus degradation and

C. A. Pattin; W. E. Caler; D. R. Carter

1996-01-01

356

Cyclic behavior of low yield point steel shear walls  

Microsoft Academic Search

This paper presents the research works on the cyclic behavior of low yield point (LYP) steel shear wall. In the LYP steel shear wall system, the LYP steel plate is used for steel panel and conventional structural steel is used for boundary frame. A series of experimental studies were carried out to examine the stiffness, strength, deformation capacity, and energy

Sheng-Jin Chen; Chyuan Jhang

2006-01-01

357

Synethesis of cyclic ketal from soybean oil and fatty esters  

Technology Transfer Automated Retrieval System (TEKTRAN)

In this work we have shown a facile and environmentally friendly reaction to form a cyclic ketal out of soybean oil, methyl soyate, methyl linoleate, and methyl oleate. There are many advantages of this reaction. First, the ketal reaction produces a branched fatty acid moiety and is reversible. S...

358

Energy dissipation in shape memory alloy wires under cyclic bending  

Microsoft Academic Search

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

Kim-Ho Ip

2000-01-01

359

Novel Cyclic Sugar Imines: Carbohydrate Mimics and Easily  

E-print Network

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

Davis, Ben G.

360

Cyclic Prefix Based Cooperative Sequential Spectrum Sensing Algorithms for OFDM  

E-print Network

) technology in- volves, 1) identifying spectrum opportunities by detecting holes (white space) whenCyclic Prefix Based Cooperative Sequential Spectrum Sensing Algorithms for OFDM Arun@ece.iisc.ernet.in, cmurthy@ece.iisc.ernet.in, prashant2413@gmail.com Abstract-- This paper considers the problem of spectrum

Sharma, Vinod

361

Intramolecular Fluorine Migration via Four-Member Cyclic Transition States  

E-print Network

Intramolecular Fluorine Migration via Four-Member Cyclic Transition States Viet Nguyen, Philip S to fluorine means that (in the minor product, at least) an F+ for O transposition occurs via adduct formation of the potential energy wells that precede and follow the central barrier. Methods for incorporation of fluorine

Morton, Thomas Hellman

362

Cyclic Oxidation Testing and Modelling: A NASA Lewis Perspective  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

363

Improving the Biopharmaceutical Properties of Cyclic Opioid Peptide Prodrugs  

E-print Network

In an attempt to improve the "drugability" of opioid peptides, cyclic prodrugs of the opioid peptide DADLE (H-Tyr-D-Ala-Gly-Phe-D-Leu-OH) were developed using a coumarinic acid linker (CA). CA-DADLE was metabolically unstable in the present of liver...

Nofsinger, Rebecca Anne

2008-05-05

364

Imperfect Financial Markets and the Cyclicality of Social Transfers  

E-print Network

to endogenous risk premia because the government cannot commit to repay its debt. The government conducts debt for financing government ex- penditures (Reinhart and Rogoff 2011) and face countercyclical of government expenditure that the cyclical correlation of social spending exhibits the biggest differences

Nesterov, Yurii

365

Effects of cyclic hydraulic pressure on osteocytes , Yan Zhao b  

E-print Network

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

You, Lidan

366

On the Construction of Skew Quasi-Cyclic Codes  

Microsoft Academic Search

In this paper we study a special type of quasi-cyclic (QC) codes called skew QC codes. This set of codes is constructed using a non- commutative ring called the skew polynomial rings F(x; ). After a brief description of the skew polynomial ring F(x; ) it is shown that skew QC codes are left submodules of the ring Rls =

Taher Abualrub; Ali Ghrayeb; Nuh Aydin; Irfan Siap

2008-01-01

367

Alta-Cyclic: a self-optimizing base caller  

E-print Network

Alta-Cyclic: a self- optimizing base caller for next-generation sequencing Yaniv Erlich1,2, Partha P Mitra1, Melissa delaBastide1, W Richard McCombie1 & Gregory J Hannon1,2 Next-generation sequencing identification of sequence variants. Next-generation sequencers are revolutionizing biological research1

Cai, Long

368

Ring strain-promoted allylic transposition of cyclic silyl ethers.  

PubMed

Relief of the ring strain of medium-sized rings promotes a regioselective allylic transposition of a C-O bond when catalyzed by rhenium oxide. Through the allylic transposition, eight-membered cyclic silyl ethers undergo ring contraction to the corresponding six-membered siloxacycles. PMID:21648455

Volchkov, Ivan; Park, Sangho; Lee, Daesung

2011-07-01

369

A Simulation of Counter-Cyclical Intervention: Some Practical Lessons  

ERIC Educational Resources Information Center

The author introduces a simulation of counter-cyclical interventions that highlights important issues surrounding the practice of government intervention. The simulation provides experiential insight as to why economists have long debated the degree of persistence exhibited by disequilibrating shocks and connects this debate to discussions about

Grawe, Nathan D.; Watts, Michael, Ed.

2007-01-01

370

Periodic travelling waves in cyclic populations: field studies and  

E-print Network

-year cycles (table 1). The same period has seen significant advances in the mathematical understandingREVIEW Periodic travelling waves in cyclic populations: field studies and reaction­diffusion models Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK Periodic travelling waves have been reported

Sherratt, Jonathan A.

371

Three-dimensional stable matching with cyclic preferences  

E-print Network

9 May 2006 Abstract We consider stable three-dimensional matchings of three genders (3GSM). Alkan­209] showed that not all instances of 3GSM allow stable matchings. Boros et al. [Boros, E., Gurvich, V to cyclic 3GSM. Based on computer search, we formulate a conjecture on stability of "strongest link" 3GSM

372

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

Microsoft Academic Search

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).

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

2011-01-01

373

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

SciTech Connect

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.

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

1984-02-01

374

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

Code of Federal Regulations, 2013 CFR

...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...

2013-07-01

375

Factors associated with early cyclicity in postpartum dairy cows.  

PubMed

The objective of this study was to evaluate factors associated with resumption of ovarian cyclicity within 21 days in milk (DIM) in dairy cows. Cows (n=768) from 2 herds in north Florida had their ovaries scanned at 173, 213, and 243 DIM. Cows that had a corpus luteum ?20mm at 173 or at 213 DIM or that had a corpus luteum <20mm in 2 consecutive examinations were determined to be cyclic by 213 DIM. The following information was collected for up to 14 DIM: calving season, parity, calving problems, metabolic problems, metritis, mastitis, digestive problems, lameness, body weight loss, dry period length, and average daily milk yield. Body condition was scored at 173 DIM. Multivariable mixed logistic regression analysis was performed using the GLIMMIX procedure of SAS. Variables with P?0.2 were considered in each model. Herd was included as a random variable. Three models were constructed: model 1 included all cows, model 2 included only cows from dairy 1 that had daily body weights available, and model 3 included only multiparous cows with a previous dry period length recorded. In model 1, variables associated with greater cyclicity by 213 DIM were calving in the summer and fall rather than in the winter or spring, being multiparous rather than primiparous, and not having metabolic or digestive problems. In model 2, variables associated with greater cyclicity by 213 DIM were calving in the summer and fall, not having metritis or digestive problems and not losing >28 kg of BW within 14 DIM. In model 3, variables associated with greater cyclicity by 213 DIM were absence of metabolic problems and dry period ?76 d. In summary, cyclicity by 213 DIM was negatively associated with calving in winter or spring, primiparity, metritis, metabolic or digestive problems, loss of >28 kg of body weight, and a dry period >76d. Strategies preventing extended dry period length and loss of BW, together with reductions in the incidence of metritis as well as metabolic and digestive problems should improve early cyclicity postpartum. PMID:25465552

Vercouteren, M M A A; Bittar, J H J; Pinedo, P J; Risco, C A; Santos, J E P; Vieira-Neto, A; Galvo, K N

2015-01-01

376

Cyclic Oxidation Modeling Program Rewritten for MS Windows  

NASA Technical Reports Server (NTRS)

Turbine superalloy components are subject to high-temperature oxidation during operation. Protection is often conferred by coatings designed to form slow-growing, adherent oxide scales. Degradation by oxidation is exacerbated by the thermal cycling encountered during normal aircraft operations. Cooling has been identified as the major contributor to stresses in the oxidation scales, and it may often cause some oxide scale spallation with a proportional loss of protective behavior. Overall oxidation resistance is, thus, studied by the weight change behavior of alloy coupons during high-temperature cyclic oxidation in furnace or burner rig tests. The various characteristics of this behavior are crucial in understanding the performance of alloys at high temperatures. This new modeling effort helps in the understanding of the major factors involved in the cyclic oxidation process. Weight change behavior in cyclic oxidation is typified by an initial parabolic weight gain response curve that eventually exhibits a maximum, then transitions into a linear rate of weight loss due to spalling. The overall shape and magnitude of the curve are determined by the parabolic growth rate, kp, the cycle duration, the type of oxide scale, and the regular, repetitive spalling process. This entire process was modeled by a computer program called the Cyclic Oxidation Spalling Program (COSP) previously developed at the NASA Glenn Research Center. Thus, by supplying appropriate oxidation input parameters, one can determine the best fit to the actual data. These parameters describe real behavior and can be used to compare alloys and project cyclic oxidation behavior for longer times or under different cycle frequencies.

Smialek, James L.; Auping, Judith V.

2002-01-01

377

Family of prokaryote cyclic nucleotide-modulated ion channels.  

PubMed

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

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

2014-05-27

378

Family of prokaryote cyclic nucleotide-modulated ion channels  

PubMed Central

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 (2432%) 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

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

2014-01-01

379

Acceleration and Classical Electromagnetic Radiation  

E-print Network

Classical radiation from an accelerated charge is reviewed along with the reciprocal topic of accelerated observers detecting radiation from a static charge. This review commemerates Bahram Mashhoon's 60th birthday.

E. N. Glass

2008-01-09

380

Aging effects on the cyclic deformation mechanisms of a duplex stainless steel  

Microsoft Academic Search

Aging effects on the cyclic deformation mechanisms of an AISI-329 duplex stainless steel have been studied on the basis of the cyclic hardening-softening response, cyclic stress-strain curve and substructure evolution within the individual phases. The cyclic behavior of an unaged and two aged materials shows, in terms of plastic strain amplitude (?pl), three well-defined stages. In the first regime, at

L. Llanes; A. Mateo; L. Iturgoyen; M. Anglada

1996-01-01

381

Constellation Acceleration Study December 18, 2008  

E-print Network

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

Christian, Eric

382

Particle Acceleration at Relativistic Shocks  

E-print Network

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.

Yves A. Gallant

2002-01-15

383

Exploring Acceleration with an Android  

NSDL National Science Digital Library

Students conduct an experiment to study the acceleration of a mobile Android device. During the experiment, they run an application created with MIT's App Inventor that monitors linear acceleration in one-dimension. Students use an acceleration vs. time equation to construct an approximate velocity vs. time graph. Students will understand the relationship between the object's mass and acceleration and how that relates to the force applied to the object, which is Newton's second law of motion.

IMPART RET Program, College of Information Science & Technology,

384

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."

385

Overview of accelerators in medicine  

SciTech Connect

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.

Lennox, A.J. [Fermi National Accelerator Lab., Batavia, IL (US)]|[Rush Univ., Chicago, IL (US)

1993-06-01

386

Liquid chromatographytandem mass spectrometry and accurate m\\/ z measurements of cyclic peptide cyanobacteria toxins  

Microsoft Academic Search

Microcystins are cyclic peptide hepatotoxins that are produced by several genera of cyanobacteria. We briefly review the molecular structural features of 67 reported cyclic heptapeptide microcystins and a related cyclic pentapeptide toxin. These substances present a significant analytical challenge because multiple toxins are often found in any given cyanobacteria or water sample, and it is likely that some structural variants

William L. Budde; S PETERMAN

2005-01-01

387

Cyclic nucleotide binding proteins in the Arabidopsis thaliana and Oryza sativa genomes  

Microsoft Academic Search

Cyclic nucleotides are ubiquitous intracellular messengers. Until recently, the roles of cyclic nucleotides in plant cells have proven difficult to uncover. With an understanding of the protein domains which can bind cyclic nucleotides (CNB and GAF domains) we scanned the completed genomes of the higher plants Arabidopsis thaliana (mustard weed) and Oryza sativa (rice) for the effectors of these signalling

Dave Bridges; Marie E Fraser; Greg B. G. Moorhead

2005-01-01

388

Odd cyclic surface separators in planar graphs Petr A. Golovach a  

E-print Network

Odd cyclic surface separators in planar graphs Petr A. Golovach a Marcin Kami´nski b,1 Dimitrios M of Athens, Greece Key words: planar graphs, odd cycles, irrelevant vertex Given a plane graph G and two, and an odd cyclic surface separator if C is an odd cycle. We consider the problem of finding odd cyclic

Dimitrios, Thilikos

389

CYCLIC STEADY STATES OF TREADED ROLLING BODIES SANJAY GOVINDJEE, TREVOR POTTER, AND JON WILKENING  

E-print Network

CYCLIC STEADY STATES OF TREADED ROLLING BODIES SANJAY GOVINDJEE, TREVOR POTTER, AND JON WILKENING of cyclic steady states of motion. The scheme advocated permits one to determine the entire transient many cycles until a cyclic steady state is reached. 1. Introduction The analysis of finitely deformable

Wilkening, Jon

390

Spatiotemporal dynamics of guanosine 3 ,5 -cyclic monophosphate revealed by a genetically  

E-print Network

Spatiotemporal dynamics of guanosine 3 ,5 -cyclic monophosphate revealed by a genetically encoded. Tsien, December 29, 2000 To investigate the dynamics of guanosine 3 ,5 -cyclic monophos- phate (c green fluorescent protein The importance of the guanosine 3 ,5 -cyclic monophosphate (cGMP) second

Tsien, Roger Y.

391

7 CFR 1412.33 - Payment yield for counter-cyclical payments for covered commodities.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Payment yield for counter-cyclical payments for covered...SUBSEQUENT CROP YEARS Establishment of Yields for Direct and Counter-Cyclical Payments 1412.33 Payment yield for counter-cyclical payments for...

2011-01-01

392

7 CFR 1412.33 - Payment yield for counter-cyclical payments for covered commodities.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Payment yield for counter-cyclical payments for covered...SUBSEQUENT CROP YEARS Establishment of Yields for Direct and Counter-Cyclical Payments 1412.33 Payment yield for counter-cyclical payments for...

2013-01-01

393

7 CFR 1412.33 - Payment yield for counter-cyclical payments for covered commodities.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Payment yield for counter-cyclical payments for covered...SUBSEQUENT CROP YEARS Establishment of Yields for Direct and Counter-Cyclical Payments 1412.33 Payment yield for counter-cyclical payments for...

2012-01-01

394

7 CFR 1412.33 - Payment yield for counter-cyclical payments for covered commodities.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Payment yield for counter-cyclical payments for covered...SUBSEQUENT CROP YEARS Establishment of Yields for Direct and Counter-Cyclical Payments 1412.33 Payment yield for counter-cyclical payments for...

2010-01-01

395

7 CFR 1412.33 - Payment yield for counter-cyclical payments for covered commodities.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Payment yield for counter-cyclical payments for covered...SUBSEQUENT CROP YEARS Establishment of Yields for Direct and Counter-Cyclical Payments 1412.33 Payment yield for counter-cyclical payments for...

2014-01-01

396

Stress state dependence of cyclic ratchetting behavior of two rail steels  

Microsoft Academic Search

Cumulative inelastic deformation or ratchetting occurs during cyclic loading in the presence of a mean stress. This problem has received considerable recent attention. The nonlinear kinematic hardening rule originally proposed by Armstrong and Frederick (AF rule) [1966] has been widely used for description of the overall character of hysteresis response during cyclic plasticity. However, this model generally overpredicts cyclic strain

D. L. McDowell

1995-01-01

397

Cyclic electron transfer in plant leaf Pierre Joliot* and Anne Joliot  

E-print Network

Photosys- tem (PS) II is inhibited, a cyclic electron flow around PSI operates transiently at a rate close process in algae or plants operates according to two nonmutually exclusive modes: linear and cyclic) in broken chloroplasts. In unicellular algae, a cyclic electron flow operates in anaerobic conditions (3, 4

398

Inner Functions and Cyclic Composition Operators on H 2( B n )  

Microsoft Academic Search

The present paper shows that the algebra C generated by {C?|??Aut(Bn)} is cyclic on H2(Bn), and any nonconstant function f?H2(Bn) is a cyclic vector of C. In addition, the hypercyclic and cyclic composition operators will be discussed.

Chen Xiaoman; Cao Guangfu; Guo Kunyu

2000-01-01

399

Creep, stress relaxation and biaxial ratchetting of type 304 stainless steel after cyclic preloading  

Microsoft Academic Search

A series of tests for creep, stress relaxation, and biaxial ratchetting of type 304 stainless steel after cyclic preloading were carried out to investigate their interaction. The interesting fact was pointed out that back stress in cyclic plasticity played an important role to describe creep, relaxation, and biaxial ratchetting following cyclic preloading. Then, the test results showed that the material

Hiromasa Ishikawa; Katsuhiko Sasaki

1994-01-01

400

Cyclic mutually unbiased bases, Fibonacci polynomials and Wiedemann's Ulrich Seyfarth and Kedar S. Ranade  

E-print Network

Cyclic mutually unbiased bases, Fibonacci polynomials and Wiedemann's conjecture Ulrich Seyfarth) Cyclic mutually unbiased bases, Fibonacci polynomials and Wiedemann's conjecture Ulrich Seyfarth1,a relate the construction of a complete set of cyclic mutually unbiased bases, i.e., mutually unbiased

401

A Theoretical Note on Concepts and the Need for Cyclic Concept Maps  

ERIC Educational Resources Information Center

This article examines concepts and propositions from a theoretical perspective, and establishes the need for and develops an extension to Concept Maps (CMaps), called Cyclic Concept Maps (Cyclic CMaps). Cyclic CMaps are considered to be an appropriate tool for representing knowledge of functional or dynamical relationships between concepts. CMaps,

Safayeni, Frank; Derbentseva, Natalia; Canas, Alberto J.

2005-01-01

402

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

ERIC Educational Resources Information Center

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

Leung, Allen; Lopez-Real, Francis

2003-01-01

403

New techniques for particle accelerators  

SciTech Connect

A review is presented of the new techniques which have been proposed for use in particle accelerators. Attention is focused upon those areas where significant progress has been made in the last two years--in particular, upon two-beam accelerators, wakefield accelerators, and plasma focusers. 26 refs., 5 figs., 1 tab.

Sessler, A.M.

1990-06-01

404

Accelerator research studies  

SciTech Connect

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.

Not Available

1993-01-01

405

Accelerometer: Centripetal Acceleration  

NSDL National Science Digital Library

Students work as physicists to understand centripetal acceleration concepts. They also learn about a good robot design and the accelerometer sensor. They also learn about the relationship between centripetal acceleration and centripetal forcegoverned by the radius between the motor and accelerometer and the amount of mass at the end of the robot's arm. Students graph and analyze data collected from an accelerometer, and learn to design robots with proper weight distribution across the robot for their robotic arms. Upon using a data logging program, they view their own data collected during the activity. By activity end , students understand how a change in radius or mass can affect the data obtained from the accelerometer through the plots generated from the data logging program. More specifically, students learn about the accuracy and precision of the accelerometer measurements from numerous trials.

2014-09-18

406

Hypervelocity plate acceleration  

SciTech Connect

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.

Marsh, S.P.; Tan, T.H.

1991-01-01

407

Review of ion accelerators  

SciTech Connect

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.

Alonso, J.

1990-06-01

408

Pulsed electromagnetic gas acceleration  

NASA Technical Reports Server (NTRS)

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.

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1971-01-01

409

Plasma wave accelerator. II  

SciTech Connect

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.

Mori, W.; Joshi, C.; Dawson, J.M.

1982-01-01

410

Accelerator research studies  

SciTech Connect

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 first 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, TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams; TASK C, Study of a Gyroklystron High-power Microwave Source for Linear Colliders. In this report we document the progress that has been made during the past year for each of the three tasks.

Not Available

1992-01-01

411

Linear induction accelerator  

DOEpatents

A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.

Buttram, M.T.; Ginn, J.W.

1988-06-21

412

ATLAS accelerator laboratory report  

SciTech Connect

The operation of the ATLAS Accelerator is reported. Modifications are reported, including the installation of conductive tires for the Pelletron chain pulleys, installation of a new high frequency sweeper system at the entrance to the linac, and improvements to the rf drive ports of eight resonators to correct failures in the thermally conductive ceramic insulators. Progress is reported on the positive-ion injector upgrade for ATLAS. Also reported are building modifications and possible new uses for the tandem injector. (LEW)

Den Hartog, P.

1986-01-01

413

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

414

Accelerating QDP++ using GPUs  

E-print Network

Graphic Processing Units (GPUs) are getting increasingly important as target architectures in scientific High Performance Computing (HPC). NVIDIA established CUDA as a parallel computing architecture controlling and making use of the compute power of GPUs. CUDA provides sufficient support for C++ language elements to enable the Expression Template (ET) technique in the device memory domain. QDP++ is a C++ vector class library suited for quantum field theory which provides vector data types and expressions and forms the basis of the lattice QCD software suite Chroma. In this work accelerating QDP++ expression evaluation to a GPU was successfully implemented leveraging the ET technique and using Just-In-Time (JIT) compilation. The Portable Expression Template Engine (PETE) and the C API for CUDA kernel arguments were used to build the bridge between host and device memory domains. This provides the possibility to accelerate Chroma routines to a GPU which are typically not subject to special optimisation. As an application example a smearing routine was accelerated to execute on a GPU. A significant speed-up compared to normal CPU execution could be measured.

Frank Winter

2011-05-11

415

TRACKING ACCELERATOR SETTINGS.  

SciTech Connect

Recording setting changes within an accelerator facility provides information that can be used to answer questions about when, why, and how changes were made to some accelerator system. This can be very useful during normal operations, but can also aid with security concerns and in detecting unusual software behavior. The Set History System (SHS) is a new client-server system developed at the Collider-Accelerator Department of Brookhaven National Laboratory to provide these capabilities. The SHS has been operational for over two years and currently stores about IOOK settings per day into a commercial database management system. The SHS system consists of a server written in Java, client tools written in both Java and C++, and a web interface for querying the database of setting changes. The design of the SHS focuses on performance, portability, and a minimal impact on database resources. In this paper, we present an overview of the system design along with benchmark results showing the performance and reliability of the SHS over the last year.

D OTTAVIO,T.; FU, W.; OTTAVIO, D.P.

2007-10-15

416

Accelerated Profile HMM Searches  

PubMed Central

Profile hidden Markov models (profile HMMs) and probabilistic inference methods have made important contributions to the theory of sequence database homology search. However, practical use of profile HMM methods has been hindered by the computational expense of existing software implementations. Here I describe an acceleration heuristic for profile HMMs, the multiple segment Viterbi (MSV) algorithm. The MSV algorithm computes an optimal sum of multiple ungapped local alignment segments using a striped vector-parallel approach previously described for fast Smith/Waterman alignment. MSV scores follow the same statistical distribution as gapped optimal local alignment scores, allowing rapid evaluation of significance of an MSV score and thus facilitating its use as a heuristic filter. I also describe a 20-fold acceleration of the standard profile HMM Forward/Backward algorithms using a method I call sparse rescaling. These methods are assembled in a pipeline in which high-scoring MSV hits are passed on for reanalysis with the full HMM Forward/Backward algorithm. This accelerated pipeline is implemented in the freely available HMMER3 software package. Performance benchmarks show that the use of the heuristic MSV filter sacrifices negligible sensitivity compared to unaccelerated profile HMM searches. HMMER3 is substantially more sensitive and 100- to 1000-fold faster than HMMER2. HMMER3 is now about as fast as BLAST for protein searches. PMID:22039361

Eddy, Sean R.

2011-01-01

417

Oxidised cosmic acceleration  

SciTech Connect

We give detailed proofs of several new no-go theorems for constructing flat four-dimensional accelerating universes from warped dimensional reduction. These new theorems improve upon previous ones by weakening the energy conditions, by including time-dependent compactifications, and by treating accelerated expansion that is not precisely de Sitter. We show that de Sitter expansion violates the higher-dimensional null energy condition (NEC) if the compactification manifold M is one-dimensional, if its intrinsic Ricci scalar R-ring vanishes everywhere, or if R-ring and the warp function satisfy a simple limit condition. If expansion is not de Sitter, we establish threshold equation-of-state parameters w below which accelerated expansion must be transient. Below the threshold w there are bounds on the number of e-foldings of expansion. If M is one-dimensional or R-ring everywhere vanishing, exceeding the bound implies the NEC is violated. If R-ring does not vanish everywhere on M, exceeding the bound implies the strong energy condition (SEC) is violated. Observationally, the w thresholds indicate that experiments with finite resolution in w can cleanly discriminate between different models which satisfy or violate the relevant energy conditions.

Wesley, Daniel H., E-mail: D.H.Wesley@damtp.cam.ac.uk [Centre for Theoretical Cosmology, DAMTP, Cambridge University, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2009-01-15

418

Acceleration in Linear and Circular Motion  

ERIC Educational Resources Information Center

Describes the construction of a simple accelerometer and explains its use in demonstrating acceleration, deceleration, constant speed, measurement of acceleration, acceleration and the inclined plane and angular and radial acceleration. (GS)

Kellington, S. H.; Docherty, W.

1975-01-01

419

Influence of high-frequency cyclical stimulation on the bone fracture-healing process: mathematical and experimental models.  

PubMed

Mechanical stimulation affects the evolution of healthy and fractured bone. However, the effect of applying cyclical mechanical stimuli on bone healing has not yet been fully clarified. The aim of the present study was to determine the influence of a high-frequency and low-magnitude cyclical displacement of the fractured fragments on the bone-healing process. This subject is studied experimentally and computationally for a sheep long bone. On the one hand, the mathematical computational study indicates that mechanical stimulation at high frequencies can stimulate and accelerate the process of chondrogenesis and endochondral ossification and consequently the bony union of the fracture. This is probably achieved by the interstitial fluid flow, which can move nutrients and waste from one place to another in the callus. This movement of fluid modifies the mechanical stimulus on the cells attached to the extracellular matrix. On the other hand, the experimental study was carried out using two sheep groups. In the first group, static fixators were implanted, while, in the second one, identical devices were used, but with an additional vibrator. This vibrator allowed a cyclic displacement with low magnitude and high frequency (LMHF) to be applied to the fractured zone every day; the frequency of stimulation was chosen from mechano-biological model predictions. Analysing the results obtained for the control and stimulated groups, we observed improvements in the bone-healing process in the stimulated group. Therefore, in this study, we show the potential of computer mechano-biological models to guide and define better mechanical conditions for experiments in order to improve bone fracture healing. In fact, both experimental and computational studies indicated improvements in the healing process in the LMHF mechanically stimulated fractures. In both studies, these improvements could be associated with the promotion of endochondral ossification and an increase in the rate of cell proliferation and tissue synthesis. PMID:21969676

Gmez-Benito, Mara Jos; Gonzlez-Torres, Libardo Andrs; Reina-Romo, Esther; Grasa, Jorge; Seral, Beln; Garca-Aznar, Jos Manuel

2011-11-13

420

Muon Acceleration - RLA and FFAG  

SciTech Connect

Various acceleration schemes for muons are presented. The overall goal of the acceleration systems: large acceptance acceleration to 25 GeV and 'beam shaping' can be accomplished by various fixed field accelerators at different stages. They involve three superconducting linacs: a single pass linear Pre-accelerator followed by a pair of multi-pass Recirculating Linear Accelerators (RLA) and finally a non-scaling FFAG ring. The present baseline acceleration scenario has been optimized to take maximum advantage of appropriate acceleration scheme at a given stage. The solenoid based Pre-accelerator offers very large acceptance and facilitates correction of energy gain across the bunch and significant longitudinal compression trough induced synchrotron motion. However, far off-crest acceleration reduces the effective acceleration gradient and adds complexity through the requirement of individual RF phase control for each cavity. The RLAs offer very efficient usage of high gradient superconducting RF and ability to adjust path-length after each linac pass through individual return arcs with uniformly periodic FODO optics suitable for chromatic compensation of emittance dilution with sextupoles. However, they require spreaders/recombiners switchyards at both linac ends and significant total length of the arcs. The non-scaling Fixed Field Alternating Gradient (FFAG) ring combines compactness with very large chromatic acceptance (twice the injection energy) and it allows for large number of passes through the RF (at least eight, possibly as high as 15).

Alex Bogacz

2011-10-01

421

A Strip-Yield Model for Predicting the Growth of Part-Through Cracks Under Cyclic Loading  

NASA Technical Reports Server (NTRS)

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.

Daniewicz, S. R.; Newman, J. C., Jr. (Technical Monitor)

2000-01-01

422

Effects of cyclic stress distribution models on fatigue life predictions  

NASA Astrophysics Data System (ADS)

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.

Sutherland, H. J.; Veers, P. S.

1994-10-01

423

Cyclic silylated onium ions of group 15 elements.  

PubMed

Five- and six-membered cyclic silylated onium ions of group 15 elements I were synthesized by intramolecular cyclization of transient silylium ions II. Silylium ions II were prepared by the hydride transfer reaction from silanes III using trityl cation as hydride acceptor. It was found that smaller ring systems could not be obtained by this approach. In these cases tritylphosphonium ions IV were isolated instead. Cations I and IV were isolated in the form of their tetrakispentafluorphenyl borates and characterized by multinuclear NMR spectroscopy and, in two cases, by X-ray diffraction analysis. Cyclic onium ions I showed no reactivity similar to that of isoelectronic intramolecular borane/phosphane frustrated Lewis pairs (FLPs). The results of DFT computations at the M05-2X level suggest that the strength of the newly formed Si-E linkage is the major reason for inertness of I[B(C6F5)4] versus molecular hydrogen. PMID:25664605

Reimann, Matti; Schfer, Andr; Panisch, Robin; Schmidtmann, Marc; Bolte, Michael; Mller, Thomas

2015-03-01

424

Improving on nature: making a cyclic heptapeptide orally bioavailable.  

PubMed

The use of peptides in medicine is limited by low membrane permeability, metabolic instability, high clearance, and negligible oral bioavailability. The prediction of oral bioavailability of drugs relies on physicochemical properties that favor passive permeability and oxidative metabolic stability, but these may not be useful for peptides. Here we investigate effects of heterocyclic constraints, intramolecular hydrogen bonds, and side chains on the oral bioavailability of cyclic heptapeptides. NMR-derived structures, amide H-D exchange rates, and temperature-dependent chemical shifts showed that the combination of rigidification, stronger hydrogen bonds, and solvent shielding by branched side chains enhances the oral bioavailability of cyclic heptapeptides in rats without the need for N-methylation. PMID:25219505

Nielsen, Daniel S; Hoang, Huy N; Lohman, Rink-Jan; Hill, Timothy A; Lucke, Andrew J; Craik, David J; Edmonds, David J; Griffith, David A; Rotter, Charles J; Ruggeri, Roger B; Price, David A; Liras, Spiros; Fairlie, David P

2014-11-01

425

Endometriosis of the conus medullaris causing cyclic radiculopathy.  

PubMed

Intramedullary spinal cord hematomas are a rare neurosurgical pathological entity typically arising from vascular and neoplastic lesions. Endometriosis is an extremely rare cause of intramedullary spinal cord hematoma, with only 5 previously reported cases in the literature. Endometriosis is characterized by ectopic endometrial tissue, typically located in the female pelvic cavity, that causes a cyclical pain syndrome, bleeding, and infertility. In the rare case of intramedullary endometriosis of the spinal cord, symptoms include cyclical lower-extremity radiculopathies and voiding difficulties, and can acutely cause cauda equina syndrome. The authors report a case of endometriosis of the conus medullaris, the first to include radiological, intraoperative, and histopathological imaging. A brief review of the literature is also presented, with discussion including etiological theories surrounding intramedullary endometriosis. PMID:25192376

Steinberg, Jeffrey A; Gonda, David D; Muller, Karra; Ciacci, Joseph D

2014-11-01

426

Cyclic creep analysis from elastic finite-element solutions  

NASA Technical Reports Server (NTRS)

A uniaxial approach was developed for calculating cyclic creep and stress relaxation at the critical location of a structure subjected to cyclic thermomechanical loading. This approach was incorporated into a simplified analytical procedure for predicting the stress-strain history at a crack initiation site for life prediction purposes. An elastic finite-element solution for the problem was used as input for the simplified procedure. The creep analysis includes a self-adaptive time incrementing scheme. Cumulative creep is the sum of the initial creep, the recovery from the stress relaxation and the incremental creep. The simplified analysis was exercised for four cases involving a benchmark notched plate problem. Comparisons were made with elastic-plastic-creep solutions for these cases using the MARC nonlinear finite-element computer code.

Kaufman, A.; Hwang, S. Y.

1986-01-01

427

Engine cyclic durability by analysis and material testing  

NASA Technical Reports Server (NTRS)

The problem of calculating turbine engine component durability is addressed. Nonlinear, finite-element structural analyses, cyclic constitutive behavior models, and an advanced creep-fatigue life prediction method called strainrange partitioning were assessed for their applicability to the solution of durability problems in hot-section components of gas turbine engines. Three different component or subcomponent geometries are examined: a stress concentration in a turbine disk; a louver lip of a half-scale combustor linear; and a squealer tip of a first-stage high-pressure turbine blade. Cyclic structural analyses were performed for all three problems. The computed strain-temperature histories at the critical locations of the combustor linear and turbine blade components were imposed on smooth specimens in uniaxial, strain-controlled, thermomechanical fatigue tests of evaluate the structural and life analysis methods.

Kaufman, A.; Halford, G. R.

1984-01-01

428

[Cyclic nucleotide-gated channels and sperm function].  

PubMed

The cyclic nucleotide-gated (CNG) channel is a nonselective cation channel and one of the main entrances of Ca2+ influxion into cells. CNG channels are opened by direct binding of cyclic nucleotides. Six different genes encode the CNG protein, 4 A subunits and 2 B subunits. The activity of CNG channels can be regulated by Ca2+/Ca(2+)-binding proteins (CaM) and phosphorylation/dephosphorylation. Recently, extensive attention has been drawn to the researches on CNG channels in the reproductive system, and many studies show that CNG channels play a pivotal role in sperm motility, capacitation and acrosome reaction. This article focuses on the relationship of CNG channels with sperm function. PMID:23700737

Xu, Jian-Hua; Du, Jing

2013-03-01

429

Engine cyclic durability by analysis and material testing  

NASA Technical Reports Server (NTRS)

The problem of calculating turbine engine component durability is addressed. Nonlinear, finite-element structural analyses, cyclic constitutive behavior models, and an advanced creep-fatigue life prediction method called strainrange partitioning were assessed for their applicability to the solution of durability problems in hot-section components of gas turbine engines. Three different component or subcomponent geometries are examined: a stress concentration in a turbine disk; a louver lip of a half-scale combustor liner; and a squealer tip of a first-stage high-pressure turbine blade. Cyclic structural analyses were performed for all three problems. The computed strain-temperature histories at the critical locations of the combustor linear and turbine blade components were imposed on smooth specimens in uniaxial, strain-controlled, thermomechanical fatigue tests of evaluate the structural and life analysis methods.

Kaufman, A.; Halford, G. R.

1983-01-01

430

Cyclic stretching of soft substrates induces spreading and growth  

NASA Astrophysics Data System (ADS)

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, 15% cyclic stretching over a frequency range of 0.0110?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.

Cui, Yidan; Hameed, Feroz M.; Yang, Bo; Lee, Kyunghee; Pan, Catherine Qiurong; Park, Sungsu; Sheetz, Michael

2015-02-01

431

Dual cyclic power saving technique for XG-PON.  

PubMed

In a passive optical network (PON), energy conservation is an important system design goal to satisfy the global demands for an energy efficient green network. In this paper, we show that a separate period control for the transmitter and receiver of an optical transceiver can result in better power saving performances in PON systems. Then, we propose a power saving mode called the Dual Cyclic Sleep (DCS) mode. We have implemented the DCS mode in an ETRI XG-PON system and conducted experiments to show the power saving efficiency of the proposed DCS mode. The results indicate that the DCS mode provides higher power saving efficiency than the doze and cyclic sleep modes. PMID:25322186

Kim, Geunyong; Kim, Sungchang; Lee, Dongsoo; Yoo, Hark; Lim, Hyuk

2014-08-25

432

Matrix cracking in laminated composites under monotonic and cyclic loadings  

NASA Technical Reports Server (NTRS)

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.

Allen, David H.; Lee, Jong-Won

1991-01-01

433

Cyclic Plasticity under Shock Loading in an HCP Metal  

SciTech Connect

Plate impact experiments with pressures from 2 to 20 GPa, including one shock-partial release-reshock experiment, were performed on vacuum hot-pressed S-200F Beryllium. This hexagonal close-packed (HCP) metal shows significant plasticity effects in such conditions. The experiments were modeled in a Lagrangian hydrocode using an experimentally calibrated Preston-Tonks-Wallace (PTW) constitutive model. By using the shock data to constrain a high rate portion of PTW, the model was able to generally match plasticity effects on the measured wave profile (surface velocity) during the shock loading, but not unloading. A backstress-based cyclic plasticity model to capture the quasi-elastic release (Bauschinger-type effect) was explored in order to match the unloading and reloading portions of the measured wave profiles. A comparison is made with other approaches in the literature to capture the cyclic plasticity in shock conditions.

Prime, Michael B. [Los Alamos National Laboratory; Hunter, Abigail [Los Alamos National Laboratory; Canfield, Thomas R. [Los Alamos National Laboratory; Adams, Chris D. [Los Alamos National Laboratory

2012-06-08

434

Improvements of cyclic somatic embryogenesis of cassava (Manihot esculenta Crantz).  

PubMed

In cassava a cyclic system of somatic embryogenesis was developed. Primary (torpedo shaped or germinated) embryos, originating from leaf lobes, could only be obtained after culture on solid medium. Cyclic embryos, originating from embryos, could be obtained in both liquid and on solid medium. The production of embryos in liquid medium was distinctly higher, faster and more synchronized than on solid medium. Lower densities and fragmentation of starting embryos improved the production significantly. The highest production found was 32.1 embryos per initial embryo. In all treatments the explants initiated multiple embryos. The production of single embryos was achieved by pressing starting embryos through a fine meshed sieve, indicating that embryos can be produced from a piece of tissue with a restricted number of cells. The shoot conversion rate of embryos from liquid medium was comparable with that of embryos from solid medium. PMID:24197025

Raemakers, C J; Schavemaker, C M; Jacobsen, E; Visser, R G

1993-02-01

435

Low severity coal liquefaction promoted by cyclic olefins  

SciTech Connect

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.

Curtis, C.W.

1991-01-01

436

Evaluation of Cyclic Behavior of Aircraft Turbine Disk Alloys  

NASA Technical Reports Server (NTRS)

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.

Shahani, V.; Popp, H. G.

1978-01-01

437

Association of cyclic GMP with gene expression of polytene chromosomes of Drosophila melanogaster.  

PubMed

The distribution of cyclic nucleotides on polytene chromosomes isolated from Drosophilia melanogaster salivary glands was examined by using an indirect immunofluorescent technique. With a fixative that minimized the loss of chromosomal proteins, cyclic GMP, but not cyclic AMP, was observed distributed along the chromosomes. The subchromosomal distribution of cyclic GMP correlated with genetically active sites on the chromosomes. After heat-shock treatments, the intensity of cyclic GMP fluorescence was markedly enhanced at specific loci on the chromosomes, with locus 93D as the most intensely fluorescent. Autoradiographic analysis with [3H]uridine revealed that 93D was the most transcriptionally active locus within a particular nucleus. These observations suggest that cyclic GMP may participate in processes associated with transcription on polytene chromosomes. The involvement of cyclic GMP in nuclear events associated with gene expression is discussed. PMID:206901

Spruill, W A; Hurwitz, D R; Lucchesi, J C; Steiner, A L

1978-03-01

438

Creep, stress relaxation and biaxial ratchetting of type 304 stainless steel after cyclic preloading  

SciTech Connect

A series of tests for creep, stress relaxation, and biaxial ratchetting of type 304 stainless steel after cyclic preloading were carried out to investigate their interaction. The interesting fact was pointed out that back stress in cyclic plasticity played an important role to describe creep, relaxation, and biaxial ratchetting following cyclic preloading. Then, the test results showed that the material behavior due to creep after cyclic preloading could be represented by the modified Bailey-Norton law with stress levels evaluated from the current center of the yield surface, i.e., back stress which was determined by the hybrid constitutive model for cyclic plasticity proposed by the authors. In addition, biaxial ratchetting of axial strain induced by cyclic shear straining after cyclic preloading was expressed by the shear stress amplitude, the number of cycle and the axial stress level from the current center.

Ishikawa, Hiromasa; Sasaki, Katsuhiko (Hokkaido Univ., Sapporo (Japan). Dept. of Mechanical Engineering 2)

1994-04-01

439

Wnt Signaling Pathways Mediated by Ca2+ and Cyclic GMP  

NSDL National Science Digital Library

Wnts are secreted glycoprotein ligands that bind to and signal through Frizzleds, which are receptors of the seven-transmembrane, heterotrimeric guanine nucleotide-binding protein (G protein) -coupled receptor family. Wnt-Frizzled signaling is critical in a wide spectrum of developmental roles including cell fate, polarity, differentiation, migration, and proliferation. The Wnt family in mammals includes nearly 20 members and some, such as Wnt-4, -5A, and -11, activate Frizzleds that do not normally lead to the stabilization of intracellular concentrations of ?-catenin, but instead operate largely in a ?-catenin-independent manner. Studies (first in Xenopus and zebrafish, and later in mammalian cells) demonstrated that activation of Frizzled-2 by Wnt-5A stimulated the phosphatidylinositol pathway and an increase in intracellular Ca2+ concentration. Characterization of the proximal signaling revealed that Wnt-5A activates Frizzled-2, G proteins, and the G protein effector phospholipase C? (PLC?), stimulating an accumulation of intracellular inositol trisphosphate (IP3) and diacylglycerol (DAG). Elevation of IP3 leads to intracellular Ca2+ release and subsequent activation of Ca2+-calmodulin-dependent protein kinase II, as well as the calcium-sensitive protein phosphatase calcineurin. Elevation of intracellular DAG activates protein kinase C (PKC). These pathways allow Wnt-5A to regulate the activity of transcription factors that control those genes activated in response to Wnt-5A. The G protein Gt2 (known also as transducin2) and its effector, guanosine 3?,5?-monophosphate (cyclic GMP) phosphodiesterase, are activated also by the Wnt-Frizzled-2 pathway. The sharp decline in intracellular cyclic GMP, which can be blocked by selective cyclic GMP phosphodiesterase inhibitors, is required for Wnt-5A stimulation of primitive endoderm formation in mouse totipotent teratocarcinoma cells and Wnt-5A stimulation of early development in zebrafish embryos. Science Viewpoint H.-y. Wang, C. C. Malbon, Wnt signaling, Ca2+, and cyclic GMP: Visualizing Frizzled functions. Science 300, 1529-1530 (2003). [Abstract] [Full Text

Hsien-yu Wang (State University of New York at Stony Brook; REV)

2003-09-09

440

Cyclic ADP Ribose as a Calcium-Mobilizing Messenger  

NSDL National Science Digital Library

This Perspective by Galione and Churchill is one in a series on intracellular calcium release mechanisms. The authors review the evidence for cyclic adenosine diphosphate ribose (cADPR) being a second messenger involved in regulating intracellular calcium. In addition, the physiological stimuli and responses mediated by cADPR are discussed. The Perspective is accompanied by a movie showing a calcium wave triggered by cADPR.

Antony Galione (Department of Pharmacology; University of Oxford REV)

2000-07-18

441

Direct activation of cardiac pacemaker channels by intracellular cyclic AMP  

Microsoft Academic Search

CYCLIC AMP acts as a second messenger in the modulation of several ion channels1-9 that are typically controlled by a phosphorylation process10. In cardiac pacemaker cells, adrenaline and acetylcholine regulate the hyperpolarization-activated current (if), but in opposite ways; this current is involved in the generation and modulation of pacemaker activity11. These actions are mediated by cAMP and underlie control of

Dario Difrancesco; Paolo Tortora

1991-01-01

442

CYCLIC TRINUCLEAR GOLD(I) COMPOUNDS: SYNTHESIS, STRUCTURES AND  

E-print Network

CYCLIC TRINUCLEAR GOLD(I) COMPOUNDS: SYNTHESIS, STRUCTURES AND SUPRAMOLECULAR ACID-BASE p Tl(I) and Ag(I). The acidic, neutral [Hg(C6F4)3]3 interacts with TR(carb) and TR(bzim) as seen by X-ray solid state and solution NMR measurements. Recently it has been shown that the neutral pi acids C6F6

Abdou, Hanan E.

443

Analysis Of The Interface Behavior Under Cyclic Loading  

SciTech Connect

This paper analyses the frictional behavior between soil and structures under cyclic loading conditions. In particular, the attention is focused on the stress degradation occurring in sand-metal interface tests and on the relevant parameters playing a role in such kind of tests. Also, the paper reports the analysis of the experimental data from the constitutive point of view with a two-surface elastoplastic model.

Mortara, Giuseppe [Department of Mechanics and Materials, University of Reggio Calabria (Italy)

2008-07-08

444

Optimizing Incremental Maintenance of Minimal Bisimulation of Cyclic Graphs  

Microsoft Academic Search

\\u000a Graph-structured databases have numerous recent applications including the Semantic Web, biological databases and XML, among\\u000a many others. In this paper, we study the maintenance problem of a popular structural index, namely bisimulation, of a possibly cyclic data graph. In comparison, previous work mainly focuses on acyclic graphs. In the context of database applications, it is\\u000a natural to compute minimal bisimulation

Jintian Deng; Byron Choi; Jianliang Xu; Sourav S. Bhowmick

2011-01-01

445

More on Scheduling Block-Cyclic Array Redistribution  

Microsoft Academic Search

This article is devoted to the run-time redistribution of one-dimensional arrays that are distributedin a block-cyclic fashion over a processor grid. In a previous paper [2], we have reportedhow to derive optimal schedules made up of successive communication-steps. In this paper weassume that successive steps may overlap. We show how to obtain an optimal scheduling forthe most general case, namely,

Frederic Desprez; Stphane Domas; Jack Dongarra; Antoine Petitet; Cyril Randriamaro; Yves Robert

1998-01-01

446

Cyclic nucleotides in tissues during long-term hypokinesia  

NASA Technical Reports Server (NTRS)

Male Wistar rates were kept hypokinetic by placing them in small containers for 22 days. Blood plasma cAMP content was subsequently found increased, and cGMP content decreased, in the experimental animals. Liver and thymus cAMP content was similar in the control and experimental animals. There was a 20 and 38% decrease of cAMP content in the kidneys and spleen, respectively. Hypokinesia's reduction of cyclic nucleotides seems to inhibit RNA and protein synthesis.

Makeyeva, V. F.; Komolova, G. S.; Yegorov, I. A.; Serova, L. V.; Chelnaya, N. A.

1981-01-01

447

Design of tetraplex specific ligands: cyclic naphthalene diimide.  

PubMed

Cyclic naphthalene diimide 1 bound to hybrid-type tetraplex DNA from 5'-AGGG(TTAGGG)3-3' (K = 8.6 10(6) M(-1)) with 260-fold greater affinity than binding to a double stranded oligonucleotide consisting of 5'-GGG AGG TTT CGC-3' and 3'-CCC TCC AAA GCG-5' (nK = 3.3 10(4) M(-1)) with 0.5 ?M of IC50 for telomerase activity. PMID:24752309

Esaki, Yugo; Islam, Md Monirul; Fujii, Satoshi; Sato, Shinobu; Takenaka, Shigeori

2014-06-01

448

About the diversity in cyclic prefixed single-carrier systems  

Microsoft Academic Search

This paper analyzes to what extent the multipath diversity is extracted by a cyclic prefixed single-carrier (CPSC) transmission. The state-of-the-art is currently pessimistic on that issue, and has to be moderated: if it is true that the asymptotical, i.e.at infinite signal to noise ratio (SNR), diversity order achieved by CPSC is equal to one, we prove that the block size

Bertrand Devillers; Jrme Louveaux; Luc Vandendorpe

2008-01-01

449

Intestinal amebiasis: cyclic suppression of the immune response  

Microsoft Academic Search

The cellular immune response was evaluated in a C3H\\/HeJ mouse model of intestinal amebiasis at 560 days postinoculation withEntamoeba histolytica. At various intervals, spleen lymphocytes were obtained from infected and noninfected control mice and cultured with concanavalin A (Con A), pokeweed mitogen (PWM), or ameba antigen.E. histolytica infection induced a cyclic depression of DNA synthesis when spleen lymphocytes were stimulated

Prabir K. Ghosh; Carlos Castellanos-Barba; Librado Ortiz-Ortiz

1995-01-01

450

A different look on cyclic prefix for SC\\/FDE  

Microsoft Academic Search

We investigate the use of a known symbol sequence - a so-called unique word (UW) - instead of the well-known cyclic prefix (as it is used in OFDM, orthogonal frequency division multiplexing, systems) for a single carrier system with frequency domain equalization (SC\\/FDE). The considered SC\\/FDE system is similar to the one proposed in the IEEE 802.16.3c target group. It

H. Witschnig; T. Mayer; A. Springer; A. Koppler; L. Maurer; M. Huemer; R. Weigel

2002-01-01

451

Three-dimensional stable matching with cyclic preferences  

Microsoft Academic Search

We consider stable three-dimensional matchings of three genders (3GSM). Alkan [Alkan, A., 1988. Non-existence of stable threesome matchings. Mathematical Social Sciences 16, 207209] showed that not all instances of 3GSM allow stable matchings. Boros et al. [Boros, E., Gurvich, V., Jaslar, S., Krasner, D., 2004. Stable matchings in three-sided systems with cyclic preferences. Discrete Mathematics 286, 110] showed that if

Kimmo Eriksson; Jonas Sjstrand; Pontus Strimling

2006-01-01

452

Effects of Cyclic Intraocular Pressure on Conventional Outflow Facility  

PubMed Central

Purpose In vivo, biomechanical stress plays an important role in tissue physiology and pathology, affecting cell and tissue behavior. Even though conventional outflow tissues are constantly exposed to dynamic changes in intraocular pressure, effects of such biomechanical stressors on outflow function have not been analyzed. The purpose of the present study was to determine the effect(s) of ocular pulse on conventional outflow facility in perfused anterior segments. Methods The anterior segment perfusion model was used to investigate the impact of ocular pulsation on human and porcine outflow facility. To determine tissue viability of human anterior segments, three complementary techniques (postperfusion morphology and cell density of outflow tissues plus central corneal thickness measurements over time of perfusion) were used. Results A consistent decrease in outflow facility was observed in response to cyclic intraocular pressure in both porcine (?29.96% 6.56; P = 0.009) and human (?27.65% 8.26; P = 0.010) perfused anterior segments. Viability data showed no significant difference between control and experimental anterior segments, with respect to postperfusion histologic evaluations (P = 0.227) or change in central corneal thickness over time (P = 0.289). In contrast, the cellularity of the trabecular meshwork in experimental (cyclically pulsed) anterior segments (333.86 22.15 nuclei/field of view) was greater than in the control eyes (290.47 17.60, P = 0.05). Conclusions Decreased outflow facility in cyclically pulsed anterior segments is not a function of cell or tissue damage, but rather is an active response of the conventional outflow tissues to a biomechanical stimulus. In fact, the observation of increased cellularity in tissues exposed to cyclic stress suggests a physiological benefit of mechanical stress to outflow cells in organ culture. PMID:18172103

Ramos, Renata F.; Stamer, W. Daniel

2008-01-01

453

Cyclic pulse coding for hybrid fast BOTDA/Raman sensor  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a fully hybrid distributed sensing scheme that uses a single narrow-band laser to perform fast measurement of the BFS using BOTDA and simultaneous temperature measurement based on spontaneous Raman scattering over 10 km of single mode fiber. The use of cyclic pulse coding effectively reduces the pump peak power levels required for accurate Raman-based distributed temperature measurement, enhancing at the same time the speed of the BFS measurement in the BOTDA technique.

Muanenda, Yonas; Taki, Mohammad; Toccafondo, Iacopo; Signorini, Alessandro; Nannipieri, Tiziano; Oton, Claudio J.; Di Pasquale, Fabrizio

2014-05-01

454

Enhanced catalyst stability for cyclic co methanation operations  

DOEpatents

Carbon monoxide-containing gas streams are passed over a catalyst to deposit a surface layer of active surface carbon thereon essentially without the formation of inactive coke. The active carbon is thereafter reacted with steam or hydrogen to form methane. Enhanced catalyst stability for long term, cyclic operation is obtained by the incorporation of an alkali or alkaline earth dopant in a silica binding agent added to the catalyst-support additive composition.

Risch, Alan P. (New Fairfield, CT); Rabo, Jule A. (Armonk, NY)

1983-01-01

455

Viscometry study of ethylenecyclic olefin copolymers  

Microsoft Academic Search

Viscometric measurements, in varied conditions, were performed with commercial and synthesized samples of cyclic olefin copolymers (COC), based on ethylene and norbornene. High density polyethylenes (HDPE) samples were also analysed for comparison purposes. Five different equations were used to calculate intrinsic viscosities and viscometric constant values: Huggins, Kraemer, SchulzBlaschke, by graphic extrapolation, and SolomonCiuta, DebChanterjee and again SchulzBlaschke, through a

Marcia C Delpech; Fernanda M. B Coutinho; Maria Eunice S Habibe

2002-01-01

456

Static and cyclic loading of fiber-reinforced dental resin  

Microsoft Academic Search

Objective: The aim of this study was to evaluate the flexure strength of unidirectional fiber-reinforced resins under static and cyclic loading with and without thermal cycling.Methods: The fiber-reinforced resin materials chosen for this project were commercially available endodontic posts and commercially procured bar samples. For all materials, controls for flexure strength were tested in air and in water using three-point

James L Drummond; Mahendra S Bapna

2003-01-01

457

Biosynthesis of cyclic bis(bibenzyls) in Marchantia polymorpha  

Microsoft Academic Search

Using sterile thallus tissue of Marchantia polymorpha, the biosynthesis of the cyclic bis(bibenzyl) marchantin A was investigated. The synthesis of the radioactively and 13C-labelled precursors for the application experiments is described. Feeding experiments showed that rings A and C of the marchantin molecule are derived from the benzene ring of l-phenylalanine via trans-cinnamic acid and p-coumaric acid. Further application of

Susanne Friederich; Ulrich H Maier; Brigitte Deus-Neumann; Yoshinori Asakawa; Meinhart H. Zenk

1999-01-01

458

Menstrual Cyclicity After Metformin Therapy in Polycystic Ovary Syndrome  

Microsoft Academic Search

Objective: To assess the effect of insulin-lowering treatment on menstrual cyclicity in polycystic ovary syndrome (PCOS).Methods: Forty oligoamenorrheic women with PCOS were recruited in a prospective clinical study to receive metformin for a minimum period of 6 months. Twenty-two women completed the study. Serum LH, FSH, free testosterone, and glucose and insulin response to oral glucose load were measured both

Elsy Velzquez M; Arnaldo Acosta; Soaira G Mendoza

1997-01-01

459

A cyclic nucleotide-gated conductance in olfactory receptor cilia  

Microsoft Academic Search

Olfactory transduction is thought to be initiated by the binding of odorants to specific receptor proteins in the cilia of olfactory receptor cells (reviewed in refs 1-3). The mechanism by which odorant binding could initiate membrane depolarization is unknown, but the recent discovery of an odorant-stimulated adenylate cyclase in purified olfactory cilia4,5 suggests that cyclic AMP may serve as an

Tadashi Nakamura; Geoffrey H. Gold

1987-01-01

460

Vasorelaxant activity of cyclic peptide, cyclosquamosin B, from Annona squamosa  

Microsoft Academic Search

A cyclic octapeptide, cyclosquamosin B (2), isolated from the seeds of Annona squamosa showed a vasorelaxant effect on rat aorta. It showed a slow relaxation activity against norepinephrine (NE)-induced contractions of rat aorta with\\/without endothelium. It showed inhibition effect on vasocontraction of depolarized aorta with high concentration potassium, but moderately inhibition effect on NE-induced contraction in the presence of nicardipine.

Hiroshi Morita; Toru Iizuka; Chee-Yan Choo; Kit-Lam Chan; Koichi Takeya; Junichi Kobayashi

2006-01-01

461

Analysis of elevated temperature cyclic deformation of austenitic stainless steels  

Microsoft Academic Search

The stress relaxation behavior of 304 and 316 stainless steels during cyclic deformation at 538 and 650°C with various hold times and strain amplitudes has been analyzed in terms of a power-law equation of state which includes internal stress and drag stress as structure variables. At 650°C the internal sress in 304 appears to be zero and microstructural recovery plays

R. W. Rohde; J. C. Swearengen

1977-01-01

462

On the construction of skew quasi-cyclic codes  

Microsoft Academic Search

In this paper, we study a special type of quasi-cyclic (QC) codes called skew QC codes. This set of codes is constructed using a noncommutative ring called the skew polynomial ring F[x;]. After a brief description of the skew polynomial ring F[x;], it is shown that skew QC codes are left submodules of the ring Rsl=( F[x;]\\/(xs-1) )l. The notions

Taher Abualrub; Ali Ghrayeb; Nuh Aydin; Irfan Siap

2010-01-01

463

Conformationally constrained cyclic peptides: powerful scaffolds for asymmetric catalysis.  

PubMed

Cyclic peptides containing a disulfide bridge were identified as a simple and versatile coordination sphere for asymmetric catalysis. Upon complexation with Cu(2+) ions they catalyze Diels-Alder and Friedel-Crafts reactions with high enantioselectivities of up to 99%?ee and 86%?ee, respectively. Moreover, the peptides ligands were systematically optimized with the assistance of "Alanine Scanning". This biomolecular design could greatly expand the choice of peptide scaffolds for artificial metallopeptide catalysts. PMID:24898630

Zheng, Lifei; Marcozzi, Alessio; Gerasimov, Jennifer Y; Herrmann, Andreas

2014-07-14

464

Adjustable-Length Strut Withstands Large Cyclic Loads  

NASA Technical Reports Server (NTRS)

Adjustable-length strut designed for installation in structure subjected to large cyclic loads. Partly resembles large turnbuckle: includes oppositely threaded eyebolts engaging correspondingly threaded holes at opposite ends of shaft, and shaft turned to adjust length. However, unlike in turnbuckle, length setting not fixed by use of simple jam nuts: instead, length setting fixed by use of more complex threaded-end flanges partly resembling jam nuts but function somewhat differently.

Carner, Fred P.

1995-01-01

465

APT accelerator. Topical report  

SciTech Connect

The Accelerator Production of Tritium (APT) project, sponsored by Department of Energy Defense Programs (DOE/DP), involves the preconceptual design of an accelerator system to produce tritium for the nation`s stockpile of nuclear weapons. Tritium is an isotope of hydrogen used in nuclear weapons, and must be replenished because of radioactive decay (its half-life is approximately 12 years). Because the annual production requirements for tritium has greatly decreased since the end of the Cold War, an alternative approach to reactors for tritium production, based on a linear accelerator, is now being seriously considered. The annual tritium requirement at the time this study was undertaken (1992-1993) was 3/8 that of the 1988 goal, usually stated as 3/8-Goal. Continued reduction in the number of weapons in the stockpile has led to a revised (lower) production requirement today (March, 1995). The production requirement needed to maintain the reduced stockpile, as stated in the recent Nuclear Posture Review (summer 1994) is approximately 3/16-Goal, half the previous level. The Nuclear Posture Review also requires that the production plant be designed to accomodate a production increase (surge) to 3/8-Goal capability within five years, to allow recovery from a possible extended outage of the tritium plant. A multi-laboratory team, collaborating with several industrial partners, has developed a preconceptual APT design for the 3/8-Goal, operating at 75% capacity. The team has presented APT as a promising alternative to the reactor concepts proposed for Complex-21. Given the requirements of a reduced weapons stockpile, APT offers both significant safety, environmental, and production-fexibility advantages in comparison with reactor systems, and the prospect of successful development in time to meet the US defense requirements of the 21st Century.

Lawrence, G.; Rusthoi, D. [comp.] [ed.

1995-03-01

466

VLHC accelerator physics  

SciTech Connect

A six-month design study for a future high energy hadron collider was initiated by the Fermilab director in October 2000. The request was to study a staged approach where a large circumference tunnel is built that initially would house a low field ({approx}2 T) collider with center-of-mass energy greater than 30 TeV and a peak (initial) luminosity of 10{sup 34} cm{sup -2}s{sup -1}. The tunnel was to be scoped, however, to support a future upgrade to a center-of-mass energy greater than 150 TeV with a peak luminosity of 2 x 10{sup 34} cm{sup -2} sec{sup -1} using high field ({approx} 10 T) superconducting magnet technology. In a collaboration with Brookhaven National Laboratory and Lawrence Berkeley National Laboratory, a report of the Design Study was produced by Fermilab in June 2001. 1 The Design Study focused on a Stage 1, 20 x 20 TeV collider using a 2-in-1 transmission line magnet and leads to a Stage 2, 87.5 x 87.5 TeV collider using 10 T Nb{sub 3}Sn magnet technology. The article that follows is a compilation of accelerator physics designs and computational results which contributed to the Design Study. Many of the parameters found in this report evolved during the study, and thus slight differences between this text and the Design Study report can be found. The present text, however, presents the major accelerator physics issues of the Very Large Hadron Collider as examined by the Design Study collaboration and provides a basis for discussion and further studies of VLHC accelerator parameters and design philosophies.

Michael Blaskiewicz et al.

2001-11-01

467

Cyclic Prefix Signaling for Pulse Shape Modulation UWB RAKE Receivers  

NASA Astrophysics Data System (ADS)

Combining transmission of ultra wideband pulses, organized in blocks, with the inclusion of cyclic prefixing pulses yields a pulsewidth periodic signal at the receiver. Although unknown, this signal fits perfectly the diversity exploitive architecture of a RAKE receiver. Aiming to profit from this signal arrangement, we propose a pulse shape modulation system employing a RAKE receiver that estimates this periodic signal during a training interval and uses the estimated values for detection of data symbols. Our proposal relies on the invariability of the multipath propagation channel during the transmission of a UWB packet, the adequate application of the cyclic prefix, and the fact that different transmitted pulses result in different periodic signals at the receiver. This system is equivalent to transforming the multipath nature of the UWB propagation channel into a multichannel digital communications affected solely by additive noise. Our proposal is important because it ameliorates the performance of a pulse shape modulation RAKE receiver. On the other hand, the cost of our proposed system resides in the inefficiencies product of the cyclic prefix inclusion.

Cartagena Gordillo, Alex; Kohno, Ryuji

468

Cyclic process for producing methane with catalyst regeneration  

DOEpatents

Carbon monoxide-containing gas streams are passed over a catalyst capable of catalyzing the disproportionation of carbon monoxide so as to deposit a surface layer of active surface carbon on the catalyst essentially without formation of inactive coke thereon. The surface layer is contacted with steam and is thus converted to methane and CO.sub.2, from which a relatively pure methane product may be obtained. For practical commercial operations utilizing the two-step process of the invention of a cyclic basis, nickel, cobalt, ruthenium, thenium and alloys thereof are especially prepared for use in a metal state, with CO disproportionation being carried out at temperatures up to about 350.degree. C. and with the conversion of active surface carbon to methane being carried out by reaction with steam. The catalyst is employed in such cyclic operations without the necessity for employing a regeneration step as part of each processing cycle. Inactive carbon or coke that tends to form on the catalyst over the course of continuous operations utilizing such cyclic process is effectively and advantageously removed, on a periodic basis, in place of conventional burn off with an inert stream containing a low concentration of oxygen.

Frost, Albert C. (Congers, NY); Risch, Alan P. (New Fairfield, CT)

1980-01-01

469

Self-Assembled Surfactant Cyclic Peptide Nanostructures as Stabilizing Agents  

PubMed Central

A number of cyclic peptides including [FR]4, [FK]4, [WR]4, [CR]4, [AK]4, and [WK]n (n = 3-5) containing L-amino acids were produced using solid-phase peptide synthesis. We hypothesized that an optimal balance of hydrophobicity and charge could generate self-assembled nanostructures in aqueous solution by intramolecular and/or intermolecular interactions. Among all the designed peptides, [WR]n (n = 3-5) generated self-assembled vesicle-like nanostructures at room temperature as shown by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and/or dynamic light scattering (DLS). This class of peptides represents the first report of surfactant-like cyclic peptides that self-assemble into nanostructures. A plausible mechanistic insight into the self-assembly of [WR]5 was obtained by molecular modeling studies. Modified [WR]5 analogues, such as [WMeR]5, [WR(Me)2]5, [WMeR(Me)2]5, and [WdR]5, exhibited different morphologies to [WR]5 as shown by TEM observations. [WR]5 exhibited a significant stabilizing effect for generated silver nanoparticles and glyceraldehyde-3-phosphate dehydrogenase activity. These studies established a new class of surfactant-like cyclic peptides that self-assembled into nanostructures and could have potential applications for the stabilization of silver nanoparticles and protein biomolecules. PMID:24187575

Mandal, Dindyal; Oh, Donghoon; Ye, Guofeng; Banerjee, Antara; Yadav, Arpita; Parang, Keykavous

2013-01-01

470

Low severity coal liquefaction promoted by cyclic olefins  

SciTech Connect

Low severity coal liquefaction allows for solubilization of coal with reduced gas make. These lower severity conditions may result in some selective bond rupture. Promotion of coal solubilization through hydrogen transfer using highly active and effective hydrogen donors is the objective of this study. The highly effective donors being tested are cyclic olefins. Representative cyclic olefins are isotetralin, which is 1,4,5,8-tetrahydronaphthalene, and 1,4,5,8,9,10-hexahydroanthracene. These compounds are hydroaromatics without aromatic rings and have been shown to be highly effective donors. The objective of the work performed in this study during this quarter was to evaluate reaction parameters for low severity liquefaction reactions using the cyclic olefin, hexahydroanthracene, and the aromatic, anthracene. These model compounds were reacted under a variety of conditions to evaluate their reactivity without coal. The reactions were performed under both thermal and catalytic conditions. Finely divided catalysts from different molybdenum precursors were used to determine their activity in promoting hydrogenation and hydrogen transfer at low severity conditions. The catalysts used were Molyvan L, sulfurized oxymolybdenum dithiocarbamate, molybdenum naphthenate, and Molyvan 822, organo molybdenum dithiocarbamate.

Curtis, C.W.

1992-07-27

471

Modeling Step-Strain Relaxation and Cyclic Deformations of Elastomers  

NASA Technical Reports Server (NTRS)

Data for step-strain relaxation and cyclic compressive deformations of highly viscous short elastomer cylinders are modeled using a large strain rubber viscoelastic constitutive theory with a rate-independent friction stress term added. In the tests, both small and large amplitude cyclic compressive strains, in the range of 1% to 10%, were superimposed on steady state compressed strains, in the range of 5% to 20%, for frequencies of 1 and 10 Hz. The elastomer cylinders were conditioned prior to each test to soften them. The constants in the viscoclastic-friction constitutive theory are determined by employing a nonlinear least-squares method to fit the analytical stresses for a Maxwell model, which includes friction, to measured relaxation stresses obtained from a 20% step-strain compression test. The simulation of the relaxation data with the nonlinear model is successful at compressive strains of 5%, 10%, 15%, and 20%. Simulations of hysteresis stresses for enforced cyclic compressive strains of 20% +/- 5% are made with the model calibrated by the relaxation data. The predicted hysteresis stresses are lower than the measured stresses.

Johnson, A.R.; Mead, J. L.

2000-01-01

472

From pairwise to group interactions in games of cyclic dominance  

NASA Astrophysics Data System (ADS)

We study the rock-paper-scissors game in structured populations, where the invasion rates determine individual payoffs that govern the process of strategy change. The traditional version of the game is recovered if the payoffs for each potential invasion stem from a single pairwise interaction. However, the transformation of invasion rates to payoffs also allows the usage of larger interaction ranges. In addition to the traditional pairwise interaction, we therefore consider simultaneous interactions with all nearest neighbors, as well as with all nearest and next-nearest neighbors, thus effectively going from single pair to group interactions in games of cyclic dominance. We show that differences in the interaction range affect not only the stationary fractions of strategies but also their relations of dominance. The transition from pairwise to group interactions can thus decelerate and even revert the direction of the invasion between the competing strategies. Like in evolutionary social dilemmas, in games of cyclic dominance, too, the indirect multipoint interactions that are due to group interactions hence play a pivotal role. Our results indicate that, in addition to the invasion rates, the interaction range is at least as important for the maintenance of biodiversity among cyclically competing strategies.

Szolnoki, Attila; Vukov, Jeromos; Perc, Matja

2014-06-01

473

Introduction to Korean Accelerator Science and Activities in Industrial Accelerators  

NASA Astrophysics Data System (ADS)

After 20 years of the first large-scale accelerator in Korea, the Pohang Light Source (PLS) of 2.0 GeV at POSTECH, its upgrade (PLS-II) is now under commissioning with energy of 3.0 GeV. The users' service for synchrotron radiation is scheduled in April 2012. There are five big accelerator projects in various stages of construction, namely a high-intensity proton linac of 100 MeV, the PAL-XFEL of 10-GeV, a carbon therapy cyclotron of 400 MeV/u, and rare isotope accelerators for isotope separator on-line (ISOL) and In-flight Fragmentation (IFF). There are also strong demands for industrial uses of accelerators, especially in sterilization applications. In this paper, we report the current status of accelerator projects and its science in Korea, along with a brief review of accelerator R&D going back to the early 1960s at universities.

Namkung, Won

2012-03-01

474

Accelerating Commercial Remote Sensing  

NASA Technical Reports Server (NTRS)

Through the Visiting Investigator Program (VIP) at Stennis Space Center, Community Coffee was able to use satellites to forecast coffee crops in Guatemala. Using satellite imagery, the company can produce detailed maps that separate coffee cropland from wild vegetation and show information on the health of specific crops. The data can control coffee prices and eventually may be used to optimize application of fertilizers, pesticides and irrigation. This would result in maximal crop yields, minimal pollution and lower production costs. VIP is a mechanism involving NASA funding designed to accelerate the growth of commercial remote sensing by promoting general awareness and basic training in the technology.

1995-01-01

475

Accelerated Degradation of Polymers  

NSDL National Science Digital Library

For this laboratory exercise, you will monitor changes in the visual appearance of the samples, chemical changes and molecular weight changes as a function of exposure condition. Analysis of the neat and degraded systems will be done using visual evaluation, FTIR analysis and GPC analysis. After in-class presentation, completion of hands-on laboratory experiment and review of the information provided, you should be able to: Confidently discuss the mechanism of breakdown for a polymeric material exposed to various environmental conditions. Prepare samples and record an accurate account of their preparation for use in an outdoor environment and in an accelerated weathering chamber (Q-sun).

DeRosa, Rebecca L.

2008-09-26

476

Kinematics: Speed, Velocity & Acceleration  

NSDL National Science Digital Library

The following resource is a NFL sponsored, National Science Foundation funded program intended to teach students about scientific concepts by using the popular sport of Football. Each lesson is accompanied by an informative and fast paced video. In this lesson, students will explore kinematics on the playing field. NSF-funded scientists Tony Schmitz from the University of Florida and John Ziegert of Clemson University explain how the kinematic concepts of position, velocity and acceleration can be used to define how a running back moves.

2010-01-01

477

Accelerated Innovation Pilot  

NASA Technical Reports Server (NTRS)

Opportunities: I. Engage NASA team (examples) a) Research and technology calls . provide suggestions to AES, HRP, OCT. b) Use NASA@Work to solicit other ideas; (possibly before R+D calls). II. Stimulate collaboration (examples) a) NHHPC. b) Wharton Mack Center for Technological Innovation (Feb 2013). c) International ] DLR ] :envihab (July 2013). d) Accelerated research models . NSF, Myelin Repair Foundation. III. Engage public Prizes (open platform: InnoCentive, yet2.com, NTL; Rice Business Plan, etc.) IV. Use same methods to engage STEM.

Davis, Jeffrey

2012-01-01

478

Precipitation under cyclic strain in solution-treated Al4wt%Cu I: mechanical behavior  

SciTech Connect

Solution-treated AL-4wt%Cu was strain-cycled at ambient temperature and above, and the precipitation and deformation behaviors investigated by TEM. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy super-saturation generated by cyclic strain and the presence of a continually refreshed dislocation density to provide heterogeneous nucleation sites. Texture effects as characterized by Orientation Imaging Microscopy appear to be responsible for latent hardening in specimens tested at room temperature, with increasing temperatures leading to a gradual hardening throughout life due to precipitation. Specimens exhibiting rapid precipitation hardening appear to show a greater effect of texture due to the increased stress required to cut precipitates in specimens machined from rolled plate at an angle corresponding to a lower average Schmid factor. The accelerated formation of grain boundary precipitates appears to be partially responsible for rapid inter-granular fatigue failure at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

Farrow, Adam M [Los Alamos National Laboratory; Laird, Campbell [UNIV OF PENNSYLVANIA

2008-01-01

479

Successful completion of a cyclic ground test of a mercury ion auxiliary propulsion system  

NASA Technical Reports Server (NTRS)

An engineering model Ion Auxiliary Propulsion System (IAPS) 8-cm thruster (S/N 905) has completed a life test at NASA Lewis Research Center. The mercury ion thruster successfully completed and exceeded the test goals of 2557 on/off cycles and 7057 hr of operation at full thrust. The final 1200 cycles and 3600 hr of the life test were conducted using an engineering model of the IAPS power electronics unit (PEU) and breadboard digital controller and interface unit (DCIU). This portion of the test is described in this paper with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were constant throughout the test with only minor variations. The engineering model power electronics unit operated without malfunction; the flight software in the digital controller and interface unit was exercised and verified. Post-test inspection of the thruster revealed facility enhanced accelerator grid erosion but overall the thruster was in good condition. It was concluded that the thruster performance was not drastically degraded by time or cycles. Additional cyclic testing is currently under consideration.

Francisco, David R.; Low, Charles A., Jr.; Power, John L.

1988-01-01

480

One-pot conversions of olefins to cyclic carbonates and secondary allylic and homoallylic amines to cyclic carbamates.  

PubMed

Sequential treatment of a 1,2-disubstituted olefin with m-CPBA, Br3CCO2H, and DBU results in the one-pot, stereospecific conversion of the olefin to the corresponding disubstituted cyclic carbonate (1,3-dioxolan-2-one). The reaction proceeds via an initial epoxidation followed by S(N)2-type epoxide ring opening by Br3CCO2H and subsequent base-promoted carbonate formation upon elimination of bromoform. When a solution of a secondary allylic or homoallylic amine and Br3CCO2H is sequentially treated with m-CPBA then DBU, the product of the reaction is a cyclic carbamate (1,3-oxazolidin-2-one or 1,3-oxazinan-2-one). PMID:20954691

Davies, Stephen G; Fletcher, Ai M; Kurosawa, Wataru; Lee, James A; Poce, Giovanna; Roberts, Paul M; Thomson, James E; Williamson, David M

2010-11-19

481

Effects of Cyclic Loading on the Uniaxial Behavior of Nitinol  

NASA Astrophysics Data System (ADS)

The widespread development and use of implants made from NiTi is accompanied by the publication of many NiTi material characterization studies. These publications have increased significantly the knowledge about the mechanical properties of NiTi. However, this knowledge also increased the complexity of the numerical simulation of NiTi implants or devices. This study is focused on the uniaxial behavior of NiTi tubing due to cyclic loading and had the goal to deliver both precise and application-oriented results. Single aspects of this study have already been published (Wagner in Ein Beitrag zur strukturellen und funktionalen Ermdung von Drhten und Federn aus NiTi-Formgedaechtnislegierungen, Ph.D. Thesis, 2005; Eucken and Duerig in Acta Metall 37:2245-2252, 1989; Yawny et al. in Z Metallkd 96:608-618, 2005); however, there is no publication known that shows all the single effects combined in a "duty cycle case." It was of particular importance to summarize the main effects of pre-strain and subsequent small or large strain amplitudes on the material properties. The phenomena observed were captured in an extended Abaqus Nitinol material model, presented by Rebelo et al. (A Material Model for the Cyclic Behavior of Nitinol, SMST Extended Abstracts 2010). The cyclic tensile tests were performed using a video extensometer to obtain accurate strain measurement on small electro-polished dog-bone specimen that were incorporated into a stent framework so that standard manufacturing methods could be used for the fabrication. This study indicates that a prestrain beyond 6% strain alters the transformation plateaus and if the cyclic displacement amplitude is large enough, additional permanent deformations are observed, the lower plateau and most notably the upper plateau change. The changes to the upper plateau are very interesting in the sense that an additional stress plateau develops: its "start stress" is lowered thereby creating a new plateau up to the highest level of cyclic strain, followed by resuming the original plateau until full transformation. This study was conducted in the course of the work of a consortium of several stent manufacturers, SAFE Technology Limited and Dassault Systmes Simulia Corp., dedicated to the development of fatigue laws suitable for life prediction of Nitinol devices.

Schlun, M.; Zipse, A.; Dreher, G.; Rebelo, N.

2011-07-01

482

Accelerating the loop expansion  

SciTech Connect

This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

Ingermanson, R.

1986-07-29

483

Broadband accelerator control network  

SciTech Connect

A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating system has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel.

Skelly, J.; Clifford, T.; Frankel, R.

1983-01-01

484

Particle acceleration in pulsar magnetospheres  

NASA Technical Reports Server (NTRS)

The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.

Baker, K. B.

1978-01-01

485

Magnetic Insulation for Electrostatic Accelerators  

NASA Astrophysics Data System (ADS)

The voltage gradient which can be sustained between electrodes without electrical breakdowns is usually one of the most important parameters in determining the performance which can be obtained in an electrostatic accelerator. We have recently proposed a technique which might permit reliable operation of electrostatic accelerators at higher electric field gradients, perhaps also with less time required for the conditioning process in such accelerators. The idea is to run an electric current through each accelerator stage so as to produce a magnetic field which envelopes each electrode and its electrically conducting support structures. Having the magnetic field everywhere parallel to the conducting surfaces in the accelerator should impede the emission of electrons, and inhibit their ability to acquire energy from the electric field, thus reducing the chance that local electron emission will initiate an arc. A relatively simple experiment to assess this technique is being planned. If successful, this technique might eventually find applicability in electrostatic accelerators for fusion and other applications.

Grisham, L. R.

2011-09-01

486

Laser acceleration and its future  

PubMed Central

Laser acceleration is based on the concept to marshal collective fields that may be induced by laser. In order to exceed the material breakdown field by a large factor, we employ the broken-down matter of plasma. While the generated wakefields resemble with the fields in conventional accelerators in their structure (at least qualitatively), it is their extreme accelerating fields that distinguish the laser wakefield from others, amounting to tiny emittance and compact accelerator. The current research largely falls on how to master the control of acceleration process in spatial and temporal scales several orders of magnitude smaller than the conventional method. The efforts over the last several years have come to a fruition of generating good beam properties with GeV energies on a table top, leading to many applications, such as ultrafast radiolysis, intraoperative radiation therapy, injection to X-ray free electron laser, and a candidate for future high energy accelerators. PMID:20228616

Tajima, Toshiki

2010-01-01

487

Magnetic Insulation for Electrostatic Accelerators  

SciTech Connect

The voltage gradient which can be sustained between electrodes without electrical breakdowns is usually one of the most important parameters in determining the performance which can be obtained in an electrostatic accelerator. We have recently proposed a technique which might permit reliable operation of electrostatic accelerators at higher electric field gradients, perhaps also with less time required for the conditioning process in such accelerators. The idea is to run an electric current through each accelerator stage so as to produce a magnetic field which envelopes each electrode and its electrically conducting support structures. Having the magnetic field everywhere parallel to the conducting surfaces in the accelerator should impede the emission of electrons, and inhibit their ability to acquire energy from the electric field, thus reducing the chance that local electron emission will initiate an arc. A relatively simple experiment to assess this technique is being planned. If successful, this technique might eventually find applicability in electrostatic accelerators for fusion and other applications.

Grisham, L. R. [Princeton Plasma Physics Laboratory, P. O. Box 451, Princeton, New Jersey 08543 (United States)

2011-09-26

488

Activation of the adenylyl cyclase/cyclic AMP/protein kinase A pathway in endothelial cells exposed to cyclic strain  

NASA Technical Reports Server (NTRS)

The aim of this study was to assess the involvement of the adenylyl cyclase/cyclic AMP/protein kinase A pathway (AC) in endothelial cells (EC) exposed to different levels of mechanical strain. Bovine aortic EC were seeded to confluence on flexible membrane-bottom wells. The membranes were deformed with either 150 mm Hg (average 10% strain) or 37.5 mm Hg (average 6% strain) vacuum at 60 cycles per minute (0.5 s strain; 0.5 s relaxation) for 0-60 min. The results demonstrate that at 10% average strain (but not 6% average strain) there was a 1.5- to 2.2-fold increase in AC, cAMP, and PKA activity by 15 min when compared to unstretched controls. Further studies revealed an increase in cAMP response element binding protein in EC subjected to the 10% average strain (but not 6% average strain). These data support the hypothesis that cyclic strain activates the AC/cAMP/PKA signal transduction pathway in EC which may occur by exceeding a strain threshold and suggest that cyclic strain may stimulate the expression of genes containing cAMP-responsive promoter elements.

Cohen, C. R.; Mills, I.; Du, W.; Kamal, K.; Sumpio, B. E.

1997-01-01

489

Evaluation of the gas production economics of the gas hydrate cyclic thermal injection model. [Cyclic thermal injection  

SciTech Connect

The objective of the work performed under this directive is to assess whether gas hydrates could potentially be technically and economically recoverable. The technical potential and economics of recovering gas from a representative hydrate reservoir will be established using the cyclic thermal injection model, HYDMOD, appropriately modified for this effort, integrated with economics model for gas production on the North Slope of Alaska, and in the deep offshore Atlantic. The results from this effort are presented in this document. In Section 1, the engineering cost and financial analysis model used in performing the economic analysis of gas production from hydrates -- the Hydrates Gas Economics Model (HGEM) -- is described. Section 2 contains a users guide for HGEM. In Section 3, a preliminary economic assessment of the gas production economics of the gas hydrate cyclic thermal injection model is presented. Section 4 contains a summary critique of existing hydrate gas recovery models. Finally, Section 5 summarizes the model modification made to HYDMOD, the cyclic thermal injection model for hydrate gas recovery, in order to perform this analysis.

Kuuskraa, V.A.; Hammersheimb, E.; Sawyer, W.

1985-05-01

490

Modern electron accelerators for radiography  

SciTech Connect

Over the past dozen years or so there have been significant advances in electron accelerators designed specifically for radiography of hydrodynamic experiments. Accelerator technology has evolved to accomodate the radiographers' contitiuing quest for multiple images in t h e and space:, improvements in electron beam quality have resulted in smaller radiographic spot sizes for better resolution, while higher radiation do% now provides imprcwed penetration of large, dense objects. Inductive isolation and acceleration techniques have played a ley rob in these advances.

Ekdahl, C. A. (Carl A.)

2001-01-01

491

Acceleration in de Sitter spacetimes  

NASA Astrophysics Data System (ADS)

We propose a definition of uniform accelerated frames in de Sitter spacetimes applying the Nachtmann method of introducing coordinates using suitable point-dependent isometries. In order to recover the well-known Rindler approach in the flat limit, we require the transformation between the static frame and the accelerated one to depend continuously on acceleration, obtaining thus the natural generalization of the Rindler transformation to the de Sitter spacetimes of any dimensions.

Cotaescu, Ion I.

2015-02-01

492

Coherent multimoded dielectric wakefield accelerators.  

SciTech Connect

There has recently been a study of the potential uses of multimode dielectric structures for wakefield acceleration [1]. This technique is based on adjusting the wakefield modes of the structure to constructively interfere at certain delays with respect to the drive bunch, thus providing an accelerating gradient enhancement over single mode devices. In this report we examine and attempt to clarify the issues raised by this work in the light of the present state of the art in wakefield acceleration.

Power, J.

1998-07-16

493

Influence of the Combustion Energy Release on Surface Accelerations of an HCCI Engine  

SciTech Connect

Large cyclic variability along with increased combustion noise present in low temperature combustion (LTC) modes of internal combustion engines has driven the need for fast response, robust sensors for diagnostics and feedback control. Accelerometers have been shown as a possible technology for diagnostics and feedback control of advanced LTC operation in internal combustion engines. To make better use of this technology, an improved understanding is necessary of the effect of energy release from the combustion process on engine surface vibrations. This study explores the surface acceleration response for a single-cylinder engine operating with homogeneous charge compression ignition (HCCI) combustion. Preliminary investigation of the engine surface accelerations is conducted using a finite element analysis of the engine cylinder jacket along with consideration of cylindrical modes of the engine cylinder. Measured in-cylinder pressure is utilized as a load input to the FE model to provide an initial comparison of the computed and measured surface accelerations. Additionally, the cylindrical cavity resonant modes of the engine geometry are computed and the in-cylinder pressure frequency content is examined to verify this resonant behavior. Experimental correlations between heat release and surface acceleration metrics are then used to identify specific acceleration frequency bands in which characteristics of the combustion heat release process is detected with minimal structural resonant influence. Investigation of a metric capable of indicting combustion phasing is presented. Impact of variations in the combustion energy release process on the surface accelerations is discussed.

Massey, Jeffery A [ORNL; Eaton, Scott J [ORNL; Wagner, Robert M [ORNL

2009-01-01

494

Compact accelerator for medical therapy  

DOEpatents

A compact accelerator system having an integrated particle generator-linear accelerator with a compact, small-scale construction capable of producing an energetic (.about.70-250 MeV) proton beam or other nuclei and transporting the beam direction to a medical therapy patient without the need for bending magnets or other hardware often required for remote beam transport. The integrated particle generator-accelerator is actuable as a unitary body on a support structure to enable scanning of a particle beam by direction actuation of the particle generator-accelerator.

Caporaso, George J.; Chen, Yu-Jiuan; Hawkins, Steven A.; Sampayan, Stephen E.; Paul, Arthur C.

2010-05-04

495

High field gradient particle accelerator  

DOEpatents

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.

Nation, John A. (Ithaca, NY); Greenwald, Shlomo (Haifa, IL)

1989-01-01

496

High field gradient particle accelerator  

DOEpatents

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

Nation, J.A.; Greenwald, S.

1989-05-30

497

Ibudilast attenuates astrocyte apoptosis via cyclic GMP signalling pathway in an in vitro reperfusion model.  

PubMed

We examined the effect of 3-isobutyryl-2-isopropylpyrazolo[1,5-a]pyridine (ibudilast), which has been clinically used for bronchial asthma and cerebrovascular disorders, on cell viability induced in a model of reperfusion injury. Ibudilast at 10 - 100 microM significantly attenuated the H(2)O(2)-induced decrease in cell viability. Ibudilast inhibited the H(2)O(2)-induced cytochrome c release, caspase-3 activation, DNA ladder formation and nuclear condensation, suggesting its anti-apoptotic effect. Phosphodiesterase inhibitors such as theophylline, pentoxyfylline, vinpocetine, dipyridamole and zaprinast, which increased the guanosine-3',5'-cyclic monophosphate (cyclic GMP) level, and dibutyryl cyclic GMP attenuated the H(2)O(2)-induced injury in astrocytes. Ibudilast increased the cyclic GMP level in astrocytes. The cyclic GMP-dependent protein kinase inhibitor KT5823 blocked the protective effects of ibudilast and dipyridamole on the H(2)O(2)-induced decrease in cell viability, while the cyclic AMP-dependent protein kinase inhibitor KT5720, the cyclic AMP antagonist Rp-cyclic AMPS, the mitogen-activated protein/extracellular signal-regulated kinase inhibitor PD98059 and the leukotriene D(4) antagonist LY 171883 did not. KT5823 also blocked the effect of ibudilast on the H(2)O(2)-induced cytochrome c release and caspase-3-like protease activation. These findings suggest that ibudilast prevents the H(2)O(2)-induced delayed apoptosis of astrocytes via a cyclic GMP, but not cyclic AMP, signalling pathway. PMID:11454657

Takuma, K; Lee, E; Enomoto, R; Mori, K; Baba, A; Matsuda, T

2001-07-01

498

Alpha 2-adrenergic receptor-mediated sensitization of forskolin-stimulated cyclic AMP production.  

PubMed Central

Preincubation of HT29 human colonic adenocarcinoma cells with alpha 2-adrenergic agonists resulted in a 10- to 20-fold increase in forskolin-stimulated cyclic AMP production as compared to cells preincubated without agonist. Similar results were obtained using either a [3H]adenine prelabeling assay or a cyclic AMP radioimmunoassay to measure cyclic AMP levels. This phenomenon, which is termed sensitization, is alpha 2-adrenergic receptor-mediated and rapid in onset and reversal. Yohimbine, an alpha 2-adrenergic receptor-selective antagonist, blocked norepinephrine-induced sensitization, whereas prazosin (alpha 1-adrenergic) and sotalol (beta-adrenergic) did not. The time for half-maximal sensitization was 5 min and the half-time for reversal was 10 min. Only a 2-fold sensitization of cyclic AMP production stimulated by vasoactive intestinal peptide was observed, indicating that sensitization is relatively selective for forskolin. Sensitization reflects an increased production of cyclic AMP and not a decreased degradation of cyclic AMP, since incubation with a phosphodiesterase inhibitor and forskolin did not mimic sensitization. Increasing the levels of cyclic AMP during the preincubation (using a phosphodiesterase inhibitor) had no effect on sensitization, indicating that sensitization is not caused by decreased cyclic AMP levels during the preincubation. This rapid and dramatic sensitization of forskolin-stimulated cyclic AMP production is a previously unreported effect that can be added to the growing list of alpha 2-adrenergic responses that are not mediated by a decrease in cyclic AMP. PMID:2881298

Jones, S B; Toews, M L; Turner, J T; Bylund, D B

1987-01-01

499

Ethanol-induced loss of brain cyclic AMP binding proteins: correlation with growth suppression  

SciTech Connect

Brain hypoplasia secondary to maternal ethanol consumption is a common fetal defect observed in all models of fetal alcohol syndrome. The molecular mechanism by which ethanol inhibits growth is unknown but has been hypothesized to involve ethanol-induced changes in the activity of cyclic-AMP stimulated protein kinase. Acute and chronic alcohol exposure elevate cyclic AMP level in many tissues, including brain. This increase in cyclic AMP should increase the phosphorylating activity of kinase by increasing the amount of dissociated (active) kinase catalytic subunit. In 7-day embryonic chick brains, ethanol-induced growth suppression was correlated with increased brain cyclic AMP content but neither basal nor cyclic AMP stimulated kinase catalytic activity was increased. However, the lev