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1

Sucker rod coupling  

SciTech Connect

An anti-friction sucker rod coupling is described for connecting a pair of sucker rods and centralizing them in a tubing string, comprising: an elongate, rigid, substantially cylindrical body member, each end of the body member forming means for threadably connecting the body member with a sucker rod. The body member further forms a transversely extending, substantially diametric, generally vertical slot extending therethrough. The body member further forms a pin bore, such pin bore extending transversely through the body member so as to intersect the slot substantially perpendicularly; a wheel member positioned within the slot to rotate in a generally vertical plane. The wheel member has a portion thereof extending beyond the periphery of the body member to engage the inner surface of the tubing string and centralize the coupling; and a pin mounted in the pin bore and supporting member thereon, whereby the wheel member is rotatable within the slot; the wheel member having sufficient clearance between its side surfaces and the wall surfaces of the slot, when the wheel member is centered in the slot on the pin, whereby the wheel member may shift along the pin to assist in ejecting sand and oil from the slot.

Klyne, A.A.

1986-11-11

2

Analysis of sucker rod and sinkerbar failures  

SciTech Connect

This report presents results of a study of performance and failures of the sucker rod/sinkerbar string used in beam-pumping operations through metallography, finite element analysis, and failure data collection. Metallography showed that the microstructure of the steel bar stock needs to be considered to improve the fatigue resistance of the sucker rod strings. The current specification based on tensile strength, or yield strength, may not be appropriate since failure occurs because of fatigue and not yielding, and tensile strength is not always a good measure of fatigue resistance. Finite element analysis of the threaded connection quantitatively assesses the coupling designs under various loading conditions. Subcritical fractures in metallography are also suggested by calculated stress distribution in threaded coupling. Failure data illustrates both magnitude and frequency of failures, as well as categorizing the suspected cause of failure. Application of the results in each of these project areas is expected to yield improved choice of metal bar stock, thread design, and make-up practices which can significantly reduce the frequency of sucker rod failures. Sucker rod failures today are not inherent in the process, but can be minimized through the application of new technology and observation of common-sense practices.

Waggoner, J.R.; Buchheit, R.G.

1993-03-01

3

Wear simulation of sucker rod couplings  

SciTech Connect

This paper reports that sucker rod strings are devices used to actuate pumps located at the bottom of oil wells. The individual rods are connected together by threaded couplings. Since the couplings have a larger diameter than the rods, they sometimes contact the inside diameter of the tubing during the up and down pumping cycle. Usually, this is not problem unless buckling occurs in the downstroke; however, this can lead to accelerated wear of the coupling and tubing. In nonvertical wells (offset, deviated, or slanted), the contact is more severe and rapid wear takes place. Couplings are more easily replaced during shutdowns; it is very important to minimize wear to tubing since it is virtually impossible to replace. TRIBONIC 20, an iron-based alloy containing approximately 13% Mn, 5% Si, 5.5% Cr, and 5% Ni, was laboratory evaluated to determine whether or not it could solve the sucker rod coupling-production tubing wear problem. The alloy demonstrated outstanding wear resistance both to itself and in protecting type 1019 steel.

Schumacher, W.J. (Armco, Inc., Middletown, OH (United States))

1991-09-01

4

Gas Interference in Sucker Rod Pump  

NASA Astrophysics Data System (ADS)

Commonly used artificial lift or dewatering system is sucker rod pump and gas interference of the pump is the biggest issue in the oil and gas industry. Gas lock or fluid pound problems occur due to the gas interference when the pump has partially or completely unfilled plunger barrel. There are several techniques available in the form of patents to solve these problems but those techniques have positive as well as negative aspects. Some of the designs rely on the leakage and some of the designs rely on the mechanical arrangements etc to break the gas lock. The present article compares the existing gas interference handling techniques.

Samad, Abdus

2010-10-01

5

Composite models for combined rod and fluid dynamics in sucker-rod pumping well systems  

SciTech Connect

This study presents the derivation and the numerical solution of composite models in which both the rod string and the fluid dynamics are coupled so as to accurately account for the effects of viscous friction in sucker-rod pumped wells. A viscous damped hyperbolic first order partial differential equation is coupled to the time derivative of Hooke's law to model the rod string motion and Navier Stokes equations are used to model the fluid dynamics in the rod-tubing annulus. A set of four equations comprise the composite model from which four sub-models for different flow scenarios are considered. The equations are solved numerically by a shock capturing algorithm known as the MacCormack Explicit Scheme which is a two-step predictor-corrector scheme and is second order accuracy in time and space. Five example problems covering various pump setting depths, fluid properties and surface pumping unit kinematics are presented to study the effects of certain important variables. From the analyses of the results of these example problems it is concluded that (1) while the effects of fluid dynamics may appear masked in shallow to medium depth sucker-rod pumped wells, they can not be ignored in deeper wells where large discrepancies occur in the prediction of system parameters, (2) the load range decreases moderately as viscosity increases and the predicted polished rod horsepower does not change significantly over the range of viscosities studied in shallow to medium depth sucker-rod pumped wells, (3) the presence of small quantities of the gas phase in the fluid column reduces system peak torque and precipitate the need for smaller counterbalance weights and (4) the influence of two-phase gas-liquid flow in the rod-tubing annulus on system design parameters declines with increasing pump setting depth. The results are compared against other design models appearing in the literature.

Lekia, S.D.L.

1989-01-01

6

Using a Microcomputer To Perform Design Calculations for a Sucker Rod Pumping System  

Microsoft Academic Search

Sucker rod computations are both tedious and time consuming. Each time a pumping parameter is changed, such as rod designation, pumping speed, the calculation must be repeated. Three programs to handle these calculations have been written for the Hewlett Packard HP 87 XM microcomputer. The first program is a dynamic analysis program for either an API Class I or Class

J. C. Purcupile; T. H. Nicol

1985-01-01

7

Mobil tests new flexible sucker-rod system in Hugoton field  

Microsoft Academic Search

For the past 3 y, Mobil Oil Corp. has been testing flexible sucker-rod systems for dewatering gas wells in the Hugoton field. The intent of the system is to provide the strength of conventional rods but to achieve superior corrosion resistance. The ''Flexirod'' system being tested is a joint development of Bethlehem Steel Co. and E. I. duPont de Nemours

1974-01-01

8

Improving the reliability of guiding mechanisms in values of sucker-rod well pumps  

SciTech Connect

This article reports on research conducted at the Azerbaijan Scientific-Research and Projects Institute for Petroleum to develop new types of valve-guiding mechanisms for sucker-rod well pumps which have high resistance to hydroabrasive and corrosive/mechanical wear and the required strength for the given load conditions. A new type of ball valve with an elastic guiding mechanism was developed for NSV1-32 and NSV1-43 sucker-rod well pumps. The new type of guiding mechanism can be made by modern high-production techniques of cold stamping which considerably reduces technological expenses compared to investment casting. Comparative tests were conducted with guiding mechanisms of elastic and rigid types (cups made for standard valves and cups of similar design with thicker ribs). The results of field tests of sucker-rod well pumps with elastic guiding mechanisms showed that they have high operating strength and wear resistance.

Sotnik, V.I.; Rustamov, E.M.; Stepanova, I.S.

1984-09-01

9

Enhanced oil recovery. Operators fight corrosion with fiberglass injection pipe, casing and sucker rods  

SciTech Connect

Operators have been fighting corrosion in the Permian Basin since the first oil (along with saltwater and H/sub 2/S gas) was produced. However, with ever- increasing attempts to squeeze more oil out of the ground through secondary and tertiary recovery methods, a new high in corrosive properties has been reached. It starts when waterflooding is introduced, and reaches its maximum effect when CO/sub 2/ is injected to recover tertiary oil. Corrosion strikes whenever contaminated water, H/sub 2/S or wet CO/sub 2/ is injected or produced. Even the dry CO/sub 2/ used in most tertiary injection projects becomes extremely corrosive when it contacts water or wet surfaces. Amoco is designing its injection and production facilities to be corrosion resistant. A major element in the fight against corrosion at Scurry Area Canyon Reef Operators Committee in the Kelly-Snyder field in Scurry County, Texas, has been the use of glass fiber-reinforced plastic (FRP) materials in high pressure surface injection pipes, saltwater gathering lines, casing liners and sucker rods. Amoco has used fiberglass flowlines for injection wells in waterflood operations as well as FRP sucker rods in producing wells.

Wash, R.

1983-04-01

10

Environmental stimuli promoting sucker initiation in sugarcane  

Microsoft Academic Search

The presence of suckers, late-formed tillers, in mature sugarcane crops reduces the sugar concentration of harvested material to the detriment of profitability. The amount of suckering varies with cultivar and season. However, the environmental stimuli promoting suckering, i.e. the number of suckers, are not understood. This paper describes the effects on suckering of increasing soil moisture, nitrogen, and the level

G. D. Bonnett; B. Salter; N. Berding; A. P. Hurney

2005-01-01

11

Suckers in headwater tributaries, Wyoming  

USGS Publications Warehouse

Bluehead sucker (Catostomus discobolus) and flannelmouth sucker (Catostomus latipinnis) populations are declining throughout these species' native ranges in the Upper Colorado River Basin. In order to conserve these populations, an understanding of population dynamics is needed. Using age estimates from pectoral fin rays, we describe age and growth of these 2 species in 3 Wyoming stream systems: Muddy Creek, the Little Sandy River, and the Big Sandy River. Within all 3 stream systems, flannelmouth suckers were longer-lived than bluehead suckers, with maximum estimated ages of 16 years in Muddy Creek, 18 years in Little Sandy Creek, and 26 years in the Big Sandy River. Bluehead suckers had maximum estimated ages of 8 years in Muddy Creek, 10 years in Little Sandy Creek, and 18 years in the Big Sandy River. These maximum estimated ages were substantially greater than in other systems where scales have been used to estimate ages. Mean lengths at estimated ages were greater for flannelmouth suckers than for bluehead suckers in all 3 streams and generally less than values published from other systems where scales were used to estimate ages. Our observations of long life spans and slow growth rates among bluehead suckers and flannelmouth suckers were probably associated with our use of fin rays to estimate ages as well as the populations being in headwater tributaries near the northern edges of these species' ranges.

Sweet, D. E.; Compton, R. I.; Hubert, W. A.

2009-01-01

12

Low turbulence rod guide  

SciTech Connect

This patent describes an improved sucker rod guide for fixedly engaging around a sucker rod at a selected location along the length of the rod. It comprises a substantially cylindrical polymeric body having a longitudinal axis, a terminal end substantially continually tapered to the rod, a radially-inward surface and a radially outward surface, the radially inward surface of the body adjacent to and in tripping engagement with the rod when the rod guide is fixedly engaged around the rod; and a plurality of substantially continuous, longitudinal vanes carried by the body, a vane having a selected length and width, and longitudinally disposed along the radially outward surface of the guide body, extending radially away from the guide body and having a radially outside wear surface.

Olinger, E.L.

1992-05-26

13

Morphometric and Meristic Differences among Bluehead Suckers, Flannelmouth Suckers, White Suckers, and Their Hybrids: Tools for the Management of Native Species in the Upper Colorado River Basin  

Microsoft Academic Search

Hybridization with nonnative fishes is a major factor influencing the status of native catostomids in the Colorado River basin. In Wyoming, hybridization with nonnative white suckers Catostomus commersonii is a particular concern in the conservation of native bluehead suckers C. discobolus and flannelmouth suckers C. latipinnis. The purpose of this study was to describe the meristic and morphometric characteristics of

Michael C. Quist; Michael R. Bower; Wayne A. Hubert; Thomas L. Parchman; David B. McDonald

2009-01-01

14

Rangewide molecular structuring in the Utah sucker ( Catostomus ardens )  

Microsoft Academic Search

The Utah sucker ( Catostomus ardens ) is endemic to the Bonneville Basin and the upper Snake River drainage in western North America, and is thought to hybridize with the federally endangered June sucker ( Chasmistes liorus mictus ) in Utah Lake (Bonneville Basin). Here we describe the discovery of a major subdivision in Utah suckers (4.5% mitochondrial sequence divergence)

K. E. M OCK; R. P. E VANS; M. CRAWFORD; B. L. C ARDALL; S. U. J ANECKE; M. P. MILLER

2006-01-01

15

A wall climbing robot with simple suckers  

Microsoft Academic Search

A new type of wall climbing robot to clean window is proposed in this paper. The developed robot can climb the vertical pane by rotating a crawler that has general purpose suckers. The robot can climb more simply and safely than other methods because it uses a simple mechanism. As the result of the experiments, it is confirmed that the

Nobuhiro Okada; Kyohei Yamanaka; Eiji Kondo

2009-01-01

16

FACTORS INFLUENCING GROWTH AND SURVIVAL OF WHITE SUCKER, CATOSTOMUS COMMERSONI  

EPA Science Inventory

Growth responses of the white sucker, Catostomus commersoni, were examined in relation to the influence of temperature, body size, season, daylength, light intensity, food ration level and food quality. Sucker growth was maximum at a temperature range of 19-26C, depending upon ex...

17

Root suckering patterns in Populus euphratica (Euphrates poplar, Salicaceae)  

Microsoft Academic Search

To understand the spatial structure of monospecific Tugai forests (Xinjiang Province, China) growing as gallery woods nourished\\u000a by ground water, root suckering in Populus euphratica was studied by a combination of morphological and molecular analyses. Seedlings grow a deep tap root and keep this as adult\\u000a trees, whereas root suckers never develop a tap root but utilize the horizontally stretching

Martin Wiehle; Pascal Eusemann; Niels Thevs; Martin Schnittler

2009-01-01

18

The morphology and adhesion mechanism of Octopus vulgaris suckers.  

PubMed

The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species. PMID:23750233

Tramacere, Francesca; Beccai, Lucia; Kuba, Michael; Gozzi, Alessandro; Bifone, Angelo; Mazzolai, Barbara

2013-06-04

19

The Morphology and Adhesion Mechanism of Octopus vulgaris Suckers  

PubMed Central

The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species.

Tramacere, Francesca; Beccai, Lucia; Kuba, Michael; Gozzi, Alessandro; Bifone, Angelo; Mazzolai, Barbara

2013-01-01

20

Hazard assessment of selenium to endangered razorback suckers (Xyrauchen texanus).  

PubMed

A hazard assessment was conducted based on information derived from two reproduction studies conducted with endangered razorback suckers (Xyrauchen texanus) at three sites near Grand Junction, CO, USA. Selenium contamination of the upper and lower Colorado River basin has been documented in water, sediment, and biota in studies by US Department of the Interior agencies and academia. Concern has been raised that this selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The reproduction studies with razorback suckers revealed that adults readily accumulated selenium in various tissues including eggs, and that 4.6 microg/g of selenium in food organisms caused increased mortality of larvae. The selenium hazard assessment protocol resulted in a moderate hazard at the Horsethief site and high hazards at the Adobe Creek and North Pond sites. The selenium hazard assessment was considered conservative because an on-site toxicity test with razorback sucker larvae using 4.6 microg/g selenium in zooplankton caused nearly complete mortality, in spite of the moderate hazard at Horsethief. Using the margin of uncertainty ratio also suggested a high hazard for effects on razorback suckers from selenium exposure. Both assessment approaches suggested that selenium in the upper Colorado River basin adversely affects the reproductive success of razorback suckers. PMID:12150431

Hamilton, Steven J; Holley, Kathleen M; Buhl, Kevin J

2002-05-27

21

Rodding Surgery  

MedlinePLUS

... requires incisions around the joints. 3 The Fassier-Duval rod system approved by the US Food and ... can lengthen during growth Dubow-Bailey rod Fassier-Duval rod Non-telescopic rods Kirschner wires (K-wires) ...

22

String Vibrations  

NSDL National Science Digital Library

This site, by Andrew Davidhazy at the Rochester Institute of Technology, describes how to make interesting and artistic photographs of a vibrating string. Davidhazy explains how the string is vibrated, how the string is lit, and even the exposure time and the effect it has on the resulting image. Four images of the vibrating string are included.

2006-12-29

23

A Proposed Standard Weight Equation for Blue Suckers  

Microsoft Academic Search

Length and weight data were obtained from 46 populations of blue suckers Cycleptus elongatus (N = 8,811 fish) across the species' geographic distribution to develop a standard weight (Ws) equation. The Ws equation was derived using the empirical percentile technique applied to fish between 240 and 809 mm total length (TL). We calculated a quadratic model and a linear model

Ben C. Neely; Martin J. Hamel; Kirk D. Steffensen

2008-01-01

24

Polyculture of Endangered Bonytails and Razorback Suckers in Recirculated Water  

Microsoft Academic Search

Bonytails Gila elegans and razorback suckers Xyrauchen texanus are imperiled fish species that are endemic to the Colorado River system in the southwestern United States. Captive propagation is a component of the recovery plan for each species, which are sometimes cultured together indoors in water reuse systems. A 3 × 2 factorial design was selected for examining the co-culture of

James P. Henne; Matthew M. Romero; Gary J. Carmichael

2007-01-01

25

String Theory  

NASA Astrophysics Data System (ADS)

After reviewing the original motivation for the formulation of string theory and what we learned from it, I discuss some of the implications of the holographic principle and of string dualities for the question of the building blocks of nature.

Susskind, Leonard

2013-01-01

26

Hammered Strings  

NASA Astrophysics Data System (ADS)

In the next three chapters we consider the science of hammered string instruments. In this chapter, we present a brief discussion of vibrating strings excited by a hard or soft hammer. Chapter 20 discusses the most important hammered string instrument, the piano - probably the most versatile and popular of all musical instruments. Chapter 21 discusses hammered dulcimers, especially the American folk dulcimer.

Rossing, Thomas D.

27

A rod pumping system to reduce lifting costs  

SciTech Connect

Rising costs of artificial lift operations are a growing concern to producers in maintaining efficient and profitable performance. A new long stroke sucker rod pumping system has been developed to minimize the impact of these rising costs. This new system results from a broad development project involving evaluation of all system components. Performance results to date confirm achievement of reduced overall operating costs as a result of the performance characteristics of this system.

Tait, H.C.; Hamilton, R.M.

1983-02-01

28

Folded strings  

NASA Astrophysics Data System (ADS)

Recent progress on the complete set of solutions of two dimensional classical string theory in any curved spacetime is reviewed. When the curvature is smooth, the string solutions are deformed folded string solutions as compared to flat spacetime folded strings that were known for 19 years. However, surprizing new stringy behavior becomes evident at singularities such as black holes. The global properties of these solutions require that the "bare singularity region" of the black hole be included along with the usual black hole spacetime. The mathematical structure needed to describe the solutions include a recursion relation that is analogous to the transfer matrix of lattice theories. This encodes lattice properties on the worldsheet on the one hand and the geometry of spacetime on the other hand. A case is made for the presence of folded strings in the quantum theory of non-critical strings for d ? 2.

Bars, Itzhak

29

Waving Strings  

NSDL National Science Digital Library

Unless you really haven't been paying attention to the world around you, you know that plucked strings produce sounds. Carlos Santana demonstrates this on a regular basis. Because stringed instruments are so commonly used to produce sounds, we're going to spend a chapter figuring out what exactly those strings are doing when you pluck them. We're going to be analyzing what happens when you produce waves on strings. These waves produce sounds, but they are not themselves sound waves.

Robertson, William C.

2003-01-01

30

Signals controlling root suckering and adventitious shoot formation in aspen (Populus tremuloides).  

PubMed

We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. Defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also exerted a significant inhibitory effect. Removal of mature leaves had only a minor effect on root suckering. Removal of a continuous band of bark (girdling) at the base of the stem consistently stimulated growth of adventitious shoots from the stem below the girdle and occasionally promoted root suckering. Exogenous application of indole-3-acetic acid to excised stumps inhibited root suckering and basal stem sprouting. Naphthylphthalamic acid (NPA), an auxin polar transport inhibitor, had no effect on root suckering or stem sprouting when it was applied to the bark of the basal stem. However, NPA significantly increased root suckering when it was applied to the exposed surface of xylem after girdling. These results suggest that polar transport of auxin in the xylem parenchyma is an important inhibitor of root suckering. On decapitated stems, vacuum extraction of xylem sap from the root system lowered the frequency of root suckering compared with decapitation alone, indicating that substance(s) originating in the root system also play a significant role in controlling root suckering. PMID:16452082

Wan, Xianchong; Landhäusser, Simon M; Lieffers, Victor J; Zwiazek, Janusz J

2006-05-01

31

String Thing  

NSDL National Science Digital Library

String Thing is an interactive online game in which learners change a virtual string's tension, length, and gauge to create different musical pitches. Educators can use this game as an introduction to sound and before completing any activities on music or building instruments. Alternatively, educators can use this game to review or assess these concepts.

Wgbh

2010-01-01

32

Overview of Endangered Suckers in the Klamath Basin: Does it Take One to Know One?  

Microsoft Academic Search

Severe water quality problems in the Klamath Basin of Oregon and California have led to critical fisheries concerns for the region. In the Upper Klamath Basin, two fish species, the Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were listed as federally endangered in 1988. These species are large, long-lived, lake-dwelling fishes endemic to the Upper Klamath Basin.

R. S. Shively; S. Vanderkooi

2005-01-01

33

Spatial and Temporal Movements of White Sucker: Implications for Use as a Sentinel Species  

Microsoft Academic Search

White suckers Catostomus commersonii are widely distributed in rivers of North America and often used in environmental monitoring. The species' value as a sentinel has been questioned because some populations are known to travel long distances during spawning migrations and therefore can be exposed to multiple environments. The movements of white suckers in a 65-km reach of the Saint John

Chad A. Doherty; R. Allen Curry; Kelly R. Munkittrick

2010-01-01

34

Do Endangered Razorback Suckers Have Poor Larval Escape Performance Relative to Introduced Rainbow Trout?  

Microsoft Academic Search

Poor recruitment has generated the hypothesis that the endangered razorback sucker Xyrauchen texanus is particularly vulnerable to predation early in its life history. We compared the escape responses of razorback suckers, which are adapted to the historically warm waters of the Colorado River, with those of rainbow trout Oncorhynchus mykiss, an introduced coldwater species, throughout early development at water temperatures

Heather M. Wesp; Alice C. Gibb

2003-01-01

35

Vanishing Rods  

NSDL National Science Digital Library

This is a quick activity/demonstration that introduces learners to the concept of index of refraction. Learners place stirring rods in a jar of water and notice they can see them clearly. They will be surprised when they place the stirring rods in a jar of vegetable oil and the rods appear practically invisible! This is a dramatic demonstration that effectively illustrates how light can bend and fool the eye.

University, Colorado S.

2009-01-01

36

Cosmic strings  

SciTech Connect

Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs.

Bennett, D.P.

1988-07-01

37

Test report for drill string seal pressure test  

Microsoft Academic Search

A basic question was asked concerning the drill string which is used in rotary Mode coring operations: ``...what is the volume leak rate loss in a drill rod string under varying condiditons of the joint boxes and pins being either dry or coated with lubricant...``. A Variation of this was to either have an o-ring installed or absent on the

1996-01-01

38

Cosmic Strings and Superconducting Cosmic Strings.  

National Technical Information Service (NTIS)

The possible consequences of forming cosmic strings and superconducting cosmic strings in the early universe are discussed. Lecture 1 describes the group theoretic reasons for, and the field theoretic reasons why, cosmic strings can form in spontaneously ...

E. Copeland

1988-01-01

39

Plucked Strings  

NASA Astrophysics Data System (ADS)

In the next ten chapters we will discuss the science of plucked string instruments. Acoustic guitars and lutes are discussed in Chap. 3. Portuguese guitars, used in fado music, are discussed in Chap. 4 and guitars in Chap. 5, while electric guitars are discussed in Chap. 22. Banjos are discussed in Chap. 5, while mandolins are the subject of Chap. 6. Zithers and psalteries, especially Baltic psalteries, are discussed in Chap. 7. Harpsichords are discussed in Chap. 8, while harps are discussed in Chap. 9 and 10. Finally, plucked string instruments from Asia, such as the kito, shamisen, biwa, gayageum, geomungo, ch'in, p'I-p'a, and sitar are discussed in Chap. 11. These instruments are very different in character and in their musical roles, but they all depend upon plucked strings vibrating and exciting one or more soundboards or radiating surfaces.

Rossing, Thomas D.

40

Hairy strings  

SciTech Connect

Zero modes of the world-sheet spinors of a closed string can source higher order moments of the bulk supergravity fields. In this work, we analyze various configurations of closed strings focusing on the imprints of the quantized spinor vacuum expectation values onto the tails of bulk fields. We identify supersymmetric arrangements for which all multipole charges vanish; while for others, we find that one is left with Neveu-Schwarz-Neveu-Schwarz, and Ramond-Ramond dipole and quadrupole moments. Our analysis is exhaustive with respect to all the bosonic fields of the bulk and to all higher order moments. We comment on the relevance of these results to entropy computations of hairy black holes of a single charge or more, and to open/closed string duality.

Sahakian, Vatche [Keck Laboratory, Harvey Mudd College, Claremont, California 91711 (United States)

2006-01-15

41

75 FR 38441 - Endangered and Threatened Wildlife and Plants; Revised Critical Habitat for Santa Ana Sucker  

Federal Register 2010, 2011, 2012, 2013

...FR 65070)); however, a revised map including this new area is included...sucker. We reviewed aerial imagery, topographic maps, and information in our files...i)(B); b. By removing the map of subunit 1A; and c. By...

2010-07-02

42

String Theory  

NSDL National Science Digital Library

While few people toss around terms like Astroparticle Physics and Superstring Theory, we've all found ourselves staring out in to space on a starry night wondering what's out there, why it's arranged the way it is, and where it all came from. For some, it simply comes down to strings. This September 2, 2003 New York Times article does a good job of summarizing the history and specifics of string theory and the paradox of its many offerings (1). One-time egistration is required to access any New York Times articles. The next site is the homepage of the Kavli Institute for Theoretical Physics at the University of California Santa Barbara and home to some of the most intense thinking with regards to theoretical physics in the world (2). Going from highly technical to more popularly palatable, NOVA offers the third site (3 ). Called, The Elegant Universe, the upcoming NOVA special is based on Columbia University professor Brian Greene's highly acclaimed book of the same title. As the site states, "Eleven dimensions, parallel universes, and a world made out of strings. It's not science fiction, it's string theory." The next site takes you directly to the virtual home of string theory (4 ). Here you will find the basics on the topic as well as what scientists have found so far and where they're headed next. Probably the most definitive site devoted to the topic. The fifth site is another informative look at superstring theory and is provided by John Pierre at MIT. While a very basic Web site, in terms of design, it offers a great tutorial on strings in addition to a glossary and reference list (5 ). The final link (6 ) will take you "Beyond Einstein, from the Big Bang to Black Holes." The site, provided by NASA, offers insights into the history and structure of the universe.

Morgan, John P.

43

New 2-naphthyloxyacetates for trunk sucker growth control on grapevine ( Vitis vinifera L.)  

Microsoft Academic Search

Eighteen new hexyl esters of 2-naphthyloxyacetic acid (ß-NOA) were synthesized and their efficiency on sucker control of grapevine was investigated. Different solutions (0.5, 1, and 2%, w\\/w concentrations) of each compound were sprayed on suckers and the wilting effect after 4, 10, and 30 days after treatment was evaluated. Esters derived from primary and secondary alcohols gave a rapid control of

Marcello Dolci; Francesco Galeotti; Paolo Curir; Luca Schellino; Giuliana Gay

2004-01-01

44

Inspiration, simulation and design for smart robot manipulators from the sucker actuation mechanism of cephalopods.  

PubMed

Octopus arms house 200-300 independently controlled suckers that can alternately afford an octopus fine manipulation of small objects and produce high adhesion forces on virtually any non-porous surface. Octopuses use their suckers to grasp, rotate and reposition soft objects (e.g., octopus eggs) without damaging them and to provide strong, reversible adhesion forces to anchor the octopus to hard substrates (e.g., rock) during wave surge. The biological 'design' of the sucker system is understood to be divided anatomically into three functional groups: the infundibulum that produces a surface seal that conforms to arbitrary surface geometry; the acetabulum that generates negative pressures for adhesion; and the extrinsic muscles that allow adhered surfaces to be rotated relative to the arm. The effector underlying these abilities is the muscular hydrostat. Guided by sensory input, the thousands of muscle fibers within the muscular hydrostats of the sucker act in coordination to provide stiffness or force when and where needed. The mechanical malleability of octopus suckers, the interdigitated arrangement of their muscle fibers and the flexible interconnections of its parts make direct studies of their control challenging. We developed a dynamic simulator (ABSAMS) that models the general functioning of muscular hydrostat systems built from assemblies of biologically constrained muscular hydrostat models. We report here on simulation studies of octopus-inspired and artificial suckers implemented in this system. These simulations reproduce aspects of octopus sucker performance and squid tentacle extension. Simulations run with these models using parameters from man-made actuators and materials can serve as tools for designing soft robotic implementations of man-made artificial suckers and soft manipulators. PMID:18037726

Grasso, Frank W; Setlur, Pradeep

2007-10-16

45

Musculoskeletal determinants of pelvic sucker function in Hawaiian stream gobiid fishes: interspecific comparisons and allometric scaling.  

PubMed

Gobiid fishes possess a distinctive ventral sucker, formed from fusion of the pelvic fins. This sucker is used to adhere to a wide range of substrates including, in some species, the vertical cliffs of waterfalls that are climbed during upstream migrations. Previous studies of waterfall-climbing goby species have found that pressure differentials and adhesive forces generated by the sucker increase with positive allometry as fish grow in size, despite isometry or negative allometry of sucker area. To produce such scaling patterns for pressure differential and adhesive force, waterfall-climbing gobies might exhibit allometry for other muscular or skeletal components of the pelvic sucker that contribute to its adhesive function. In this study, we used anatomical dissections and modeling to evaluate the potential for allometric growth in the cross-sectional area, effective mechanical advantage (EMA), and force generating capacity of major protractor and retractor muscles of the pelvic sucker (m. protractor ischii and m. retractor ischii) that help to expand the sealed volume of the sucker to produce pressure differentials and adhesive force. We compared patterns for three Hawaiian gobiid species: a nonclimber (Stenogobius hawaiiensis), an ontogenetically limited climber (Awaous guamensis), and a proficient climber (Sicyopterus stimpsoni). Scaling patterns were relatively similar for all three species, typically exhibiting isometric or negatively allometric scaling for the muscles and lever systems examined. Although these scaling patterns do not help to explain the positive allometry of pressure differentials and adhesive force as climbing gobies grow, the best climber among the species we compared, S. stimpsoni, does exhibit the highest calculated estimates of EMA, muscular input force, and output force for pelvic sucker retraction at any body size, potentially facilitating its adhesive ability. PMID:23450656

Maie, Takashi; Schoenfuss, Heiko L; Blob, Richard W

2013-02-28

46

String primer  

NASA Astrophysics Data System (ADS)

This is the written version of a set of introductory lectures to string theory. The lectures were given at the Universidad Autónoma de Madrid in the semester 1997/98 and at the VI Escuela de Otoño de Física Teórica, held in Santiago de Compostela (10-23 september 1998).

Alvarez, Enrique; Meessen, Patrick

1999-02-01

47

String Theory  

Microsoft Academic Search

For each $n > 0$, two alternative axiomatizations of the theory of strings over $n$ alphabetic characters are presented. One class of axiomatizations derives from Tarski's system of the Wahrheitsbegriff and uses the $n$ characters and concatenation as primitives. The other class involves using $n$ character-prefixing operators as primitives and derives from Hermes' Semiotik. All underlying logics are second order.

John Corcoran; William Frank; Michael Maloney

1974-01-01

48

Coupled economic-coastline modeling with suckers and free riders  

NASA Astrophysics Data System (ADS)

erosion is a natural trend along most sandy coastlines. Humans often respond to shoreline erosion with beach nourishment to maintain coastal property values. Locally extending the shoreline through nourishment alters alongshore sediment transport and changes shoreline dynamics in adjacent coastal regions. If left unmanaged, sandy coastlines can have spatially complex or simple patterns of erosion due to the relationship of large-scale morphology and the local wave climate. Using a numerical model that simulates spatially decentralized and locally optimal nourishment decisions characteristic of much of U.S. East Coast beach management, we find that human erosion intervention does not simply reflect the alongshore erosion pattern. Spatial interactions generate feedbacks in economic and physical variables that lead to widespread emergence of "free riders" and "suckers" with subsequent inequality in the alongshore distribution of property value. Along cuspate coastlines, such as those found along the U.S. Southeast Coast, these long-term property value differences span an order of magnitude. Results imply that spatially decentralized management of nourishment can lead to property values that are divorced from spatial erosion signals; this management approach is unlikely to be optimal.

Williams, Zachary C.; McNamara, Dylan E.; Smith, Martin D.; Murray, A. Brad.; Gopalakrishnan, Sathya

2013-06-01

49

Overview of Endangered Suckers in the Klamath Basin: Does it Take One to Know One?  

NASA Astrophysics Data System (ADS)

Severe water quality problems in the Klamath Basin of Oregon and California have led to critical fisheries concerns for the region. In the Upper Klamath Basin, two fish species, the Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were listed as federally endangered in 1988. These species are large, long-lived, lake-dwelling fishes endemic to the Upper Klamath Basin. Declining population trends for both species were noted as early as the mid 1960's, however, the severity of these declines were not evident until the mid 1980's. At the time of listing, population structures were dominated by older individuals with little evidence of recent significant recruitment into adult populations. In the early 1990s there was evidence of recruitment for Lost River suckers. Successive years of large fish kills in Upper Klamath Lake from 1995 to 1997, however, substantially reduced adult populations of both Lost River and shortnose suckers. Additionally, the 1995 and 1996 fish kills appeared to have been selective for larger-sized individuals and would have disproportionately affected females and resulted in an overall lower reproductive potential. Water quality and physical habitat limitations are considered to be the most limiting factors to species recovery. Life history patterns of Lost River and shortnose suckers in Upper Klamath Lake have been severely disrupted by recurrent periods of poor water quality that appear to be the root cause of fish kills and likely negatively influence the production of juvenile suckers. Habitat degradation around Upper Klamath Lake and in its tributaries likely contributes to water quality problems and also limits the physical habitat needed for successful adult sucker spawning as well as larval and juvenile rearing. Ultimately, a better understanding of the factors that influence water quality in Upper Klamath Lake as well as developing a sound strategy for habitat restoration is needed to promote recovery of these species. Future challenges fisheries biologists in the Klamath Basin face include developing a better understanding of sucker population dynamics and habitat requirements at different life stages. One of the largest challenges, however, will be the integration of biological information on suckers with an improved understanding of water quality and physical habitat processes.

Shively, R. S.; Vanderkooi, S.

2005-12-01

50

Evolutionary Divergence of Duplicate Copies of the Growth Hormone Gene in Suckers (Actinopterygii: Catostomidae)  

PubMed Central

Catostomid fishes (suckers) have duplicate copies of the growth hormone gene and other nuclear genes, due to a genome duplication event early in the group’s history. Yet, paralogs of GH in suckers are more than 90% conserved in nucleotide (nt) and amino acid (aa) sequence. Within paralogs across species, variation in nt and aa sequence averages 3.33% and 4.46% for GHI, and 3.22% and 2.43% for GHII, respectively. Selection tests suggest that the two GH paralogs are under strong purifying selection. Consensus trees from phylogenetic analysis of GH coding region data for 23 species of suckers, other cypriniform fishes and outgroups resolved cypriniform relationships and relationships among GHI sequences of suckers more or less consistently with analyses based on other molecular data. However, the analysis failed to resolve all sucker GHI and GHII sequences as monophyletic sister groups. This unexpected topology did not differ significantly from topologies constrained to make all GH sequences monophyletic. We attribute this result either to limitations in our GHII data set or convergent adaptive changes in GHII of tribe Catostomini.

Bart, Henry L.; Reneau, Paulette C.; Doosey, Michael H.; Bell, Charles D.

2010-01-01

51

Spontaneous formation of stringlike clusters and smectic sheets for colloidal rods confined in thin wedgelike gaps.  

PubMed

Monodispersed colloidal rods of ?-FeOOH with sizes ranging from 270 to 580 nm in length and 50 to 80 nm in width were synthesized. Narrow wedgelike gaps (0 to 700 nm in height) were formed around the inner bottom edge of the suspension glass cells. Optical microscopic observations revealed the formation of stringlike clusters of the rods and smectic sheets (by spontaneous side-by-side clustering of the strings) in the isotropic phase of the rod suspensions confined in narrow gaps; the electrolyte (HCl) concentrations of the suspensions are 5-40 mM, at which inter-rod interactions are attractive. The strings exhibit different colors that were used to investigate the structures of the strings with the help of interference color theory for thin films. The results are as follows. (1) The rods, lying flat on the gap bottom, are connected side-by-side and stacked upward to form stringlike clusters with different thicknesses depending on the gap height. (2) The stacking numbers (Nsr) of the rods are estimated to be 1-5. With Nsr increasing from 2 to 5, the volume fractions (?) of the rods in the strings increased typically from 0.25-0.3 to 0.35-0.42 to reach limiting values (close to the ? values of the rods in the bulk smectic phase). (3) Unexpected low-? strings are found in regions with an intermediate height in the gaps. These behaviors of ? may be caused by thermal fluctuations of the strings. PMID:23876087

Maeda, Hideatsu; Maeda, Yoshiko

2013-08-05

52

Effects of natural exposure to copper and zinc on egg size and larval copper tolerance in white sucker (Catostomus commersoni)  

Microsoft Academic Search

Sucker eggs were collected from a metal-contaminated site where previous collections had documented a maternal yolk factor associated with an increased larval copper tolerance during yolk nutrition. In this study, white sucker eggs were divided into groups which were water hardened and\\/or incubated at the contaminated site or a reference (control) site. Incubation at the contaminated site was associated with

K. R. Munkittrick; D. G. Dixon

1989-01-01

53

Associations between Water Quality and Daily Growth of Juvenile Shortnose and Lost River Suckers in Upper Klamath Lake, Oregon  

Microsoft Academic Search

Poor water quality from hypereutrophic Upper Klamath Lake in south-central Oregon has been suspected of contributing to the recruitment failure of two endangered endemic fish species, the Lost River sucker Deltistes luxatus and the shortnose sucker Chasmistes brevirostris. We used otolith daily increment widths as a proxy for juvenile somatic growth to construct two growth models: (1) a linear mixed-effects

Mark R. Terwilliger; Douglas F. Markle; Jacob Kann

2003-01-01

54

Restoration of rooting competence in mature Faidherbia albida , a Sahelian leguminous tree, through serial root sucker micrografting  

Microsoft Academic Search

Faidherbia albida is an essential leguminous tree of arid areas of Africa which is widely used in agroforestry. This species naturally produces root suckers. Their morphogenetic ability has been used to initiate a rejuvenation\\/reinvigoration process in mature subjects. The proposed method contains two stages. The first stage generates the first ramets : our results have shown that suckers picked from

P. Danthu; B. Hane; P. Sagna; Y. K. Gassama

2002-01-01

55

Milt characteristics, reproductive performance, and larval survival and development of white sucker exposed to bleached kraft mill effluent  

Microsoft Academic Search

White sucker from a Lake Superior bay which receives bleached kraft mill effluent (BKME) show increased hepatic mixed-function oxygenase (MFO) activity, reduced plasma sex steroid levels, decreased egg and gonad size, a decrease in the occurrence of secondary sexual characteristics, and an increased age to maturation. This study evaluated the reproductive performance of that white sucker population relative to a

M. E. McMaster; C. B. Portt; K. R. Munkittrick; D. G. Dixon

1992-01-01

56

Structural changes in gills of Lost River suckers exposed to elevated pH and ammonia concentrations  

Microsoft Academic Search

The Lost River sucker (Deltistes luxatus) is a federally listed, endangered fish that occurs primarily in Upper Klamath Lake—a hypereutrophic lake in southern Oregon, USA. A decline of the sucker population in the lake over the past few decades has been partly attributed to adverse water quality conditions, including elevated pH and ammonia concentrations that occur during summer cyanobacterial blooms.

Hilary M. Lease; James A. Hansen; Harold L. Bergman; Joseph S. Meyer

2003-01-01

57

Response of Larval Lost River and Shortnose Suckers to Wetland Restoration at the Williamson River Delta, Oregon  

Microsoft Academic Search

Population declines of the federally endangered Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris have been linked to several factors, including the loss of larval nursery habitat associated with lake fringe and riparian wetlands. Restoration of deltaic wetlands in the Williamson River delta, Oregon, is regarded as one strategy that may increase larval nursery habitat and survival. This

John D. Crandall; Leslie B. Bach; Nathan Rudd; Mark Stern; Matt Barry

2008-01-01

58

The "Magic" String  

NSDL National Science Digital Library

The "Magic" String is a discrepant event that includes a canister with what appears to be the end of two strings protruding from opposite sides of it. Due to the way the strings are attached inside the canister, it appears as if the strings can magically

Hoover, Todd F.

2010-10-01

59

What is String Theory?  

Microsoft Academic Search

The first part is an introduction to conformal field theory and string perturbation theory. The second part deals with the search for a deeper answer to the question posed in the title. Contents: 1. Conformal Field Theory 2. String Theory 3. Vacua and Dualities 4. String Field Theory or Not String Field Theory 5. Matrix Models

Joseph Polchinski

1994-01-01

60

Evidence for string substructure  

SciTech Connect

The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes.

Bergman, O.

1996-06-01

61

Vacuum String Field Theory  

Microsoft Academic Search

This is a brief review of vacuum string field theory, a new approach to open string field theory based on the stable vacuum of the tachyon. We discuss the sliver state explaining its role as a projector in the space of half-string functionals. We review the construction of D-brane solutions in vacuum string field theory, both in the algebraic approach

Leonardo Rastelli; Ashoke Sen; Barton Zwiebach

2001-01-01

62

Stringing spins and spinning strings  

NASA Astrophysics Data System (ADS)

We apply recently developed integrable spin chain and dilatation operator techniques in order to compute the planar one-loop anomalous dimensions for certain operators containing a large number of scalar fields in Script N = 4 Super Yang-Mills. The first set of operators, belonging to the SO(6) representations [J,L-2J,J], interpolate smoothly between the BMN case of two impurities (J = 2) and the extreme case where the number of impurities equals half the total number of fields (J = L/2). The result for this particular [J,0,J] operator is smaller than the anomalous dimension derived by Frolov and Tseytlin [44] for a semiclassical string configuration which is the dual of a gauge invariant operator in the same representation. We then identify a second set of operators which also belong to [J,L-2J,J] representations, but which do not have a BMN limit. In this case the anomalous dimension of the [J,0,J] operator does match the Frolov-Tseytlin prediction. We also show that the fluctuation spectra for this [J,0,J] operator is consistent with the string prediction.

Beisert, Niklas; Staudacher, Matthias; Minahan, Joseph A.; Zarembo, Konstantin

2003-09-01

63

Fluid mechanics of strings  

NASA Astrophysics Data System (ADS)

We consider conserved currents in an interacting network of one-dimensional objects (or strings). Singular currents localized on a single string are considered in general, and a formal procedure for coarse graining over many strings is developed. This procedure is applied to strings described by the Nambu-Goto action, such as cosmic strings. In addition to conserved currents corresponding to the energy-momentum tensor, we consider an antisymmetric tensor of conserved currents related to the string tangent vector. Under the assumption of local equilibrium we derive a complete set of hydrodynamic equations for strings.

Schubring, Daniel; Vanchurin, Vitaly

2013-10-01

64

D strings and F strings from string loops  

NASA Astrophysics Data System (ADS)

Since the background fields of the string low energy action are supposed to be the long range manifestation of a condensate of strings, the addition of world sheet actions to the low energy effective action needs some string theoretic explanation. In this paper we suggest that this may be understood as being due to string loop effects. We first present arguments using an equation due to Tseytlin and then more rigorously in the particular case of type IIB theory by invoking the Fischler-Susskind effect. The argument provides further justification for SL(2,Z) duality between D-strings and F (fundamental)-strings. In an Appendix we comment on recent attempts to relate the type IIA membrane to the 11-dimensional membrane.

de Alwis, S. P.; Sato, K.

1996-06-01

65

String driven inflation  

SciTech Connect

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig.

Turok, N.

1987-11-01

66

Occurrences of Catostomid Fishes (Suckers) in the North Canadian River and Lake Eufaula, Oklahoma  

Microsoft Academic Search

A 17-year survey of the North Canadian (Beaver) River, Lake Eufaula, and the Canadian River below Lake Eufaula by the Oklahoma State Health Department between 1976 and 1992 produced seven species of catostomid fishes. During a review of historical fish collections, we found two additional sucker species, for a total of nine catostomids from the drainage. The new species were

Jimmie Pigg; Robert Gibbs

1995-01-01

67

Effects of aspen ( Populus tremuloides ) sucker removal on postfire conifer regeneration in central Alaska  

Microsoft Academic Search

This experiment tests the effects of early canopy development by asexually regenerating aspen (Populus tremuloides Michx.) on conifer recruitment after fire in central Alaska. The establishment and growth of three conifer species were observed in response to aboveground removal of aspen suckers for three seasons after burning by wildfire. Of the three species, Pinus contorta Dougl. ex Loud. had the

Jill F. Johnstone

2005-01-01

68

Gender Representations in BET’s 106 & Park and Sucker Free on MTV: A Content Analysis  

Microsoft Academic Search

A content analysis was conducted on the shows 106 & Park and Sucker Free on MTV for the time period of July 1st to August 31st 2006. Of the 92 videos shown, 43 were selected via random sample to create two ‘composite weeks’ for the viewing period of these shows. Coders were graduate and doctoral students in Florida State University

Kiva LaTouché

2007-01-01

69

Oxidative Stress and Bioindicators of Reproductive Function in Pulp and Paper Mill Effluent Exposed White Sucker  

Microsoft Academic Search

This study investigates oxidative stress and bioindicators of reproductive function in wild white sucker (Catostomus commer- soni) collected from environments receiving pulp and paper mill effluent discharges in northern Ontario. Samples were collected over an eight-year period adjacent to three pulp and paper mills using a variety of processing and bleaching techniques. Fish col- lected downstream of pulp and paper

Ken D. Oakes; Mark E. McMaster; Andrea C. Pryce; Kelly R. Munkittrick; Cam B. Portt; L. Mark Hewitt; Dan D. MacLean; Glen J. Van Der Kraak

2003-01-01

70

Control rod cluster arrangement  

SciTech Connect

This patent describes a nuclear reactor including nuclear core which is cooled and moderated by light water, the nuclear core comprising a plurality of parallel arranged openings therethrough and interspersed among the fuel assemblies. A control rod cluster arrangement comprises load follow control rod cluster assemblies with each load follow control rod cluster assembly being adapted to slidingly fit within each of some of the fuel assemblies in the parallel arranged openings, the load follow control rod cluster assemblies each comprising a plurality of elongated parallel arranged rods attached to a single spider, and including a first group of rods and a second group of rods, the first group of rods and the second each consisting of a plurality of absorber rods. The first group of rods consist of absorber rods taken from the group consisting of B/sub 4/C, hafnium, or silver-indium-cadmium and the second group of rods consist of absorber rods each consisting of stainless steel, the first group of rods and the second group of rods each being integrally attached at all times to the single spider, the absorber rods of the second group of rods being dispersed throughout the control rod cluster assembly. The first group of rods have a first neutron capture cross section and the second group of rods have a second neutron capture cross section different from the first cross section.

Orr, W.L.; Doshi, P.K.; Mildrum, C.M.; Freeman, T.R.

1987-02-10

71

String axiverse  

NASA Astrophysics Data System (ADS)

String theory suggests the simultaneous presence of many ultralight axions, possibly populating each decade of mass down to the Hubble scale 10-33eV. Conversely the presence of such a plenitude of axions (an axiverse) would be evidence for string theory, since it arises due to the topological complexity of the extra-dimensional manifold and is ad hoc in a theory with just the four familiar dimensions. We investigate how several upcoming astrophysical experiments will be observationally exploring the possible existence of such axions over a vast mass range from 10-33eV to 10-10eV. Axions with masses between 10-33eV to 10-28eV can cause a rotation of the cosmic microwave background polarization that is constant throughout the sky. The predicted rotation angle is independent of the scale of inflation and the axion decay constant, and is of order ?˜1/137 -within reach of the just launched Planck satellite. Axions in the mass range 10-28eV to 10-18eV give rise to multiple steps in the matter power spectrum, providing us with a snapshot of the axiverse that will be probed by galaxy surveys-such as BOSS, and 21 cm line tomography. Axions in the mass range 10-22eV to 10-10eV can affect the dynamics and gravitational wave emission of rapidly rotating astrophysical black holes through the Penrose superradiance process. When the axion Compton wavelength is of order of the black hole size, the axions develop superradiant atomic bound states around the black hole nucleus. Their occupation number grows exponentially by extracting rotational energy and angular momentum from the ergosphere, culminating in a rotating Bose-Einstein axion condensate emitting gravitational waves. For black holes lighter than ˜107 solar masses accretion cannot replenish the spin of the black hole, creating mass gaps in the spectrum of rapidly rotating black holes that diagnose the presence of destabilizing axions. In particular, the highly rotating black hole in the X-ray binary LMC X-1 implies an upper limit on the decay constant of the QCD axion fa?2×1017GeV, much below the Planck mass. This reach can be improved down to the grand unification scale fa?2×1016GeV, by observing smaller stellar mass black holes.

Arvanitaki, Asimina; Dimopoulos, Savas; Dubovsky, Sergei; Kaloper, Nemanja; March-Russell, John

2010-06-01

72

Rotation of a rigid body on a string and related problems  

Microsoft Academic Search

The book deals with some aspects of rigid body dynamics that usually arise in solving practical problems. Emphasis is placed on the study of the rotation of rigid bodies on a weightless nonstretchable absolutely flexible string and on a so-called string suspension consisting of a system of ponderable rigid rods connected in series through Hook joints. Attention is given to

Aleksandr Yu. Ishlinskij; Vladimir A. Storozhenko; Mariya E. Temchenko

1991-01-01

73

Closest string with outliers  

PubMed Central

Background Given n strings s1, …, sn each of length ? and a nonnegative integer d, the CLOSEST STRING problem asks to find a center string s such that none of the input strings has Hamming distance greater than d from s. Finding a common pattern in many – but not necessarily all – input strings is an important task that plays a role in many applications in bioinformatics. Results Although the closest string model is robust to the oversampling of strings in the input, it is severely affected by the existence of outliers. We propose a refined model, the CLOSEST STRING WITH OUTLIERS (CSWO) problem, to overcome this limitation. This new model asks for a center string s that is within Hamming distance d to at least n – k of the n input strings, where k is a parameter describing the maximum number of outliers. A CSWO solution not only provides the center string as a representative for the set of strings but also reveals the outliers of the set. We provide fixed parameter algorithms for CSWO when d and k are parameters, for both bounded and unbounded alphabets. We also show that when the alphabet is unbounded the problem is W[1]-hard with respect to n – k, ?, and d. Conclusions Our refined model abstractly models finding common patterns in several but not all input strings. We initialize the study of the computability of this model and show that it is sensitive to different parameterizations. Lastly, we conclude by suggesting several open problems which warrant further investigation.

2011-01-01

74

Wave on a String  

NSDL National Science Digital Library

Watch a string vibrate in slow motion. Wiggle the end of the string and make waves, or adjust the frequency and amplitude of an oscillator. Adjust the damping and tension. The end can be fixed, loose, or open.

Simulations, Phet I.; Dubson, Michael; Adams, Wendy; Harlow, Danielle

2004-06-01

75

Twisted strings and orbifolds  

SciTech Connect

Orbifold compactifications provide a practical approach to string symmetry breaking. They have the potential to bridge the gap between string theory and the physics of the standard model. 7 refs., 5 figs.

Bagger, J.A.

1986-08-01

76

Techniques for Monitoring Razorback Sucker in the Lower Colorado River, Hoover to Parker Dams, 2006-2007. Final Report.  

National Technical Information Service (NTIS)

Trammel netting is generally the accepted method of monitoring razorback sucker in reservoirs, but this method is ineffective for monitoring this fish in rivers. Trammel nets set in the current become fouled with debris, and nets set in backwaters capture...

B. Goettlicher E. Best G. A. Mueller J. Lantow J. Millosovich M. Santee R. Wydoski S. Hiebert

2008-01-01

77

Minimal string theory  

Microsoft Academic Search

We summarize recent progress in the understanding of minimal string theory, focusing on the worldsheet description of physical operators and D-branes. We review how a geometric interpretation of minimal string theory emerges naturally from the study of the D-branes. This simple geometric picture ties together many otherwise unrelated features of minimal string theory, and it leads directly to a worldsheet

Nathan Seiberg; David Shih

2005-01-01

78

Challenges for string cosmology  

NASA Astrophysics Data System (ADS)

We critically assess the twin prospects of describing the observed universe in string theory, and using cosmological experiments to probe string theory. For the purposes of this short review, we focus on the limitations imposed by our incomplete understanding of string theory. After presenting an array of significant obstacles, we indicate a few areas that may admit theoretical progress in the near future.

Burgess, C. P.; McAllister, Liam

2011-10-01

79

PARALLEL STRINGS - PARALLEL UNIVERSES  

Microsoft Academic Search

Sometimes different parts of the battery community just don't seem to operate on the same level, and attitudes towards parallel battery strings are a prime example of this. Engineers at telephone company central offices are quite happy operating 20 or more parallel strings on the same dc bus, while many manufacturers warn against connecting more than four or five strings

Jim McDowall; Saft America

80

Control rod drive  

Microsoft Academic Search

A control rod drive uses gravitational forces to insert one or more control rods upwardly into a reactor core from beneath the reactor core under emergency conditions. The preferred control rod drive includes a vertically movable weight and a mechanism operatively associating the weight with the control rod so that downward movement of the weight is translated into upward movement

Hawke; Basil C

1986-01-01

81

Rod examination gauge  

DOEpatents

The present invention is directed to a semi-automatic rod examination gauge for performing a large number of exacting measurements on radioactive fuel rods. The rod examination gauge performs various measurements underwater with remote controlled machinery of high reliability. The rod examination gauge includes instruments and a closed circuit television camera for measuring fuel rod length, free hanging bow measurement, diameter measurement, oxide thickness measurement, cladding defect examination, rod ovality measurement, wear mark depth and volume measurement, as well as visual examination. A control system is provided including a programmable logic controller and a computer for providing a programmed sequence of operations for the rod examination and collection of data.

Bacvinskas, W.S.; Bayer, J.E.; Davis, W.W.; Fodor, G.; Kikta, T.J.; Matchett, R.L.; Nilsen, R.J.; Wilczynski, R.

1991-12-31

82

Behavior and Passage Performance of Northern Pike, Walleyes, and White Suckers in an Experimental Raceway  

Microsoft Academic Search

The willingness and ability of wild adult northern pike Esox lucius, walleyes Sander vitreus, and white suckers Catostomus commersonii to ascend a 25- or 50-m experimental raceway against various water velocities (35–120 cm\\/s at 8 cm from the bottom) was measured. The probability that a fish of any given species would enter the raceway from its holding tank was significantly

Stephan J. Peake

2008-01-01

83

Economic Analysis of Tissue-cultured Banana and Sucker-propagated Banana  

Microsoft Academic Search

An economic analysis of tissue-cultured banana (TCB) and sucker-propagated banana (SPB) has been presented through studying their costs and returns. The factors influencing the costs of their production have been identified and resource-use efficiency has been studied. The risks in cultivation of tissue-cultured banana have been highlighted. The study has been conducted in the Theni district of Tamil Nadu using

T. Alagumani

2005-01-01

84

Effective size, census size, and genetic monitoring of the endangered razorback sucker, Xyrauchen texanus  

Microsoft Academic Search

For the past several decades the Lake Mohave population of the federally endangered razorback sucker, Xyrauchen texanus, has had no natural recruitment because of intensive predation on larvae by non-native fishes. In response to impending extirpation,\\u000a a repatriation program was implemented where larval razorbacks are collected from the wild following natural spawning, reared\\u000a in protective custody, and then repatriated at

Thomas F. Turner; Thomas E. Dowling; Paul C. Marsh; Brian R. Kesner; Anne T. Kelsen

2007-01-01

85

Gravitational field of vacuum domain walls and strings  

Microsoft Academic Search

The gravitational properties of vacuum domain walls and strings are studied in the linear approximation of general relativity. These properties are shown to be very different from those of regular massive planes and rods. It is argued that the domain walls are gravitationally unstable and collapse at a certain time approx.t\\/sub c\\/ after their creation. If the vacuum walls ever

Alexander Vilenkin

1981-01-01

86

Semilocal cosmic string networks  

SciTech Connect

We report on a large-scale numerical study of networks of semilocal cosmic strings in flat space in the parameter regime in which they are perturbatively stable. We find a population of segments with an exponential length distribution and indications of a scaling network without significant loop formation. Very deep in the stability regime strings of superhorizon size grow rapidly and ''percolate'' through the box. We believe these should lead at late times to a population of infinite strings similar to topologically stable strings. However, the strings are very light; scalar gradients dominate the energy density, and the network has thus a global texturelike signature. As a result, the observational constraints, at least from the temperature power spectrum of the cosmic microwave background, on models predicting semilocal strings should be closer to those on global textures or monopoles, rather than on topologically stable gauged cosmic strings.

Achucarro, Ana [Instituut-Lorentz, Universiteit Leiden, P. O. Box 9506, 2300 RA, Leiden (Netherlands); Department of Theoretical Physics, University of the Basque Country UPV-EHU, 48080 Bilbao (Spain); Salmi, Petja [Instituut-Lorentz, Universiteit Leiden, P. O. Box 9506, 2300 RA, Leiden (Netherlands); Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Urrestilla, Jon [Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States)

2007-06-15

87

Axions from string decay  

SciTech Connect

We have studied numerically the evolution and decay of axion strings. These global defects decay mainly by axion emission and thus contribute to the cosmological axion energy density. The relative importance of this source relative to misalignment production of axions depends on the spectrum. Radiation spectra for various string loop configurations are presented. They support the contention that the string decay contribution is of the same order of magnitude as the contribution from misalignment.

Hagmann, C., LLNL

1998-07-09

88

Drill string enclosure  

DOEpatents

This invention is comprised of a drill string enclosure which consists of six component parts, including; a top bracket, an upper acrylic cylinder, an acrylic drill casing guide, a lower acrylic cylinder, a bottom bracket, and three flexible ducts. The upper acrylic cylinder is optional based upon the drill string length. The drill string enclosure allows for an efficient drill and sight operation at a hazardous waste site.

Jorgensen, D.K.; Kuhns, D.J.; Wiersholm, O.; Miller, T.A.

1992-12-31

89

Heterotic cosmic strings  

SciTech Connect

We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion.

Becker, Katrin; Becker, Melanie; Krause, Axel [Radcliffe Institute, Harvard University, Cambridge, Massachusetts 02138 (United States) and Mitchell Institute for Fundamental Physics, Texas A and M University, College Station, Texas 77843 (United States); Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States) and Mitchell Institute for Fundamental Physics, Texas A and M University, College Station, Texas 77843 (United States)

2006-08-15

90

Pull Rod Assembly.  

National Technical Information Service (NTIS)

A pull rod assembly comprising a pull rod having three peripheral grooves, a piston device including an adaptor ring and a seal ring, said piston device being mounted on the pull rod by a split ring retainer situated in one groove and extending into an in...

O. C. Cioletti

1988-01-01

91

Rod Lock Mechanism.  

National Technical Information Service (NTIS)

The patent application describes a fluid pressure mechanism for locking a movable rod or similar member in selected positions of adjustment. The mechanism includes a fluid housing having at least one annular rod-gripper element encircling a movable rod. I...

E. F'Geppert

1982-01-01

92

Introduction to string field theory  

SciTech Connect

An action is proposed for an interacting closed bosonic string. Our formalism relies heavily on ideas discussed by Witten for the open bosonic string. The gauge fixed quantum action for the fully interacting open bosonic string is obtained.

Lykken, J.; Raby, S.

1986-01-01

93

CONTROL ROD DRIVE  

DOEpatents

Accurate and controlled drive for the control rod is from an electric motor. A hydraulic arrangement is provided to balance a piston against which a control rod is urged by the application of fluid pressure. The electric motor drive of the control rod for normal operation is made through the aforementioned piston. In the event scramming is required, the fluid pressure urging the control rod against the piston is relieved and an opposite fluid pressure is applied. The lack of mechanical connection between the electric motor and control rod facilitates the scramming operation.

Chapellier, R.A.; Rogers, I.

1961-06-27

94

Rotation of a rigid body on a string and related problems  

NASA Astrophysics Data System (ADS)

The book deals with some aspects of rigid body dynamics that usually arise in solving practical problems. Emphasis is placed on the study of the rotation of rigid bodies on a weightless nonstretchable absolutely flexible string and on a so-called string suspension consisting of a system of ponderable rigid rods connected in series through Hook joints. Attention is given to the history of the origin and evolution of the motion of string-suspended rigid bodies with cavities completely filled by an ideal incompressible liquid. The various stationary motions of rigid bodies suspended on a string or supported on a string suspension are investigated with reference to their stability and bifurcation. Some problems associated with the practical application of the string suspension in some mechanical devices are discussed.

Ishlinskij, Aleksandr Yu.; Storozhenko, Vladimir A.; Temchenko, Mariya E.

95

CRUCIFORM CONTROL ROD JOINT  

DOEpatents

An invention is described which relates to nuclear reactor control rod components and more particularly to a joint between cruciform control rod members and cruciform control rod follower members. In one embodiment this invention provides interfitting crossed arms at adjacent ends of a control rod and its follower in abutting relation. This holds the members against relative opposite longitudinal movement while a compression member keys the arms against relative opposite rotation around a common axis. Means are also provided for centering the control rod and its follower on a common axis and for selectively releasing the control rod from its follower for the insertion of a replacement of the control rod and reuse of the follower. (AEC)

Thorp, A.G. II

1962-08-01

96

Extreme cosmic string  

NASA Astrophysics Data System (ADS)

This paper deals with the geometry of supermassive cosmic strings. We use an approach that enforces the spacetime of cosmic strings to also satisfy the conservation laws of a cylindric gravitational topological defect, that is, a spacetime kink. In the simplest case of kink number unity the entire energy range of supermassive strings then becomes quantized so that only cylindrical defects with a linear energy density G?=1/4 (critical string) and G?=1/2 (extreme string) are allowed to occur in this range. It has been seen that the internal spherical coordinate ? of the string metric embedded in a Euclidean three-space also evolves on imaginary values, leading to the creation of a covering shell of a broken phase that protects the core with trapped energy, even for G?=1/2. Then, the conical singularity becomes a removable horizon singularity. We reexpress the extreme string metric in the Finkelstein-McCollum standard form and remove the geodesic incompleteness by using the Kruskal technique. The z=const sections of the resulting metric are the same as the hemispherical section of the metric of a de Sitter kink. Some physical consequences from these results, including the possibility that the extreme string drives inflation and thermal effects in its core, are also discussed.

González-Díaz, Pedro F.

1995-11-01

97

String Theory and Cosmology  

ScienceCinema

It appears that string theory can give rise to many different 4d worlds, manifesting different values of fundamental parameters such as the cosmological constant. We discuss the structure of this 'landscape' of string vacua, and show that some aspects are amenable to calculation. We also describe simple models of inflation, dark energy, and particle physics that have been proposed in this context

98

String Theory Phenomenology  

Microsoft Academic Search

We review the qualitative features of string theory compactifications with low energy effective theory close to (supersymmetric versions of) the Standard Model of Particle Physics. We cover Calabi-Yau compactifications of heterotic strings, intersecting brane models, and the recent setup of F-theory models.

Angel Uranga

2010-01-01

99

String Theory Phenomenology  

NASA Astrophysics Data System (ADS)

We review the qualitative features of string theory compactifications with low energy effective theory close to (supersymmetric versions of) the Standard Model of Particle Physics. We cover Calabi-Yau compactifications of heterotic strings, intersecting brane models, and the recent setup of F-theory models.

Uranga, Angel

2010-11-01

100

Spatial and temporal variation in abundance of Diplostomum spp. in walleye ( Stizostedion vitreum ) and white suckers ( Catostomus commersoni ) from the St. Lawrence River  

Microsoft Academic Search

Abundances of eye flukes (Diplostomum spp.) were compared between walleye (Stizostedion vitreum) and white suckers (Catostomus commersoni ) collected in late summer 1997 from Lake St. Louis and Lake St. Pierre, two expansions of the St. Lawrence River in Quebec, Canada. The white sucker, a benthic consumer, was more heavily in- fected than the walleye, a pelagic piscivore, in both

David J. Marcogliese; Pierre Dumont; Andrée D. Gendron; Yves Mailhot; Emmanuelle Bergeron; J. Daniel McLaughlin

2001-01-01

101

Rapid Out-Migration of Lost River and Shortnose Sucker Larvae from In-River Spawning Beds to In-Lake Rearing Grounds  

Microsoft Academic Search

We examined the process of larval out-migration of endangered Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris from spawning grounds in the Williamson and Sprague rivers to rearing grounds in Upper Klamath Lake. Most downstream movement occurred at night, when larvae drifted in surface currents at the center of the channel. During daylight, larvae were absent from the

Michael Cooperman; Douglas F. Markle

2003-01-01

102

Stable Charged Cosmic Strings  

SciTech Connect

We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius {approx_equal}10{sup -18} m. The vacuum remains stable in our model, because neutral strings are not energetically favored.

Weigel, H. [Physics Department, Stellenbosch University, Matieland 7602 (South Africa); Quandt, M. [Institute for Theoretical Physics, Tuebingen University, D-72076 Tuebingen (Germany); Graham, N. [Department of Physics, Middlebury College , Middlebury, Vermont 05753 (United States)

2011-03-11

103

Conformal techniques in string theory and string field theory  

Microsoft Academic Search

The application of some conformal and Riemann surface techniques to string theory and string field theory is described. First a brief review of Riemann surface techniques and of the Polyakov approach to string theory is presented. This is followed by a discussion of some features of string field theory and of its Feynman rules. Specifically, it is shown that the

Steven B. Giddings

1988-01-01

104

Conformal Techniques in String Theory and String Field Theory  

Microsoft Academic Search

The application of some conformal and Riemann surface techniques to string theory and string field theory is described. First a brief review of Riemann surface techniques and of the Polyakov approach to string theory is presented. This is followed by a discussion of some features of string field theory and of its Feynman rules. Specifically, it is shown that the

Steven B. Giddings

1987-01-01

105

Coalescence of two viscoelastic droplets connected by a string  

NASA Astrophysics Data System (ADS)

A new type of coalescence of viscoelastic droplets is described and analyzed. A viscoelastic drop of polyisobutene (PIB) containing high molar mass PIB (HPIB), suspended in polydimethylsiloxane, is separated into two droplets connected by a string, which is called ``bead-string-bead'' (BSB), through repeated elongation and relaxation in a four-roll mill rheometer. Upon flow cessation, the two drops are pulled to approach each other by the string and eventually coalesce. This process exhibits interesting features: The string remains stable like a rod without capillary breakup; the string length and the merging force decay exponentially with time; the string diameter may not change significantly through the approach. The string in BSB is more stable than that of the capillary thinning process of beads on string in jet or fixed-end rheometer. These phenomena are modeled based on the force balance of the viscoelasticity of HPIB systems, viscous drag, and the Laplace force. The model prediction agrees with the experimental observation reasonably well, revealing the viscoelastic nature of the coalescence of two droplets. The characteristic time of drop approach is comparable to that of the pulling stress decay. The condition of keeping a constant diameter in BSB approach creates a status where both drop approach and stress decay exponentially with the same characteristic time, which is comparable to the material relaxation time. This case allows the model to analyze the relationships between critical string diameter and the material parameter as well as the process parameters and to discuss the microscopic images of the BSB process.

Yang, Jianmao; Xu, Yuanze

2008-04-01

106

Cosmic Strings and the String Dilation.  

National Technical Information Service (NTIS)

In the paper the authors shall discuss another mechanism of dilaton production. Oscillating loops of cosmic string, which could be formed at a symmetry-breaking phase transition in the early universe, will copiously emit dilatons, as long as the character...

T. Damour A. Vilenkin

1996-01-01

107

Assessment Practices of String Teachers  

Microsoft Academic Search

The purpose of this study was to explore string teachers? assessment practices related to string program success. Additionally, the study examined the relationship between teacher characteristics and string program success. This study was conducted by surveying string teachers (N = 201) from around the country. The survey was designed based on the independent variables of teacher characteristics and assessment practices,

Sara Anne Duncan

2009-01-01

108

String Field Theory  

NASA Astrophysics Data System (ADS)

String theory has emerged as the leading candidate for a unified field theory of all known forces. However, it is impossible to trust the various phenomenological predictions of superstring theory based on classical solutions alone. It appears that the crucial problem of the theory, breaking ten dimensional space-time down to four dimensions, must be solved nonperturbatively before we can extract reliable predictions. String field theory may be the only formalism in which we can resolve this decisive question. Only a rigorous calculation of the true vacuum of the theory will determine which of the many classical solutions the theory actually predicts. In this review article, we summarize the rapid progress in constructing string field theory actions, such as the development of the covariant BRST theory. We also present the newer geometric formulation of string field theory, from which the BRST theory and the older light cone theory can be derived from first principles. This geometric formulation allows us to derive the complete field theory of strings from two geometric principles, in the same way that general relativity and Yang-Mills theory can be derived from two principles based on global and local symmetry. The geometric formalism therefore reduces string field theory to a problem of finding an invariant under a new local gauge group we call the universal string group (USG). Thus, string field theory is the gauge theory of the universal string group in much the same way that Yang-Mills theory is the gauge theory of SU(N). Thus, the geometric formulation places superstring theory on the same rigorous group theoretical level as general relativity and gauge theory.

Kaku, Michio

109

Temporal and Spatial Distribution of Endangered Juvenile Lost River and Shortnose Suckers in Relation to Environmental Variables in Upper Klamath Lake, Oregon: 2008 Annual Data Summary  

USGS Publications Warehouse

Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were listed as endangered in 1988 for a variety of reasons including apparent recruitment failure. Upper Klamath Lake, Oregon, and its tributaries are considered the most critical remaining habitat for these two species. Age-0 suckers are often abundant in Upper Klamath Lake throughout the summer months, but catches decline dramatically between late August and early September each year and age-1 and older sub-adult suckers are rare. These rapid declines in catch rates and a lack of substantial recruitment into adult sucker populations in recent years suggests sucker populations experience high mortality between their first summer and first spawn. A lack of access to, or abundance of, optimal rearing habitat may exacerbate juvenile sucker mortality or restrict juvenile growth or development. Summer age-0 sucker habitat use and distribution has been studied extensively, but many uncertainties remain about age-1 and older juvenile habitat use, distribution, and movement patterns within Upper Klamath Lake. We designed a study to examine seasonal changes in distribution of age-1 suckers in Upper Klamath Lake as they relate to depth and water quality. In this document, which meets our annual data summary and reporting obligations, we discuss the results of our second annual spring and summer sampling effort. Catch data collected in 2007 and 2008 indicate seasonal changes in age-1 and older juvenile sucker habitat use coincident with changes in water quality, which were previously undocumented. In both years during April and May, age-1 and older juvenile suckers were found in shallow water environments. Then, as water temperatures began to warm throughout Upper Klamath Lake in June, age-1 and older juvenile suckers primarily were captured along the western shore in some of the deepest available environments. Following a dramatic decrease in dissolved oxygen concentrations in Eagle Ridge Trench, juvenile suckers were no longer found along the western shore but were captured throughout the rest of Upper Klamath Lake. When dissolved oxygen concentrations were 4 milligrams per liter or greater along the western shore, juvenile sucker captures were again concentrated in that area. Although this pattern indicates that low dissolved oxygen concentration or another related water-quality limitation may force juvenile suckers to leave the western shore, it is unclear as to why age-1 and older juveniles might be attracted to the area in the first place. Understanding this apparent behavior could be important to managing habitat for these species. In this data summary, we also describe the distribution of catches of age-0 suckers and other fishes in Upper Klamath Lake. These data corroborate previous studies that describe age-0 sucker habitat as shallow relative to depths available in Upper Klamath Lake. In this study, we did not seek, nor find additional clarification on age-0 sucker habitat use and distribution in Upper Klamath Lake. Our brief description of the distribution and abundance of all other fish species caught provides a context in which to assess the rarity of juvenile suckers within the fish community of Upper Klamath Lake.

Burdick, Summer M.; VanderKooi, Scott P.

2010-01-01

110

Pull rod assembly  

SciTech Connect

This patent describes a pull rod assembly. It comprises: a pull rod having three peripheral grooves, a piston device including an adaptor ring and a seal ring. The piston device is mounted on the pull rod by a split ring retainer situated in one groove and extending into an interior groove in the adaptor and a resilient split ring retained in another groove and positioned to engage the piston device and to retain the seal on its adaptor.

Cioletti, O.C.

1990-05-22

111

Pull rod assembly  

DOEpatents

A pull rod assembly comprising a pull rod having three peripheral grooves, a piston device including an adaptor ring and a seal ring, said piston device being mounted on the pull rod by a split ring retainer situated in one groove and extending into an interior groove in the adaptor and a resilient split ring retained in another groove and positioned to engage the piston device and to retain the seal on its adaptor.

Cioletti, O.C.

1988-04-21

112

Status of rod consolidation  

SciTech Connect

Two of the factors that need to be taken into account with rod consolidation are (1) the effects on rods from their removal from the fuel assembly and (2) the effects on rods as a result of the consolidation process. Potential components of both factors are described in the report. Discussed under (1) are scratches on the fuel rod surfaces, rod breakage, crud, extended burnup, and possible cladding embrittlement due to hydrogen injection at BWRs. Discussed under (2) are the increased water temperature (less than 10/sup 0/C) because of closer packing of the rods, formation of crevices between rods in the close-packed mode, contact with dissimilar metals, and the potential for rapid heating of fuel rods following the loss of water from a spent fuel storage pool. Another factor that plays an important role in rod consolidation is the cost of disposal of the nonfuel-bearing components of the fuel assembly. Also, the dose rate from the components - especially Inconel spacer grids - can affect the handling procedures. Several licensing issues that exist are described. A list of recommendations is provided. 98 refs., 5 figs., 5 tabs.

Bailey, W.J.

1985-04-01

113

Effects of soil temperature and time of decapitation on sucker initiation of intact Populus tremuloides root systems  

Microsoft Academic Search

In a growth chamber experiment, root suckering of aspen (Populus tremuloides Michx.) was assessed in relation to timing of cutting and soil temperature. Aspen seedlings were grown in large pots for 3 years before experimentation. In a 2 \\/2 factorial experiment, 3-year-old seedlings were cut at the end of the dormant period or after leaf flush and grown at two

SIMON M. LANDHAUSSER; VICTOR J. LIEFFERS; Tara Mulak

2006-01-01

114

Stocking of Endangered Razorback Suckers in the Lower Colorado River Basin over Three Decades: 1974–2004  

Microsoft Academic Search

The razorback sucker Xyrauchen texanus was historically widespread and abundant throughout the larger streams of the Colorado River basin, ranging from Sonora, Mexico, to Wyoming. The species was federally listed as endangered in 1991 because it has been extirpated from most of its range. Its decline is attributed to habitat loss and predation by nonnative fishes. Thirty years of federal

Jason D. Schooley; Paul C. Marsh

2007-01-01

115

Assessment of Population Status for a White Sucker ( Catostomus commersoni ) Population Exposed to Bleached Kraft Pulp Mill Effluent  

EPA Science Inventory

Credible ecological risk assessments often need to include analysis of population-level impacts. In the present study, a predictive model was developed to translate changes in the fecundity and the age structure of a breeding population of white sucker (Catostomus commersoni) co...

116

The QCD Effective String  

NASA Astrophysics Data System (ADS)

QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values.

Espriu, Domenec

2003-10-01

117

Drill String Failure Analyses.  

National Technical Information Service (NTIS)

The report contains analyses of major drill string failures incurred during 15 years of Deep Sea Drilling Project (DSDP) wireline coring operations. Operating experience and means to reduce such losses is also described. This operational experience and fa...

M. N. A. Peterson

1983-01-01

118

String Cosmology and Chaos.  

National Technical Information Service (NTIS)

A striking prediction of string theory is that its 'gravitational sector' is richer than that of General Relativity: it contains several a priori massless fields in addition to the Einstein graviton. The authors consider that these fields represent an int...

T. Damour

2002-01-01

119

New supersymmetric string compactifications  

Microsoft Academic Search

We describe a new class of supersymmetric string compactifications to 4d Minkowski space. These solutions involve type II strings propagating on (orientifolds of) non Calabi-Yau spaces in the presence of background NS and RR fluxes. The simplest examples have descriptions as cosets, generalizing the three-dimensional nilmanifold. They can also be thought of as twisted tori. We derive a formula for

Shamit Kachru; Michael B. Schulz; Prasanta K. Tripathy; Sandip P. Trivedi

2003-01-01

120

Matrix string theory  

Microsoft Academic Search

Via compactification on a circle, the matrix mode] of M-theory proposed by Banks et a]. suggests a concrete identification between the large N limit of two-dimensional N = 8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the

Robbert Dijkgraaf; Erik Verlinde; Herman L Verlinde

1997-01-01

121

Constraints on string cosmology  

NASA Astrophysics Data System (ADS)

String theory contains sources like orientifold planes that support higher derivative interactions. These interactions make static flux compactifications possible which are forbidden in supergravity. They can also lead to violations of the strong energy condition which is needed for an accelerating universe. We examine how large a violation is possible in the context of the heterotic string compactified to four dimensions. We find that de Sitter solutions are still not possible but that classically forbidden anti-de Sitter solutions are possible.

Green, Stephen R.; Martinec, Emil J.; Quigley, Callum; Sethi, Savdeep

2012-04-01

122

String-string duality conjecture in six dimensions and charged solitonic strings  

Microsoft Academic Search

It has recently been conjectured that the type IIA string theory compactified on K3 and the heterotic string theory compactified on a four dimensional torus describe identical string theories. The fundamental heterotic string can be regarded as a non-singular soliton solution of the type IIA string theory with a semi-infinite throat. We show that this solution admits 24 parameter non-singular

Ashoke Sen

1995-01-01

123

Hydroball string sensing system  

DOEpatents

A hydroball string sensing system for a nuclear reactor that includes stainless tubes positioned to guide hydroball strings into and out of the nuclear reactor core. A sensor such as an ultrasonic transducer transmitter and receiver is positioned outside of the nuclear reactor core and adjacent to the tube. The presence of an object such a bullet member positioned at an end a hydroball string, or any one of the hydroballs interrupts the transmission of ultrasound from the transmitter to the receiver. Alternatively, if the bullet member and hydroballs include a ferritic material, either a Hall effect sensor or other magnetic field sensors such as a magnetic field rate of change sensor can be used to detect the location and position of a hydroball string. Placing two sensors along the tube with a known distance between the sensors enables the velocity of a hydroball string to be determined. This determined velocity can be used to control the flow rate of a fluid within the tube so as to control the velocity of the hydroball string.

Hurwitz, Michael J. (Pittsburgh, PA); Ekeroth, Douglas E. (Delmont, PA); Squarer, David (Pittsburgh, PA)

1991-01-01

124

Instabilities of twisted strings  

NASA Astrophysics Data System (ADS)

A linear stability analysis of twisted flux-tubes (strings) in an SU(2) semilocal theory — an Abelian-Higgs model with two charged scalar fields with a global SU(2) symmetry — is carried out. Here the twist refers to a relative phase between the two complex scalars (with linear dependence on, say, the z coordinate), and importantly it leads to a global current flowing along the the string. Such twisted strings bifurcate with the Abrikosov-Nielsen-Olesen (ANO) solution embedded in the semilocal theory. Our numerical investigations of the small fluctuation spectrum confirm previous results that twisted strings exhibit instabilities whose amplitudes grow exponentially in time. More precisely twisted strings with a single magnetic flux quantum admit a continuous family of unstable eigenmodes with harmonic z dependence, indexed by a wavenumber kin[-km, km]. Carrying out a perturbative semi-analytic analysis of the bifurcation, it is found that the purely numerical results are very well reproduced. This way one obtains not only a good qualitative description of the twisted solutions themselves as well as of their instabilities, but also a quantitative description of the numerical results. Our semi-analytic results indicate that in close analogy to the known instability of the embedded ANO vortex a twisted string is also likely to expand in size caused by the spreading out of its magnetic flux.

Forgács, Péter; Lukács, Árpád

2009-12-01

125

Foucault Rod Model  

NSDL National Science Digital Library

The Foucault Rod model displays the vibration of a circumnavigating rod. One end of the rod is firmly secured to a support. The free end of the rod has a weight attached, like the bob of a pendulum. The support of the rod is circumnavigating a central axis. The plane of swing of the Foucault rod is affected by the rotation in the same way as the Foucault pendulum is. The simulation shows simultaneously the motion with respect to the inertial coordinate system, and the motion as seen from a co-rotating point of view. For the co-rotating view there is a close-up view and an overview. You can examine and modify this simulation if you have EJS installed by right-clicking within the plot and selecting âOpen EJS Modelâ from the pop-up menu item. The Foucault Rod model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_nl_teunissen_foucault_rod.jar file will run the program if Java is installed. Additional information about this model can be found by visiting the authorâs web site: http://www.cleonis.nl/index.htm.

Teunissen, Cleon

2009-11-03

126

FUEL ROD CLUSTERS  

DOEpatents

A cluster of nuclear fuel rods and a tubular casing therefor through which a coolant flows in heat-exchange contact with the fuel rods is described. The fuel rcds are held in the casing by virtue of the compressive force exerted between longitudinal ribs of the fuel rcds and internal ribs of the casing or the internal surfaces thereof.

Schultz, A.B.

1959-08-01

127

Haptic distal spatial perception mediated by strings: haptic "looming".  

PubMed

Five experiments tested a haptic analog of optical looming, demonstrating string-mediated haptic distal spatial perception. Horizontally collinear hooks supported a weighted string held taut by a blindfolded participant's finger midway between the hooks. At the finger, the angle between string segments increased as the finger approached collinearity with the hooks, just as the optical angle subtended by an approaching object increases. The vertical force component at the finger is potentially informative for perception, approaching zero at finger-hook collinearity. In Experiment 1, participants judged hook height reasonably accurately. To retain force relationships but eliminate immediate skin contact, Experiment 2 employed a hand-held rod; results replicated those of Experiment 1. Experiment 3 replicated Experiment 2 using a ring instead of a rod. In all three experiments, estimated hook height closely paralleled actual height, r > .9. Experiments 4 and 5 showed that participants could project impending finger-hook collinearity when finger contact with the string was interrupted during its traverse. Perceivers' estimate errors were nearly perfectly predicted by height-force ratio relationships (Rs > .96). Outcomes are related to optical and acoustic looming, dynamic touch, tau theory, and Gibsonian perceptual theory. PMID:21688938

Cabe, Patrick A

2011-10-01

128

Flashover Performance of Artificially Contaminated and ICED Long-Rod Transmission Line Insulators  

Microsoft Academic Search

The 60 Hz flashover performance of 230 kV and 500 kV long-rod polymer insulators is compared to standard ceramic suspension insulator strings under moderate ice conditions. The tests on clean and heavily pre-contaminated insulators were performed indoors to minimize the effects of wind and temperature variations. In general, contaminated and iced long-rod insulators with disc-shaped sheds of uniform diameter do

E. A. Cherney

1980-01-01

129

Gyrating strings: A new instability of black strings?  

NASA Astrophysics Data System (ADS)

A thermodynamic argument is presented suggesting that near-extremal spinning D1-D5-P black strings become unstable when their angular momentum exceeds Jcrit=3Q1Q5/2?(2). In contrast, the dimensionally reduced black holes are thermodynamically stable. The proposed instability involves a phase in which the spin angular momentum above Jcrit is transferred to gyration of the string in space, i.e., to orbital angular momentum of parts of the string about the mean location in space. Thus the string becomes a rotating helical coil. We note that an instability of this form would yield a counter-example to the Gubser-Mitra conjecture, which proposes a particular link between dynamic black string instabilities and the thermodynamics of black strings. There may also be other instabilities associated with radiation modes of various fields. Our arguments also apply to the D-brane bound states associated with these black strings in weakly coupled string theory.

Marolf, Donald; Palmer, Belkis Cabrera

2004-10-01

130

Nonlinearity and noise at the rod - rod bipolar cell synapse  

PubMed Central

In the retina, rod bipolar (RBP) cells synapse with many rods, and suppression of rod outer segment and synaptic noise is necessary for their detection of rod single photon responses (SPRs). Depending on the rods’ signal to noise ratio (SNR), the suppression mechanism will likely eliminate some SPRs as well, resulting in decreased quantum efficiency. We examined this synapse in rabbit, where 100 rods converge onto each RBP. Suction electrode recordings showed that rabbit rod SPRs were difficult to distinguish from noise (independent SNR estimates were 2.3 and 2.8). Nonlinear transmission from rods to RBPs improved response detection (SNR = 8.7), but a large portion of the rod SPRs were discarded. For the dimmest flashes, the loss approached 90%. Despite the high rejection ratio, noise of two distinct types were apparent in the RBP traces: low amplitude rumblings and discrete events that resembled the SPR. The SPR-like event frequency suggests they result from thermal isomerizations of rhodopsin, which occured at the rate 0.033 s?1rod?1. The presence of low amplitude noise is explained by a sigmoidal input-output relationship at the rod - RBP synapse and the input of noisy rods. The rabbit rod SNR and RBP quantum efficiency are the lowest yet reported, suggesting that the quantum efficiency of the rod - RBP synapse may depend on the SNR in rods. These results point to the possibility that fewer photoisomerizations are discarded for species such as primate, which has a higher rod SNR.

Trexler, E. Brady; Casti, Alexander R.R.; Zhang, Yu

2010-01-01

131

String Theory: Science or Philosophy?  

NSDL National Science Digital Library

This video segment from NOVA discusses the challenge of proving the scientific validity of string theory, in question because strings may be too small to ever be seen or detected, and therefore tested.

Foundation, Wgbh E.

2004-02-20

132

Random Strings and Sequence Comparisons.  

National Technical Information Service (NTIS)

Sequence analysis is concerned with the comparison of finitely long strings of letters drawn from a finite alphabet. This dissertation considers two models of comparing random strings and examines the random length of their resulting features, the longest...

D. E. T. Foulser

1986-01-01

133

String radiative backreaction  

SciTech Connect

We discuss radiative backreaction for global strings described by the Kalb-Ramond action with an analogous derivation to that for the point electron in classical electrodynamics. We show how local corrections to the equations of motion allow one to separate the self-field of the string from that of the radiation field. Modifications to this {open_quote}{open_quote}local backreaction approximation{close_quote}{close_quote} circumvent the runaway solutions, allowing these corrections to be used to evolve string trajectories numerically. Comparisons are made with analytic and numerical radiation calculations from previous work and the merits and limitations of this approach are discussed. {copyright} {ital 1995 The American Physical Society.}

Battye, R.A.; Shellard, E.P. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge, CB3 9EW (United Kingdom)]|[Isaac Newton Institute for Mathematical Sciences, Clarkson Road, Cambridge CB3 0EH (United Kingdom)

1995-12-01

134

Quantum String Theory  

NASA Astrophysics Data System (ADS)

String theories seem to have created a breakthrough in theoretical physics. At long last a unified theory of all the fundamental interactions, including gravity, looks possible. This, according to theorist Stephen Hawking, will mark the end of theoretical physics as we have known it, since we will then have a single consistent theory within which to explain all natural phenomena from elementary particles to galactic superclusters. Strings themselves are extremely tiny entities, smaller than the Planck scale, which form loops whose vibrational harmonics can be used to model all the standard elementary particles. Of course the mathematical complexities of the theory are daunting, and physicists are still at a very early stage in understanding how strings and their theoretical cousins superstrings can be used. This proceedings volume gives an overview of the intense recent work in the field and reports latest developments.

Kawamoto, Noboru; Kugo, Taichiro

135

Introduction to string theory  

NASA Astrophysics Data System (ADS)

These notes are based on a set of six introductory lectures given jointly by the authors. After developing the canonical methods we discuss the covariant quantization of the bosonic as well as the fermionic string. Conformal field theory methods are also introduced and used to calculate the anomaly coefficient (c), as well as the critical dimensions for bosonic and superstrings. We briefly sketch the BRS quantization and then offer an elementary derivation of the anomaly in the ghost number current. Finally, we address the one-loop partition function of the bosonic string and the question of SL(2,Z) invariance.

Randjbar-Daemi, S.; Strathdee, J.

1987-10-01

136

Strings, standing waves and harmonics  

NSDL National Science Digital Library

This website from the University of New South Wales contains basic information about how stringed instruments produce sound. The site discusses plucked string sound and bowed string sound, standing waves, and harmonics. There are many helpful animations and pictures to illustrate concepts.

Wolfe, Joe

2009-11-16

137

String Theory and Gauge Theories  

ScienceCinema

We will see how gauge theories, in the limit that the number of colors is large, give string theories. We will discuss some examples of particular gauge theories where the corresponding string theory is known precisely, starting with the case of the maximally supersymmetric theory in four dimensions which corresponds to ten dimensional string theory. We will discuss recent developments in this area.

138

New Connections Between String Theories  

Microsoft Academic Search

We consider the R-->0 limit of toroidal compactification in various string theories. This leads to new connections between seemingly different string theories: IIA and IIB, open and closed, oriented and unoriented. We also find two new extended objects which can couple consistently to strings: the Dirichlet-brane and the orientifold plane.

Jin Dai; R. G. Leigh; Joseph Polchinski

1989-01-01

139

Conformal Collineations in String Cosmology  

NASA Astrophysics Data System (ADS)

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

Baysal, Hüsnü; Camci, U.?ur; Tarhan, ?smail; Yilmaz, ?hsan; Yavuz, ?lhami; Dolgov, A.

140

Recent Developments in String Theory  

Microsoft Academic Search

The purpose of this short review is to present progresses in string theory in the recent past. There have been very important developments in our understanding of string dynamics, especially in the nonperturbative aspects. In this context, dualities play a cardinal role. The string theory provides a deeper understanding of the physics of special class of black holes from a

Jnanadeva Maharana

1999-01-01

141

Open string fields as matrices  

Microsoft Academic Search

We study the matter part of the algebra of open string fields using the 3-string vertex over the sliver state, which we call ``comma vertex.'' We show that the matter part of open string fields can be written as matrices. This talk is based on [1]. .

Kazumi Okuyama

2002-01-01

142

Demographics and Chronology of a Spawning Aggregation of Blue Sucker (Cycleptus elongatus) in the Grand River, Missouri, USA  

USGS Publications Warehouse

The blue sucker (Cycleptus elongatus) was sampled as individuals arrived, spawned, and departed from a spawning riffle in the Grand River of northcentral Missouri, USA. The Grand River basin was not known to support blue sucker reproduction with few individuals ever recorded. The spawning site is unique in character for the lower river. Individuals began arriving in early April when water temperatures reached 10-12??C. Females with freely-flowing roe were sampled in late April after a large rise in river stage and concurrent lowering of the water temperature 4-5 degrees to 16.5??C. The spawning aggregation had a mean age of 15 y and ranged from 9 to 22 y based on scales that probably underestimated true ages. Males outnumbered females 5.5:1. Mean length was 659 mm for males and 721 mm for females. Females were longer at age than males and no significant age-length relationship was evident.

Vokoun, J. C.; Guerrant, T. L.; Rabeni, C. F.

2003-01-01

143

Cosmic D-strings as axionic D-term strings  

SciTech Connect

In this work we derive nonsingular BPS string solutions from an action that captures the essential features of a D-brane-anti-D-brane system compactified to four dimensions. The model we consider is a supersymmetric Abelian Higgs model with a D-term potential coupled to an axion-dilaton multiplet. The strings in question are axionic D-term strings which we identify with the D-strings of type II string theory. In this picture the Higgs field represents the open string tachyon of the D-D pair and the axion is dual to a Ramond-Ramond form. The crucial term allowing the existence of nonsingular BPS strings is the Fayet-Iliopoulos term, which is related to the tensions of the D-string and of the parent branes. Despite the presence of the axion, the strings are BPS and carry finite energy, due to the fact that the space gets very slowly decompactified away from the core, screening the long range axion field (or equivalently the theory approaches an infinitely weak 4D coupling). Within our 4D effective action we also identify another class of BPS string solutions (s-strings) which have no ten-dimensional analog, and can only exist after compactification.

Blanco-Pillado, Jose J.; Dvali, Gia; Redi, Michele [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, New York 10003 (United States)

2005-11-15

144

Survival Rates and Movement of Hatchery-Reared Razorback Suckers in the Upper Colorado River Basin, Utah and Colorado  

Microsoft Academic Search

We used tag–recapture data to estimate apparent survival and capture probability for 119,129 hatchery-reared, federally endangered razorback suckers Xyrauchen texanus stocked into upper Colorado River basin streams during 1995–2005. Effects investigated included reach, year, and season of stocking; fish total length (TL) at time of stocking; survival in the first year after stocking versus in subsequent years; and sampling effort.

Koreen A. Zelasko; Kevin R. Bestgen; Gary C. White

2010-01-01

145

Loss of glutathione S-transferases in pollution-associated liver neoplasms in white suckers (Catostomus commersoni) from Lake Ontario.  

PubMed

White suckers (Catostomus commersoni) are one of two species of bottom-feeding fish in which various liver neoplasms are more prevalent in urban/industrial sites in western Lake Ontario than in less polluted sites in the Great Lakes. Previous studies indicate that white suckers excrete metabolites of various polycyclic aromatic hydrocarbons (PAHs) in bile, and that glutathione transferase (GST)-mediated conjugation is a major detoxification pathway for the PAH benzo[alpha]pyrene. To determine whether hepatocarcinogenesis in these wild fish is associated with induced GST-dependent resistance to carcinogens, we examined the expression of immunoreactive GSTs in liver neoplasms and putatively preneoplastic altered hepatocellular foci from white suckers collected from several polluted sites in western Lake Ontario. Histological sections of liver with altered hepatocellular foci, hepatocellular adenomas, hepatocellular carcinomas, bile duct adenomas and bile duct carcinomas were examined for GST immunoreactivity by the peroxidase-antiperoxidase (PAP) technique with polyclonal antiserum specific for all major GST isoenzyme subunits found in normal liver of white suckers. All bile duct adenomas, bile duct carcinomas and hepatocellular carcinomas were markedly or completely deficient in immunoreactive GST in comparison with surrounding normal hepatocytes. The majority of the hepatocellular adenomas were also deficient. Most altered hepatocellular foci had normal GST staining, but several GST-deficient altered hepatocellular foci were observed. However, none of the preneoplastic or advanced liver neoplasms expressed induced GST, suggesting that carcinogenesis is not associated with selection for GST-dependent resistance. Loss of hepatocellular GSTs may be incidental to neoplastic progression in these fish, or might be important in increasing susceptibility of some preneoplastic populations of hepatocytes to further DNA damage by environmental or endogenous chemicals that are normally detoxified by GSTs. PMID:1660792

Stalker, M J; Kirby, G M; Kocal, T E; Smith, I R; Hayes, M A

1991-12-01

146

Effects of natural exposure to copper and zinc on egg size and larval copper tolerance in white sucker (Catostomus commersoni)  

SciTech Connect

Sucker eggs were collected from a metal-contaminated site where previous collections had documented a maternal yolk factor associated with an increased larval copper tolerance during yolk nutrition. In this study, white sucker eggs were divided into groups which were water hardened and/or incubated at the contaminated site or a reference (control) site. Incubation at the contaminated site was associated with a decreased egg size and an increased deformity rate, but had no effect on fertilization rate or larval size. Incubation in contaminated streams increased the larval whole-body metal content, and decreased the tolerance and resistance of larvae exposed to copper in laboratory bioassays. An increase in water temperature accelerated the developmental rate of the larvae, but had no detectable effect on copper tolerance. Although metals did enter the eggs during water hardening, there was no difference in egg metallothionein content, and the lack of obvious hepatic activity until several days after hatching may prevent the formation of protective proteins. The authors hypothesize that the transfer of metals to white sucker eggs in association with yolk precursors, and the subsequent mobilization of these metals during yolk utilization, can account for the observed differences in larval tolerance and growth.

Munkittrick, K.R.; Dixon, D.G. (Univ. of Waterloo, Ontario (Canada))

1989-08-01

147

Tag loss and short-term mortality associated with passive integrated transponder tagging of juvenile Lost River suckers  

USGS Publications Warehouse

Passive integrated transponder (PIT) tags are commonly used to mark small catostomids, but tag loss and the effect of tagging on mortality have not been assessed for juveniles of the endangered Lost River sucker Deltistes luxatus. I evaluated tag loss and short-term (34-d) mortality associated with the PIT tagging of juvenile Lost River suckers in the laboratory by using a completely randomized design and three treatment groups (PIT tagged, positive control, and control). An empty needle was inserted into each positive control fish, whereas control fish were handled but not tagged. Only one fish expelled its PIT tag. Mortality rate averaged 9.8 ± 3.4% (mean ± SD) for tagged fish; mortality was 0% for control and positive control fish. All tagging mortalities occurred in fish with standard lengths of 71 mm or less, and most of the mortalities occurred within 48 h of tagging. My results indicate that 12.45- × 2.02-mm PIT tags provide a viable method of marking juvenile Lost River suckers that are 72 mm or larger.

Burdick, Summer M.

2011-01-01

148

Milt characteristics, reproductive performance, and larval survival and development of white sucker exposed to bleached kraft mill effluent.  

PubMed

White sucker from a Lake Superior bay which receives bleached kraft mill effluent (BKME) show increased hepatic mixed-function oxygenase (MFO) activity, reduced plasma sex steroid levels, decreased egg and gonad size, a decrease in the occurrence of secondary sexual characteristics, and an increased age to maturation. This study evaluated the reproductive performance of that white sucker population relative to a similar reference population. Spawning male white sucker from the BKME site had reduced spermatozoan motility but no significant differences in milt volume, spermatocrit levels, or seminal plasma constituents. BKME male and female fish had equal or greater fertilization potential compared to both male and female fish at the reference site. There was no difference either in the hatchability of the eggs or in larval size at hatch. BKME larvae did show reduced growth rates by 24 days posthatch but showed equal rates of yolk utilization. No difference in larval MFO activity was detected between sites at 21 days posthatch, indicating no parental transfer of induction to the progeny. PMID:1375142

McMaster, M E; Portt, C B; Munkittrick, K R; Dixon, D G

1992-02-01

149

Exotic nonrelativistic string  

SciTech Connect

We construct a classical nonrelativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the noncommutative structure of the model. Under double-dimensional reduction the model reduces to the exotic nonrelativistic particle in 2+1 dimensions.

Casalbuoni, Roberto; Gomis, Joaquim; Longhi, Giorgio [Department of Physics, University of Florence, INFN, Florence (Italy) and Galileo Galilei Institute for Theoretical Physics, Florence (Italy); PH-TH Division, CERN, CH -1211 Geneva 23 (Switzerland) and Departament d'Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona (Spain); Department of Physics, University of Florence and INFN, Florence (Italy)

2007-12-15

150

String Cosmology: A Review  

SciTech Connect

We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the structure of an ultraviolet-complete theory.

McAllister, Liam P.; Silverstein, Eva

2007-10-22

151

Experimenting with Guitar Strings  

NASA Astrophysics Data System (ADS)

What follows is a description of a simple experiment developed in a nonmathematical general education science course on sound and light for fine arts students in which a guitar is used with data collection hardware and software to verify the properties of standing waves on a string.

Lopresto, Michael C.

2006-11-01

152

Power from Random Strings  

Microsoft Academic Search

We consider sets of strings with high Kolmogorov complexity, mainly in resource-boundedsettings but also in the traditional recursion-theoretic sense. We present e#cient reductions,showing that these sets are hard and complete for various complexity classes.

Eric Allender; Harry Buhrman; Michal Koucký; Dieter Van Melkebeek; Detlef Ronneburger

2002-01-01

153

Wing on a String  

ERIC Educational Resources Information Center

In this article, the authors present an activity that shows students how flight occurs. The "wing on a string" is a simple teacher-made frame that consists of PVC pipe, fishing line, and rubber bands--all readily available hardware store items. The only other materials/tools involved are a sheet of paper, some pieces of a soda straw, a stapler,…

Fitzgerald, Mike; Brand, Lance

2004-01-01

154

Wing on a String  

ERIC Educational Resources Information Center

|In this article, the authors present an activity that shows students how flight occurs. The "wing on a string" is a simple teacher-made frame that consists of PVC pipe, fishing line, and rubber bands--all readily available hardware store items. The only other materials/tools involved are a sheet of paper, some pieces of a soda straw, a stapler,…

Fitzgerald, Mike; Brand, Lance

2004-01-01

155

Z' Physics from Strings  

Microsoft Academic Search

Many extensions of the standard model, especially grand unified theories and superstring models, predict the existence of additional Z' bosons and associated exotic chiral supermultiplets. It has recently been argued that for classes of string motivated models with supergravity mediated supersymmetry breaking there are two scenarios for the additional Z's: either the mass is in the accessible range < O(1

P. Langacker

1999-01-01

156

The quasiopen string  

NASA Astrophysics Data System (ADS)

The quasiopen string in D dimensions is defined by the Nambu-Goto action and the boundary conditions (x'+x)(??,?)= V?(x'-x)(??,?), where ?=?1 and ?2 denote the ends of the string, x'??x/??, and the V? (?=1,2) are real symmetric orthogonal matrices. (The usual open string corresponds to V1=V2=-1.) We impose Poincaré invariance in d dimensions, dstring action. A choice of thetai giving a tachyon-free spectrum is thus possible if d<=10.

Roy, S. M.; Singh, Virendra

1987-03-01

157

String cosmology: a review  

NASA Astrophysics Data System (ADS)

We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the data of an ultraviolet-complete theory.

McAllister, Liam; Silverstein, Eva

2008-02-01

158

Drill string shock absorber  

Microsoft Academic Search

A telescopic shock absorber for use in a drill string includes a resilient arrangement to cushion telescopic contraction and extension of the shock absorber in response to shock loads and vibrations imparted during drilling. The shock absorber operates independently of the drilling fluid pressure conducted through the structure during drilling operations. A dampening system assists in cushioning the shock loads

E. A. Anderson; D. D. Webb

1985-01-01

159

Remarks on string solitons  

SciTech Connect

We consider generalized self-duality equations for U(2r) Yang-Mills theory on R{sup 8} with quaternionic structure. We employ the extended ADHM method in eight dimensions to construct exact soliton solutions of the low-energy effective theory of the heterotic string.

Loginov, E. K. [Department of Physics, Ivanovo State University Ermaka Street 39, Ivanovo, 153025 (Russian Federation)

2008-05-15

160

Antisymmetric string actions  

NASA Astrophysics Data System (ADS)

An action is presented for the free bosonic string on external flat space in terms of an antisymmetric second-rank string background tensor which is classically equivalent to the Nambu-Goto action. Both action and field equations are entirely described in terms of 2D world-sheet forms, without any reference to a 2D metric tensor background. The analysis of its canonical formulation shows how the quadratic Virasoro constraints are generated in this case and what their connection with the Bianchi identities are. Since in the orthonormal gauge the reduced action coincides with the standard one, it has the same critical dimension D = 26. The existence of an interaction term of a purely geometric structure stemming in the extrinsic curvature is pointed out. Its action and the new string field equations are then derived. This polynomial antisymmetric string action is uniformly generalized in order to describe d < D-dimensional extended objects in D-dimensional flat space. On leave of absence from Departamento de Física, Universidad Simon Bolívar, Apartado 80659, Caracas 1080A, Venezuela.

Aragone, C.

1986-12-01

161

Device for balancing parallel strings  

DOEpatents

A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

Mashikian, Matthew S. (Storrs, CT)

1985-01-01

162

String theories and millisecond pulsars  

NASA Astrophysics Data System (ADS)

We discuss the two ways of connecting string theories (cosmic, fundamental and the connection between them) to the observational reality: (i) radioastronomy observations (millisecond pulsar timing), and (ii) elementary particle phenomenology (compactification schemes). We study the limits imposed on the string parameter G? by recent millisecond pulsar timings. Cosmic strings derived from GUTs agree with (i). For cosmic strings derived from fundamental strings themselves there is contradiction between (i) and (ii). One of these scenarios connecting string theory to reality must be revised (or the transition from fundamental into cosmic strings rejected). Meanwhile, millisecond pulsar can select one scenario, or reject both of them. UA 336 Laboratoire Associé au CNRS, Observatoire de Meudon et Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05, France.

Sanchez, N.; Signore, M.

1988-11-01

163

String Quantization in Curved Spacetimes:. Null String Approach  

NASA Astrophysics Data System (ADS)

We study quantum strings in strong gravitational fields. The relevant small parameter is g = Rc ? {T0} where Rc is the curvature of the spacetime and T0 is the string tension. Within our systematic expansion we obtain to zeroth-order the null string (string with zero tension), while the first-order correction incorporates the string dynamics. We apply our formalism to quantum null strings in de Sitter spacetime. After a reparametrization of the worldsheet coordinates, the equations of motion are simplified. The quantum algebra generated by the constraints is considered, ordering the momentum operators to the right of the coordinate operators. No critical dimension appears. It is anticipated, however, that the conformal anomaly will appear when the first-order corrections proportional to T0, are introduced.

de Vega, H. J.; Giannakis, I.; Nicolaidis, A.

164

Sequestering in string compactifications  

NASA Astrophysics Data System (ADS)

We study the mediation of supersymmetry breaking in string compactifications whose moduli are stabilized by nonperturbative effects. We begin with a critical review of arguments for sequestering in supergravity and in string theory. We then show that geometric isolation, even in a highly warped space, is insufficient to achieve sequestering: in type IIB compactifications, nonperturbative superpotentials involving the Kähler moduli introduce cross-couplings between well-separated visible and hidden sectors. The scale of the resulting soft terms depends on the moduli stabilization scenario. In the Large Volume Scenario, nonperturbative superpotential contributions to the soft trilinear A terms can introduce significant flavor violation, while in KKLT compactifications their effects are negligible. In both scenarios, the contributions to the ? and B? parameters cannot be ignored in general. We conclude that sequestered supersymmetry breaking is possible in nonperturbatively-stabilized compactifications only if a mechanism in addition to bulk locality suppresses superpotential cross-couplings.

Berg, Marcus; Marsh, David; McAllister, Liam; Pajer, Enrico

2011-06-01

165

Gonihedric string equation  

NASA Astrophysics Data System (ADS)

Arguing that the equation for the gonihedric string should have a generalized Dirac form, we found a new equation which corresponds to a symmetric solution of the Majorana commutation relations and has a non-Jacobian form. The corresponding generalized gamma-matrices are anticommuting and guarantee unitarity at all orders of v/c. The previous solution was in a Jacobian form and admits unitarity at zero order. Explicit formulas for the mass spectrum lead to nonzero string tension M2j>=M2(j+1)2. The equation does not admit tachyonic solutions, but still has unwanted ghost solutions. We discuss also new dual transformation of the Dirac equation and of the proposed generalizations.

Savvidy, G. K.

1998-10-01

166

Axions in String Theory  

SciTech Connect

In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fa is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fa is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fa to be well below the GUT scale.

Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC; Witten, Edward; /Princeton, Inst. Advanced Study

2006-06-09

167

Correspondence principle for black holes and strings  

Microsoft Academic Search

For most black holes in string theory, the Schwarzschild radius in string units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the horizon drops below the size of a string, the typical black hole state becomes a typical state of strings and D-branes with the same charges, and

Gary T. Horowitz; Joseph Polchinski

1997-01-01

168

A Warped Cosmic String  

SciTech Connect

We present a cosmic string solution in Einstein-Yang-Mills Gauss-Bonnet theory on a warped 5 dimensional space-time conform the Randall-Sundrum-2 theory. In a simplipied model, we find an exact solutions with exponential decreasing or periodic warp function. In a more general setting, where the metric- and Yang-Mills components depend on both scales and one of the YM components resides in the bulk, we find a time dependent numerical solution.

Slagter, R. J. [Institute of Physics, University of Amsterdam and ASFYON, Astronomisch Fysisch Onderzoek Nederland, 1405EP Bussum (Netherlands)

2010-06-23

169

Z' Physics from Strings  

Microsoft Academic Search

Many extensions of the standard model, especially grand unified theories and\\u000asuperstring models, predict the existence of additional Z' bosons and\\u000aassociated exotic chiral supermultiplets. It has recently been argued that for\\u000aclasses of string motivated models with supergravity mediated supersymmetry\\u000abreaking there are two scenarios for the additional Z's: either the mass is in\\u000athe accessible range < O(1

Paul Langacker

1998-01-01

170

Swinging on a String  

NSDL National Science Digital Library

Students explore how pendulums work and why they are useful in everyday applications. In a hands-on activity, they experiment with string length, pendulum weight and angle of release. In an associated literacy activity, students explore the mechanical concept of rhythm, based on the principle of oscillation, in a broader biological and cultural context â in dance and sports, poetry and other literary forms, and communication in general.

Integrated Teaching And Learning Program

171

Pentaquarks in string dynamics  

Microsoft Academic Search

The masses of uudds¯, uuddd¯, and uussd¯ pentaquarks are evaluated in the framework of both the Effective Hamiltonian approach to QCD and spinless Salpeter equation using the Jaffe-Wilczek diquark approximation and the string interaction for the diquark-diquark-antiquark system. The masses of the light pentaquarks are found to be in the region above 2 GeV. Similar calculations yield the mass of

I. M. Narodetskii; C. Semay; B. Silvestre-Brac; Yu. A. Simonov

2005-01-01

172

Anyons from Strings  

SciTech Connect

The Nambu-Goto string in a three-dimensional (3D) Minkowski spacetime is quantized preserving Lorentz invariance and parity. The spectrum of massive states contains anyons. An ambiguity in the ground state energy is resolved by the 3D N=1 Green-Schwarz superstring, which has massless ground states describing a dilaton and dilatino, and first-excited states of spin 1/4.

Mezincescu, Luca [Department of Physics, University of Miami, Coral Gables, Florida 33124 (United States); Townsend, Paul K. [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2010-11-05

173

Anyons from strings.  

PubMed

The Nambu-Goto string in a three-dimensional (3D) Minkowski spacetime is quantized preserving Lorentz invariance and parity. The spectrum of massive states contains anyons. An ambiguity in the ground state energy is resolved by the 3D N=1 Green-Schwarz superstring, which has massless ground states describing a dilaton and dilatino, and first-excited states of spin 1/4. PMID:21231159

Mezincescu, Luca; Townsend, Paul K

2010-11-05

174

Rod contributions to color perception: Linear with rod contrast  

Microsoft Academic Search

At mesopic light levels, an incremental change in rod activation causes changes in color appearance. In this study, we investigated how rod mediated changes in color perception varied as a function of the magnitude of the rod contrast. Rod-mediated changes in color appearance were assessed by matching them with cone-mediated color changes. A two-channel four-primary colorimeter allowed independent control of

Dingcai Cao; Joel Pokorny; Vivianne C. Smith; Andrew J. Zele

2008-01-01

175

From fields to strings  

NASA Astrophysics Data System (ADS)

The quest for unification / G. G. Ross -- Chaos, symmetry and string cosmology / T. Damour -- Extra dimensions and branes / C. Csáki -- Looking at the cosmological constant from infinite-volume bulk -- New old inflation -- Conformal fixed points of unidentified gauge theories / A. M. Polyakov -- SL(2, Z) action on three-dimensional conformal field theories with Abelian symmetry / E. Witten -- Logarithmic conformal field theory or how to compute a torus amplitude on the sphere / M. Flohr -- Logarithmic conformal field theories and strings in changing backgrounds / N. E. Mavromatos -- Finite density states in integrable conformal field theories / N. Mann and J. Polchinski -- Conformal field theory at central charge c = 0 and two-dimensional critical systems with quenched disorder / V. Gurarie and A. W. W. Ludwig -- Boundary states and broken bulk symmetries in WA[symbol] minimal models / A. F. Caldeira and J. F. Wheater -- Lectures on AdS/CFT / J. M. Maldacena -- The search for a holographic dual to AdS[symbol] x S[symbol] x S[symbol] x S[symbol] / S. Gukov ... [et al.] -- Chern-Simons gauge theory and the AdS[symbol]/CFT[symbol] correspondence / S. Gukov ... [et al.] -- Spinning strings and AdS/CFT duality / A. A. Tseytlin -- R-symmetries, algebraic geometry, and AdS/CFT / A. Ritz.

Shifman, Misha; Vainshtein, Arkady; Wheater, J. F.

176

Dynamics of strings between walls  

SciTech Connect

Configurations of vortex-strings stretched between or ending on domain walls were previously found to be 1/4 BPS states. Among zero modes of string positions, the center of mass of strings in each region between two adjacent domain walls is shown to be non-normalizable whereas the rests are normalizable. We study dynamics of vortex-strings stretched between separated domain walls by using two methods, the moduli space (geodesic) approximation of full 1/4 BPS states and the charged particle approximation for string endpoints in the wall effective action. In the first method we obtain the effective Lagrangian explicitly and find the 90 degree scattering for head-on collision. In the second method the domain wall effective action is assumed to be U(1){sup N} gauge theory, and we find a good agreement between two methods for well separated strings. This talk is based on the work [1].

Eto, Minoru [INFN, Sezione di Pisa, Largo Pontecorvo, 3, Ed. C, 56127 Pisa (Italy); Fujimori, Toshiaki; Nagashima, Takayuki [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Nitta, Muneto [Department of Physics, Keio University, Hiyoshi, Yokohama, Kanagawa 223-8521 (Japan); Ohashi, Keisuke [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, CB3 0WA (United Kingdom); Sakai, Norisuke [Department of Mathematics, Tokyo Woman's Christian University, Tokyo 167-8585 (Japan)

2008-11-23

177

Reduced growth and survival of larval razorback sucker fed selenium-laden zooplankton  

USGS Publications Warehouse

Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from <0.4 to 78 ??g/L, and concentrations in zooplankton ranged from 2.3 to 91 ??g/g dry weight. Static renewal tests were conducted for 20 to 25 days using reference water with selenium concentrations of <1.1 ??g/L. In all studies, 80-100% mortality occurred in 15-20 days. In the 28-day-old larvae, fish weight was significantly reduced 25% in larvae fed zooplankton containing 12 ??g/g selenium. Whole-body concentrations of selenium ranged from 3.7 to 14.3 ??g/g in fish fed zooplankton from the reference site (Sheppard Bottom pond 1) up to 94 ??g/g in fish fed zooplankton from North Roadside Pond. Limited information prior to the studies suggested that the Sheppard pond 1 site was relatively clean and suitable as a reference treatment; however, the nearly complete mortality of larvae and elevated concentrations of selenium in larvae and selenium and other elements in zooplankton indicated that this site was contaminated with selenium and other elements. Selenium concentrations in whole-body larvae and in zooplankton from all sites were close to or greater than toxic thresholds where adverse effects occur in fish. Delayed mortality occurred in larvae fed the two highest selenium concentrations in zooplankton and was thought due to an interaction with other elements. ?? 2004 Elsevier Inc. All rights reserved.

Hamilton, S. J.; Buhl, K. J.; Bullard, F. A.; McDonald, S. F.

2005-01-01

178

Experimenting with string musical instruments  

NASA Astrophysics Data System (ADS)

What follows are several investigations involving string musical instruments developed for and used in a Science of Sound & Light course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when used in physics, represent reality that can actually be observed, in this case, the operation of string musical instruments.

LoPresto, Michael C.

2012-03-01

179

Evolution of cosmic string networks  

SciTech Connect

We summarize our new results on cosmic strings. These results include: the application of non-equilibrium statistical mechanics to cosmic string evolution, a simple ''one scale'' model for the long strings which has a great deal of predictive power, results from large scale numerical simulations, and a discussion of the observational consequences of our results. An upper bond on G/mu/ of approximately 10/sup /minus/7/ emerges from the millisecond pulsar gravity wave bound. We discuss how numerical uncertainties affect this. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences. 22 refs.

Albrecht, A.; Turok, N.

1989-06-01

180

Non-supersymmetric string theory  

NASA Astrophysics Data System (ADS)

A class of non-supersymmetric string backgrounds can be constructed using twists that involve space-time fermion parity. We propose a non-perturbative definition of string theory in these backgrounds via gauge theories with supersymmetry softly broken by twisted boundary conditions. The perturbative string spectrum is reproduced, and qualitative effects of the interactions are discussed. Along the way, we find an interesting mechanism for inflation. The end state of closed string tachyon condensation is a highly excited state in the gauge theory which, in all likelihood, does not have a geometric interpretation.

Martinec, Emil J.; Robbins, Daniel; Sethi, Savdeep

2011-10-01

181

Torsional Waves in Composite Rods.  

National Technical Information Service (NTIS)

The propagation of torsional waves in composite, infinitely long, traction-free, circular, cylindrical rods is investigated on the basis of the three-dimensional linear theory of elasticity. The composite rods consist of an internal circular rod made of o...

A. E. Armenakas

1965-01-01

182

Cosmological String Theory with Thermal Energy.  

National Technical Information Service (NTIS)

An attempt to construct a cosmological scenario directly from string theory is made. Cosmological string theory was presented by Antoniadis, Bachas, Ellis and Nanopoulos. They also expect loop effects on cosmological string theory. In this paper, we point...

K. Shiraishi

1988-01-01

183

Efficacy of hydrogen peroxide in controlling mortality associated with saprolegniasis on walleye, white sucker, and paddlefish eggs  

USGS Publications Warehouse

The efficacy of hydrogen peroxide in controlling saprolegniasis on eggs of walleye Stizostedion vitreum, white sucker Catostomus commersoni, and paddlefish Polyodon spathula was evaluated at four private, state, and federal production hatcheries participating in an Investigational New Animal Drug efficacy study (experiment 1; walleyes) and in a laboratory-based miniature egg jar incubation system (experiment 2; walleyes, white suckers, and paddlefish). Naturally occurring fungal infestations (saprolegniasis) were observed on eggs in both experiments. Confirmatory diagnosis of infested eggs from one hatchery in experiment 1 identified the pathogen as Saprolegnia parasitica. During experiment 1, eggs were treated daily for 15 min with either 0, 500, or 750 mg/L of hydrogen peroxide, and one trial compared a 500-mg/L hydrogen peroxide treatment with a formalin treatment at 1,667 mg/L. Saprolegniasis infestation was observed in control egg jars, whereas treatment with either formalin or hydrogen peroxide virtually eliminated the infestation. Hydrogen peroxide treatments of 500 mg/L either increased egg hatch or were as effective as physical removal of infested eggs in controlling mortality. Although treatment with formalin at 1,667 mg/L significantly increased the percent eye-up of walleye eggs compared with that of those treated with hydrogen peroxide at 500 mg/L, the difference was only 1.9-2.6%. In experiment 2, noneyed eggs were treated for 15 min every other day with 0, 283, 565, or 1,130 mg/L of hydrogen peroxide until the viable eggs hatched. Saprolegniasis infestation engulfed most control eggs, whereas infestation of treated eggs was either reduced or not visible. Hydrogen peroxide significantly increased egg hatch for all three species tested in experiment 2. Although hydrogen peroxide treatments as low as 283 mg/L significantly increased walleye and white sucker hatch, treatments between 500 and 1,000 mg/L are more likely to be effective in production egg incubation systems.

Gaikowski, M. P.; Rach, J. J.; Drobish, M.; Hamilton, J.; Harder, T.; Lee, L. A.; Moen, C.; Moore, A.

2003-01-01

184

Effects of total dissolved gas supersaturated water on lethality and catalase activity of Chinese sucker (Myxocyprinus asiaticus Bleeker)*  

PubMed Central

Total dissolved gas (TDG) supersaturation caused by dam sluicing can result in gas bubble trauma (GBT) in fish and threaten their survival. In the present study, Chinese suckers (Myxocyprinus asiaticus Bleeker) were exposed to TDG supersaturated water at levels ranging from 120% to 145% for 48 h. The median lethal concentration (LC50) and the median lethal time (LT50) were determined to evaluate acute lethal effects on Chinese suckers. The results showed that the LC50 values of 4, 6, 8, and 10 h were 142%, 137%, 135%, and 130%, respectively. The LT50 values were 3.2, 4.7, 7.8, 9.2, and 43.4 h, respectively, when TDG supersaturated levels were 145%, 140%, 135%, 130%, and 125%. Furthermore, the biological responses in Chinese suckers were studied by assaying the catalase (CAT) activities in gills and muscles at the supersaturation level of 140% within LT50. The CAT activities in the gills and muscle tissues exhibited a regularity of a decrease after an increase. CAT activities in the muscles were increased significantly at 3/5LT50 (P<0.05) and then came back to the normal level. However, there were no significant differences between the treatment group (TDG level of 140%) and the control group (TDG level of 100%) on CAT activities in the gills before 3/5LT50 (P>0.05), but the activities were significantly lower than the normal level at 4/5LT50 and LT50 (P<0.05).

Chen, Shi-chao; Liu, Xiao-qing; Jiang, Wen; Li, Ke-feng; Du, Jun; Shen, Dan-zhou; Gong, Quan

2012-01-01

185

Hafnium stainless steel absorber rod for control rod  

SciTech Connect

This patent describes an improvement in a control rod having a stainless steel body for enclosing a neutron absorbing poison, the control rod having movement along an axial direction for insertion into and out of a nuclear reactor for controlling a nuclear reaction. The improvement comprising: a piece of hafnium; a piece of stainless steel joined to the hafnium by a thin diffusion interface created by friction welding. The hafnium and the stainless steel oriented serially in the axial direction with the thin diffusion interface disposed normal to the axial direction of the control rod movement; means for confining the hafnium to movement along the axial direction with the control rod; and means for attaching the piece of stainless steel to the remaining portion of the control rod to load the weld therebetween under compression or tension during the control rod movement. Whereby the thin diffusion interface is loaded in tension or compression only upon dynamic movement of the control rod.

Charnley, J.E.; Cearley, J.E.; Dixon, R.C.; Izzo, K.R.; Aiello, L.L.

1989-08-01

186

Conformal Supergravity in Twistor-String Theory  

Microsoft Academic Search

Conformal supergravity arises in presently known formulations of twistor-string theory either via closed strings or via gauge-singlet open strings. We explore this sector of twistor-string theory, relating the relevant string modes to the particles and fields of conformal supergravity. We use the twistor-string theory to compute some tree level scattering amplitudes with supergravitons. Since the supergravitons interact with the same

Nathan Berkovits; Edward Witten

2004-01-01

187

Influence of cytokinin levels on in vitro propagation of shy suckering chrysanthemum “Arka Swarna” and activation of endophytic bacteria  

Microsoft Academic Search

In an effort to develop a sustainable protocol for the micropropagation of a shy suckering elite chrysanthemum cv. Arka Swarna\\u000a (yellow pompon type), in vitro cultures were established using surface-sterilized nodal microcuttings (1–1.5 cm) from polyhouse-grown plants on MS medium\\u000a containing 3% sucrose, 0.25% phytagel, and 5 ?M benzyl adenine (BA) or kinetin. Microbial contamination in the range of 6–24%\\u000a was encountered

Bindu Panicker; Pious Thomas; Tolety Janakiram; Rangarajan Venugopalan; Sathyanarayana B. Narayanappa

2007-01-01

188

Peeling U(1)-gauge cosmic strings  

SciTech Connect

We numerically investigate collisions of cosmic strings carrying different winding numbers. We find that for strings with winding numbers n/sub 1/ and n/sub 2/, intercommutation occurs by peeling a string of winding number chemically bondn/sub 1/-n/sub 2/chemically bond from the string with the larger winding number. The resulting string connects the original colliding strings to form a state of three joined strings, but because of the peeling the eventual result is a reduction in the winding numbers of the network. Stable astrophysical strings with large winding number are thus unlikely to persist. All simulations have gauge/scalar-field mass ratio = 2. .AE

Laguna, P.; Matzner, R.A.

1989-04-24

189

Locked-wrap fuel rod  

DOEpatents

A method for spacing fast reactor fuel rods using a wire wrapper improved by orienting the wire-wrapped fuel rods in a unique manner which introduces desirable performance characteristics not attainable by previous wire-wrapped designs. Use of this method in a liquid metal fast breeder reactor results in: (a) improved mechanical performance, (b) improved rod-to-rod contact, (c) reduced steel volume, and (d) improved thermal-hydraulic performance. The method produces a "locked wrap" design which tends to lock the rods together at each of the wire cluster locations.

Kaplan, Samuel (Los Gatos, CA); Chertock, Alan J. (San Francisco, CA); Punches, James R. (San Jose, CA)

1977-01-01

190

SAFETY SYSTEM FOR CONTROL ROD  

DOEpatents

A structure for monitoring the structural continuity of a control rod foi a neutron reactor is presented. A electric conductor readily breakable under mechanical stress is fastened along the length of the control rod at a plurality of positions and forms a closed circuit with remote electrical components responsive to an open circuit. A portion of the conductor between the control rod and said components is helically wound to allow free and normally unrestricted movement of the segment of conductor secured to the control rod relative to the remote components. Any break in the circuit is indicative of control rod breakage. (AEC)

Paget, J.A.

1963-05-14

191

Drill string gas data  

SciTech Connect

Data and supporting documentation were compiled and analyzed for 26 cases of gas grab samples taken during waste-tank core sampling activities between September 1, 1995 and December 31, 1997. These cases were tested against specific criteria to reduce uncertainties associated with in-tank sampling location and conditions. Of the 26 possible cases, 16 qualified as drill-string grab samples most likely to represent recently released waste gases. The data from these 16 ``confirmed`` cases were adjusted to remove non-waste gas contributions from core-sampling activities (argon or nitrogen purge), the atmospheric background, and laboratory sampler preparation (helium). The procedure for subtracting atmospheric, laboratory, and argon purge gases was unambiguous. No reliable method for determining the exact amount of nitrogen purge gas was established. Thus, the final set of ``Adjusted`` drill string gas data for the 6 nitrogen-purged cases had a greater degree of uncertainty than the final results for the 10 argon-purged cases. Including the appropriate amounts of uncertainty, this final set of data was added to the set of high-quality results from the Retained Gas Sampler (RGS), and good agreement was found for the N{sub 2}, H{sub 2}, and N{sub 2}O mole fractions sampled from common tanks. These results indicate that under favorable sampling conditions, Drill-String (DS) grab samples can provide reasonably accurate information about the dominant species of released gas. One conclusion from this set of total gas data is that the distribution of the H{sub 2} mole fractions is bimodal in shape, with an upper bound of 78%.

Siciliano, E.R.

1998-05-12

192

Open String Gravity?  

NASA Astrophysics Data System (ADS)

We present a new application of Boundary String Field Theory: calculating the induced-gravity action on a D-brane. Using a simple quadratic tachyon potential to model a D-brane fluctuating in the flat target space we derive the effective action in terms of the extrinsic curvature to all orders in alpha'. We identify both the Born-Infeld structure as well as the Einstein-Hilbert term at order alpha'. This corroborates the conjectured existence of the latter term in the brane-world scenarios. The higher order terms in Ricci scalar and extrinsic curvature suggest a pattern which calls for an explanation.

Cheung, Yeuk-Kwan E.; Laidlaw, Mark; Savvidy, Konstantin

2004-12-01

193

Sequestering in string theory  

NASA Astrophysics Data System (ADS)

We study sequestering, a prerequisite for flavor-blind supersymmetry breaking in several high-scale mediation mechanisms, in compactifications of type IIB string theory. We find that although sequestering is typically absent in unwarped backgrounds, strongly warped compactifications do readily sequester. The AdS/CFT dual description in terms of conformal sequestering plays an important role in our analysis, and we establish how sequestering works both on the gravity side and on the gauge theory side. We pay special attention to subtle compactification effects that can disrupt sequestering. Our result is a step toward realizing an appealing pattern of soft terms in a KKLT compactification.

Kachru, Shamit; McAllister, Liam; Sundrum, Raman

2007-10-01

194

Pentaquarks in string dynamics  

Microsoft Academic Search

The masses of $uudd\\\\bar s $, $uudd\\\\bar d$, and $uuss\\\\bar d$ pentaquarks are\\u000aevaluated in a framework of both the Effective Hamiltonian approach to QCD and\\u000aspinless Salpeter using the Jaffe-Wilczek diquark approximation and the string\\u000ainteraction for the diquark-diquark-antiquark system. The masses of the light\\u000apentaquarks are found to be in the region above 2 GeV. The similar calculations

I. M. Narodetskii; C. Semay; B. Silvestre-Brac; Yu. A. Simonov

2005-01-01

195

Safety rod latch inspection  

SciTech Connect

During an attempt to raise control rods from the 100 K reactor in December, one rod could not be withdrawn. Subsequent investigation revealed that a small ``button`` in the latch mechanism had broken off of the ``lock plunger`` and was wedged in a position that prevented rod withdrawal. Concern that this failure may have resulted from corrosion or some other metallurgical problem resulted in a request that SRL examine six typical latch mechanisms from the 100 L reactor by use of radiography and metallography. During the examination of the L-Area latches, a failed latch mechanism from the 100 K reactor was added to the investigation. Fourteen latches that had a history of problems were removed from K-Area and sent to SRL for inclusion in this study the week after the original seven assemblies were examined, bringing the total of latch assemblies discussed in this report to twenty one. Results of the examination of the K-Area latch that initiated this study is not included in this report.

Leader, D.R.

1992-02-01

196

Safety rod latch inspection  

SciTech Connect

During an attempt to raise control rods from the 100 K reactor in December, one rod could not be withdrawn. Subsequent investigation revealed that a small button'' in the latch mechanism had broken off of the lock plunger'' and was wedged in a position that prevented rod withdrawal. Concern that this failure may have resulted from corrosion or some other metallurgical problem resulted in a request that SRL examine six typical latch mechanisms from the 100 L reactor by use of radiography and metallography. During the examination of the L-Area latches, a failed latch mechanism from the 100 K reactor was added to the investigation. Fourteen latches that had a history of problems were removed from K-Area and sent to SRL for inclusion in this study the week after the original seven assemblies were examined, bringing the total of latch assemblies discussed in this report to twenty one. Results of the examination of the K-Area latch that initiated this study is not included in this report.

Leader, D.R.

1992-02-01

197

Energy in a String Wave  

ERIC Educational Resources Information Center

|When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is…

Ng, Chiu-king

2010-01-01

198

String theory and water waves  

NASA Astrophysics Data System (ADS)

We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain {\\hat{c}}<1 string theories non-perturbatively. We are able to embed the type 0A and 0B (A, A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We observe that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A, D) minimal string backgrounds. We explain how these and several string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painlevé IV equation plays a key role in organizing the string theory physics, joining its siblings, Painlevé I and II, whose roles have previously been identified in this minimal string context.

Iyer, Ramakrishnan; Johnson, Clifford V.; Pennington, Jeffrey S.

2011-01-01

199

Geometry, Topology and String Theory.  

National Technical Information Service (NTIS)

A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string problems of a given classical space-time se...

U. Varadarajan

2003-01-01

200

Small instantons in string theory  

Microsoft Academic Search

A long-standing puzzle about the heterotic string has been what happens when an instanton shrinks to zero size. It is argued here that the answer at the quantum level is that an extra SU(2) gauge symmetry appears that is supported in the core of the instanton. Thus in particular the quantum heterotic string has vacua with higher rank than is

Edward Witten

1996-01-01

201

String theory and noncommutative geometry  

Microsoft Academic Search

We extend earlier ideas about the appearance of noncommutative geometry in string theory with a nonzero B-field. We identify a limit in which the entire string dynamics is described by a minimally coupled (supersymmetric) gauge theory on a noncommutative space, and discuss the corrections away from this limit. Our analysis leads us to an equivalence between ordinary gauge fields and

Nathan Seiberg; Edward Witten

1999-01-01

202

String theory on group manifolds  

Microsoft Academic Search

A number of issues concerning affine Lie algebras and string propagation on group manifolds are addressed. We show that a 1 + 1 dimensional quantum field theory which gives a realization of current algebra (for any non-abelian Lie group G) will always give rise to an ``integrable'' representation. It is known that string propagation on the group manifold can give

Doron Gepner; Edward Witten

1986-01-01

203

Towards inflation in string theory  

Microsoft Academic Search

We investigate the embedding of brane inflation into stable compactifications of string theory. At first sight a warped compactification geometry seems to produce a naturally flat inflaton potential, evading one well known difficulty of brane antibrane scenarios. Careful consideration of the closed string moduli reveals a further obstacle: superpotential stabilization of the compactification volume typically modifies the inflaton potential and

Shamit Kachru; Renata Kallosh; Andrei Linde; Juan Maldacena; Liam McAllister; Sandip P. Trivedi

2003-01-01

204

Bethe Ansatz for Quantum Strings  

Microsoft Academic Search

We propose Bethe equations for the diagonalization of the hamiltonian of quantum strings on AdS 5 × S 5 at large string tension and restricted to certain large charge states from a closed fraktur sfraktur u(2) subsector. The ansatz differs from the recently proposed all-loop gauge theory asymptotic Bethe ansatz by additional factorized scattering terms for the local excitations. We

Gleb Arutyunov; Sergey Frolov; Matthias Staudacher

2004-01-01

205

Experimenting with String Musical Instruments  

ERIC Educational Resources Information Center

|What follows are several investigations involving string musical instruments developed for and used in a "Science of Sound & Light" course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when…

LoPresto, Michael C.

2012-01-01

206

Energy in a String Wave  

ERIC Educational Resources Information Center

When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is termed…

Ng, Chiu-king

2010-01-01

207

Self-driven flexible string  

NASA Astrophysics Data System (ADS)

Based on the equation of the self-driven oscillator, as model for the non-contact atomic force microscopy in ultra high vacuum, we introduce the classical self-driven flexible string. The equation of this system includes a frictional term and a time delayed term for the feedback loop. Solutions for the self-driven string equation are presented.

Budau, P.

2003-10-01

208

Topological Strings and Quantum Curves  

NASA Astrophysics Data System (ADS)

This thesis presents several new insights on the interface between mathematics and theoretical physics, with a central role for fermions on Riemann surfaces. First of all, the duality between Vafa-Witten theory and WZW models is embedded into string theory. Secondly, this model is generalized to a web of dualities connecting topological string theory and N=2 supersymmetric gauge theories to a configuration of D-branes that intersect over a Riemann surface. This description yields a new perspective on topological string theory in terms of a KP integrable system based on a quantum curve. Thirdly, this thesis describes a geometric analysis of wall-crossing in N=4 string theory. And lastly, it offers a novel approach to construct metastable vacua in type IIB string theory.

Hollands, Lotte

2009-11-01

209

Cosmic necklaces from string theory  

SciTech Connect

We present the properties of a cosmic superstring network in the scenario of flux compactification. An infinite family of strings, the (p,q) strings, are allowed to exist. The flux compactification leads to a string tension that is periodic in p. Monopoles, appearing here as beads on a string, are formed in certain interactions in such networks. This allows bare strings to become cosmic necklaces. We study network evolution in this scenario, outlining what conditions are necessary to reach a cosmologically viable scaling solution. We also analyze the physics of the beads on a cosmic necklace, and present general conditions for which they will be cosmologically safe, leaving the network's scaling undisturbed. In particular, we find that a large average loop size is sufficient for the beads to be cosmologically safe. Finally, we argue that loop formation will promote a scaling solution for the interbead distance in some situations.

Leblond, Louis [Texas A and M University, Mitchell Institute for Fundamental Physics, College Station, Texas, 77840 (United States); Wyman, Mark [Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo, ON, N2L 2Y5 (Canada)

2007-06-15

210

Summing Planar Bosonic Open Strings  

SciTech Connect

In earlier work, planar graphs of massless {phi}{sup 3} theory were summed with the help of the light cone world sheet picture and the mean field approximation. In the present article, the same methods are applied to the problem of summing planar bosonic open strings. They find that in the ground state of the system, string boundaries form a condensate on the world sheet, and a new string emerges from this summation. Its slope is always greater than the initial slope, and it remains non-zero even when the initial slope is set equal to zero. If they assume the initial string tends to a field a theory in the zero slope limit, this result provides evidence for string formation in field theory.

Bardakci, Korkut

2006-02-16

211

Subcritical string and large N QCD  

SciTech Connect

We pursue the possibility of using subcritical string theory in 4 spacetime dimensions to establish a string dual for large N QCD. In particular we study the even G-parity sector of the 4 dimensional Neveu-Schwarz dual resonance model as the natural candidate for this string theory. Our point of view is that the open string dynamics given by this model will determine the appropriate subcritical closed string theory, a tree level background of which should describe the sum of planar multiloop open string diagrams. We examine the one-loop open string diagram, which contains information about the closed string spectrum at weak coupling. Higher loop open string diagrams will be needed to determine closed string interactions. We also analyze the field theory limit of the one-loop open string diagram and recover the correct running coupling behavior of the limiting gauge theory.

Thorn, Charles B. [Institute for Fundamental Theory, Department of Physics, University of Florida, Gainesville Florida 32611 (United States)

2008-10-15

212

Host specificity of Lepeophtheirus crassus (Wilson and Bere) (Copepoda: Caligidae) parasitic on the marlin sucker Remora osteochir (Cuvier) in the Atlantic Ocean.  

PubMed

Three species of remoras--Remora brachyptera (Lowe), Remora osteochir (Cuvier), and Remora remora (Linnaeus)--were collected from 4 species of billfishes--Istiophorus platypterus (Shaw), Makaira nigricans Lacepéde, Tetrapturus albidus Poey, and Tetrapturus pfluegeri Robins and de Sylva--on board a Japanese long-liner Shoyo Maru during her cruise in 2002 across the Atlantic. However, only the marlin sucker (R. osteochir) was found to carry a parasitic copepod, Lepeophtheirus crassus (Wilson and Bere, 1936). Although 12 species of parasitic copepods have been reported from billfishes around the world ocean, none of them is L. crassus. Thus, L. crassus is considered a parasite specific to the marlin sucker. PMID:17152964

Ho, Ju-shey; Collete, Bruce B; Madinabeitia, Ione

2006-10-01

213

String bit models for superstring  

SciTech Connect

We extend the model of string as a polymer of string bits to the case of superstring. We mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string we work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei-invariant theory in [({ital D}{minus}2)+1]-dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in {ital D}{minus}2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in {ital D}-dimensional space-time enjoying the full {ital N}=2 Poincare supersymmetric dynamics of type II-B superstring.

Bergman, O.; Thorn, C.B. [Institute for Fundamental Theory, Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

1995-11-15

214

String bit models for superstring  

SciTech Connect

The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.

Bergman, O.; Thorn, C.B.

1995-12-31

215

String Formatting Considered Harmful for Novice Programmers  

ERIC Educational Resources Information Center

|In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found that 8% of all the…

Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.

2010-01-01

216

Automata on Guarded Strings and Applications  

Microsoft Academic Search

Guarded strings are like ordinary strings over a finite alphabet P, except that atoms of the free Boolean algebra on a set of atomic tests B alternate with the symbols of P. The regular sets of guarded strings play the same role in Kleene algebra with tests as the regular sets of ordinary strings do in Kleene algebra. In this

Dexter Kozen

217

Fermionic zero modes of supergravity cosmic strings  

Microsoft Academic Search

Recent developments in string theory suggest that cosmic strings could be formed at the end of brane inflation. Supergravity provides a realistic model to study the properties of strings arising in brane inflation. Whilst the properties of cosmic strings in flat space-time have been extensively studied there are significant complications in the presence of gravity. We study the effects of

Philippe Brax; Carsten van de Bruck; Anne-Christine Davis; Stephen C. Davis

2006-01-01

218

Comma vertex and string field algebra  

NASA Astrophysics Data System (ADS)

We study the matter part of the algebra of open string fields using the 3-string vertex over the sliver state, which we call ``comma vertex''. By generalizing this comma vertex to the N-string overlap, we obtain a closed form of the Neumann coefficients in the N-string vertex and discuss its relation to the oscillator representation of wedge states.

Furuuchi, Kazuyuki; Okuyama, Kazumi

2001-09-01

219

Comma vertex and string field algebra  

Microsoft Academic Search

We study the matter part of the algebra of open string fields using the 3-string vertex over the sliver state, which we call ``comma vertex''. By generalizing this comma vertex to the N-string overlap, we obtain a closed form of the Neumann coefficients in the N-string vertex and discuss its relation to the oscillator representation of wedge states.

Kazuyuki Furuuchi; Kazumi Okuyama

2001-01-01

220

Reactor control rod timing system  

DOEpatents

A fluid driven jet-edge whistle timing system for control rods of a nuclear reactor for producing real-time detection of the timing of each control rod in its scram operation. An important parameter in reactor safety, particularly for liquid metal fast breeder reactors (LMFBR), is the time deviation between the time the control rod is released and the time the rod actually reaches the down position. The whistle has a nearly pure tone signal with center frequency (above 100 kHz) far above the frequency band in which the energy of the background noise is concentrated. Each control rod can be fitted with a whistle with a different frequency so that there is no ambiguity in differentiating the signal from each control rod.

Wu, Peter T. K. (Clifton Park, NY)

1982-01-01

221

Reheating closed string inflation  

SciTech Connect

Protecting the inflationary potential from quantum corrections typically requires symmetries that constrain the form of couplings of the inflaton to other sectors. We will explore how these restrictions affect reheating in models with UV completions. In particular, we look at how reheating occurs when inflation is governed by closed strings, using N-flation as an example. We find that coupling the inflaton preferentially to the standard modelis difficult, and hidden sectors are typically reheated. Observational constraints are only met by a fraction of the models. In some working models, relativistic relics in the hidden sector provide dark matter candidates with masses that range from keV to PeV, with lighter masses being preferred.

Green, Daniel [SLAC and Department of Physics, Stanford University, Stanford, California 94305-4060 (United States)

2007-11-15

222

Form of Growing Strings  

NASA Astrophysics Data System (ADS)

Patterns and forms adopted by nature are often the results of simple dynamical paradigms. Here we show that a growing self-interacting string attached to a tracking origin, modeled to resemble nascent polypeptides in vivo, develops helical structures which are more pronounced at the growing end. We also show that the dynamic growth ensemble shares several features of an equilibrium ensemble in which the growing end of the polymer is under an effective stretching force. A statistical analysis of native states of proteins shows that the signature of this nonequilibrium phenomenon has been fixed by evolution at the C terminus, the growing end of a nascent protein. These findings suggest how evolution may have built on the properties of a generic nonequilibrium growth process in favoring helical structures in nascent chains.

Marenduzzo, D.; Hoang, T. X.; Seno, F.; Vendruscolo, M.; Maritan, A.

2005-08-01

223

Nonsingular stationary global strings  

SciTech Connect

A field-theoretical model for nonsingular global cosmic strings is presented. The model is a nonlinear sigma model with a potential term for a self-gravitating complex scalar field. Nonsingular stationary solutions with angular momentum and possibly linear momentum are obtained by assuming an oscillatory dependence of the scalar field on t, {phi}, and z. This dependence has an effect similar to gauging the global U(1) symmetry of the model, which is actually a Kaluza-Klein reduction from four to three spacetime dimensions. The method of analysis can be regarded as an extension of the gravito-electromagnetism formalism beyond the weak field limit. Some D=3 self-dual solutions are also discussed.

Verbin, Y. [Department of Natural Sciences, Open University of Israel, P.O.B. 39328, Tel Aviv 61392 (Israel); Larsen, A.L. [Department of Physics, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark)

2004-10-15

224

Drill string safety valve  

SciTech Connect

A multi position safety valve is disclosed retainable within an internal portion of a drill string casing (s) and responsive to the greater differential pressure in an internal fluid passage to displace a valve head relative to a valve seat (VS) from its normal partially open position to either a wide open or a closed position. The valve head is attached to a valve stem that extends through a valve chamber and slideably mounted in opposite closed ends of a valve body and returnable to and maintained in the partially open position by opposing compression springs situated between opposite ends of the valve body and one side of an intermediate abutment of the valve stem and an intervening disc on the opposite side thereof. The disc 38 is moveable into and out of seating engagement with an intermediate stop by one spring and the intermediate abutment of the valve stem respectively.

Aumann, J.T.

1983-07-05

225

Wormholes in string theory  

SciTech Connect

We discuss the wormhole effective interactions in string theory, thought of as a sum over two-dimensional field theories on different world sheets. The effective interactions are calculated in the dilute wormhole approximation,'' initially by considering the Green's functions on higher-genus Riemann surfaces, and then by calculating the effect of a complete basis of wave functions on scattering amplitudes for a surface with a boundary. The sum over wormholes is equivalent to having a world sheet of trivial topology and summing over different space-time and matter-field backgrounds. To leading order these consist of the massless fluctuations, since the tachyon cancels out when a sum is done over different spin structures going through the wormhole. In this way we recover quantized general relativity as an effective theory, from a sum over field theories on higher-genus Riemann surfaces.

Lyons, A. (Theoretical Physics Institute, Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)); Hawking, S.W. (Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (UK))

1991-12-15

226

Gravitational field of a global string  

SciTech Connect

The gravitational field of a straight global string is derived in the linear approximation to general relativity, and the resulting trajectories of test particles are found. Part of the gravitational effect of global strings is a deficit angle which increases logarithmically with the distance to the string core. In this regard, a global string resembles a gauge string. A new feature, not present for gauge strings, is a repulsive gravitational potential outside the core. The lensing properties of the global string, as well as other classical effects, are studied.

Harari, D.; Sikivie, P.

1988-06-15

227

Automatic safety rod for reactors  

DOEpatents

An automatic safety rod for a nuclear reactor containing neutron absorbing material and designed to be inserted into a reactor core after a loss-of-core flow. Actuation is based upon either a sudden decrease in core pressure drop or the pressure drop decreases below a predetermined minimum value. The automatic control rod includes a pressure regulating device whereby a controlled decrease in operating pressure due to reduced coolant flow does not cause the rod to drop into the core.

Germer, John H. (San Jose, CA)

1988-01-01

228

Concentric steaming string downhole apparatus  

SciTech Connect

A downhole concentric tubing string is disclosed for use in distributing steam, or other hot fluid to separated subsurface formations along a well bore. The apparatus includes elements for deflecting the steam from one string into the annulus of a cased well for injection through openings into the formation, elements for conducting the steam in another of the concentric string to a second set of openings for injection into another portion of the formation, and elements for isolating and separating the two separate injection intervals.

Anderson, G.W.; Hutchison, S.O.

1983-08-23

229

Geometry, topology, and string theory  

SciTech Connect

A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.

Varadarajan, Uday

2003-07-10

230

Charting the Landscape of Supercritical String Theory  

SciTech Connect

Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories.

Hellerman, Simeon; Swanson, Ian [School of Natural Sciences, Institute for Advanced Study Princeton, New Jersey 08540 (United States)

2007-10-26

231

Charting the landscape of supercritical string theory.  

PubMed

Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories. PMID:17995316

Hellerman, Simeon; Swanson, Ian

2007-10-24

232

Comparisons of Precision and Bias with Two Age Interpretation Techniques for Opercular Bones of Longnose Sucker, a Long-Lived Northern Fish  

Microsoft Academic Search

Two preparations of opercular bones for estimating age of longnose suckers Catastomus catastomus revealed that annuli were obscured by dense bone and undetected when the whole operculum technique was used. By thin-sectioning the opercula, we removed the dense bone, revealing previously obscured annuli. Using opercula collected from older fish in Labrador, Canada, we found that the dense bone overgrowth led

Robert C. Perry; John M. Casselman

2012-01-01

233

Survival of Lost River suckers (Deltistes luxatus) challenged with Flavobacterium columnare during exposure to sublethal ammonia concentrations at ph 9.5.  

PubMed

The Lost River sucker (Deltistes luxatus) is a federally listed, endangered species inhabiting the hypereutrophic waters of Upper Klamath Lake in southern Oregon, USA. High pH (> or =10) and elevated ammonia concentrations (> or =1 mg NH(3)-N/L) often occur during blooms of cyanobacteria (Aphanizomenon flos-aquae) in the lake, with major fish kills sometimes following a mid- or late-summer "crash" of the cyanobacterial population. Previous histopathology analyses and bacterial sampling indicated that infections of the pathogenic bacterium Flavobacterium columnare might contribute to the fish kills. We hypothesized that prior exposure to adverse water quality conditions increases the susceptibility of Lost River suckers to F. columnare infections. To test this, we exposed juvenile Lost River suckers to four sublethal ammonia concentrations at pH 9.4 for 62 d. On day 31, fish in half of the aquaria were exposed to F. columnare. As expected, survival of the Lost River suckers decreased in aquaria inoculated with F. columnare. Ninety-four percent of the fish that died were infected by F. columnare in the gills, kidney, or skin, whereas none of the survivors or unexposed control fish was infected. However, contrary to our hypothesis, survival of the fish exposed to F. columnare increased significantly (p < 0.05) as unionized ammonia concentrations increased. Our results suggest that complex interactions can complicate prediction of the responses of fish to concurrent chemical stressors and bacterial pathogens. PMID:16328623

Morris, Jeffrey M; Snyder-Conn, Elaine; Foott, J Scott; Holt, Richard A; Suedkamp, Michael J; Lease, Hilary M; Clearwater, Susan J; Meyer, Joseph S

2005-11-15

234

Green tissue within the haustorium of the dwarf mistletoe Korthalsella (Viscaceae). An ultrastructural comparison between chloroplasts of sucker and aerial stem tissues  

Microsoft Academic Search

Summary Korthalsella (Viscaceae) is a dwarf mistletoe attached to its host branch by a single haustorium. Plants are leafless with flattened or cylindrical stems that function in photosynthesis. When a fresh haustorium is cut the sucker within the host appears bright green. Transmission electron microscopy reveals that this greening is due to chloroplasts, but that their organization differs from those

Brian A. Fineran

1995-01-01

235

Exposure to bleached kraft pulp mill effluent disrupts the pituitary-gonadal axis of white sucker at multiple sites  

SciTech Connect

Recent studies have demonstrated reproductive problems in white sucker (Catostomus commersoni) exposed to bleached kraft pulp mill effluent (BKME) at Jackfish Bay on Lake Superior. These fish exhibit delayed sexual maturity, reduced gonadal size, reduced secondary sexual characteristics, and circulating steroid levels depressed relative to those of reference populations. The present studies were designed to evaluate sites in the pituitary-gonadal axis of prespawning white sucker affected by BKME exposure. At the time of entry to the spawning stream, plasma levels of immunoreactive gonadotropin (GtH)-II (LH-type GtH) in male and female white sucker were 30- and 50-fold lower, respectively, than the levels in fish from a reference site. A single intraperitoneal injection of D-Arg6, Pro9N-Et sGnRH (sGnRH-A, 0.1 mg/kg) increased plasma GtH levels in male and female fish at both sites, although the magnitude of the response was greatly reduced in BKME-exposed fish. Fish at the BKME site did not ovulate in response to sGnRH-A, while 10 of 10 fish from the reference site ovulated within 6 hr. Plasma 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) levels were depressed in BKME-exposed fish and unlike fish at the reference site, failed to increase in response to sGnRH-A. Testosterone levels in both sexes and 11-ketostestosterone levels in males were elevated in fish from the reference site but were not further increased by GnRH treatment. In contrast, BKME-exposed fish exhibit a transitory increase in testosterone levels in response to the GnRH analog. In vitro incubations of ovarian follicles obtained from fish at the BKME site revealed depressed basal secretion of testosterone and 17,20 beta-P and reduced responsiveness to the GtH analog human chorionic gonadotropin and to forskolin, a direct activator of adenylate cyclase.

Van Der Kraak, G.J.; Munkittrick, K.R.; McMaster, M.E.; Portt, C.B.; Chang, J.P. (Department of Zoology, University of Guelph, Ontario (Canada))

1992-08-01

236

Bentonite Rods Assure Ground Rod Installation In Problem Soils  

Microsoft Academic Search

Ground rods are an effective means of obtaining and maintaining a low resistance to remote ground. However, present methods of installation fail in rocky or hardpan soils. A technique has been developed that assures installation regardless of the subsoil conditions and offers a reduction in resistance of up to 36% per rod.

Warren Jones

1980-01-01

237

String and Sticky Tape Experiments.  

ERIC Educational Resources Information Center

Explains how to demonstrate the fundamentals of one dimensional kinematics such as Newton's third law of motion, and collision between bodies, using simple materials of marbles, strings, sticky tape, drinking straws, and rubber bands. (GA)

Edge, R. D., Ed.

1979-01-01

238

Macroscopic Constraints on String Unification.  

National Technical Information Service (NTIS)

The comparison of string theory with experiment requires a huge extrapolation from the microscopic distances, of order of the Planck length, up to the macroscopic laboratory distances. The quantum effects give rise to large corrections to the macroscopic ...

T. R. Taylor

1989-01-01

239

Wave Propagation on a String  

NSDL National Science Digital Library

An animated example of wave propagation on a string composed of two segments of different densities and velocities. Fortran and Unix/GMT source code used to make the animation are available for download from the same site.

240

Spin chains and string theory.  

PubMed

Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit. PMID:15524978

Kruczenski, Martin

2004-10-15

241

QCD string and chiral symmetry  

NASA Astrophysics Data System (ADS)

We assume that QCD can be described in a certain kinematical regime by an effective string theory. This hadronic string must couple to background chiral fields in a chirally invariant manner, taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is totally unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values.

Andrianov, A. A.; Espriu, D.

2003-04-01

242

Aspects of topological string theory  

NASA Astrophysics Data System (ADS)

Two aspects of the topological string and its applications are considered in this thesis. Firstly, non-perturbative contributions to the OSV conjecture relating four-dimensional extremal black holes and the closed topological string partition function are studied. A new technique is formulated for encapsulating these contributions for the case of a Calabi-Yau manifold constructed by fibering two line bundle over a torus, with the unexpected property that the resulting non-perturbative completion of the topological string partition function is such that the black hole partition function is equal to a product of a chiral and an anti-chiral function. This new approach is considered both in the context of the requirement of background independence for the topological string, and for more general Calabi-Yau manifolds. Secondly, this thesis provides a microscopic derivation of the open topological string holomorphic anomaly equations proposed by Walcher in arXiv:0705.4098 under the assumption that open string moduli do not contribute. In doing so, however, new anomalies are found for compact Calabi-Yau manifolds when the disk one-point functions (string to boundary amplitudes) are non-zero. These new anomalies introduce coupling to wrong moduli (complex structure moduli in A-model and Kahler moduli in B-model), and spoil the recursive structure of the holomorphic anomaly equations. For vanishing disk one-point functions, the open string holomorphic anomaly equations can be integrated to solve for amplitudes recursively, using a Feynman diagram approach, for which a proof is presented.

Cook, Paul L. H.

243

Geometric precipices in string cosmology  

SciTech Connect

We consider the effects of graviton multiplet fields on transitions between string gas phases. Focusing on the dilaton field, we show that it may obstruct transitions between different thermodynamic phases of the string gas, because the sign of its dimensionally reduced, T-duality invariant, part is conserved when the energy density of the Universe is positive. Thus, many interesting solutions for which this sign is positive end up in a future curvature singularity. Because of this, some of the thermodynamic phases of the usual gravitating string gases behave like superselection sectors. For example, a past-regular Hagedorn phase and an expanding Friedmann-Robertson-Walker (FRW) phase dominated by string momentum modes cannot be smoothly connected in the framework of string cosmology with positive sources. The singularity separates them like a geometric precipice in the moduli space, preventing the dynamics of the theory from bridging across. Sources which simultaneously violate the positivity of energy and null energy condition (NEC) could modify these conclusions. We provide a quantitative measure of positivity of energy and NEC violations that would be necessary for such transitions. These effects must dominate the Universe at the moment of transition, altering the standard gas pictures. At present, it is not known how to construct such sources from first principles in string theory.

Kaloper, Nemanja [Department of Physics, University of California, Davis, California 95616 (United States); Watson, Scott [Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2008-03-15

244

Dry Rod Consolidation Technology Project Results.  

National Technical Information Service (NTIS)

The Dry Rod Consolidation Technology (DRCT) Project conducted at the Idaho National Engineering Laboratory (INEL), in 1987 demonstrated the technical feasibility of a dry horizontal fuel rod consolidation process. Fuel rods from Westinghouse 15 /times/ 15...

B. L. Griebenow C. K. Mullen E. M Feldman K. Vinjamuri R. J. Lynch

1988-01-01

245

Intercommutation of Semilocal Strings and Skyrmions  

SciTech Connect

We study the intercommuting of semilocal strings and Skyrmions for a wide range of internal parameters, velocities, and intersection angles by numerically evolving the equations of motion. We find that the collisions of strings and strings, strings and Skyrmions, and Skyrmions and Skyrmions all lead to intercommuting for a wide range of parameters. Even the collisions of unstable Skyrmions and strings lead to intercommuting, demonstrating that the phenomenon of intercommuting is very robust, extending to dissimilar field configurations that are not stationary solutions. Even more remarkably, at least for the semilocal U(2) formulation considered here, all intercommutations trigger a reversion to Nielsen-Olesen strings.

Laguna, Pablo; Natchu, Vishnu; Matzner, Richard A.; Vachaspati, Tanmay [Department of Astronomy and Astrophysics, IGPG, CGWP, Penn State University, University Park, Pennsylvania 16802 (United States); Center for Relativity, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-7079 (United States)

2007-01-26

246

Toroidal compactification of open and closed bosonic strings  

SciTech Connect

Using the duality transformation between open string loops and closed string exchanges, the known compactifications of the closed bosonic string on tori described by even self-dual lattices are coupled to similarly compactified open strings.

Dunbar, D.C.

1988-05-01

247

Status of rod consolidation, 1988  

SciTech Connect

It is estimated that the spent fuel storage pools at some domestic light-water reactors will run out of space before 2003, the year that the US Department of Energy currently predicts it will have a repository available. Of the methods being studied to alleviate the problem, rod consolidation is one of the leading candidates for achieving more efficient use of existing space in spent fuel storage pools. Rod consolidation involves mechanically removing all the fuel rods from the fuel assembly hardware (i.e., the structural components) and placing the fuel rods in a close-packed array in a canister without space grids. A typical goal of rod consolidation systems is to insert the fuel rods from two fuel assemblies into a canister that has the same exterior dimensions as one standard fuel assembly (i.e., to achieve a consolidation or compaction ratio of 2:1) and to compact the nonfuel-bearing structural components from those two fuel assemblies by a factor of 10 to 20. This report provides an overview of the current status of rod consolidation in the United States and a small amount of information on related activities in other countries. 85 refs., 36 figs., 5 tabs.

Bailey, W.J.

1989-01-01

248

Cosmic strings from supersymmetric flat directions  

SciTech Connect

Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra Abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost-flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the Abelian Higgs model, these flat-direction cosmic strings have the extreme type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding-mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multitension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultrahigh-energy cosmic rays or nonthermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.

Cui Yanou; Morrissey, David E. [Michigan Center for Theoretical Physics (MCTP), Physics Department, University of Michigan, Ann Arbor, Michigan 48109 (United States); Martin, Stephen P. [Physics Department, Northern Illinois University, DeKalb, Illinois 60115 (United States); Fermilab National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510 (United States); Wells, James D. [Michigan Center for Theoretical Physics (MCTP), Physics Department, University of Michigan, Ann Arbor, Michigan 48109 (United States); CERN, Theory Division, CH-1211 Geneva 23 (Switzerland)

2008-02-15

249

Quantum vortex strings: A review  

SciTech Connect

The quantum worldsheet dynamics of vortex strings contains information about the 4d non-Abelian gauge theory in which the string lives. Here I tell this story. The string worldsheet theory is typically some variant of the CP{sup N-1} sigma-model, describing the orientation of the string in a U(N) gauge group. Qualitative parallels between 2d sigma-models and 4d non-Abelian gauge theories have been known since the 1970s. The vortex string provides a quantitative link between the two. In 4d theories with N=2 supersymmetry, the exact BPS spectrum of the worldsheet coincides with the bulk spectrum in 4d. Moreover, by tuning parameters, the CP{sup N-1} sigma-model can be coaxed to flow to an interacting conformal fixed point which is related to the 4d Argyres-Douglas fixed point. For theories with N=1 supersymmetry, the worldsheet theory suffers dynamical supersymmetry breaking and, more interestingly, supersymmetry restoration, in a way which captures the physics of Seiberg's quantum deformed moduli space.

Tong, David [Department of Applied, Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 OBA (United Kingdom)], E-mail: d.tong@damtp.cam.ac.uk

2009-01-15

250

Review of haploporid (Trematoda) genera with ornate muscularisation in the region of the oral sucker, including four new species and a new genus.  

PubMed

Species of the Haploporidae Nicoll, 1914 with elaborate muscularisation of the oral sucker belong in three trematode genera, including three new species and a new genus from the intestine of fishes in Australian waters. Spiritestis Nagaty, 1948 is resurrected and S. herveyensis n. sp. is described from the mullet Moolgarda seheli (Forsskål) collected in Hervey Bay, Queensland, Australia; the latter differs from S. arabii Nagaty, 1948 in that the position of the genital pore is pharyngeal rather than post-pharyngeal and the geographical range is off Australia rather than the Red Sea. A new genus is proposed for two new species, with a uniquely ornamented oral sucker, which infect Australian scatophagids. Members of Capitimitta n. g. are distinguished from Waretrema Srivastava, 1937, species of which have a simple oral sucker with six radially arranged anterior muscular lobes, in that their oral sucker is V-shaped with six embedded muscular finger-like structures in the anteroventral portion. The relatively small C. darwinensis n. sp., collected from Selenotoca multifasciata (Richardson) at Darwin, Northern Territory, Australia, is distinguished from C. costata n. sp., collected from Scatophagus argus (Linnaeus) in the same locality and S. multifasciata off Brisbane, Australia, and by having smaller eggs, a vitellarium commencing at a level close to the ventral sucker rather than at greater than one ovarian length posterior to the ventral sucker, and shorter tegumental body spines. Sequence data of a c.2,500 bp region of the 3' end of 18S, the entire ITS region and the 5' end of the 28S revealed that Spiritestis and Capitimitta are not as closely related as some morphological features would suggest and are probably not the closest relative of each other. What has been reported as Waretrema piscicolum Srivastava, 1937 probably consists of several species, some in different genera, and one, based on material collected by Dr Masaaki Machida, is proposed as Spiritestis machidai n. sp. from Crenimugil crenilabis (Forsskål) off Japan. Phylogenetic hypotheses, based on analysis of an alignment of partial 28S sequences with other haploporids, provide a framework for the evaluation of interrelationships within the Haploporidae. These analyses show that: (1) Spiritestis and Capitimitta are supported within the Haploporidae; (2) branches to Forticulcita Overstreet, 1982, Saccocoelioides Szidat, 1954, Spiritestis and Capitimitta create a clade that is sister to haploporines from the Mediterranean Sea; (3) the branch to Saccocoelioides, Spiritestis and Capitimitta create a polytomy; and (4) the two new species of Capitimitta, plus an immature specimen of an unnamed species, form a monophyletic clade. PMID:23299754

Pulis, Eric E; Overstreet, Robin M

2013-01-09

251

Fundamental string solutions in open string field theories  

SciTech Connect

In Witten's open cubic bosonic string field theory and Berkovits' superstring field theory we investigate solutions of the equations of motion with appropriate source terms, which correspond to Callan-Maldacena solution in Born-Infeld theory representing fundamental strings ending on the D-branes. The solutions are given in order by order manner, and we show some full order properties in the sense of {alpha}{sup '} expansion. In superstring case we show that the solution is 1/2 BPS in full order.

Michishita, Yoji [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142 (United States)

2006-02-15

252

Inheriting Spacelike Conformal Killing Vectors in String Cosmology  

NASA Astrophysics Data System (ADS)

We study the consequences of the existence of spacelike conformal Killing vectors (SpCKV) parallel to xa for cosmic strings and string fluid in the context of general relativity. The inheritance symmetries of the cosmic strings and string fluid are discussed in the case of SpCKV. Furthermore we examine proper homothetic spacelike Killing vectors for the cosmic strings and string fluid.

Baysal, Hüsnü

253

Orientifolds, RG Flows, and Closed String Tachyons.  

National Technical Information Service (NTIS)

We discuss the fate of certain tachyonic closed string theories from two perspectives. In both cases our approach involves studying directly configurations with finite negative tree-level cosmological constant. Closed string analogues of orientifolds, whi...

S. Kachru J. Kumar E. Silverstein

1999-01-01

254

Energy and Momentum Transport in String Waves  

ERIC Educational Resources Information Center

Formulas are derived for the energy, momentum, and angular momentum transmitted by waves of arbitrary shape in an inextensible string by pure transverse waves in a string using Tait's procedure. (Author/CP)

Juenker, D. W.

1976-01-01

255

Aspects of Closed String Tachyons in Type II\\/Type 0 String Theory  

Microsoft Academic Search

Abstract In this thesis we review the aspects of the closed string tachyons appearing in the type II and type 0 string theories. One of the most studied theories of the closed string is non-supersymmetric orbifolds in type II string theory. The system in which we have most interest is the one given by the deformation of orbifolds in type

Ryuji Nobuyama

256

Hopf Algebra Symmetry and String  

NASA Astrophysics Data System (ADS)

We investigate the Hopf algebra structure in string worldsheet theory and give a unified formulation of the quantization of string and the space-time symmetry. We reformulate the path integral quantization of string as a Drinfeld twist at the worldsheet level. The coboundary relation shows that the Drinfeld twist defines a module algebra which is equivalent to operators with normal ordering. Upon applying the twist, the space-time diffeomorphism is deformed into a twisted Hopf algebra, while the Poincaré symmetry is unchanged. This suggests a characterization of the symmetry: unbroken symmetries are twist invariant Hopf subalgebras, while broken symmetries are realized as twisted ones. We provide arguments that relate this twisted Hopf algebra to symmetries in path integral quantization.

Asakawa, T.; Mori, M.; Watamura, S.

2008-10-01

257

String solutions of Hofstadter problem  

NASA Astrophysics Data System (ADS)

We study the Bethe Ansatz equations for the Hofstadter problem discovered by Wiegmann and Zabrodin. We formulate an approximate solution to these equations which is analogous to the string solution of the exactly solvable 1D XXZ chain. We found a string solution for all energy levels for irrational flux. The key to the solution is that eigenfunction for one particular value of the flux can be written in terms of solutions at another (simpler) value of the flux, giving rise to a hierarchy picture of states, and making contact with conventional ways to classify fractal spectra. This string solution is the first occasion where tools from exactly solvable models are being applied to obtain analytical results in a model exhibiting multifractal properties. Finally, we compare our analytical results with numerical computer analysis.

Abanov, A. G.; Talstra, J. C.; Wiegmann, P. B.

1997-03-01

258

Cambridge Cosmology: Cosmic Strings and Other Defects  

NSDL National Science Digital Library

This section of Cambridge Cosmology discusses cosmic strings and other defects in our Universe. It begins with phase transitions in the early Universe, and how cosmic strings and other defects formed early on. Cosmic string evolution and dynamics are discussed while looking at high-resolution numerical cosmic string simulations. Also covered are possible explanations for the origin of large-scale structures (such as galaxies) and texture models of these structures.

Shellard, Paul; Martins, Carlos; Sornborger, Andrew

259

BPS nature of 3-string junctions  

Microsoft Academic Search

We study BPS-saturated classical solutions for the world-sheet theory of a D-string in the presence of a point charge. These solutions are interpreted as describing planar 3-string junctions, which arise because the original D-string is deformed by the presence of the inserted charge. We compute the angles of the junctions and show that the vector sum of string tensions is

Keshav Dasgupta; Sunil Mukhi

1998-01-01

260

NonRelativistic Closed String Theory  

Microsoft Academic Search

We construct a Galilean invariant non-gravitational closed string theory\\u000awhose excitations satisfy a non-relativistic dispersion relation. This theory\\u000acan be obtained by taking a consistent low energy limit of any of the\\u000aconventional string theories, including the heterotic string. We give a finite\\u000afirst order worldsheet Hamiltonian for this theory and show that this string\\u000atheory has a sensible perturbative

Jaume Gomis; Hirosi Ooguri

2000-01-01

261

Fast Frequent String Mining Using Suffix Arrays  

Microsoft Academic Search

Mining frequent strings in databases has many interesting applications, e.g., in computational biology. We focus on a special kind of constraint-based frequent string mining, namely computing all strings that are frequent in one database and infrequent in another. We present a method to find such strings by using the suffix- and lcp-arrays, which can be computed extremely fast and space

Johannes Fischer; Volker Heun; Stefan Kramer

2005-01-01

262

Twenty-five questions for string theorists  

SciTech Connect

In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.

Binetruy, Pierre; /Orsay, LPT; Kane, G.L.; /Michigan U., MCTP; Lykken, Joseph D.; /Fermilab; Nelson, Brent D.; /Pennsylvania U.

2005-09-01

263

Hopf solitons and elastic rods  

NASA Astrophysics Data System (ADS)

Hopf solitons in the Skyrme-Faddeev model are stringlike topological solitons classified by the integer-valued Hopf charge. In this paper we introduce an approximate description of Hopf solitons in terms of elastic rods. The general form of the elastic rod energy is derived from the field theory energy and is found to be an extension of the classical Kirchhoff rod energy. Using a minimal extension of the Kirchhoff energy, it is shown that a simple elastic rod model can reproduce many of the qualitative features of Hopf solitons in the Skyrme-Faddeev model. Features that are captured by the model include the buckling of the charge three solution, the formation of links at charges five and six, and the minimal energy trefoil knot at charge seven.

Harland, Derek; Speight, Martin; Sutcliffe, Paul

2011-03-01

264

Modeling Fractions with Cuisenaire Rods  

NSDL National Science Digital Library

In this interactive activity adapted for grades 3–5 from Annenberg Learner’s Teaching Math Grades 6–8, use virtual Cuisenaire® Rods to represent fractions and to perform operations with fractions.

Foundation, Wgbh E.

2012-06-29

265

LOFT nuclear fuel rod behavior  

SciTech Connect

An overview of the calculational models used to predict fuel rod response for Loss-of-Fluid Test (LOFT) data from the first LOFT nuclear test is presented and discussed and a comparison of predictions with experimental data is made.

Niebruegge, D.A.; Tolman, E.L.

1979-01-01

266

Mathieu moonshine and string compactifications  

NASA Astrophysics Data System (ADS)

There is a `Mathieu moonshine' relating the elliptic genus of K3 to the sporadic group M 24. Here, we give evidence that this moonshine extends to part of the web of dualities connecting heterotic strings compactified on K3 × T 2 to type IIA strings compactified on Calabi-Yau threefolds. We demonstrate that dimensions of M 24 representations govern the new supersymmetric index of the heterotic compactifications, and appear in the Gromov-Witten invariants of the dual Calabi-Yau threefolds, which are elliptic fibrations over the Hirzebruch surfaces.

Cheng, Miranda C. N.; Dong, Xi; Duncan, John F. R.; Harvey, Jeffrey A.; Kachru, Shamit; Wrase, Timm

2013-09-01

267

Relativistic string coupled to massless scalar field  

SciTech Connect

The classical relativistic string is coupled to a massless scalar field via an interaction involving the whole volume bounded by its world history--a drum. The source of the field, however, as well as variations of the action with respect to drum histories, are localized on the string. In a local approximation, the string tension originates entirely in the massless field.

Lund, F.

1986-05-15

268

Relativistic string coupled to massless scalar field  

NASA Astrophysics Data System (ADS)

The classical relativistic string is coupled to a massless scalar field via an interaction involving the whole volume bounded by its world history-a drum. The source of the field, however, as well as variations of the action with respect to drum histories, are localized on the string. In a local approximation, the string tension originates entirely in the massless field.

Lund, Fernando

1986-05-01

269

Two Movements for String Orchestra and Percussion  

Microsoft Academic Search

Two Movements for String Orchestra and Percussion is a musical work for a string orchestra and percussion ensemble with specific staging requirements. The percussion battery is placed in the center of the performance stage while the string orchestra is split into two equal groups situated on either side of the percussion. This layout offers a unique visual\\/spatial element that was

Gonzalo L. Gonzalez

2005-01-01

270

Chern-Simons Theory and Topological Strings  

Microsoft Academic Search

We review the relation between Chern-Simons gauge theory and topological string theory on noncompact Calabi-Yau spaces. This relation has made possible to give an exact solution of topological string theory on these spaces to all orders in the string coupling constant. We focus on the construction of this solution, which is encoded in the topological vertex, and we emphasize the

Marcos Marino

2004-01-01

271

Introduction to the theory of strings  

SciTech Connect

These lectures present, from an introductory perspective, some basic aspects of the quantum theory of strings. They treat (1) the kinematics, spectrum, and scattering amplitude of the bosonic string, (2) the spectrum and supersymmetry of Green-Schwarz superstring, and (3) the identification of the underlying gauge invariances of the string theory. 43 refs.

Peskin, M.E.

1985-10-01

272

Sigma Models and Renormalization of String Loops.  

National Technical Information Service (NTIS)

An extension of the ''(sigma)-model (beta)-functions - string equations of motion'' correspondence to the string loop level is discussed. Special emphasis is made on how the renormalization group acts in string loops and, in particular, on the renormaliza...

A. A. Tseytlin

1989-01-01

273

Non-Abelian Strings and Axions  

SciTech Connect

Axion-like fields can have a strong impact on non-Abelian strings. I discuss axion connection to such strings and its implications in two cases: (i) axion localized on the strings, and (ii) axions propagating in the four-dimensional bulk.

Shifman, M. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, MN 55455 (United States)

2010-08-30

274

Noncommutative Tachyons And String Field Theory  

Microsoft Academic Search

It has been shown recently that by turning on a large noncommutativity parameter, the description of tachyon condensation in string theory can be drastically simplified. We reconsider these issues from the standpoint of string field theory, showing that, from this point of view, the key fact is that in the limit of a large B-field, the string field algebra factors

Edward Witten

2000-01-01

275

String theory dynamics in various dimensions  

Microsoft Academic Search

The strong coupling dynamics of string theories in dimension d ? 4 are studied. It is argued, among other things, that eleven-dimensional supergravity arises as a low energy limit of the ten-dimensional Type IIA superstring, and that a recently conjectured duality between the heterotic string and Type IIA superstrings controls the strong coupling dynamics of the heterotic string in five,

Edward Witten

1995-01-01

276

A First Course in String Theory  

Microsoft Academic Search

An accessible introduction to string theory, this book provides a detailed and self-contained demonstration of the main concepts involved. The first part deals with basic ideas, reviewing special relativity and electromagnetism while introducing the concept of extra dimensions. D-branes and the classical dynamics of relativistic strings are discussed next, and the quantization of open and closed bosonic strings in the

Barton Zwiebach

2004-01-01

277

String Field Theory Around the Tachyon Vacuum  

Microsoft Academic Search

Assuming that around the tachyon vacuum the kinetic term of cubic open string field theory is made purely of ghost operators we are led to gauge invariant actions which manifestly implement the absence of open string dynamics around this vacuum. We test this proposal by showing the existence of lump solutions of arbitrary codimension in this string field theory. The

Leonardo Rastelli; Ashoke Sen; Barton Zwiebach

2000-01-01

278

Conformal invariance, supersymmetry and string theory  

Microsoft Academic Search

Covariant quantization of string theories is developed in the context of conformal field theory and the BRST quantization procedure. The BRST method is used to covariantly quantize superstrings, and in particular to construct the vertex operators for string emission as well as the supersymmetry charge. The calculation of string loop diagrams is sketched. We discuss how conformal methods can be

Daniel Friedan; Emil Martinec; Stephen Shenker

1986-01-01

279

Transverse structure of the QCD string  

SciTech Connect

The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length {beta} defined from the slope of its gravitational form factor, is given by (d-1/2{pi}{sigma})log({beta}/4r{sub 0}) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2{pi}{sigma})log(r/r{sub 0}). We also obtain predictions for transition form factors among closed-string states.

Meyer, Harvey B. [Johannes Gutenberg Universitaet Mainz, Institut fuer Kernphysik, 55099 Mainz (Germany)

2010-11-15

280

String theory and classical integrable systems  

Microsoft Academic Search

We discuss different formulations and approaches to string theory and 2d quantum gravity. The generic idea to get a unique description of many different string vacua altogether is demonstrated on the examples in 2d conformal, topological and matrix formulations. The last one naturally brings us to the appearance of classical integrable systems in string theory. Physical meaning of the appearing

A. Marshakov; P. N. Lebedev

1994-01-01

281

Covariant Calculus for Effective String Theories  

Microsoft Academic Search

A covariant calculus for the construction of effective string theories is developed. Effective string theory, describing quantum string-like excitations in arbitrary dimension, has in the past been constructed using the principles of conformal field theory, but not in a systematic way. Using the freedom of choice of field definition, a particular field definition is made in a systematic way to

N. D. Hari Dass; Peter Matlock

2007-01-01

282

String-Matching and Other Products.  

National Technical Information Service (NTIS)

The string-matching problem considered is to find all occurrences of a given pattern as a substring of another longer string. When the pattern is simply a given string of symbols, there is an algorithm due to Morris, Knuth and Pratt which has a running ti...

M. J. Fischer M. S. Paterson

1974-01-01

283

Reminiscence on the Birth of String Theory  

Microsoft Academic Search

These are my personal impressions of the environment in which string theory\\u000awas born, and what the important developments affecting my work were during the\\u000ahadronic string era, 1968-1974. I discuss my motivations and concerns at the\\u000atime, particularly in my work on loop amplitudes and on closed strings.

Joel A. Shapiro

2007-01-01

284

Applying perceptual knowledge to string instrument synthesis  

Microsoft Academic Search

This paper gives an overview of the research that aims at more efcient sound synthesis by applying per- ceptual knowledge on parameter selection and quantization. The scope of the research is limited to string instrument sounds. Many string synthesis models, like the plucked string model, are controlled paramet- rically, which enables studying the effects of individual features separately. The paper

Hanna Jarvel

285

New critical dimensions for string theories  

Microsoft Academic Search

The open string dynamics which include the Liouville field theory following Polyakov and Gervais-Neveu are shown to enjoy the same remarkable properties as the celebrated string theories in D = 26 or D = 10 dimensions, provided D is changed to D = 7 or 13 for the purely bosonic string and to D = 3 or 5 for superstrings.

A. Bilal; J.-L. Gervais

1987-01-01

286

The Physics of "String Passing through Ice"  

ERIC Educational Resources Information Center

One of the oldest yet interesting experiments related to heat and thermodynamics is placing a string on a block of ice and hanging two masses from the ends of the string. Sometime later, it is discovered that the string has passed through the ice without cutting it in half. A simple explanation of this effect is that the pressure caused by the…

Mohazzabi, Pirooz

2011-01-01

287

Periodicity and repetitions in parameterized strings  

Microsoft Academic Search

One of the most beautiful and useful notions in the Mathematical Theory of Strings is that of a Period, i.e., an initial piece of a given string that can generate that string by repeating itself at regular intervals. Periods have an elegant mathematical structure and a wealth of applications [F. Mignosi and A. Restivo, Periodicity, Algebraic Combinatorics on Words, in:

Alberto Apostolico; Raffaele Giancarlo

2008-01-01

288

Natural language insensitive short textual string compression  

Microsoft Academic Search

There are applications (such as Internet search engines) where short textual strings, for example abstracts or pieces of Web pages, need to be compressed independently of each other. The usual adaptive compression algorithms perform poorly on these short strings due to the lack of necessary data to learn. In this manuscript, we introduce a compression algorithm targeting short text strings;

Cornel Constantinescu; Jennifer Q. Trelewicz; Ronald B. Arps

2004-01-01

289

The Physics of "String Passing through Ice"  

ERIC Educational Resources Information Center

|One of the oldest yet interesting experiments related to heat and thermodynamics is placing a string on a block of ice and hanging two masses from the ends of the string. Sometime later, it is discovered that the string has passed through the ice without cutting it in half. A simple explanation of this effect is that the pressure caused by the…

Mohazzabi, Pirooz

2011-01-01

290

Extremal black holes and elementary string states  

Microsoft Academic Search

Some of the extremal black hole solutions in string theory have the same quantum numbers as the Bogomol'nyi saturated elementary string states. We explore the possibility that these black holes can be identified to elementary string excitations. It is shown that stringy effects could correct the Bekenstein-Hawking formula for the black hole entropy in such a way that it correctly

Ashoke Sen

1996-01-01

291

Hydrothermal synthesis of hydroxyapatite rods  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAP) rods were synthesized from dicalcium phosphate anhydrous (CaHPO4, DCPA) and calcium carbonate (CaCO3) by the hydrothermal method from 120 to 180 °C. Both cuttlebone (aragonite polymorph of CaCO3) and CaCO3 chemical (calcite polymorph of CaCO3) were used as CaCO3 sources. The nucleation and growth of HAP rods mainly occurred on DCPA particles, while some HAP rods also grew from aragonite particles. The nucleation and growth of ?-tricalcium phosphate (?-TCP) particles on the surface of calcite particles were observed at the beginning of the reaction of DCPA and calcite, and some HAP rods were also found to grow out of ?-TCP particles. After the hydrothermal reaction at 140 °C for 24 h, most products are HAP with a small amount of ?-TCP synthesized as a byproduct. The HAP rods synthesized were ˜200 nm in width and several microns in length. The reaction mechanism and growth process of HAP rods are discussed.

Zhang, Xing; Vecchio, Kenneth S.

2007-10-01

292

Snubber assembly for a control rod drive  

Microsoft Academic Search

A snubber cartridge assembly is mounted to the nozzle of a control rod drive mechanism to insure that the snubber assembly will be located within the liquid filled section of a nuclear reactor vessel whenever the control rod drive is assembled thereto. The snubber assembly includes a piston mounted proximate to the control rod connecting end of the control rod

1978-01-01

293

Altered performance of white sucker populations in the Manitouwadge chain of lakes is associated with changes in benthic macroinvertebrate communities as a result of copper and zinc contamination  

SciTech Connect

White sucker (Catostomus commersoni) collected from the Manitouwadge chain of lakes show a lower growth rate and fecundity in lakes contaminated with copper and zinc from a mixed metal mine. This study evaluated whether the changes in performance of the fish were related to direct impacts of the metals or indirect impacts associated with changes in food availability. Concentrations of metals in the water and sediment of lakes in the Manitouwadge chain were elevated, relative to reference sites. The concentrations of Cu and Zn in the digesta of white sucker were significantly higher, as were the levels of both Cu and Zn in liver, kidney, and gill tissue. Muscle and spleen levels of Cu and Zn were significantly lower or not different from controls. Tissue levels were within the homeostatic range for Cu and Zn. However, the total density of invertebrates varied from greater than 25,000 m-2 at control sites to less than 13,000 m-2 at contaminated sites, and the number of genera recorded was more than 50% lower in shallow water samples. There was almost a complete absence of several invertebrate taxa at contaminated sites, including Plecoptera, Ephemeroptera, Odonata, Trichoptera, Amphipoda, and Unionidae. Diptera accounted for 78 to 96% of the total numbers of individuals at metal-contaminated sites as compared with 40 to 75% at the control sites. An analysis of white sucker stomach contents showed that the contents closely reflected the benthic composition observed in the natural substrate. Changes in food availability and feeding activity were correlated with previous changes documented in the growth, fecundity, and lipid levels of white sucker.

Munkittrick, K.R.; Miller, P.A.; Barton, D.R.; Dixon, D.G. (University of Waterloo, Ontario (Canada))

1991-06-01

294

NEUTRONIC REACTOR CONTROL ROD DRIVE APPARATUS  

DOEpatents

ABS>A suspension mechanism between a vertically movable nuclear reactor control rod and a rod extension, which also provides information for the operator or an automatic control signal, is described. A spring connects the rod extension to a drive shift. The extension of the spring indicates whether (1) the rod is at rest on the reactor, (2) the rod and extension are suspended, or (3) the extension alone is suspended, the spring controlling a 3-position electrical switch.

Oakes, L.C.; Walker, C.S.

1959-12-15

295

Remote multiple string well completion  

SciTech Connect

In a remotely installed underwater well apparatus, a tubular body, typically a multiple string tubing hanger, is landed in a position oriented rotationally with respect to a reference point on the apparatus and a seal device is then energized by the same tool employed to land and orient the tubular body.

Kirkland, K.G.

1981-09-15

296

Metastable Quivers in String Compactifications  

SciTech Connect

We propose a scenario for dynamical supersymmetry breaking in string compactifications based on geometric engineering of quiver gauge theories. In particular we show that the runaway behavior of fractional branes at del Pezzo singularities can be stabilized by a flux superpotential in compact models. Our construction relies on homological mirror symmetry for orientifolds.

Diaconescu, Duiliu-Emanuel; /Rutgers U., Piscataway; Donagi, Ron; /Pennsylvania U. /SLAC; Florea, Bogdan; /SLAC

2007-01-08

297

String universality in ten dimensions.  

PubMed

We show that the N=1 supergravity theories in ten dimensions with gauge groups U(1){496} and E{8}×U(1){248} are not consistent quantum theories. Cancellation of anomalies cannot be made compatible with supersymmetry and Abelian gauge invariance. Thus, in ten dimensions all supersymmetric theories of gravity without known inconsistencies are realized in string theory. PMID:20868028

Adams, Allan; Taylor, Washington; Dewolfe, Oliver

2010-08-10

298

String Universality in Ten Dimensions  

SciTech Connect

We show that the N=1 supergravity theories in ten dimensions with gauge groups U(1){sup 496} and E{sub 8}xU(1){sup 248} are not consistent quantum theories. Cancellation of anomalies cannot be made compatible with supersymmetry and Abelian gauge invariance. Thus, in ten dimensions all supersymmetric theories of gravity without known inconsistencies are realized in string theory.

Adams, Allan; Taylor, Washington; DeWolfe, Oliver [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Physics, 390 UCB, University of Colorado, Boulder, Colorado 80309 (United States)

2010-08-13

299

Black Holes in String Theory  

Microsoft Academic Search

This thesis is devoted to trying to find a microscopic quantum description of black holes. We consider black holes in string theory which is a quantum theory of gravity. We find that the ``area law'' black hole entropy for extremal and near-extremal charged black holes arises from counting microscopic configurations. We study black holes in five and four spacetime dimensions.

Juan Mart n Maldacena

1996-01-01

300

Spin chains and string theory  

Microsoft Academic Search

Recently, an impressive agreement was found between anomalous dimen- sions of certain operators in N = 4 SYM and rotating strings with two angular mo- menta in the bulk of AdS5 × S5. A one-loop field theory computation, which involves solving a Heisenberg chain by means of the Bethe ansatz agrees with the large angular momentum limit of a rotating

Martin Kruczenski

301

String Physics at the LHC  

SciTech Connect

The LHC program will include the identification of events with single high-k{sub T} photons as probes of new physics. We show that this channel is uniquely suited to search for experimental evidence of TeV-scale open string theory.

Anchordoqui, Luis A. [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States)

2008-11-23

302

Localized gravity in string theory.  

PubMed

We propose a string realization of the AdS4 brane in AdS5 that is known to localize gravity. Our theory is M D5 branes in the near horizon geometry of N D3 branes, where M and N are appropriately tuned. PMID:11497820

Karch, A; Randall, L

2001-07-23

303

String amplitudes in arbitrary dimensions  

NASA Astrophysics Data System (ADS)

We calculate gravitational dressed tachyon correlators in non critical dimensions. The 2D gravity part of the theory is constrained to constant curvature. Then scaling dimensions of gravitational dressed vertex operators are equal to their bare conformal dimensions. Considering the model as d+2 dimensional critical string we calculate poles of generalized Shapiro-Virasoro amplitudes.

Förste, Stefan

1992-09-01

304

Algebras, BPS states, and strings  

Microsoft Academic Search

We clarify the role played by BPS states in the calculation of threshold corrections of D = 4, N = 2 heterotic string compactifications. We evaluate these corrections for some classes of compactifications and show that they are sums of logarithmic functions over the positive roots of generalized Kac-Moody algebras. Moreover, a certain limit of the formulae suggests a reformulation

Jeffrey A. Harvey; Gregory Moore

1996-01-01

305

Eichler integrals and String Theory  

Microsoft Academic Search

In this article, it is shown how to obtain objects called Eichler integrals in the mathematical literature that can be used for calculating scattering amplitudes in String Theory. These Eichler integrals are also new examples of Eichler integrals with poles. The concept of an Eichler integral is closely related to the concept of automorphic forms. Although automorphic forms have a

Leonidas Sandoval Junior

306

Duality symmetries in string theory  

SciTech Connect

The search for a unified theory of quantum gravity and gauge interactions leads naturally to string theory. This field of research has received a revival of interest after the discovery of duality symmetries in recent years. We present a self contained account of some non-perturbative aspects of string theory which have been recently understood. The spectrum and interactions of the five consistent superstring theories in ten dimensions are recollected and the fundamental principles underlying this initial stage in the construction of the theory are briefly reviewed. We next discuss some evidences that these apparently different superstrings are just different aspects of one unique theory. The key to this development is given by the non-perturbative duality symmetries which have modified and improved our understanding of string dynamics in many ways. In particular, by relating the fundamental objects of one theory to solitons of another theory, they have unraveled the presence of extended objects in the theory which stand on an equal footing with strings. We introduce these higher dimensional objects, named D-branes, and discuss applications of D-brane physics.

Nunez, Carmen A. [Instituto de Astronomia y Fisica del Espacio-CONICET C.C. 67-Suc. 28, 1428 Buenos Aires (Argentina)

1999-10-25

307

Primordial Fluctuations in String Cosmology  

NASA Astrophysics Data System (ADS)

This thesis is dedicated to the study of inflationary scenarios based on string theory. Inflation is a brief period of accelerated expansion in the very early Universe which gives natural explanations for problems of the Standard Big Bang Model (SBBM) of cosmology. The phenomenological success of inflation provides the motivation for numerous efforts to establish its connection with particle physics. As a promising contender for a unified theory at very high energy scales, string theory is an obvious framework to look for the theoretical foundations of inflation; we therefore try to determine the characteristic features of string-inspired inflationary scenarios, along with their observational consequences. In particular, we shall be interested in models of brane inflation, in which the inflaton field has non-canonical dymanics and where the era of reheating is interpreted as the mutual annihilation of (anti-)branes. This document contains an introduction to cosmology and string theory as well as the model building efforts untertaken at their intersection in recent years. The scientific articles published during the thesis are represented by a short summary each and are available separately on the arXiv.

Lorenz, Larissa C.

2010-02-01

308

Localized Gravity in String Theory  

SciTech Connect

We propose a string realization of the AdS{sub 4} brane in AdS{sub 5} that is known to localize gravity. Our theory is M D5 branes in the near horizon geometry of N D3 branes, where M and N are appropriately tuned.

Karch, Andreas; Randall, Lisa

2001-08-06

309

RV strings of maximum curvature  

SciTech Connect

To design an effective interceptor for a string of reentry vehicles (RV's) released by a post-boost vehicle (PBV), it is necessary to have information about possible geometries of the string when it reaches a given altitude above the target. The geometry of the string, assumed for simplicity to contain three RV's, is determined by the motion of the PBV which is controlled by varying its thrust direction. Of interest in this study is maximizing the curvature of the string, which is represented by the distance of RV{sub 2} from the line joining RV{sub 1} and RV{sub 3} when RV{sub 1} reaches the intercept attitude, subject to the constraints that all three RV's must land within 3000 ft distance of the target. The maximum curvature problem is formulated as a parameter optimization problem and solved by a nonlinear programming code known as GRG2. The thrust angles are assumed to be piecewise linear, and a total of 21 parameters is used. The maximum curvature is shown to be approximately 2900 ft. 4 refs., 8 figs.

Hull, D.G. (Texas Univ., Austin, TX (United States)); Zazworsky, R.M. (Sandia National Labs., Albuquerque, NM (United States))

1991-01-01

310

Monopole accretion by cosmic strings  

SciTech Connect

The authors study the accretion of super-heavy magnetic monopoles, around cosmic string loops in the very early universe. For sufficiently massive monopoles, a possible result of this accretion process is the formation of monopole-black holes, leading ultimately to monopole-to-photon ratio comparable to the limits required by neutron star observations.

Matheson, A.M. (Brown Univ., Providence, RI (USA). Dept. of Physics); Upton, D.M. (Graduate School of Business Administration, Harvard University, Soldier Field, Boston, MA (US))

1990-07-20

311

The Official String Theory Web Site  

NSDL National Science Digital Library

The Official String Theory Web Site, created by a group of highly educated physicists, is a great resource for everyone interested in physics and the string theory. It begins with educational and stimulating discussion about theoretical physics and the basics of string theory. Users can find out about the experimental tests and the math used by string theorists. Visitors can take a trip through the Big Bang, view amazing images of black holes, and learn about the history of string theory. Students and educators can listen to interviews of the many scientists who contributed to this informative site.

312

Cosmic string scaling in flat space  

SciTech Connect

We investigate the evolution of infinite strings as a part of a complete cosmic string network in flat space. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. Our results confirm that the wiggles on the strings obey a scaling law described by universal power spectrum. The average distance between long strings also scales accurately with the time. These results suggest that small-scale structure will also scale in an expanding universe, even in the absence of gravitational damping.

Vanchurin, Vitaly; Olum, Ken; Vilenkin, Alexander [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States)

2005-09-15

313

Randall-Sundrum and strings  

NASA Astrophysics Data System (ADS)

We investigate stringy excitations in Randall-Sundrum effective theories for electroweak symmetry breaking arising from embedding in string theory. RS is dual to a confining gauge theory, which we expect to have “QCD strings”, or color flux tubes. Stringy constructions of RS-like theories allow us to investigate the mass of these string states, which typically grows with a small fractional power of the number of colors N of the dual gauge theory. There are two known strong constraints on N for RS-like theories. The first arises from demanding that the Standard Model gauge couplings do not have a Landau pole at low scales. The second arises from demanding that the first-order confining phase transition in the early universe is able to proceed without leaving an empty universe, i.e. that the rate of bubble nucleation is not too small. We find that these constraints on N imply that string states are generically at most a factor of a few heavier than the lightest KK states, and we cannot self-consistently remain in the limit N,? ? 1. We examine various string constructions of AdS or RS-like backgrounds, including orbifolds, theories on M5-branes, theories on D4-branes, and the recent F-theory construction of Polchinski and Silverstein. In every case we find that there are strong bounds on the mass of new stringy states. We briefly discuss important phenomenological implications due to the presence of such light stringy excitations, such as precision electroweak and flavor observables, as well as collider signals.

Reece, Matthew; Wang, Lian-Tao

2010-07-01

314

Spermiogenesis and spermatozoon ultrastructure of Hunterella nodulosa (Cestoda: Caryophyllidea), a monozoic parasite of suckers (Catostomidae) in North America.  

PubMed

Spermiogenesis and ultrastructure of mature spermatozoon of the caryophyllidean cestode Hunterella nodulosa, a parasite of suckers (Catostomidae), have been studied by transmission electron microscopy. This monozoic tapeworm is unique in its mode of attachment and represents the second North American species studied. The process of spermiogenesis of H. nodulosa follows the general pattern already described in other caryophyllideans. The most characteristic feature is the presence of a slight rotation of the flagellar bud, which seems to be a typical character of spermiogenesis in this cestode group. The mature spermatozoon of H. nodulosa is characterized by the presence of one axoneme of 9 + "1" type of the trepaxonematan flatworms surrounded by a semi-arc of cortical microtubules in its anterior extremity, parallel nucleus and cortical microtubules arranged in a parallel pattern, which corresponds to the Type III pattern of cestode spermatozoa according to Levron et al. (2010). Comparison of the present data with those available for other caryophyllideans did not reveal substantial differences, even though they belong to different families, infect different hosts (catostomid, cyprinid and siluriform fishes) and occur in distant zoogeographical regions. This indicates uniformity of the process of sperm formation and spermatozoon ultrastructure in one of the evolutionarily most ancient groups of tapeworms. PMID:23136798

Yoneva, Aneta; Levron, Celine; Oros, Mikulás; Orosová, Martina; Scholz, Tomás

2012-09-01

315

Trampling, defoliation and physiological integration affect growth, morphological and mechanical properties of a root-suckering clonal tree  

PubMed Central

Background and Aims Grazing is a complex process involving the simultaneous occurrence of both trampling and defoliation. Clonal plants are a common feature of heavily grazed ecosystems where large herbivores inflict the simultaneous pressures of trampling and defoliation on the vegetation. We test the hypothesis that physiological integration (resource sharing between interconnected ramets) may help plants to deal with the interactive effects of trampling and defoliation. Methods In a field study, small and large ramets of the root-suckering clonal tree Populus simonii were subjected to two levels of trampling and defoliation, while connected or disconnected to other ramets. Plant responses were quantified via survival, growth, morphological and stem mechanical traits. Key Results Disconnection and trampling increased mortality, especially in small ramets. Trampling increased stem length, basal diameter, fibrous root mass, stem stiffness and resistance to deflection in connected ramets, but decreased them in disconnected ones. Trampling decreased vertical height more in disconnected than in connected ramets, and reduced stem mass in disconnected ramets but not in connected ramets. Defoliation reduced basal diameter, leaf mass, stem mass and leaf area ratio, but did not interact with trampling or disconnection. Conclusions Although clonal integration did not influence defoliation response, it did alleviate the effects of trampling. We suggest that by facilitating resource transport between ramets, clonal integration compensates for trampling-induced damage to fine roots.

Xu, Liang; Yu, Fei-Hai; van Drunen, Elles; Schieving, Feike; Dong, Ming; Anten, Niels P. R.

2012-01-01

316

Stuck fuel rod capping sleeve  

DOEpatents

A stuck fuel rod capping sleeve to be used during derodding of spent fuel assemblies if a fuel rod becomes stuck in a partially withdrawn position and, thus, has to be severed. The capping sleeve has an inner sleeve made of a lower work hardening highly ductile material (e.g., Inconel 600) and an outer sleeve made of a moderately ductile material (e.g., 304 stainless steel). The inner sleeve may be made of an epoxy filler. The capping sleeve is placed on a fuel rod which is then severed by using a bolt cutter device. Upon cutting, the capping sleeve deforms in such a manner as to prevent the gross release of radioactive fuel material

Gorscak, Donald A. (Bethel Park, PA); Maringo, John J. (McKeesport, PA); Nilsen, Roy J. (Upper St. Clair, PA)

1988-01-01

317

Advanced gray rod control assembly  

DOEpatents

An advanced gray rod control assembly (GRCA) for a nuclear reactor. The GRCA provides controlled insertion of gray rod assemblies into the reactor, thereby controlling the rate of power produced by the reactor and providing reactivity control at full power. Each gray rod assembly includes an elongated tubular member, a primary neutron-absorber disposed within the tubular member said neutron-absorber comprising an absorber material, preferably tungsten, having a 2200 m/s neutron absorption microscopic capture cross-section of from 10 to 30 barns. An internal support tube can be positioned between the primary absorber and the tubular member as a secondary absorber to enhance neutron absorption, absorber depletion, assembly weight, and assembly heat transfer characteristics.

Drudy, Keith J; Carlson, William R; Conner, Michael E; Goldenfield, Mark; Hone, Michael J; Long, Jr., Carroll J; Parkinson, Jerod; Pomirleanu, Radu O

2013-09-17

318

Open strings on D-branes and Hagedorn regime in string gas cosmology  

SciTech Connect

We consider early time cosmic evolution in string gas cosmology dominated by open strings attached to D-branes. After reviewing statistical properties of open strings in D-brane backgrounds, we use dilaton-gravity equations to determine the string frame fields. Although, there are distinctions in the Hagedorn regime thermodynamics and dilaton coupling as compared to closed strings, it seems difficult to avoid Jeans instability and assume thermal equilibrium simultaneously, which is already a known problem for closed strings. We also examine characteristics of a possible subsequent large radius regime in this setup.

Arslanargin, Ayse [Bogazici University, Department of Physics, 34342, Bebek, Istanbul (Turkey); Kaya, Ali [Bogazici University, Department of Physics, 34342, Bebek, Istanbul (Turkey); Feza Guersey Institute, Emek Mah. No:68, Cengelkoey, Istanbul (Turkey)

2009-03-15

319

Cosmic string induced peculiar velocities  

SciTech Connect

We calculate analytically the probability distribution for peculiar velocities on scales from 10h/sup -1/ to 60h/sup -1/ Mpc with cosmic string loops as the dominant source of primordial gravitational perturbations. We consider a range of parameters ..beta..G..mu.. appropriate for both hot (HDM) and cold (CDM) dark matter scenarios. An ..cap omega.. = 1 CDM Universe is assumed with the loops randomly placed on a smooth background. It is shown how the effects can be estimated of loops breaking up and being born with a spectrum of sizes. It is found that to obtain large scale streaming velocities of at least 400 km/s it is necessary that either a large value for ..beta..G..mu.. or the effect of loop fissioning and production details be considerable. Specifically, for optimal CDM string parameters G..mu.. = 10/sup -6/, ..beta.. = 9, h = .5, and scales of 60h/sup -1/ Mpc, the parent size spectrum must be 36 times larger than the evolved daughter spectrum to achieve peculiar velocities of at least 400 km/s with a probability of 63%. With this scenario the microwave background dipole will be less than 800 km/s with only a 10% probability. The string induced velocity spectrum is relatively flat out to scales of about 2t/sub eq//a/sub eq/ and then drops off rather quickly. The flatness is a signature of string models of galaxy formation. With HDM a larger value of ..beta..G..mu.. is necessary for galaxy formation since accretion on small scales starts later. Hence, with HDM, the peculiar velocity spectrum will be larger on large scales and the flat region will extend to larger scales. If large scale peculiar velocities greater than 400 km/s are real then it is concluded that strings plus CDM have difficulties. The advantages of strings plus HDM in this regard will be explored in greater detail in a later paper. 27 refs., 4 figs., 1 tab.

van Dalen, A.; Schramm, D.N.

1987-02-01

320

Cadmium safety rod thermal tests  

SciTech Connect

Thermal testing of cadmium safety rods was conducted as part of a program to define the response of Savannah River Site (SRS) production reactor core components to a hypothetical LOCA leading to a drained reactor tank. The safety rods are present in the reactor core only during shutdown and are not used as a control mechanism during operation; thus, their response to the conditions predicted for the LOCA is only of interest to the extent that it could impact the progression of the accident. This document provides a description of this testing.

Thomas, J.K.; Iyer, N.C.; Peacock, H.B.

1992-07-01

321

Cadmium safety rod thermal tests  

SciTech Connect

Thermal testing of cadmium safety rods was conducted as part of a program to define the response of Savannah River Site (SRS) production reactor core components to a hypothetical LOCA leading to a drained reactor tank. The safety rods are present in the reactor core only during shutdown and are not used as a control mechanism during operation; thus, their response to the conditions predicted for the LOCA is only of interest to the extent that it could impact the progression of the accident. This document provides a description of this testing.

Thomas, J.K.; Iyer, N.C.; Peacock, H.B.

1992-01-01

322

Constructing rods with given natural frequencies  

NASA Astrophysics Data System (ADS)

In this paper we present a new method for constructing axially vibrating rods having prescribed values of the first N natural frequencies, under a given set of boundary conditions. The analysis is based on the determination of the so-called quasi-isospectral rods, that is rods which have the same spectrum as a given rod, with the exception of a single eigenvalue which is free to move in a prescribed interval. The reconstruction procedure needs the specification of an initial rod whose eigenvalues must be close to the assigned eigenvalues. The rods and their normal modes can be constructed explicitly by means of closed-form expressions.

Morassi, Antonino

2013-10-01

323

Black Holes in String Theory  

NASA Astrophysics Data System (ADS)

This is a set of introductory lecture notes on black holes in string theory. After reviewing some aspects of string theory such as dualities, brane solutions, supersymmetric and non-extremal intersection rules, we analyze in detail extremal and non-extremal 5d black holes. We first present the D-brane counting for extremal black holes. Then we show that 4d and 5d non-extremal black holes can be mapped to the BTZ black hole (times a compact manifold) by means of dualities. The validity of these dualities is analyzed in detail. We present an analysis of the same system in the spirit of the adS/CFT correspondence. In the "near-horizon" limit (which is actually a near inner-horizon limit for non-extremal black holes) the black hole reduces again to the BTZ black hole. A state counting is presented in terms of the BTZ black hole.

Skenderis, Kostas

324

On noncommutative open string theories  

NASA Astrophysics Data System (ADS)

We investigate new compactifications of OM theory giving rise to a (3+1)-dimensional open string theory with non-commutative x0-x1 and x2-x3 coordinates. The theory can be directly obtained by starting with a D3-brane with parallel (near critical) electric and magnetic field components, in the presence of a RR scalar field. The magnetic parameter permits to interpolate continuously between the x0-x1 non-commutative open string theory and the x2-x3 spatial non-commutative U(N) super Yang-Mills theory. We discuss SL(2,Bbb Z) transformations of this theory. Using the supergravity description of the large-N limit, we also compute corrections to the quark-antiquark Coulomb potential arising in the NCOS theory.

Russo, Jorge G.; Sheikh-Jabbari, Mohammad M.

2000-07-01

325

The Research on Axial Vibration of Drill String with Delphi  

Microsoft Academic Search

Drill string vibration is a very prevalent phenomena, it does great effect to drilling engineering, drill string resonance is the main reason that causes the drill string fatigue. In this paper the drill string is object that is studied, the axial vibration is analyzed for the total system of drill string. The model of axial vibration is established, the rule

Han Chunjie; Yan Tie

2009-01-01

326

Probing string fragmentation in nuclear matter: Lepton-nucleus scattering  

Microsoft Academic Search

We introduce a new model for the fragmentation of strings in a “medium” of hadronic objects. These objects may be hadrons, resonances, or string pieces from the fragmentation of other strings. As a first application we treat the fragmentation of a string inside a nuclear medium, taking into account interactions of the fragmenting string with spectator nucleons (spectators of the

K. Werner; P. Koch

1990-01-01

327

Acoustical properties of drill strings  

SciTech Connect

The recovery of petrochemical and geothermal resources requires extensive drilling of wells to increasingly greater depths. Real-time collection and telemetry of data about the drilling process while it occurs thousands of feet below the surface is an effective way of improving the efficiency of drilling operations. Unfortunately, due to hostile down-hole environments, telemetry of this data is an extremely difficult problem. Currently, commercial systems transmit data to the surface by producing pressure pulses within the portion of the drilling mud enclosed in the hollow steel drill string. Transmission rates are between two and four data bits per second. Any system capable of raising data rates without increasing the complexity of the drilling process will have significant economic impact. One alternative system is based upon acoustical carrier waves generated within the drill string itself. If developed, this method would accommodate data rates up to 100 bits per second. Unfortunately, the drill string is a periodic structure of pipe and threaded tool joints, the transmission characteristics are very complex and exhibit a banded and dispersive structure. Over the past forty years, attempts to field systems based upon this transmission method have resulted in little success. This paper examines this acoustical transmission problem in great detail. The basic principles of acoustic wave propagation in the periodic structure of the drill string are examined through theory, laboratory experiment, and field test. The results indicate the existence of frequency bands which are virtually free of attenuation and suitable for data transmission at high bit rates. 9 refs., 38 figs., 2 tabs.

Drumheller, D.S.

1988-08-01

328

Black Holes in String Theory  

Microsoft Academic Search

This is a write-up of introductory lectures on black holes in string the- ory given at TASI-99. Topics discussed include: black holes, thermodynamics and the Bekenstein-Hawking entropy, the information problem; supergravity actions, conserved quantum numbers, supersymmetry and BPS states, units, duality and dimensional reduction, solution-generating; extremal M-branes and D-branes, smearing, probe actions, nonextremal branes, the Gregory-Laflamme instability; breakdown of supergravity

Amanda W. Peet

329

Charged rotating dilaton black strings  

Microsoft Academic Search

In this paper we, first, present a class of charged rotating solutions in four-dimensional Einstein-Maxwell-dilaton gravity with zero and Liouville-type potentials. We find that these solutions can present a black hole\\/string with two regular horizons, an extreme black hole or a naked singularity provided the parameters of the solutions are chosen suitable. We also compute the conserved and thermodynamic quantities,

M. H. Dehghani; N. Farhangkhah

2005-01-01

330

Magnetic strings in dilaton gravity  

Microsoft Academic Search

First, I present two new classes of magnetic rotating solutions in four-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type potential. The first class of solutions yields a four-dimensional spacetime with a longitudinal magnetic field generated by a static or spinning magnetic string. I find that these solutions have no curvature singularity and no horizons, but have a conic geometry. In these spacetimes, when

M. H. Dehghani

2005-01-01

331

A parallel string search algorithm  

Microsoft Academic Search

A new parallel processing algorithm for solving string search problems is presented. The proposed algorithm uses O(m×n) processors where n is the length of a text and m is the length of a pattern. It requires two and only two iteration steps to find the pattern in the text, while the best existing parallel algorithm needs the computation time O(loglog

Yoshiyasu Takefuji; Toshimitsu Tanaka; Kuo Chun Lee

1992-01-01

332

Counting strings, wound and bound  

NASA Astrophysics Data System (ADS)

We analyze zero mode counting problems for Dirac operators that find their origin in string theory backgrounds. A first class of quantum mechanical models for which we compute the number of ground states arises from a string winding an isometric direction in a geometry, taking into account its energy due to tension. Alternatively, the models arise from deforming marginal bound states of a string winding a circle, and moving in an orthogonal geometry. After deformation, the number of bound states is again counted by the zero modes of a Dirac operator. We count these bound states in even dimensional asymptotically linear dilaton backgrounds as well as in Euclidean Taub-NUT. We show multiple pole behavior in the fugacities keeping track of a U(1) charge. We also discuss a second class of counting problems that arises when these backgrounds are deformed via the application of a heterotic duality transformation. We discuss applications of our results to Appell-Lerch sums and the counting of domain wall bound states.

Ashok, Sujay K.; Nampuri, Suresh; Troost, Jan

2013-04-01

333

Magnetic strings in dilaton gravity  

SciTech Connect

First, I present two new classes of magnetic rotating solutions in four-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type potential. The first class of solutions yields a four-dimensional spacetime with a longitudinal magnetic field generated by a static or spinning magnetic string. I find that these solutions have no curvature singularity and no horizons, but have a conic geometry. In these spacetimes, when the rotation parameter does not vanish, there exists an electric field, and therefore the spinning string has a net electric charge which is proportional to the rotation parameter. The second class of solutions yields a spacetime with an angular magnetic field. These solutions have no curvature singularity, no horizon, and no conical singularity. The net electric charge of the strings in these spacetimes is proportional to their velocities. Second, I obtain the (n+1)-dimensional rotating solutions in Einstein-dilaton gravity with Liouville-type potential. I argue that these solutions can present horizonless spacetimes with conic singularity, if one chooses the parameters of the solutions suitable. I also use the counterterm method and compute the conserved quantities of these spacetimes.

Dehghani, M.H. [Physics Department and Biruni Observatory, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)

2005-03-15

334

Cosmological Consequences of String Axions  

SciTech Connect

Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the consequences of a measurement of these fluctuations for two additional string axions. We do so independent of any cosmological assumptions except for the axions being massless during inflation. The first axion has been shown to solve the strong CP problem for most compactifications of the heterotic string while the second axion, which does not solve the strong CP problem, obeys a mass formula which is independent of the axion scale. We find that if gravitational waves interpreted as arising from inflation are observed by the PLANCK polarimetry experiment with a Hubble constant during inflation of H{sub inf} {approx}> 10{sup 13} GeV the existence of the first axion is ruled out and the second axion cannot obey the scale independent mass formula. In an appendix we quantitatively justify the often held assumption that temperature corrections to the zero temperature QCD axion mass may be ignored for temperatures T {approx}< {Lambda}{sub QCD}.

Kain, Ben

2005-12-15

335

Constraints on Cosmic Strings Due to Black Holes Formed from Collapsed Cosmic String Loops.  

National Technical Information Service (NTIS)

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to f...

R. R. Caldwell E. Gates

1993-01-01

336

Closed String Field Theory: The Failure of BRST Cohomology for the Open String.  

National Technical Information Service (NTIS)

Open string states are constructed which describe closed strings. They are so-called spurious states. This shows that the identification of physical states with the cohomology classes generated by the BRST charge is incorrect. These states allow the compu...

P. Mansfield

1988-01-01

337

Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops.  

National Technical Information Service (NTIS)

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to f...

R. R. Caldwell E. Gates

1993-01-01

338

HYDRAULIC CONTROL ROD DRIVE MECHANISM  

Microsoft Academic Search

The hydraulic control rod drive mechanism described is housed in a ; thimble attached to and extending outward from the reactor vessel. The drive ; mechanism uses reactor coolant medium as the hydraulic fluid. Within the housing ; there are two concentrically arranged hollow, cylindrically shaped members to one ; of which the piston is attached. One of the two

Kumpf

1963-01-01

339

Status of rod consolidation, 1988  

Microsoft Academic Search

It is estimated that the spent fuel storage pools at some domestic light-water reactors will run out of space before 2003, the year that the US Department of Energy currently predicts it will have a repository available. Of the methods being studied to alleviate the problem, rod consolidation is one of the leading candidates for achieving more efficient use of

Bailey

1989-01-01

340

Cool Hot Rod (Thermal Expansion)  

NSDL National Science Digital Library

The phenomenon is thermal expansion of copper. This demonstration allows an observer to see the effect of heating (and cooling) a copper tube. When heated, the copper tube lengthens and thickens. When cooled, the tube shrinks. The lengthening of the rod rotates a toothpick with an attached flag to make the expansion visible and measurable.

341

Interactions of non-Abelian global strings  

NASA Astrophysics Data System (ADS)

Non-Abelian global strings are expected to form during the chiral phase transition. They have orientational zero modes in the internal space, associated with the vector-like symmetry SUN broken in the presence of strings. The interaction among two parallel non-Abelian global strings is derived for general relative orientational zero modes, giving a non-Abelian generalization of the Magnus force. It is shown that when the orientations of the strings are the same, the repulsive force reaches the maximum, whereas when the relative orientation becomes the maximum, no force exists between the strings. For the Abelian case we find a finite volume correction to the known result. The marginal instability of the previously known Abelian ? strings is discussed.

Nakano, Eiji; Nitta, Muneto; Matsuura, Taeko

2009-02-01

342

Rod operated rotary well valve  

SciTech Connect

A well valve for use in a tubing string in a well bore of an oil or gas well to isolate a lower portion of the well bore below a packer including a body having a longitudinal bore therethrough connectible in a well tubing string, a lower annular valve seat supported in the body for limited sliding movement, fluid seal means between the lower valve seat and the body, an upper annular valve seat supported in longitudinal spaced relation from the lower valve seat within the body, a ball valve member supported for rotation between opened and closed positions between the valve seats, pivot members secured with the ball valve member for rotating the valve member, and a longitudinally movable operator member coupled with the pivot members for moving the pivot members longitudinally while permitting the members to traverse an arcuate path as the ball valve member rotates between open and closed positions. The valve seals both upwardly and downwardly and is opened and closed without longitudinal travel of either seat or the ball valve member. The valve is useful in various types of well installations for production and testing procedures and is operable by manipulation of operator means coupled into the valve from an upper tubing string.

Fredd, J.V.

1980-10-28

343

LOFT Advanced Fuel Rod Instrumentation Development.  

National Technical Information Service (NTIS)

Advanced fuel rod instrumentation for the Loss of Fluid Test (LOFT) reactor is being developed by the Hanford Engineering Development Laboratory for the Nuclear Regulatory Commission. This effort calls for development of sensors to measure fuel rod axial ...

T. R. Billeter R. L. Brown A. I. Y. Chan C. K. Day S. C. Meyers

1978-01-01

344

Control rods in LMFBRs: a physics assessment  

SciTech Connect

This physics assessment is based on roughly 300 control rod worth measurements in ZPPR from 1972 to 1981. All ZPPR assemblies simulated mixed-oxide LMFBRs, representing sizes of 350, 700, and 900 MWe. Control rod worth measurements included single rods, various combinations of rods, and Ta and Eu rods. Additional measurements studied variations in B/sub 4/C enrichment, rod interaction effects, variations in rod geometry, neutron streaming in sodium-filled channels, and axial worth profiles. Analyses were done with design-equivalent methods, using ENDF/B Version IV data. Some computations for the sensitivities to approximations in the methods have been included. Comparisons of these analyses with the experiments have allowed the status of control rod physics in the US to be clearly defined.

McFarlane, H.F.; Collins, P.J.

1982-08-01

345

Investigation of Lightning Rod Shielding Angle  

NASA Astrophysics Data System (ADS)

This paper studies those parameters affecting the shielding angle of the lightning rod (Franklin Rod) above very tall buildings. It was recommended that the shielding angle of the lightning rod is about 45°?60°. The downward lightning leader is modeled by using discrete line charges to consider the exponential distribution of charges through the downward leader. The voltage condition used by Rizk is used to investigate the inception of the upward lightning leader. Different air conditions (relative air density and air humidity) are considered for more practical simulation. The influences of lightning parameters and lightning rod height on the shielding angle are studied. The results shows that, lightning leader parameters, lightning rod height and ground slope have series effects on the lightning rod shielding angle. Based on the results, a lightning rod shielding angle for shielding design is recommended to decrease the lightning stroke to the lightning rod.

Nayel, Mohamed

346

p-adic String Theories Provide Lattice Discretization to the Ordinary String Worldsheet  

SciTech Connect

A class of models called p-adic strings is useful in understanding the tachyonic instability of string theory. These are found to be empirically related to the ordinary strings in the p{yields}1 limit. We propose that these models provide discretization for the string worldsheet and argue that the limit is naturally thought of as a continuum limit in the sense of the renormalization group.

Ghoshal, Debashis [Harish-Chandra Research Institute, Chhatnag Road, Allahabad 211019 (India)

2006-10-13

347

Spacelike Ricci inheritance vectors in a model of string cloud and string fluid stress tensor  

NASA Astrophysics Data System (ADS)

We study the consequences of the existence of spacelike Ricci inheritance vectors (SpRIVs) parallel to xa for a model of string cloud and string fluid stress tensor in the context of general relativity. Necessary and sufficient conditions are derived for a spacetime with a model of string cloud and string fluid stress tensor to admit a SpRIV, and a SpRIV which is also a spacelike conformal Killing vector. Also, some results are obtained.

Baysal, Hüsnü; Yilmaz, Ihsan

2002-12-01

348

p-adic string theories provide lattice Discretization to the ordinary string worldsheet.  

PubMed

A class of models called p-adic strings is useful in understanding the tachyonic instability of string theory. These are found to be empirically related to the ordinary strings in the p-->1 limit. We propose that these models provide discretization for the string worldsheet and argue that the limit is naturally thought of as a continuum limit in the sense of the renormalization group. PMID:17155316

Ghoshal, Debashis

2006-10-09

349

Iconic Indexing by 2-D Strings  

Microsoft Academic Search

In this paper, we describe a new way of representing a symbolic picture by a two-dimensional string. A picture query can also be specified as a 2-D string. The problem of pictorial information retrieval then becomes a problem of 2-D subsequence matching. We present algorithms for encoding a symbolic picture into its 2-D string representation, reconstructing a picture from its

Shi-Kuo Chang; Qing-Yun Shi; Cheng-Wen Yan

1987-01-01

350

Orbifold SUSY GUT from the Heterotic String  

SciTech Connect

From the string partition function, we discuss the mass-shell and GSO projection conditions valid for Kaluza-Klein (KK) as well as massless states in the heterotic string theory compactifled on a nonprime orbifold. Using the obtained conditions we construct a 4D string standard model, which is embedded in a 6D SUSY GUT by including KK states above the compactiflcation scale. We discuss the stringy threshold corrections to gauge couplings, including the Wilson line effects.

Kyae, Bumseok [Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747 (Korea, Republic of)

2008-11-23

351

Free field theory as a string theory?  

NASA Astrophysics Data System (ADS)

An approach to systematically implement open-closed string duality for free large N gauge theories is summarised. We show how the relevant closed string moduli space emerges from a reorganisation of the Feynman diagrams contributing to free field correlators. We also indicate why the resulting integrand on moduli space has the right features to be that of a string theory on AdS. To cite this article: R. Gopakumar, C. R. Physique 5 (2004).

Gopakumar, Rajesh

2004-11-01

352

Dissecting the string theory dual of QCD  

Microsoft Academic Search

Input from QCD and string theory is used in order to elucidate basic features of the string theory dual of QCD, It is argued that the relevant string theory is a five-dimensional version of the type-0 superstring. The vacuum solution is asymptotically AdS$_5$, and the geometry near the boundary is stringy. The structure of YM perturbation theory however emerges near

Elias Kiritsis

2009-01-01

353

Advances in Inflation in String Theory  

NASA Astrophysics Data System (ADS)

We provide a pedagogical overview of inflation in string theory. We focus upon the sensitivity of inflation to Planck-scale physics, which we argue provides both the primary motivation and the central theoretical challenge for the subject. We illustrate these issues through two case studies of inflationary scenarios in string theory: warped d-brane inflation and axion monodromy inflation. Finally, we indicate how future observations can test scenarios of inflation in string theory.

Baumann, Daniel; McAllister, Liam

2009-11-01

354

A Pedestrian Approach to Covariant String Theory  

NASA Astrophysics Data System (ADS)

Ever since Professor Nambu identified the Veneziano amplitude as stemming from the antics of a string, there has been a growing amount of interest in the subject. In fact the most recent view holds that consistency between Quantum Mechanics and General Relativity may be achieved only within the framework of string theory, barring unseemly modifications of Quantum Mechanics at Planckian distances. Closed string theories already provide a modification of General Relativity at short distances.

Ramond, P.

355

Exact solutions and singularities in string theory  

SciTech Connect

We construct two new classes of exact solutions to string theory which are not of the standard plane wave of gauged WZW type. Many of these solutions have curvature singularities. The first class includes the fundamental string solution, for which the string coupling vanishes near the singularity. This suggests that the singularity may not be removed by quantum corrections. The second class consists of hybrids of plane wave and gauged WZW solutions. We discuss a four-dimensional example in detail.

Horowitz, G.T. (Isaac Newton Institute, Cambridge CB3 0EH (United Kingdom)); Tseytlin, A.A. (Theoretical Physics Group, Blackett Laboratory Imperial College, London SW7 2BZ (United Kingdom))

1994-10-15

356

String junction as a baryonic constituent  

NASA Astrophysics Data System (ADS)

We extend the model for QCD string with quarks to consider the Mercedes Benz string configuration describing the three-quark baryon. Under the assumption of adiabatic separation of quark and string junction motion we formulate and solve the classical equation of motion for the junction. We dare to quantize the motion of the junction, and discuss the impact of these modes on the baryon spectra.

Kalashnikova, Yu. S.; Nefediev, A. V.

1996-02-01

357

Relation between strings and ribbon knots  

NASA Astrophysics Data System (ADS)

A ribbon knot can be represented as the propagation of an open string in (Euclidean) space-time. By imposing physical conditions plus an ansatz on the string scattering amplitude, we get invariant polynomials of ribbon knots which correspond to Jones and Wadati et al. polynomials for ordinary knots. Motivated by the string scattering vertices, we derive an algebra which is a generalization of Hecke and Murakami-Birman-Wenzel (BMW) algebras of knots.

Ahmed, E.; El-Rifai, E. A.; Abdellatif, R. A.

1991-02-01

358

Minimal string theories and integrable hierarchies  

NASA Astrophysics Data System (ADS)

Well-defined, non-perturbative formulations of the physics of string theories in specific minimal or superminimal model backgrounds can be obtained by solving matrix models in the double scaling limit. They provide us with the first examples of completely solvable string theories. Despite being relatively simple compared to higher dimensional critical string theories, they furnish non-perturbative descriptions of interesting physical phenomena such as geometrical transitions between D-branes and fluxes, tachyon condensation and holography. The physics of these theories in the minimal model backgrounds is succinctly encoded in a non-linear differential equation known as the string equation, along with an associated hierarchy of integrable partial differential equations (PDEs). The bosonic string in (2,2m-1) conformal minimal model backgrounds and the type 0A string in (2,4 m) superconformal minimal model backgrounds have the Korteweg-de Vries system, while type 0B in (2,4m) backgrounds has the Zakharov-Shabat system. The integrable PDE hierarchy governs flows between backgrounds with different m. In this thesis, we explore this interesting connection between minimal string theories and integrable hierarchies further. We uncover the remarkable role that an infinite hierarchy of non-linear differential equations plays in organizing and connecting certain minimal string theories non-perturbatively. We are able to embed the type 0A and 0B (A,A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We find that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A,D) minimal string backgrounds. We explain how these and several other string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painleve IV equation plays a key role in organizing the string theory physics, joining its siblings, Painleve I and II, whose roles have previously been identified in this minimal string context. We then present evidence that the conjectured type II theories have smooth non-perturbative solutions, connecting two perturbative asymptotic regimes, in a 't Hooft limit. Our technique also demonstrates evidence for new minimal string theories that are not apparent in a perturbative analysis.

Iyer, Ramakrishnan

359

Twistor Strings, Gauge Theory and Gravity  

SciTech Connect

The development of new analytic and computational methods in the perturbative approach to Yang-Mills theories is of great importance to the understanding of LHC physics. Twistor string theory, a form of string theory defined on Penrose's twistor space, may provide a very efficient and powerful alternative to the usual Feynman diagram expansion of field theory. I survey the recent construction of a family of new twistor string theories which are free from world-sheet anomalies and give the space-time spectra of Einstein supergravities, with second order field equations instead of the higher derivative conformal supergravities that arose from earlier twistor strings.

Abou-Zeid, Mohab [Institut des Hautes Etudes Scientifiques 35 route de Chartres, Le Bois-Marie, 91440 Bures-sur-Yvette (France)

2008-04-21

360

A new string in ten dimensions?  

NASA Astrophysics Data System (ADS)

I suggest the possibility of a new string in ten dimensions. Evidence for this string is presented both from orientifold physics and from K-theory, along with a mystery concerning the M-theory description. Motivated by this possibility, some novel aspects of decoupling limits in heterotic/type I theories are described; specifically, the decoupled theory on type I D-strings is argued to be three-dimensional rather than two-dimensional. These decoupled theories provide the matrix model definitions of the heterotic/type I strings.

Sethi, Savdeep

2013-09-01

361

Spontaneous knotting of an agitated string.  

PubMed

It is well known that a jostled string tends to become knotted; yet the factors governing the "spontaneous" formation of various knots are unclear. We performed experiments in which a string was tumbled inside a box and found that complex knots often form within seconds. We used mathematical knot theory to analyze the knots. Above a critical string length, the probability P of knotting at first increased sharply with length but then saturated below 100%. This behavior differs from that of mathematical self-avoiding random walks, where P has been proven to approach 100%. Finite agitation time and jamming of the string due to its stiffness result in lower probability, but P approaches 100% with long, flexible strings. We analyzed the knots by calculating their Jones polynomials via computer analysis of digital photos of the string. Remarkably, almost all were identified as prime knots: 120 different types, having minimum crossing numbers up to 11, were observed in 3,415 trials. All prime knots with up to seven crossings were observed. The relative probability of forming a knot decreased exponentially with minimum crossing number and Möbius energy, mathematical measures of knot complexity. Based on the observation that long, stiff strings tend to form a coiled structure when confined, we propose a simple model to describe the knot formation based on random "braid moves" of the string end. Our model can qualitatively account for the observed distribution of knots and dependence on agitation time and string length. PMID:17911269

Raymer, Dorian M; Smith, Douglas E

2007-10-02

362

Gauge invariant actions for string models  

SciTech Connect

String models of unified interactions are elegant sets of Feynman rules for the scattering of gravitons, gauge bosons, and a host of massive excitations. The purpose of these lectures is to describe the progress towards a nonperturbative formulation of the theory. Such a formulation should make the geometrical meaning of string theory manifest and explain the many ''miracles'' exhibited by the string Feynman rules. There are some new results on gauge invariant observables, on the cosmological constant, and on the symmetries of interacting string field theory. 49 refs.

Banks, T.

1986-06-01

363

Proton decay by monopoles and strings  

SciTech Connect

Order-of-magnitude estimates are obtained for fermion-monopole and fermion-string scattering, taking into account the effect of the monopole or string on the fermion wavefunction. As a result, it is concluded that monopoles will catalyze proton decay with a strong cross-section (the Callan-Rubakov effect) whereas for strings the process has a geometrical cross-section. The difference is explained as being due to a long range attractive potential between the fermion and the monopole, and the absence of long range fields in the case of the string.

Matheson, A.

1988-01-01

364

String Theory and Gauge Theories (Strings, Gravity, and the Large N Limit of Gauge Theories)  

ScienceCinema

We will see how gauge theories, in the limit that the number of colors is large, give string theories. We will discuss some examples of particular gauge theories where the corresponding string theory is known precisely, starting with the case of the maximally supersymmetric theory in four dimensions which corresponds to ten dimensional string theory. We will discuss recent developments in this area.

365

Suffix Arrays for Multiple Strings: A Method for On-Line Multiple String Searches  

Microsoft Academic Search

Manber and Myers' suffix array for a single string is a useful data structure for solving string matching problems. In this paper, we will show how to generalize their idea to multiple strings. We call this generalization the generalized suffix array. We present algorithms for constructing a generalized suffix array and for searching the array. Let A denote the set

Fei Shi

1996-01-01

366

Control rod support having planar wear surfaces  

SciTech Connect

This patent describes a combination. It comprises: a longitudinally extending rod guide; a support for a control rod. The support being positioned within the rod guide and intended to receive and minimize scarring of the control rod; a cylindrical control rod having a convex surface and being held by a spider including vanes. The support being relatively flat and thin, and having a predetermined exterior cross-sectional configuration and including a control rod opening formed in the support and having a predetermined configuration and cross-sectional area, a channel formed in the support to receive one of the vanes and communicate with the control rod opening. The channel forming a respective pair of junctures with the control rod opening. The control rod opening including a pair of planar wear surfaces, each parallel to the axis of the control rod opening and extending laterally from the respective junctures to afford a planar-to-convex interface between the convex surface of the control rod and the planar wear surfaces of the support when the convex surface of the control rod abuts.

Veronesi, L.; Schockling, L.A.

1990-02-20

367

Rod pathways: the importance of seeing nothing  

Microsoft Academic Search

Anatomical and physiological studies of the mammalian retina have revealed two primary pathways available for the transmission of rod signals to the ganglion cells: one via ON rod bipolars, amacrine II cells, and ON and OFF cone bipolars, which is exquisitely designed for the transmission of single-photon absorption events; and a second via rod–cone gap junctions, and ON and OFF

Lindsay T. Sharpe; Andrew Stockman

1999-01-01

368

Bosonic and Baryonic String Theory in Quantum Chromodynamics  

SciTech Connect

Bosonic string formation in gauge theories is reviewed with particular attention to the confining flux in lattice QCD and its effective string theory description. Recent results on the Casimir energy of the ground state and the string excitation spectrum are analyzed in the Dirichlet string limit of large separation between static sources. The closed string-soliton (torelon) with electric flux winding around a compact dimension is discussed and a new bound state tower spectrum at baryon string junctions is presented.

Kuti, Julius [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States)

2007-02-27

369

Rod cluster having improved vane configuration  

SciTech Connect

This patent describes a pressurized water reactor vessel, the vessel defining a predetermined axial direction of the flow of coolant therewithin and having plural spider assemblies supporting, for vertical movement within the vessel, respective clusters of rods in spaced, parallel axial relationship, parallel to the predetermined axial direction of coolant flow, and a rod guide for each spider assembly and respective cluster of rods. The rod guide having horizontally oriented support plates therewithin, each plate having an interior opening for accommodating axial movement therethrough of the spider assembly and respective cluster of rods. The opening defining plural radially extending channels and corresponding parallel interior wall surfaces of the support plate.

Shockling, L.A.; Francis, T.A.

1989-09-05

370

ELECTROMAGNETIC APPARATUS FOR MOVING A ROD  

DOEpatents

An electromagnetic apparatus for moving a rod-like member in small steps in either direction is described. The invention has particular application in the reactor field where the reactor control rods must be moved only a small distance and where the use of mechanical couplings is impractical due to the high- pressure seals required. A neutron-absorbing rod is mounted in a housing with gripping uaits that engage the rod, and coils for magnetizing the gripping units to make them grip, shift, and release the rod are located outside the housing.

Young, J.N.

1958-04-22

371

Topological amplitudes in string theory  

Microsoft Academic Search

We show that certain type II string amplitudes at genus $g$ are given by the\\u000atopological partition function $F_g$ discussed recently by Bershadsky, Cecotti,\\u000aOoguri and Vafa. These amplitudes give rise to a term in the four-dimensional\\u000aeffective action of the form $\\\\sum_g F_g W^{2g}$, where $W$ is the chiral\\u000asuperfield of $N=2$ supergravitational multiplet. The holomorphic anomaly of\\u000a$F_g$

I. Antoniadis; E. Gavab; K. S. Narainc; T. R. Taylor

1994-01-01

372

Singularities and Closed String Tachyons  

SciTech Connect

A basic problem in gravitational physics is the resolution of spacetime singularities where general relativity breaks down. The simplest such singularities are conical singularities arising from orbifold identifications of flat space, and the most challenging are spacelike singularities inside black holes (and in cosmology). Topology changing processes also require evolution through classically singular spacetimes. I briefly review how a phase of closed string tachyon condensate replaces, and helps to resolve, basic singularities of each of these types. Finally I discuss some interesting features of singularities arising in the small volume limit of compact negatively curved spaces and the emerging zoology of spacelike singularities.

Silverstein, Eva; /SLAC /Stanford U., Phys. Dept.

2006-03-17

373

Extraordinary vacuum black string solutions  

SciTech Connect

In addition to the boosted static solution there are two other classes of stationary stringlike solutions of the vacuum Einstein equation in (4+1) dimensions. Each class is characterized by three parameters of mass, tension, and momentum flow along the fifth coordinate. We analyze the metric properties of one of the two classes, which was previously assumed to be naked singular, and show that the solution spectrum contains black string and wormhole in addition to the known naked singularity as the momentum flow to mass ratio increases. Interestingly, there does not exist new zero momentum solution in these cases.

Kim, Hyeong-Chan; Lee, Jungjai [Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Department of Physics, Daejin University, Pocheon, 487-711 (Korea, Republic of)

2008-01-15

374

Final report for reciprocating rod pump seal assembly (R.R.P.S.A.)  

SciTech Connect

This technology provides a simple yet clever idea for preventing oil and saltwater polluting spills by sucker rod pumping oil wells, as well as prolonging the life of the stuffing box seals and pressure lubricating the polished rod. This objective is accomplished by introducing a non-polluting, food grade, high viscosity lubricant into the void space between two sets of seals in a typical stuffing box. This safe-fluid acts as a sacrificial fluid that will be the fluid that is exposed to the atmosphere when the primary seal in the stuffing box leaks for any reason. In addition, the pressure on this sacrificial safe-fluid is maintained at the same pressure as the pressure on the produced fluid in the flow line at the pumping tee, thereby equalizing the pressure across the secondary seal in the stuffing box that separates the safe-fluid from the produced fluid. The unique feature, of equalizing the pressure across the secondary seal, is accomplished by using a pressure transmitter which is monitoring the pressure in the flow line (which is the fluid under the secondary seal) and transmitting that pressure to the safe-fluid (which is the fluid above the secondary seal) thereby equalizing the pressure across this secondary seal. The primary seal will be sealing the safe-fluid and will be operating under optimum conditions, extending the life of this primary seal. The principle of the invention was proven by equipping eight oil wells with Field Retro-Fit Packages of Independent component parts to hydro-balance the existing stuffing boxes.

NONE

1997-12-15

375

A generalized bead-rod model for Brownian dynamics simulations of wormlike chains under strong confinement.  

PubMed

This paper is aimed to develop a Brownian dynamics simulation method for strongly confined semiflexible polymers where numerical simulation plays an indispensable role in complementing theory and experiments. A wormlike chain under strong confinement is modeled as a string of virtual spherical beads connected by inextensible rods with length varying according to the confinement intensity of the chain measured by the Odijk deflection length. The model takes hydrodynamic interactions into account. The geometrical constraints associated with the inextensible rods are realized by the so-called linear constraint solver. The model parameters are studied by quantitatively comparing the simulated properties of a double-stranded DNA chain with available experimental data and theoretical predictions. PMID:16164329

Wang, Jizeng; Gao, Huajian

2005-08-22

376

A generalized bead-rod model for Brownian dynamics simulations of wormlike chains under strong confinement  

NASA Astrophysics Data System (ADS)

This paper is aimed to develop a Brownian dynamics simulation method for strongly confined semiflexible polymers where numerical simulation plays an indispensable role in complementing theory and experiments. A wormlike chain under strong confinement is modeled as a string of virtual spherical beads connected by inextensible rods with length varying according to the confinement intensity of the chain measured by the Odijk deflection length. The model takes hydrodynamic interactions into account. The geometrical constraints associated with the inextensible rods are realized by the so-called linear constraint solver. The model parameters are studied by quantitatively comparing the simulated properties of a double-stranded DNA chain with available experimental data and theoretical predictions.

Wang, Jizeng; Gao, Huajian

2005-08-01

377

Toroidal compactification of closed bosonic strings  

SciTech Connect

The boundary conditions of a free closed bosonic string propagating in a space where the compactified dimensions are toroidal limit the lattices defining the tori to be self dual, just as is required by modular invariance of the one-loop dual amplitudes. The spectra generated by the free-string oscillators for both Euclidean and Lorentzian lattice are described. 10 refs.

Slansky, R.

1986-01-01

378

Inflation from strings 2; Reheating and baryogenesis  

SciTech Connect

The authors study the reheating process which takes place after the two periods of inflation that arise from a string-inspired cosmological model. In this paper baryogenesis mechanisms and a possible solution for the magnetic monopole problem that are compatible with string-motivated inflationary scenarios are discussed.

Bento, M.C.; Bertolami, O.; Sa, P.M. (Centro de Fisica da Materia Condensada, Av. Prof. Gama Pinto, 2, 1699 Lisboa Codex (PT))

1992-04-10

379

Bandwidth Efficient String Reconciliation Using Puzzles  

Microsoft Academic Search

Abstract Of considerable interest in recent years has been the problem of exchanging correlated data with minimum communication. We thus consider the problem of exchanging two similar strings held by different hosts. Our approach involves transforming a string into a multi-set of substrings that are reconciled efcien tly using known multi-set reconciliation algorithms, and then put back together on a

Sachin Agarwal; Vikas Chauhan; Ari Trachtenberg

2006-01-01

380

Melt dumping in string stabilized ribbon growth  

DOEpatents

A method and apparatus for stabilizing the edge positions of a ribbon drawn from a melt includes the use of wettable strings drawn in parallel up through the melt surface, the ribbon being grown between the strings. A furnace and various features of the crucible used therein permit continuous automatic growth of flat ribbons without close temperature control or the need for visual inspection.

Sachs, Emanuel M. (42 Old Middlesex Rd., Belmont, MA 02178)

1986-12-09

381

String Theory: Big Problem for Small Size  

ERIC Educational Resources Information Center

|String theory is the most promising candidate theory for a unified description of all the fundamental forces that exist in nature. It provides a mathematical framework that combines quantum theory with Einstein's general theory of relativity. The typical size of a string is of the order of 10[superscript -33] cm, called the Planck length. But due…

Sahoo, S.

2009-01-01

382

Hydromonochord: Visualizing String Vibration by Water Swirls  

ERIC Educational Resources Information Center

|The hydromonochord is a horizontal vibrating string that just makes contact with the surface of a water bath. The motion of the string sets up a pattern of swirls on the surface of the water, thus complementing the usual pattern of nodes and antinodes. The device is based on the traditional monochord. A water basin (Fig. 1) has two slits in the…

Sommer, Wilfried; Meier-Boke, Ralf; Meinzer, Nicholas

2010-01-01

383

A Computer String-Grammar of English.  

ERIC Educational Resources Information Center

This volume is the fourth in a series of detailed reports on a working computer program for the syntactic analysis of English sentences into their component strings. The report (1) records the considerations involved in various decisions among alternative grammatical formulations and presents the word-subclasses, the linguistic strings, etc., for…

Sager, Naomi

384

String Theory: Big Problem for Small Size  

ERIC Educational Resources Information Center

String theory is the most promising candidate theory for a unified description of all the fundamental forces that exist in nature. It provides a mathematical framework that combines quantum theory with Einstein's general theory of relativity. The typical size of a string is of the order of 10[superscript -33] cm, called the Planck length. But due…

Sahoo, S.

2009-01-01

385

Micro string resonators as temperature sensors  

NASA Astrophysics Data System (ADS)

The resonance frequency of strings is highly sensitive to temperature. In this work we have investigated the applicability of micro string resonators as temperature sensors. The resonance frequency of strings is a function of the tensile stress which is coupled to temperature by the thermal expansion of the string and the frame clamping it. The sensitivity improves when the length and pre-stress are reduced and the difference in thermal expansion, Young's modulus and resonant mode are increased. At low tensile stress, the sensitivity becomes highly dependent on temperature. The investigation was done with silicon rich silicon nitride (SiNx), nickel (Ni) and aluminum (Al) micro strings. Aluminum strings show a relative sensitivity of up to 15+/-1 %/°C, which is more than 100 times higher than values reported by other groups for similar devices. Sub-millisecond time constants can be achieved due to the low thermal mass of the strings. A temperature resolution of 2.5×10-4 °C has been achieved with silicon nitride strings. The theoretical limit for the temperature resolution of 8×10-8 °C has not been reached yet and requires further improvement of the sensor.

Larsen, T.; Schmid, S.; Boisen, A.

2013-09-01

386

Three-dimensional gravity and string ghosts  

SciTech Connect

It is known that much of the structure of string theory can be derived from three-dimensional topological field theory and gravity. We show here that, at least for simple topologies, the string diffeomorphism ghosts can also be explained in terms of three-dimensional physics.

Carlip, S. (Department of Phyiscs, University of California, Davis, California 95616 (United States)); Kogan, I.I. (Department of Physics, University of British Columbia, Vancouver, British Columbia, V6T 2A6 (Canada))

1991-12-23

387

Quantum space foam and string theory  

SciTech Connect

String theory is originally defined as a modification of the Feynman rules in perturbation theory. It contains gravity in its perturbative spectrum. We review some recent developments which demonstrate that nonperturbative effects of quantum gravity, such as spacetime foam, arise in string theory as well.Prepared for the proceedings of 'Albert Einstein Century Conference' , Paris July 2005.

Nekrasov, Nikita [IHES, 35, Route de Chartres, Bures-sur-Yvette, F-91440 (France)

2006-11-03

388

String Theory - From Physics to Metaphysics  

Microsoft Academic Search

Currently, string theory represents the only advanced approach to a unification of all interactions, including gravity. In spite of the more than thirty years of its existence it did not make any empirically testable predictions. And it is completely unknown which physically interpretable principles could form the basis of string theory. At the moment, \\

Reiner Hedrich

2006-01-01

389

Astrophysical Black Holes in String Theory?  

Microsoft Academic Search

String theory has by now achieved a very detailed quantum description of some black holes. However, the methods have mostly been applied in settings that have very little resemblance to the real world. Fortunately many aspects of the string theory description apply to all near extremal black holes, including near-extreme Kerr black holes (rapidly spinning black holes that are common

Finn Larsen

2010-01-01

390

A Computer String-Grammar of English.  

ERIC Educational Resources Information Center

|This volume is the fourth in a series of detailed reports on a working computer program for the syntactic analysis of English sentences into their component strings. The report (1) records the considerations involved in various decisions among alternative grammatical formulations and presents the word-subclasses, the linguistic strings, etc., for…

Sager, Naomi

391

The Fate of Massive Closed Strings  

SciTech Connect

We calculate the semi-inclusive decay rate of an average string state with toroidal compactification in the the superstring theory. We also apply this calculation to a brane-inflation model in a warped geometry and find that the decay rate is greatly suppressed if the final strings are both massive and enhanced for massless radiation.

Chen Bin [Department of Physics, Peking University, Beijing 100871 (China); Li Miao; She Jianhuang [Institute of Theoretical Physics, Chinese Academy of Science, P.O.Box 2735, Beijing 100080 (China)

2005-12-02

392

Some global aspects of string compactifications  

Microsoft Academic Search

Nearly flat bosonic string vacua are examined. An analogy between compactification in string theory with tachyonic condensation and the Landau theory of solidification is pointed out. A generic frustration resulting from the incompatibility of the topologies of the plane and that of the sphere is discussed. This is a global obstacle to obtain perturbatively fixed points on compact space-time. Some

S. Elitzur; A. Forge; E. Rabinovici

1991-01-01

393

Plucked String on a Shoestring Budget  

ERIC Educational Resources Information Center

The physics of the plucked string has been treated in many articles and books. For our 12th-grade high school physics laboratory, we have built a cheap, simple sonometer apparatus for each pair of students on which they may investigate some interesting phenomena that arise when a string is plucked. Among these are the generation of harmonics…

Gluck, Paul

2009-01-01

394

Big bang models in string theory  

Microsoft Academic Search

These proceedings are based on lectures delivered at the 'RTN Winter School on Strings, Supergravity and Gauge Theories', CERN, 16 20 January 2006. The school was mainly aimed at PhD students and young postdocs. The lectures start with a brief introduction to spacetime singularities and the string theory resolution of certain static singularities. Then they discuss attempts to resolve cosmological

Ben Craps; Theoretische Natuurkunde

2006-01-01

395

From surface roughening to QCD string theory  

SciTech Connect

Surface critical phenomena and the related onset of Goldstone modes represent fundamental properties of the confining flux in Quantum Chromodynamics. New ideas on surface roughening and their implications for lattice studies of quark confinement and string formation are presented. Problems with a simple string description of the large Wilson surface are discussed.

Keisuke Jimmy Juge et al.

2001-05-23

396

Supermassive screwed cosmic string in dilaton gravity  

Microsoft Academic Search

The early universe might have undergone phase transitions at energy scales much higher than the one corresponding to the grand unified theories (GUT) scales. At these higher energy scales, the transition at which gravity separated from all other interactions, the so-called Planck era, more massive strings called supermassive cosmic strings could have been produced, with energy of about 1019 GeV.

Valdir B. Bezerra; Cristine N. Ferreira; Herman J. Mosquera Cuesta

2006-01-01

397

Meromorphic open-string vertex algebras  

NASA Astrophysics Data System (ADS)

A notion of meromorphic open-string vertex algebra is introduced. A meromorphic open-string vertex algebra is an open-string vertex algebra in the sense of Kong and the author satisfying additional rationality (or meromorphicity) conditions for vertex operators. The vertex operator map for a meromorphic open-string vertex algebra satisfies rationality and associativity but in general does not satisfy the Jacobi identity, commutativity, the commutator formula, the skew-symmetry or even the associator formula. Given a vector space h, we construct a meromorphic open-string vertex algebra structure on the tensor algebra of the negative part of the affinization of h such that the vertex algebra structure on the symmetric algebra of the negative part of the Heisenberg algebra associated to h is a quotient of this meromorphic open-string vertex algebra. We also introduce the notion of left module for a meromorphic open-string vertex algebra and construct left modules for the meromorphic open-string vertex algebra above.

Huang, Yi-Zhi

2013-05-01

398

Approximate String Matching in DNA Sequences  

Microsoft Academic Search

Approximate string matching on large DNA sequences data is very important in bioinformatics. Some studies have shown that suffix tree is an efficient data structure for ap- proximate string matching. It performs better than suffix array if the data structure can be stored entirely in the mem- ory. However, our study find that suffix array is much bet- ter than

Lok-lam Cheng; David Wai-lok Cheung; Siu-ming Yiu

2003-01-01

399

Face recognition using ensemble string matching.  

PubMed

In this paper, we present a syntactic string matching approach to solve the frontal face recognition problem. String matching is a powerful partial matching technique, but is not suitable for frontal face recognition due to its requirement of globally sequential representation and the complex nature of human faces, containing discontinuous and non-sequential features. Here, we build a compact syntactic Stringface representation, which is an ensemble of strings. A novel ensemble string matching approach that can perform non-sequential string matching between two Stringfaces is proposed. It is invariant to the sequential order of strings and the direction of each string. The embedded partial matching mechanism enables our method to automatically use every piece of non-occluded region, regardless of shape, in the recognition process. The encouraging results demonstrate the feasibility and effectiveness of using syntactic methods for face recognition from a single exemplar image per person, breaking the barrier that prevents string matching techniques from being used for addressing complex image recognition problems. The proposed method not only achieved significantly better performance in recognizing partially occluded faces, but also showed its ability to perform direct matching between sketch faces and photo faces. PMID:23955761

Chen, Weiping; Gao, Yongsheng

2013-08-15

400

Natural language insensitive short textual string compression  

NASA Astrophysics Data System (ADS)

There are applications (such as Internet search engines) where short textual strings, for example abstracts or pieces of Web pages, need to be compressed independently of each other. The usual adaptive compression algorithms perform poorly on these short strings due to the lack of necessary data to learn. In this manuscript, we introduce a compression algorithm targeting short text strings; e.g., containing a few hundred symbols. We also target natural language insensitivity, to facilitate its robust compression and fast implementation. The algorithm is based on the following findings. Applying the move-to-front transform (MTFT) after the Burrows-Wheeler transform (BWT) brings the short textual strings to a "normalized form" where the distribution of the resulting "ranks" has a shape similar over the set of natural language strings. This facilitates the use of a static coding method with few variations, which we call shortBWT, where no on-line learning is needed, to encode the ranks. Finally, for short strings, shortBWT runs very fast because the strings fit into the cache of most current computers. The introduction for this paper will review the mathematical bases of BWT and MTF, it will also review our recently published metric for rapidly pre-characterizing the compressibility of such short textual strings when using these transforms.

Constantinescu, Cornel; Trelewicz, Jennifer Q.; Arps, Ronald B.

2004-01-01

401

Cryptography in the Multi-string Model  

Microsoft Academic Search

The common random string model permits the construction of cryptographic protocols that are prov- ably impossible to realize in the standard model. In this model, a trusted party generates a random string and gives it to all parties in the protocol. However, the introduction of such a third party should set alarm bells going off: Who is this trusted party?

Jens Grothand; Rafail Ostrovsky

2007-01-01

402

Drill strings take on new look  

SciTech Connect

Over the years, drillers and operators have placed increasing demands on the drill string. As a results, components of the drill string have become more diverse in application and more durable and reliable in performance. Even today's depressed prices, several $100,000 worth of drill string equipment can be in the hole at one time. The combination of downhole mud motor, MWD tool, and high-performance PDC bit provides the operator and driller with plenty of firepower to drill ahead-but at a hefty price. Numerous laboratory and field studies have been carried out to gain a better understanding of a drill string's performance and how to improve drilling operations. More research efforts in the coming years will be directed toward downhole problems. If penetration rates can be increased, while drilling time and costs reduced, drilling becomes more economical and attractive. This article is a short synopsis of various new technologies affecting today's drill string.

Moore, S.D.

1986-04-01

403

Properties of color-Coulomb string tension  

SciTech Connect

We study the properties of the color-Coulomb string tension obtained from the instantaneous part of gluon propagators in Coulomb gauge using quenched SU(3) lattice simulation. In the confinement phase, the dependence of the color-Coulomb string tension on the QCD coupling constant is smaller than that of the Wilson loop string tension. On the other hand, in the deconfinement phase, the color-Coulomb string tension does not vanish even for T/T{sub c}=1{approx}5, the temperature dependence of which is comparable with the magnetic scaling, dominating the high temperature QCD. Thus, the color-Coulomb string tension is not an order parameter of quark-gluon plasma phase transition.

Nakagawa, Y.; Saito, T.; Toki, H. [Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Nakamura, A. [Research Institute for Information Science and Education, Hiroshima University, Higashi-Hiroshima 739-8521 (Japan); Zwanziger, D. [Physics Department, New York University, New York, New York 10003 (United States)

2006-05-01

404

Note on tachyon actions in string theory  

SciTech Connect

A number of spacetime fields in string theory (notably the metric, dilaton, bosonic and type 0 bulk closed-string tachyon, and bosonic open-string tachyon) have the following property: whenever the spacetime field configuration factorizes in an appropriate sense, the matter sector of the world-sheet theory factorizes into a tensor product of two decoupled theories. Since the beta functions for such a product theory necessarily also factorize, this property strongly constrains the form of the spacetime action encoding those beta functions. We show that this constraint alone--without needing actually to compute any of the beta functions--is sufficient to fix the form of the two-derivative action for the metric-dilaton system, as well as the potential for the bosonic open-string tachyon. We also show that no action consistent with this constraint exists for the closed-string tachyon coupled to the metric and dilaton.

Headrick, Matthew [Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454 (United States)

2009-02-15

405

Vibration monitoring system for drill string  

SciTech Connect

A vibration monitoring system is described for use in monitoring lateral and torsional vibrations in a drill string comprising: a drill string component having an outer surface; first accelerometer means A[sub 1] for measuring tangential acceleration; second accelerometer means A[sub 2] for measuring tangential acceleration; third accelerometer means A[sub 3] for measuring tangential acceleration; said first, second and third accelerometer means A[sub 1], A[sub 2] and A[sub 3] being mounted in said drill string component and being spaced from one another to measure acceleration forces on said drill string component tangentially with respect to the outer surface of said component wherein said first, second and third accelerometer means are adapted to measure and distinguish between lateral and torsional vibrations exerted on said drill string component.

Wassell, M.E.

1993-07-13

406

CMB temperature trispectrum of cosmic strings  

NASA Astrophysics Data System (ADS)

We provide an analytical expression for the trispectrum of the cosmic microwave background (CMB) temperature anisotropies induced by cosmic strings. Our result is derived for the small angular scales under the assumption that the temperature anisotropy is induced by the Gott-Kaiser-Stebbins effect. The trispectrum is predicted to decay with a noninteger power-law exponent ?-? with 6string microstructure, and thus on the string model. For Nambu-Goto strings, this exponent is related to the string mean square velocity and the loop distribution function. We then explore two classes of wave number configuration in Fourier space, the kite and trapezium quadrilaterals. The trispectrum can be of any sign and appears to be strongly enhanced for all squeezed quadrilaterals.

Hindmarsh, Mark; Ringeval, Christophe; Suyama, Teruaki

2010-03-01

407

Chronology Protection in String Theory  

NASA Astrophysics Data System (ADS)

Many solutions of General Relativity appear to allow the possibility of time travel. This was initially a fascinating discovery, but geometries of this type violate causality, a basic physical law which is believed to be fundamental. Although string theory is a proposed fundamental theory of quantum gravity, geometries with closed timelike curves have resurfaced as solutions to its low energy equations of motion. In this paper, we will study the class of solutions to low energy effective supergravity theories related to the BMPV black hole and the rotating Wave-D1-D5-brane system. Time travel appears to be possible in these geometries. We will attempt to build the causality violating regions and propose that stringy effects prohibit their construction. We will show how the geometry is corrected and that, once corrected, causality is preserved. We will track our chronology protection proposal in the dual conformal field theory. The absence of closed timelike curves in the geometry coincides with the preservation of unitarity in the conformal field theory. The agent of chronology protection for the geometries studied here mirrors the enhancon mechanism, a mechanism string theory employs to resolve a class of naked singularities

Dyson, Lisa

2004-03-01

408

String photini at the LHC  

SciTech Connect

String theories with topologically complex compactification manifolds suggest the simultaneous presence of many unbroken U(1)'s without any light matter charged under them. The gauge bosons associated with these U(1)'s do not have direct observational consequences. However, in the presence of low energy supersymmetry the gauge fermions associated with these U(1)'s, the ''photini,'' mix with the bino and extend the minimal supersymmetric standard model neutralino sector. This leads to novel signatures at the LHC. The lightest ordinary supersymmetric particle (LOSP) can decay to any one of these photini. In turn, photini may transition into each other, leading to high lepton and jet multiplicities. Both the LOSP decays and interphotini transitions can lead to displaced vertices. When the interphotini decays happen outside the detector, the cascades can result in different photini escaping the detector, leading to multiple reconstructed masses for the invisible particle. If the LOSP is charged, it stops in the detector and decays out of time to photini, with the possibility that the produced final photini vary from event to event. Observation of a plenitude of photini at the LHC would be evidence that we live in a string vacuum with a topologically rich compactification manifold.

Arvanitaki, Asimina [Berkeley Center for Theoretical Physics, University of California, Berkeley, California, 94720 (United States); Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California, 94720 (United States); Craig, Nathaniel; Dimopoulos, Savas [Department of Physics, Stanford University, Stanford, California 94305 (United States); Dubovsky, Sergei [Department of Physics, Stanford University, Stanford, California 94305 (United States); Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary Prospect, 7a, 117312 Moscow (Russian Federation); March-Russell, John [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford (United Kingdom)

2010-04-01

409

Cosmic strings and chronology protection  

NASA Astrophysics Data System (ADS)

A space consisting of two rapidly moving cosmic strings has recently been constructed by Gott that contains closed timelike curves. The global structure of this space is analyzed and it is found that, away from the strings, the space is identical to a generalized Misner space. The vacuum expectation value of the energy-momentum tensor for a conformally coupled scalar field is calculated on this generalized Misner space. It is found to diverge very weakly on the chronology horizon, but more strongly on the polarized hypersurfaces. The divergence on the polarized hypersurfaces is strong enough that when the proper geodesic interval around any polarized hypersurface is of the order of the Planck length squared, the perturbation to the metric caused by the back reaction will be of the order one. Thus we expect the structure of the space will be radically altered by the back reaction before quantum gravitational effects become important. This suggests that Hawking's ``chronology protection conjecture'' holds for spaces with a noncompactly generated chronology horizon.

Grant, James D. E.

1993-03-01

410

String Rearrangement Metrics: A Survey  

NASA Astrophysics Data System (ADS)

A basic assumption in traditional pattern matching is that the order of the elements in the given input strings is correct, while the description of the content, i.e. the description of the elements, may be erroneous. Motivated by questions that arise in Text Editing, Computational Biology, Bit Torrent and Video on Demand, and Computer Architecture, a new pattern matching paradigm was recently proposed by [2]. In this model, the pattern content remains intact, but the relative positions may change. Several papers followed the initial definition of the new paradigm. Each paper revealed new aspects in the world of string rearrangement metrics. This new unified view has already proven itself by enabling the solution of an open problem of the mathematician Cayley from 1849. It also gave better insight to problems that were already studied in different and limited situations, such as the behavior of different cost functions, and enabled deriving results for cost functions that were not yet sufficiently analyzed by previous research. At this stage, a general understanding of this new model is beginning to coalesce. The aim of this survey is to present an overview of this recent new direction of research, the problems, the methodologies, and the state-of-the-art.

Amir, Amihood; Levy, Avivit

411

Effects of rod worth and drop speed on the BWR off-center rod drop accident  

SciTech Connect

In recent years, several multidimensional coupled neutronic/thermal-hydraulic calculations of the boiling water reactor (BWR) control rod drop accident (RDA) have been performed. Typically, two-dimensional (r, z) RDA calculations require that the dropped rod be a center rod, as a result of geometric limitations; while in three-dimensional calculations, the dropped rod is generally taken to be the center rod in order to allow a quarter-core representation and limit computer running times. For typical BWR core loadings, however, the center rod is not necessarily the highest worth rod. The purpose of the present study was to determine the effect of increasing the control rod worth and the rod drop speed on the off-center RDA. An increase in either of these parameters results in an increase in peak core power and fuel enthalpy, and the objective of this study is to determine the margin to the fuel damage threshold.

Cokinos, D.M.; Carew, J.F.

1986-01-01

412

Massive neutrinos and (heterotic) string theory  

SciTech Connect

String theories in principle address the origin and values of the quark and lepton masses. Perhaps the small values of neutrino masses could be explained generically in string theory even if it is more difficult to calculate individual values, or perhaps some string constructions could be favored by generating small neutrino masses. We examine this issue in the context of the well-known three-family standard-like Z{sub 3} heterotic orbifolds, where the theory is well enough known to construct the corresponding operators allowed by string selection rules, and analyze the D- and F-flatness conditions. Surprisingly, we find that a simple seesaw mechanism does not arise. It is not clear whether this is a property of this construction, or of orbifolds more generally, or of string theory itself. Extended seesaw mechanisms may be allowed; more analysis will be needed to settle that issue. We briefly speculate on their form if allowed and on the possibility of alternatives, such as small Dirac masses and triplet seesaws. The smallness of neutrino masses may be a powerful probe of string constructions in general. We also find further evidence that there are only 20 inequivalent models in this class, which affects the counting of string vacua.

Giedt, Joel; Kane, G.L.; Langacker, Paul; Nelson, Brent D. [Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 1A7 (Canada); Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19103 (United States)

2005-06-01

413

CMB temperature bispectrum induced by cosmic strings  

NASA Astrophysics Data System (ADS)

The cosmic microwave background (CMB) bispectrum of the temperature anisotropies induced by a network of cosmic strings is derived for small angular scales, under the assumption that the principal cause of temperature fluctuations is the Gott-Kaiser-Stebbins effect. We provide analytical expressions for all isosceles triangle configurations in Fourier space. Their overall amplitude is amplified as the inverse cube of the angle and diverges for flat triangles. The isosceles configurations generically lead to a negative bispectrum with a power-law decay ?-6 for large multipole ?. However, collapsed triangles are found to be associated with a positive bispectrum whereas the squeezed triangles still exhibit negative values. We then compare our analytical estimates to a direct computation of the bispectrum from a set of 300 statistically independent temperature maps obtained from Nambu-Goto cosmic string simulations in a Friedmann-Lemaître-Robertson-Walker universe. We find good agreement for the overall amplitude, the power-law behavior, and the angle dependency of the various triangle configurations. At ?˜500 the cosmic string Gott-Kaiser-Stebbins effect contributes approximately the same equilateral CMB bispectrum amplitude as an inflationary model with |fNLloc|?103, if the strings contribute about 10% of the temperature power spectrum at ?=10. Current bounds on fNL are not derived using cosmic string bispectrum templates, and so our fNL estimate cannot be used to derive bounds on strings. However it does suggest that string bispectrum templates should be included in the search of CMB non-Gaussianities.

Hindmarsh, Mark; Ringeval, Christophe; Suyama, Teruaki

2009-10-01

414

Emergent classical strings from matrix model  

NASA Astrophysics Data System (ADS)

Generalizing the idea of hep-th/0509015 by Berenstein, Correa, and Vázquez, we study many-magnon states in an SU(2) sector of a reduced matrix quantum mechanics obtained from Script N = 4SU(N) super Yang-Mills on Bbb R × S3. Generic Q-magnon states are described as a chain of ``string-bits'' joining Q+1 eigenvalues of background matrices which form a 1/2 BPS circular droplet in the large N limit. We will concentrate on infinitely long states whose first and last eigenvalues localize at the edge of the droplet. Each constituent string-bit has a complex quasi-momentum in general, while the total quasi-momentum P of the state is real. For given Q and P, the minimum energy of the chain of string-bits is realized when the Q+1 eigenvalues are equally spaced on one and the same line segment joining the two outmost eigenvalues localized on the edge with angular difference P. Such configuration of bound string-bits precisely reproduces the dispersion relation for dyonic giant magnons in classical string theory. We also show the emergence of two-spin folded/circular strings in special infinite spin limit as particular configurations of closed chains of string-bits.

Hatsuda, Yasuyuki; Okamura, Keisuke

2007-03-01

415

High temperature control rod assembly  

DOEpatents

A high temperature nuclear control rod assembly comprises a plurality of substantially cylindrical segments flexibly joined together in succession by ball joints. The segments are made of a high temperature graphite or carbon-carbon composite. The segment includes a hollow cylindrical sleeve which has an opening for receiving neutron-absorbing material in the form of pellets or compacted rings. The sleeve has a threaded sleeve bore and outer threaded surface. A cylindrical support post has a threaded shaft at one end which is threadably engaged with the sleeve bore to rigidly couple the support post to the sleeve. The other end of the post is formed with a ball portion. A hollow cylindrical collar has an inner threaded surface engageable with the outer threaded surface of the sleeve to rigidly couple the collar to the sleeve. the collar also has a socket portion which cooperates with the ball portion to flexibly connect segments together to form a ball and socket-type joint. In another embodiment, the segment comprises a support member which has a threaded shaft portion and a ball surface portion. The threaded shaft portion is engageable with an inner threaded surface of a ring for rigidly coupling the support member to the ring. The ring in turn has an outer surface at one end which is threadably engageably with a hollow cylindrical sleeve. The other end of the sleeve is formed with a socket portion for engagement with a ball portion of the support member. In yet another embodiment, a secondary rod is slidably inserted in a hollow channel through the center of the segment to provide additional strength. A method for controlling a nuclear reactor utilizing the control rod assembly is also included.

Vollman, Russell E. (Solana Beach, CA)

1991-01-01

416

DLCQ-M(atrix) description of string theory, and supergravity  

Microsoft Academic Search

We discuss the connection between Matrix string theory and the DLCQ of string theory. Using this connection we describe the sense in which perturbative string amplitudes are reproduced in the Matrix string theory. Using recent realization of the connection between SYM and Supergravity, we suggest how to describe Matrix theory with non-flat backgrounds.

Gilad Lifschytz

1998-01-01

417

Analysis About Drill String Vibration of Horizontal Well  

Microsoft Academic Search

During the engineering of horizontal well, drill string is in the complicated moving state, strong vibration is the main reason that induces drill string failure. Drill string vibrations usually have axial vibration, lateral vibration, torsional vibration and coupling vibration, the drill string near the bottom of well usually vibrates strongly. As an example to G78-E15, the variety of vibration is

Han Chunjie; Yan Tie

2009-01-01

418

The Study on Vibration of Drill String of ERW  

Microsoft Academic Search

During exploitation of extended reach well (ERW) drilling engineer, the problem of drill string failure is very serious; drill string vibrations are main reasons. In this paper drill string of extended reach well of different part is object being studied. The models about various vibrations are set up. Modal vibrations of drill string are studied. All sorts of resonance frequencies

Han Chunjie; Yan Tie

2008-01-01

419

pp wave big bangs: Matrix strings and shrinking fuzzy spheres  

Microsoft Academic Search

We find pp wave solutions in string theory with null-like linear dilatons. These provide toy models of big bang cosmologies. We formulate matrix string theory in these backgrounds. Near the big bang ``singularity,'' the string theory becomes strongly coupled but the Yang-Mills description of the matrix string is weakly coupled. The presence of a second length scale allows us to

Sumit R. Das; Jeremy Michelson

2005-01-01

420

Metric Indexes for Approximate String Matching in a Dictionary  

Microsoft Academic Search

We consider the problem of nding all approximate occurrences of a given string q, with at most k di erences, in a nite database or dictionary of strings. The strings can be e. g. natural language words, such as the vocabulary of some document or set of documents. This has many important application in both o-line (indexed) and on-line string

Kimmo Fredriksson

2004-01-01

421

Fuel rod retention device for a nuclear reactor  

DOEpatents

A device is described for supporting a nuclear fuel rod in a fuel rod assembly which allows the rod to be removed without disturbing other rods in the assembly. A fuel rod cap connects the rod to a bolt which is supported in the assembly end fitting by means of a locking assembly. The device is designed so that the bolt is held securely during normal reactor operation yet may be easily disengaged and the fuel rod removed when desired.

Hylton, Charles L. (Madison Heights, VA)

1984-01-01

422

Reactor control rod timing system. [LMFBR  

DOEpatents

A fluid driven jet-edge whistle timing system is described for control rods of a nuclear reactor for producing real-time detection of the timing of each control rod in its scram operation. An important parameter in reactor safety, particularly for liquid metal fast breeder reactors (LMFBR), is the time deviation between the time the control rod is released and the time the rod actually reaches the down position. The whistle has a nearly pure tone signal with center frequency (above 100 kHz) far above the frequency band in which the energy of the background noise is concentrated. Each control rod can be fitted with a whistle with a different frequency so that there is no ambiguity in differentiating the signal from each control rod.

Wu, P.T.K.

1980-03-18

423

Pneumatic rod loading apparatus and method  

NASA Astrophysics Data System (ADS)

A rod feeder assembly composed of elongated tubular members arranged in vertical courses and disposed in a box, the tubular members being flush at their downstream end and provided with a loading section at the upstream or the opposite end. The tubular members are of the same length in the same course but are shorter in the upper courses. The method for automatically feeding rods into a matrix includes the steps of randomly disposing the rods on the loading sections of the tubular members, aligning and positioning the rods in the tubular members by vibrating the tubular members in an inclined disposition, and transferring the rods from the rod feeder assembly to the matrix.

Kim, Chulho

1995-06-01

424

Charged rotating dilaton black strings  

SciTech Connect

In this paper we, first, present a class of charged rotating solutions in four-dimensional Einstein-Maxwell-dilaton gravity with zero and Liouville-type potentials. We find that these solutions can present a black hole/string with two regular horizons, an extreme black hole or a naked singularity provided the parameters of the solutions are chosen suitable. We also compute the conserved and thermodynamic quantities, and show that they satisfy the first law of thermodynamics. Second, we obtain the (n+1)-dimensional rotating solutions in Einstein-dilaton gravity with Liouville-type potential. We find that these solutions can present black branes, naked singularities or spacetimes with cosmological horizon if one chooses the parameters of the solutions correctly. Again, we find that the thermodynamic quantities of these solutions satisfy the first law of thermodynamics.

Dehghani, M.H. [Physics Department and Biruni Observatory, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Farhangkhah, N. [Physics Department and Biruni Observatory, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

2005-02-15

425

String-Corrected Black Holes  

SciTech Connect

We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect -- the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive! The magnitude of this effect is related to the size of the compactification manifold.

Hubeny, Veronika; Maloney, Alexander; Rangamani, Mukund

2005-02-07

426

Locally anisotropic gravity and strings  

SciTech Connect

We shall present an introduction to the theory of gravity on locally anisotropic spaces modelled as vector bundles provided with compatible nonlinear and distinguished linear connection and metric structures (such spaces are obtained by a nonlinear connection reduction or compactification from higher dimensional spaces to lower dimensional ones and contain as particular cases various generalizations of Kaluza{endash}Klein and Finsler geometry). We shall analyze the conditions for consistent propagation of closed strings in locally anisotropic background spaces. The connection between conformal invariance, the vanishing of the renormalization group {beta}-function of the generalized {sigma}-model, and field equations of locally anisotropic gravity will be studied in detail. {copyright} 1997 Academic Press, Inc.

Vacaru, S.I. [Department of Statistical and Nuclear Physics, Institute of Applied Physics, Academy of Sciences of Moldova, 5 Academy str., Chisinau, 2028, (Republic of Moldova)

1997-05-01

427

Scaling of cosmic string loops  

SciTech Connect

We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime takes over. In this final regime the characteristic length of loops scales as 0.1t, in contrast to earlier simulations which found tiny loops. We expect the expanding-universe behavior to be qualitatively similar. If this expectation is correct, then the large loop sizes have important cosmological implications. In particular, the nucleosynthesis bound then becomes G{mu} < or approx. 10{sup -7}, much tighter than that obtained from earlier analyses.

Vanchurin, Vitaly; Olum, Ken D.; Vilenkin, Alexander [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States)

2006-09-15

428

LOFT advanced fuel rod instrumentation development  

Microsoft Academic Search

Advanced fuel rod instrumentation for the Loss of Fluid Test (LOFT) reactor is being developed by the Hanford Engineering Development Laboratory for the Nuclear Regulatory Commission. This effort calls for development of sensors to measure fuel rod axial motion, fuel centerline temperature (to 2200°C), fuel rod plenum gas pressure (to 2500 psig), and plenum gas temperature (to 1500°F). A parallel

T. R. Billeter; R. L. Brown; A. I. Y. Chan; C. K. Day; S. C. Meyers; E. M. Sheen; J. L. Stringer

1978-01-01

429

Automatic safety rod for reactors. [LMFBR  

DOEpatents

An automatic safety rod for a nuclear reactor containing neutron absorbing material and designed to be inserted into a reactor core after a loss-of-flow. Actuation is based upon either a sudden decrease in core pressure drop or the pressure drop decreases below a predetermined minimum value. The automatic control rod includes a pressure regulating device whereby a controlled decrease in operating pressure due to reduced coolant flow does not cause the rod to drop into the core.

Germer, J.H.

1982-03-23

430

Hausdorff dimension of a quantum string  

NASA Astrophysics Data System (ADS)

In the path integral formulation of quantum mechanics, Feynman and Hibbs noted that the trajectory of a particle is continuous but nowhere differentiable. We extend this result to the quantum-mechanical path of a relativistic string and find that the ``trajectory,'' in this case, is a fractal surface with Hausdorff dimension three. Depending on the resolution of the detecting apparatus, the extra dimension is perceived as ``fuzziness'' of the string world surface. We give an interpretation of this phenomenon in terms of a new form of the uncertainty principle for strings, and study the transition from the smooth to the fractal phase.

Ansoldi, S.; Aurilia, A.; Spallucci, E.

1997-08-01

431

Open string decoupling and tachyon condensation.  

SciTech Connect

The amplitudes in perturbative open string theory are examined as functions of the tachyon condensate parameter. The boundary state formalism demonstrates the decoupling of the open string modes at the non-perturbative minima of the tachyon potential via a degeneration of open world-sheets and identifies an independence of the coupling constants g{sub s} and g{sub YM} at general values of the tachyon condensate. The closed sector is generated at the quantum level; it is also generated at the classical level through the condensation of the propagating open string modes on the D-brane degrees of freedom.

Chalmers, G.; High Energy Physics

2001-06-01

432

Invariant length of a cosmic string  

SciTech Connect

The world sheet of a cosmic string is characterized by a function {ital l}, invariant under both coordinate and gauge transformations, which can be interpreted as the invariant length'' of the string. In flat space, {ital l} reduces to the invariant length of Vachaspati and Vilenkin, and gives an upper bound for the actual length of the string, and a lower bound for its energy, as measured by any inertial observer. In curved spacetime, time variations in the invariant length divide naturally into two parts: one due to the tidal tensor at points exterior to the world sheet and one due to the tidal tensor at points on the world sheet itself.

Anderson, M.R. (Department of Theoretical Physics, Research School of Physical Sciences, Australian National University, G.P.O. Box 4, Canberra, 2601 (Australia))

1990-06-15

433

Current discontinuities on superconducting cosmic strings  

SciTech Connect

The propagation of current perturbations on superconducting cosmic strings is considered. The conditions for the existence of discontinuities similar to shock waves have been found. The formulas relating the string parameters and the discontinuity propagation speed are derived. The current growth law in a shock wave is deduced. The propagation speeds of shock waves with arbitrary amplitudes are calculated. The reason why there are no shock waves in the case of time-like currents (in the 'electric' regime) is explained; this is attributable to the shock wave instability with respect to perturbations of the string world sheet.

Troyan, E., E-mail: et@iaaru.astronautiko.org; Vlasov, Yu. V. [Moscow Institute of Physics and Technology (Russian Federation)

2011-07-15

434

Type-I cosmic-string network  

NASA Astrophysics Data System (ADS)

We study the network of Type-I cosmic strings using the field-theoretic numerical simulations in the Abelian-Higgs model. For Type-I strings, the gauge field plays an important role, and thus we find that the correlation length of the strings is strongly dependent upon the parameter ?, the ratio between the masses of the scalar field and the gauge field, namely, ?=m?2/mA2. In particular, if we take the cosmic expansion into account, the network becomes densest in the comoving box for a specific value of ? for ?<1.

Hiramatsu, Takashi; Sendouda, Yuuiti; Takahashi, Keitaro; Yamauchi, Daisuke; Yoo, Chul-Moon

2013-10-01

435

Cosmic string lensing and closed timelike curves  

NASA Astrophysics Data System (ADS)

In an analysis of the gravitational lensing by two relativistic cosmic strings, we argue that the formation of closed timelike curves proposed by Gott is unstable in the presence of particles (e.g. the cosmic microwave background radiation). Because of the attractorlike behavior of the closed timelike curve, we argue that this instability is very generic. A single graviton or photon in the vicinity, no matter how soft, is sufficient to bend the strings and prevent the formation of closed timelike curves. We also show that the gravitational lensing due to a moving cosmic string is enhanced by its motion, not suppressed.

Shlaer, Benjamin; Tye, S.-H. Henry

2005-08-01

436

Reheating for closed string inflation  

NASA Astrophysics Data System (ADS)

We point out some of the outstanding challenges for embedding inflationary cosmology within string theory studying the process of reheating for models where the inflaton is a closed string mode parameterising the size of an internal cycle of the compactification manifold. A realistic model of inflation must explain the tiny perturbations in the cosmic microwave background radiation and also how to excite the ordinary matter degrees of freedom after inflation, required for the success of Big Bang Nucleosynthesis. We study these issues focusing on two promising inflationary models embedded in LARGE volume type IIB flux compactifications. We show that phenomenological requirements and consistency of the effective field theory treatment imply the presence at low energies of a hidden sector together with a visible sector, where the Minimal Supersymmetric Standard Model fields are residing. A detailed calculation of the inflaton coupling to the fields of the hidden sector, visible sector, and moduli sector, reveals that the inflaton fails to excite primarily the visible sector fields, instead hidden sector fields are excited copiously after the end of inflation. This sets severe constraints on hidden sector model building where the most promising scenario emerges as a pure N = 1 SYM theory, forbidding the kinematical decay of the inflaton to the hidden sector. In this case it is possible to reheat the Universe with the visible degrees of freedom even though in some cases we discover a new tension between TeV scale SUSY and reheating on top of the well-known tension between TeV scale SUSY and inflation.

Cicoli, Michele; Mazumdar, Anupam

2010-09-01

437

Massless radiation from heavy rotating string and Kerr/string correspondence  

NASA Astrophysics Data System (ADS)

We calculate emission rates of a massless state from a highly excited rotating string in perturbative bosonic open string theory. By averaging huge degeneracies of initial string states with specifying the mass and a single component of the angular momentum, we find thermal spectrum in a wide range of the angular momentum. We derive the temperature that characterizes the thermal spectrum from the partition function of a single rotating string from which we also find the entropy and the angular velocity of rotating strings. We also argue based on these quantities the Horowitz-Polchinski correspondence principle between rotating strings/Kerr black holes for non-extremal as well as extremal cases. In the parameter region where the Kerr black holes exist, the thermal spectrum is comparable to scalar emissions from a rotating black hole.

Matsuo, Toshihiro

2010-03-01

438

Acoustic loading effects on oscillating rod bundles  

SciTech Connect

An analytical study of the interaction between an infinite acoustic medium and a cluster of circular rods is described. The acoustic field due to oscillating rods and the acoustic loading on the rods are first solved in a closed form. The acoustic loading is then used as a forcing function for rod responses, and the acousto-elastic couplings are solved simultaneously. Numerical examples are presented for several cases to illustrate the effects of various system parameters on the acoustic reaction force coefficients. The effect of the acoustic loading on the coupled eigenfrequencies are discussed.

Lin, W.H.

1980-01-01

439

Rotation rate of rods in turbulent flow  

NASA Astrophysics Data System (ADS)

We study the motion of single small rod-like particles in turbulent flow. The orientation and position of rods are measured experimentally using Lagrangian particle tracking with images from multiple cameras in a flow between two oscillating grids. We also have performed numerical simulations of rod motion in homogeneous isotropic turbulence. The probability distribution of the rotation rate of the rods has extended tails indicating rare events with large rotation rate. Rods rotation rate is determined by the velocity gradient of the flow, so measurements of the rotation rate provides indirect access to statistics of the velocity gradient of the flow. However, tracer rods preferentially sample the flow since their orientation becomes correlated with the local axes of the velocity gradient tensor. The result is that the typical rotation rate of rods is much smaller than it would be if they were randomly oriented. The numerical simulations allow us to quantify the preferential alignment, including its dependence on rod aspect ratio. This allows measurements of the second moment of the rod rotation rate to be used to measure the energy dissipation rate in the turbulent flow.

Parsa, Shima; Calzavarini, Enrico; Toschi, Federico; Voth, Greg

2011-11-01

440

Temperature actuated automatic safety rod release  

DOEpatents

A temperature-actuated apparatus is disclosed for releasably supporting a safety rod in a nuclear reactor, comprising a safety rod upper adapter having a retention means, a drive shaft which houses the upper adapter, and a bimetallic means supported within the drive shaft and having at least one ledge which engages a retention means of the safety rod upper adapter. A pre-determined increase in temperature causes the bimetallic means to deform so that the ledge disengages from the retention means, whereby the bimetallic means releases the safety rod into the core of the reactor.

Hutter, E.; Pardini, J.A.; Walker, D.E.

1984-03-13

441

Non-critical Poincaré invariant bosonic string backgrounds and closed string tachyons  

NASA Astrophysics Data System (ADS)

A new family of non critical bosonic string backgrounds in arbitrary space-time dimension /D and with /ISO(1,D-2) Poincaré invariance are presented. The metric warping factor and dilaton agree asymptotically with the linear dilaton background. The closed string tachyon equation of motion enjoys, in the linear approximation, an exact solution of ``kink'' type interpolating between different expectation values. A renormalization group flow interpretation, based on a closed string tachyon potential of type -T2e-T, is suggested.

Álvarez, E.; Gómez, C.; Hernández, L.

2001-04-01

442

String Tension and String Susceptibility in Two-Dimensional Generalized Weingarten Model  

NASA Astrophysics Data System (ADS)

We study the two-dimensional generalized Weingarten model reduced to a point, which interpolates between the reduced Weingarten model and the large-N gauge theory. We calculate the expectation value of the Wilson loop using a Monte Carlo method and determine the string tension and string susceptibility. The numerical result suggests that the string susceptibility approaches -2 in a certain parametric region, which implies that the branched-polymer configurations are suppressed.

Hanada, M.; Kubo, F.

2007-02-01

443

The current status of observational constraints on cosmic strings  

SciTech Connect

The observational restrictions on the cosmic string scenario for the formation of large scale structure are evaluated. this restrictions are due to the spectrum of gravitational radiation emitted by oscillating string loops, anisotropies in the cosmic microwave background caused by the strings, and evaporating black holes formed from collapsed cosmic string loops. It is shown that the only free parameter of the scenario, the cosmic string mass-per-unit-length, {mu}, is severely restricted.

Caldwell, R.R.

1993-10-01

444

Open-closed string duality at tree level.  

PubMed

We study the decay of unstable D-branes in string theory in the presence of an electric field, and show that the classical open string theory results for various properties of the final state agree with the properties of closed string states into which the system is expected to decay. This suggests a duality between tree level open string theory on unstable D-branes and closed strings at high density. PMID:14611274

Sen, Ashoke

2003-10-31

445

String theories with deformed energy-momentum relations, and a possible nontachyonic bosonic string  

SciTech Connect

We consider a prescription for introducing deformed dispersion relations in the bosonic string action. We find that in a subset of such theories it remains true that the embedding coordinates propagate linearly on the world sheet. While both the string modes and the center of mass propagate with deformed dispersion relations, the speed of light remains energy independent. We consider the canonical quantization of these strings and find that it is possible to choose theories so that ghost modes still decouple, as usual. We also find that there are examples where the tachyon is eliminated from the spectrum of the free bosonic string.

Magueijo, Joao [Blackett Laboratory, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2BZ (United Kingdom); Smolin, Lee [Perimeter Institute for Theoretical Physics, Waterloo, N2J 2W9 (Canada); Department of Physics, University of Waterloo, Waterloo, N2L 3G1 (Canada)

2005-01-15

446

Effects of rod worth and drop speed on the BWR off-center rod drop accident  

SciTech Connect

BWR off-center RDA calculations have been performed for selected rod worths and drop speeds. While in all cases the peak fuel enthalpy was well below the 280 cal/g fuel criterion, a substantial sensitivity to control rod worth and rod drop speed was observed.

Cokinos, D.M.; Carew, J.F.

1985-01-01

447

The pomeron in closed bosonic string theory  

SciTech Connect

We compute the couplings of the pomeron to the first few mass levels of closed bosonic string states in flat space. We recognize the deviation from the linearity of the Regge trajectories in a five dimensional anti De Sitter background.

Fazio, A. R. [Departamento de fisica, Universidad Nacional de Colombia, Ciudad Universitaria, Bogota D.C. (Colombia)

2010-12-22

448

Open string in a nonrelativistic background  

SciTech Connect

This paper is devoted to the study of the open string description of Wilson loops and quarks in nonrelativistic quantum field theory that are expected to be dual of gravity in Schroedinger space-time.

Kluson, J. [Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlarska 2, 611 37, Brno (Czech Republic)

2010-05-15

449

Beads + String = Atoms You Can See.  

ERIC Educational Resources Information Center

Presents hands-on activities that give students a head start in learning the vocabulary and basic theory involved in understanding atomic structure. Uses beads to represent protons, neutrons, and electrons and string to represent orbitals. (DDR)

Hermann, Christine K. F.

1998-01-01

450

Axions from cosmic string and wall decay  

SciTech Connect

If inflation occurred with a reheat temperature > T{sub PQ}, axions from the decay of global axion strings and domain walls would make an important contribution to the cosmological energy density, comparable to that from vacuum misalignment. Several groups have numerically studied the evolution of axion strings and walls in the past, however substantial uncertainties remain in their contribution to the present density {Omega}{sub a,string+wall{approx}}1-100(f{sub a}/10{sup 12} GeV){sup 7/6}, where f{sub a} is the axion decay constant. I will describe the numerical methods used in our simulations and show results for several string and wall configurations.

Hagmann, Chris [Lawrence Livermore National Laboratory, L-59, 7000 East Ave, Livermore, CA (United States)

2010-08-30

451

Effective string theory and QCD scattering amplitudes  

SciTech Connect

QCD string is formed at distances larger than the confinement scale and can be described by the Polchinski-Strominger effective string theory with a nonpolynomial action, which has nevertheless a well-defined semiclassical expansion around a long-string ground state. We utilize modern ideas about the Wilson-loop/scattering-amplitude duality to calculate scattering amplitudes and show that the expansion parameter in the effective string theory is small in the Regge kinematical regime. For the amplitudes we obtain the Regge behavior with a linear trajectory of the intercept (d-2)/24 in d dimensions, which is computed semiclassically as a momentum-space Luescher term, and discuss an application to meson scattering amplitudes in QCD.

Makeenko, Yuri [Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)

2011-01-15

452

Cosmological solutions of supercritical string theory  

SciTech Connect

We study quintessence-driven, spatially flat, expanding Friedmann-Robertson-Walker cosmologies that arise naturally from string theory formulated in a supercritical number of spacetime dimensions. The tree-level potential of the string theory produces an equation of state at the threshold between accelerating and decelerating cosmologies, and the resulting spacetime is globally conformally equivalent to Minkowski space. We demonstrate that exact solutions exist with a condensate of the closed-string tachyon, the simplest of which is a Liouville wall moving at the speed of light. We rely on the existence of this solution to derive constraints on the couplings of the tachyon to the dilaton and metric in the string theory effective action. In particular, we show that the tachyon dependence of the Einstein term must be nontrivial.

Hellerman, Simeon; Swanson, Ian [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540 (United States)

2008-06-15

453

Analytic Methods in Open String Field Theory  

NASA Astrophysics Data System (ADS)

We review the basics of recent developments of analytic methods in open string field theory. We in particular explain Schnabl's analytic solution for tachyon condensation in detail, assuming only the basic knowledge on conformal field theory.

Okawa, Y.

2012-12-01

454

Beads + String = Atoms You Can See.  

ERIC Educational Resources Information Center

|Presents hands-on activities that give students a head start in learning the vocabulary and basic theory involved in understanding atomic structure. Uses beads to represent protons, neutrons, and electrons and string to represent orbitals. (DDR)|

Hermann, Christine K. F.

1998-01-01

455

Introduction to String and Superstring Theory II.  

National Technical Information Service (NTIS)

Conformal field theory is reviewed, then conformal invariance is used to rederive the basic results on the embedding dimensionality for bosonic and fermionic strings. The spectrum of the bosonic and the computation of scattering amplitudes are discussed. ...

M. E. Peskin

1987-01-01

456

String Theory, Unification and Quantum Gravity  

NASA Astrophysics Data System (ADS)

An overview is given of the way in which the unification program of particle physics has evolved into the proposal of superstring theory as a prime candidate for unifying quantum gravity with the other forces and particles of nature. A key concern with quantum gravity has been the problem of ultraviolet divergences, which is naturally solved in string theory by replacing particles with spatially extended states as the fundamental excitations. String theory turns out, however, to contain many more extended-object states than just strings. Combining all this into an integrated picture, called M-theory, requires recognition of the rôle played by a web of nonperturbative duality symmetries suggested by the nonlinear structures of the field-theoretic supergravity limits of string theory.

Stelle, K. S.

457

Tension and Damping Effects on Vibrating Strings.  

National Technical Information Service (NTIS)

Theoretical methods are presented which provide a means for calculating the correct fret position for any fretted stringed musical instrument. The two methods are judged equal in the accuracy to which they can respectively calculate fret positions. The de...

E. L. Armstrong O. J. Burchett J. W. Turnbow T. M. Churan

1969-01-01

458

Finite black hole entropy and string theory  

SciTech Connect

An accelerating observer sees a thermal bath of radiation at the Hawking temperature which is proportional to the acceleration. Also, in string theory there is a Hagedorn temperature beyond which one cannot go without an infinite amount of energy. Several authors have shown that in the context of Hawking radiation a limiting temperature for string theory leads to a limiting acceleration, which for a black hole implies a minimum distance from the horizon for an observer to remain stationary. We argue that this effectively introduces a cutoff in Rindler space or the Schwarzschild geometry inside of which accelerations would exceed this maximum value. Furthermore, this natural cutoff in turn allows one to define a finite entropy for Rindler space or a black hole as all divergences were occurring on the horizon. In all cases if a particular relationship exists between Newton's constant and the string tension then the entropy of the string modes agrees with the Bekenstein-Hawking formula.

McGuigan, M. (Institute for Fundamental Theory, University of Florida, Gainesville, Florida 32611 (United States))

1994-10-15

459

The approximability of the String Barcoding problem  

PubMed Central

The String Barcoding (SBC) problem, introduced by Rash and Gusfield (RECOMB, 2002), consists in finding a minimum set of substrings that can be used to distinguish between all members of a set of given strings. In a computational biology context, the given strings represent a set of known viruses, while the substrings can be used as probes for an hybridization experiment via microarray. Eventually, one aims at the classification of new strings (unknown viruses) through the result of the hybridization experiment. In this paper we show that SBC is as hard to approximate as Set Cover. Furthermore, we show that the constrained version of SBC (with probes of bounded length) is also hard to approximate. These negative results are tight.

Lancia, Giuseppe; Rizzi, Romeo

2006-01-01

460

The approximability of the String Barcoding problem.  

PubMed

The String Barcoding (SBC) problem, introduced by Rash and Gusfield (RECOMB, 2002), consists in finding a minimum set of substrings that can be used to distinguish between all members of a set of given strings. In a computational biology context, the given strings represent a set of known viruses, while the substrings can be used as probes for an hybridization experiment via microarray. Eventually, one aims at the classification of new strings (unknown viruses) through the result of the hybridization experiment. In this paper we show that SBC is as hard to approximate as Set Cover. Furthermore, we show that the constrained version of SBC (with probes of bounded length) is also hard to approximate. These negative results are tight. PMID:16895600

Lancia, Giuseppe; Rizzi, Romeo

2006-08-08

461

Brane Inflation: From Superstring to Cosmic Strings  

SciTech Connect

Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension {mu} is estimated to be around 10 -6 > G{mu} > 10-11, while the present observational bound is 7 x 10 -7 > G{mu}. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO.

Tye, S.-H. Henry [Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853 (United States)

2004-12-10

462

ABCD of beta ensembles and topological strings  

NASA Astrophysics Data System (ADS)

We study ?-ensembles with B N , C N , and D N eigenvalue measure and their relation with refined topological strings. Our results generalize the familiar connections between local topological strings and matrix models leading to A N measure, and illustrate that all those classical eigenvalue ensembles, and their topological string counterparts, are elated one to another via various deformations and specializations, quantum shifts and discrete quotients. We review the solution of the Gaussian models via Macdonald identities, and interpret them as conifold theories. The interpolation between the various models is plainly apparent in this case. For general polynomial potential, we calculate the partition function in the multi-cut phase in a perturbative fashion, beyond tree-level in the large- N limit. The relation to refined topological string orientifolds on the corresponding local geometry is discussed along the way.

Krefl, Daniel; Walcher, Johannes

2012-11-01

463

Reflection of drill-string extensional waves at the bit-rock contact  

NASA Astrophysics Data System (ADS)

Downward propagating extensional waves are partially reflected at the bit-rock contact. The evaluation of the reflection coefficient is important to obtain while drilling information about the acoustic properties of the formations. The scope of this work is to estimate the bit-rock reflection coefficient, assuming a flat drill bit in perfect contact with the formation. Using the low-frequency approximation, which holds when the wavelength is much larger than the lateral dimensions of the borehole, the drill-string is assumed to be a laterally free rod, and the formation an homogeneous and isotropic medium. This work shows that the reflection coefficient of the extensional waves depends, along with the elastic properties of the formation, on the ratio of the cross sections of the drill-string and borehole. The impedance of the drilled rock can be calculated from the measured reflection coefficient, which is related to the amplitude of waves produced in the string and in the formation by a working drill-bit. copyright 2002 Acoustical Society of America.

Poletto, Flavio; Malusa, Massimo

2002-06-01

464

Closed String Tachyon: Inflation and Cosmological Collapse  

Microsoft Academic Search

By compactifying a critical bosonic string theory on an internal non-flat space with a constant volume, we study the role played by the closed string tachyon in the cosmology of the effective four-dimensional space-time. The effective tachyon potential consists on a negative constant related to the internal curvature space and a polynomial with only quadratic and quartic terms of the

Celia Escamilla-Rivera; Gerardo Garcia-Jimenez; Oscar Loaiza-Brito; Octavio Obregon

2011-01-01

465

Quark-Antiquark Potential for Siegel Strings  

Microsoft Academic Search

We compute the quark-antiquark potential employing the continuum action for\\u000aQCD-like random lattice strings proposed by Siegel. The model leads to a\\u000apotential similar to those obtained from Nambu-Goto string theory but has some\\u000amodifications which we interpret as velocity dependent contributions. We also\\u000apropose to add extra terms in the action which lead to physically interesting\\u000apropagators for partons

M. Arshad Momen; G. Dastegir Al-Quaderi

2000-01-01

466

Quark-Antiquark Potential for Siegel Strings  

Microsoft Academic Search

We compute the quark-antiquark potential employing the continuum action for QCD-like random lattice strings proposed by Siegel. The model leads to a potential similar to those obtained from Nambu-Goto string theory but has some modifications which we interpret as velocity dependent contributions. We also propose to add extra terms in the action which lead to physically interesting propagators for partons

Arshad Momen; G. Dastegir Al-Quaderi

2000-01-01

467

Obtaining L-Systems Rules from Strings  

Microsoft Academic Search

This paper presents a proposal to solve the Inverse Problem of Lindenmayer in the deterministic and free-context L-system grammar class. The proposal of this paper is to show a methodology that can obtain an L-system rule from a string representing the development stage of any object. The strings used in the tests were obtained from known grammars. However, they are

Edmar Santos; Regina Célia Coelho

2009-01-01

468

Inflationary constraints on type IIA string theory  

Microsoft Academic Search

We prove that inflation is forbidden in the most well understood class of semi-realistic type IIA string compactifications: Calabi-Yau compactifications with only standard NS-NS 3-form flux, R-R fluxes, D6-branes and O6-planes at large volume and small string coupling. With these ingredients, the first slow-roll parameter satisfies epsilon >= 27\\/13 whenever V>0, ruling out both inflation (including brane\\/anti-brane inflation) and de

Mark P. Hertzberg; Shamit Kachru; Washington Taylor; Max Tegmark

2007-01-01

469

Black-string solutions with arbitrary tension  

SciTech Connect

We consider 1+4 dimensional black-string solutions which are invariant under translation along the fifth direction. The solutions are characterized by the two parameters, mass and tension, of the source. The Gregory-Laflamme solution is shown to be characterized by the tension whose magnitude is one half of the mass per unit length of the source. A general class of black-string solutions with arbitrary tension is presented and the spacetime properties of the solutions are discussed.

Lee, Chul H. [Department of Physics, and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)

2006-11-15

470

Deviation from ?CDM with cosmic strings networks  

NASA Astrophysics Data System (ADS)

In this work, we consider a network of cosmic strings to explain a possible deviation from ?CDM behaviour. We use different observational data to constrain the model and show that a small but non-zero contribution from the string network is allowed by the observational data, which can result in a reasonable departure from ?CDM evolution. But by calculating the Bayesian evidence, we show that the present data still strongly favour the concordance ?CDM model irrespective of the choice of the prior.

Kumar, Sumit; Nautiyal, Akhilesh; Sen, Anjan A.

2013-09-01

471

Another Length Scale in String Theory?  

Microsoft Academic Search

We suggest that some of the remarkable results on stringy dynamics which have\\u000abeen found recently indicate the existence of another dynamical length scale in\\u000astring theory that, at weak coupling, is much shorter than the string scale.\\u000aThis additional scale corresponds to a mass $\\\\sim m_{\\\\rm s}\\/g_{\\\\rm s}$ where\\u000a$m_{\\\\rm s}$ is the square root of the string tension

Stephen H. Shenker

1995-01-01

472

Tachyon condensation in string field theory  

Microsoft Academic Search

It has been conjectured that at a stationary point of the tachyon potential for the D-brane of bosonic string theory, the negative energy density exactly cancels the D-brane tension. We evaluate this tachyon potential by off-shell calculations in open string field theory. Surprisingly, the condensation of the tachyon mode alone into the stationary point of its cubic potential is found

Ashoke Sen; Barton Zwiebach

2000-01-01

473

Mirage pattern from the heterotic string  

SciTech Connect

We provide a simple example of dilaton stabilization in the framework of heterotic string theory. It requires a gaugino condensate and an uplifting sector similar to the one postulated in type IIB string theory. Its signature is a hybrid mediation of supersymmetry breakdown with a variant of a mirage pattern for the soft breaking terms. The setup is suited for the discussion of heterotic minimal supersymmetric standard model candidates.

Loewen, Valeri; Nilles, Hans Peter [Physikalisches Institut der Universitaet Bonn, Nussallee 12, 53115 Bonn (Germany)

2008-05-15

474

Khovanov-Rozansky Homology and Topological Strings  

NASA Astrophysics Data System (ADS)

We conjecture a relation between the sl( N) knot homology, recently introduced by Khovanov and Rozansky, and the spectrum of BPS states captured by open topological strings. This conjecture leads to new regularities among the sl( N) knot homology groups and suggests that they can be interpreted directly in topological string theory. We use this approach in various examples to predict the sl( N) knot homology groups for all values of N. We verify that our predictions pass some non-trivial checks

Gukov, Sergei; Schwarz, Albert; Vafa, Cumrun

2005-10-01

475

a Continuum String Model for D>1  

NASA Astrophysics Data System (ADS)

The non-critical string (2D gravity coupled to the matter with central charge D) is quantized by taking care of both diffeomorphism and Weyl symmetries. In incorporating the gauge fixing with respect to the Weyl symmetry, through the condition Rg=const., one modifies the classical result of Distler and Kawai. In particular one obtains the real string tension for an arbitrary value of central charge D.

Martellini, M.; Spreafico, M.; Yoshida, K.

476

Gravitational radiation from collapsing cosmic string loops  

NASA Astrophysics Data System (ADS)

It is shown that a circular loop of cosmic string collapsing at nearly the speed of light to form a black hole cannot emit more than 29% of its energy in the form of gravitational radiation. It follows from this and the upper limit on the cosmic gamma ray background, that not more than 10-12 of cosmic string loops in the early universe can have collapsed to form black holes.

Hawking, S. W.

1990-08-01

477

On the universality of string theory  

Microsoft Academic Search

String theory is accused by some of its critics to be a purely abstract mathematical discipline, having lost the contact to\\u000a the simple yet deeply rooted questions which physics provided until the beginning of this century. We argue that, in contrary,\\u000a there are indications that string theory might be linked to a fundamental principle of a quantum computational character.\\u000a In

Karl-Georg Schlesinger

2002-01-01

478

Topics in two-dimensional string theory  

Microsoft Academic Search

We explore various topics in two-dimensional string theory. Firstly, we study particle production in time-dependent backgrounds of the c = 1 matrix model, a holographic description of bosonic string theory in 1+1 dimensions. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum

Joshua L. Davis

2006-01-01

479

Heterotic little string theories and holography  

Microsoft Academic Search

It has been conjectured that little string theories in six dimensions are holographic to critical string theory in a linear dilaton background. We test this conjecture for theories arising on the worldvolume of heterotic fivebranes. We compute the spectrum of chiral primaries in these theories and compare with results following from type-I-heterotic duality and the AdS\\/CFT correspondence. We also construct

Martin Gremm; Anton Kapustin

1999-01-01

480

Quantum Hall Physics in String Theory  

Microsoft Academic Search

In certain backgrounds string theory exhibits quantum Hall-like behavior. These backgrounds provide an explicit realization of the effective non-commutative gauge theory description of the fractional quantum Hall effect (FQHE), and of the corresponding large N matrix model. I review results on the string theory realization of the two-dimensional fractional quantum Hall fluid (FQHF), and describe new results on the stringy

Oren Bergman

2004-01-01

481

Decays of near BPS heterotic strings  

SciTech Connect

The decay of highly excited massive string states in compactified heterotic string theories is discussed. We calculate the decay rate and spectrum of states carrying momentum and winding in the compactified direction. The longest lived states in the spectrum are near Bogomol'nyi-Prasad-Sommerfield (BPS) states whose decay is dominated by a single decay channel of massless radiation which brings the state closer to being BPS.

Gutperle, Michael; Krym, Darya [Department of Physics and Astronomy, UCLA, Los Angeles, California 90095-1547 (United States)

2006-10-15

482

World-volumes and string target spaces  

Microsoft Academic Search

String duality suggests a fascinating juxtoposition of world-volume and target-space dynamics. This is particularly apparent in the D-brane description of stringy solitons that forms a major focus of this article2 (which is not intended to be a comprehensive review of this extensive subject). The article is divided into four sections: • The oligarchy of string world-sheets • p-branes and world-volumes

Michael B. Green

1996-01-01

483

Semiclassical Strings and AdS\\/CFT  

Microsoft Academic Search

We discuss AdS\\/CFT duality in the sector of “semiclassical” string states with large quantum numbers. We review the coherent-state\\u000a effective action approach, in which similar 2d sigma model actions appear from the AdS5 × S5 string action and from the integrable spin chain Hamiltonian representing the N=4 super Yang-Mills dilatation operator. We\\u000a consider mostly the leading-order terms in the energies\\/anomalous

Arkady A. Tseytlin

2006-01-01

484

Les Houches Lectures on Constructing String Vacua  

Microsoft Academic Search

These lectures give a detailed introduction to constructing and analyzing string vacua suitable for phenomenological model building, with particular emphasis on F-theory flux vacua. Topics include (1) general challenges and overview of some proposed scenarios, (2) an extensive introduction to F-theory and its relation to M-theory and perturbative IIB string theory, (3) F-theory flux vacua and moduli stabilization scenarios, (4)

Frederik Denef

2008-01-01

485

Nonlinear Stochastic Drill-String Vibrations  

Microsoft Academic Search

A study of downhole vibrations of drill-strings bottom-hole assemblies is undertaken. The lateral behavior of the system is of interest. The nonlinear nature of the problem is addressed by considering a lateral clear- ance between the drill-string and the borehole that induces a stiffening of the system when exceeded. The stochastic input force is defined by its power spectral density

P. D. Spanos; L. B. Ryon Chair; A. M. Chevallier

2002-01-01

486

Vibration monitoring system for drill string  

Microsoft Academic Search

A vibration monitoring system is described for use in monitoring lateral and torsional vibrations in a drill string comprising: a drill string component having an outer surface; first accelerometer means A[sub 1] for measuring tangential acceleration; second accelerometer means A[sub 2] for measuring tangential acceleration; third accelerometer means A[sub 3] for measuring tangential acceleration; said first, second and third accelerometer

Wassell

1993-01-01

487

Rapidly moving cosmic strings and chronology protection  

NASA Astrophysics Data System (ADS)

Recently, Gott has provided a family of solutions of the Einstein equations describing pairs of parallel cosmic strings in motion. He has shown that if the strings' relative velocity is sufficiently high, there exist closed timelike curves (CTC's) in the spacetime. Here we show that if there are CTC's in such a solution, then every t=const hypersurface in the spacetime intersects CTC's. Therefore, these solutions do not contradict the chronology protection conjecture of Hawking.

Ori, Amos

1991-10-01

488

String theory, cosmology and varying constants  

Microsoft Academic Search

In string theory the coupling `constants' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation\\u000a values of some (a priori) mass less scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation\\u000a of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical\\u000a models which incorporate such

Thibault Damour

2003-01-01

489

Moduli Stabilization Using Open String Fluxes  

NASA Astrophysics Data System (ADS)

In this talk we discuss how by turning on gauge fluxes which couple to the end-points of open strings one can obtain stabilization of closed string moduli. This is done by analyzing supersymmetry constraints and RR tadpole conditions. Stabilization of complex and Kahler moduli is studied in a T6/Z2 orientifold. .

Kumar, Alok

2007-04-01

490

Nonlocal dynamics of p-adic strings  

NASA Astrophysics Data System (ADS)

We consider the construction of Lagrangians that might be suitable for describing the entire p-adic sector of an adelic open scalar string. These Lagrangians are constructed using the Lagrangian for p-adic strings with an arbitrary prime number p. They contain space-time nonlocality because of the d’Alembertian in the argument of the Riemann zeta function. We present a brief review and some new results.

Dragovich, B. G.

2010-09-01

491

String Propagation in a Black Hole Geometry  

Microsoft Academic Search

We consider string theory in the background of the two-dimensional black hole as described by theSL(2;R)=U(1) coset theory recently introduced by Witten. We study the spectrum of this conformal eld theory, and give explicit representations for the tachyon vertex operators in terms of SL(2;R) matrix elements. This is used to compute the scattering of strings o the black hole and

R. H. Dijkgraaf; E. Verlinde; H. Verlinde

1992-01-01

492

Early structure formation from cosmic string loops  

NASA Astrophysics Data System (ADS)

We examine the effects of cosmic strings on structure formation and on the ionization history of the universe. While Gaussian perturbations from inflation are known to provide the dominant contribution to the large scale structure of the universe, density perturbations due to strings are highly non-Gaussian and can produce nonlinear structures at very early times. This could lead to early star formation and reionization of the universe. We improve on earlier studies of these effects by accounting for high loop velocities and for the filamentary shape of the resulting halos. We find that for string energy scales G?gtrsim10-7, the effect of strings on the CMB temperature and polarization power spectra can be significant and is likely to be detectable by the Planck satellite. We mention shortcomings of the standard cosmological model of galaxy formation which may be remedied with the addition of cosmic strings, and comment on other possible observational implications of early structure formation by strings.

Shlaer, Benjamin; Vilenkin, Alexander; Loeb, Abraham

2012-05-01

493

From Loop Space Mechanics to Nonabelian Strings  

NASA Astrophysics Data System (ADS)

Lifting supersymmetric quantum mechanics to loop space yields the superstring. A particle charged under a fiber bundle thereby turns into a string charged under a 2-bundle, or gerbe. This stringification is nothing but categorification. We look at supersymmetric quantum mechanics on loop space and demonstrate how deformations here give rise to superstring background fields and boundary states, and, when generalized, to local nonabelian connections on loop space. In order to get a global description of these connections we introduce and study categorified global holonomy in the form of 2-bundles with 2-holonomy. We show how these relate to nonabelian gerbes and go beyond by obtaining global nonabelian surface holonomy, thus providing a class of action functionals for nonabelian strings. The examination of the differential formulation, which is adapted to the study of nonabelian p-form gauge theories, gives rise to generalized nonabelian Deligne hypercohomology. The (possible) relation of this to strings in Kalb-Ramond backgrounds, to M2/M5-brane systems, to spinning strings and to the derived category description of D-branes is discussed. In particular, there is a 2-group related to the String-group which should be the right structure 2-group for the global description of spinning strings.

Schreiber, Urs

2005-09-01

494

Aspects of string theory compactifications  

NASA Astrophysics Data System (ADS)

String Theory is defined consistently when the dimensionality of the spacetime is ten. To make contact with the apparent four-dimensional world that we live in, we need to "compactify" six of the dimensions of String Theory. This dissertation is dedicated to the study of various physical and mathematical aspects of this problem. In the first part of this dissertation, we construct the mirror of the Beauville manifold which is a Calabi-Yau 3-fold with non-abelian fundamental group. (The preservation of supersymmetry dictates that the internal space into which String Theory is compactified is a so-called Calabi-Yau manifold.) We use the conjecture of Batyrev and Borisov to find the previously misidentified mirror of its universal covering space, P7 [2,2,2,2]. The monomial-divisor mirror map is essential in identifying how the fundamental group of the Beauville manifold acts on the mirror of P7 [2,2,2,2]. Once we find the mirror of the Beauville manifold, we confirm the existence of the threshold bound state around the conifold point, which was originally conjectured in [12]. We also consider how the quantum symmetry group acts on the D-branes that become massless at the conifold point and show the action proposed in [11] is compatible with mirror symmetry. In the second part, we discuss an important subclass of D-branes on a Calabi-Yau manifold, X, which are in 1-1 correspondence with objects in D(X), the derived category of coherent sheaves on X. We study the action of the monodromies in Kahler moduli space on these D-branes. We refine and extend a conjecture of Kontsevich about the form of one of the generators of these monodromies (the monodromy about the "conifold" locus) and show that one can do quite explicit calculations of the monodromy action in many examples. As one application, we verify a prediction of Mayr about the action of the monodromy about the Landau-Ginsburg locus of the quintic. Prompted by the result of this calculation, we propose a modification of the derived category which implements the physical requirement that the shift-by-6 functor should be the identity. The last part of the dissertation is devoted to an F-theory compactification. We consider F-theory on an elliptically fibered Calabi-Yau 4-fold. We review the mechanisms used to stabilize various moduli in the theory. Especially, we take a closer look at Kahler moduli stabilization by the generation of non-perturbative superpotentials and argue that stabilization of all Kahler moduli in this way is non-generic. We consider an example where explicit analytic computation is possible and show that in this example, when all Kahler moduli are stabilized, the overall size is big enough for the supergravity approximation used here to be valid.

Park, Hyukjae

495

Control Rod Malfunction at the NRAD Reactor  

Microsoft Academic Search

The neutron Radiography Reactor (NRAD) is a training, research, and isotope (TRIGA) reactor located at the INL. The reactor is normally shut down by the insertion of three control rods that drop into the core when power is removed from electromagnets. During a routine shutdown, indicator lights on the console showed that one of the control rods was not inserted.

Thomas L. Maddock

2010-01-01

496

CONTROL ROD DRIVE MECHANISM ON THE EBWR  

Microsoft Academic Search

The control rod drive mechanlsms installed on the Argonne Experimental ; Boiling Water Reactor (EBWR) are of an externally operated lead screw and nut ; type in which the control rod extension shafts are driven through pressure ; breakdown, collected leakage seals. The mechanisms which are located below the ; reactor are fabricated from conventional industrial materials, such as carbon

Bullinger; C. F. f Kann

1958-01-01

497

Joule heating of a titanium rod  

NSDL National Science Digital Library

Use the steady-state heat conduction solution for constant heat generation in a rod to determine the maximum temperature difference between the center and surface of a titanium rod heated by electric current; also sketch temperature history from the time when current is turned on.

Powell, Adam C., IV

2002-10-04

498

Radiation Effects Problems in Nuclear Fuel Rods  

Microsoft Academic Search

This paper will review some of the radiation effects problems that have been encountered in nuclear fuel rods. Examples are drawn from both the commercial Light Water Reactors (LWR) and the new, developing Liquid Metal Fast Breeder Reactors (LMFBR). The performance of a particular fuel rod is influenced by (1) the interaction between the ceramic fuel pellet column and the

J. T. A. Roberts

1975-01-01

499

Fuzzy Ultrasonic Testing System with Columnar Rod  

Microsoft Academic Search

This paper describes an ultrasonic testing system with a columnar rod. The general ultrasonic probe is affected by transmission pulse for measurement using the direct contact method. However, if we use a columnar rod between an ultrasonic probe and a target object, we can measure without the transmission pulse. This paper describes the measurement system of the object thickness by

J. Yasui; S. Kobashi; K. Kondo; Y. Hata

2006-01-01

500

Adjuster Rod Experiments in ZED-2.  

National Technical Information Service (NTIS)

Measurements on mock-up adjuster rods were made in a ZED-2 core of 52 28-element D sub 2 O cooled fuel rods on a square pitch of 28.575 cm. Reactivity worths were obtained from critical height and level coefficient of reactivity measurements. Flux distrib...

R. T. Jones

1977-01-01