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Sample records for willebrand factor strings

  1. Active Von Willebrand Factor, thrombocytopenia and thrombosis

    NARCIS (Netherlands)

    Hulstein, J.J.J.

    2006-01-01

    Platelets and von Willebrand factor (VWF) are unable to interact in circulation. To induce an interaction, a conversion of VWF to a platelet-binding conformation is required. At higher shear stresses, the first step in thrombus formation is binding of VWF to the subendothelium. This results in

  2. Of von Willebrand factor and platelets.

    Science.gov (United States)

    Bryckaert, Marijke; Rosa, Jean-Philippe; Denis, Cécile V; Lenting, Peter J

    2015-01-01

    Hemostasis and pathological thrombus formation are dynamic processes that require multiple adhesive receptor-ligand interactions, with blood platelets at the heart of such events. Many studies have contributed to shed light on the importance of von Willebrand factor (VWF) interaction with its platelet receptors, glycoprotein (GP) Ib-IX-V and αIIbβ3 integrin, in promoting primary platelet adhesion and aggregation following vessel injury. This review will recapitulate our current knowledge on the subject from the rheological aspect to the spatio-temporal development of thrombus formation. We will also discuss the signaling events generated by VWF/GPIb-IX-V interaction, leading to platelet activation. Additionally, we will review the growing body of evidence gathered from the recent development of pathological mouse models suggesting that VWF binding to GPIb-IX-V is a promising target in arterial and venous pathological thrombosis. Finally, the pathological aspects of VWF and its impact on platelets will be addressed.

  3. Von Willebrand Factor Gene Variants Associate with Herpes simplex Encephalitis

    Czech Academy of Sciences Publication Activity Database

    Abdelmagid, N.; Bereczky-Veress, B.; Atanur, S.; Musilová, Alena; Zídek, Václav; Saba, L.; Warnecke, A.; Khademi, M.; Studahl, M.; Aurelius, E.; Hjalmarsson, A.; Garcia-Dias, A.; Denis, C. V.; Bergström, T.; Sköldenberg, B.; Kockum, I.; Aitman, T.; Hübner, N.; Olsson, T.; Pravenec, Michal; Diez, M.

    2016-01-01

    Roč. 11, č. 5 (2016), e0155832 E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) 7E10067; GA MŠk(CZ) LL1204 Institutional support: RVO:67985823 Keywords : Von Willebrand Factor gene * Herpes simplex encephalitis * rat * humans Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.806, year: 2016

  4. No evidence for a direct effect of von Willebrand factor's ABH blood group antigens on von Willebrand factor clearance

    NARCIS (Netherlands)

    Groeneveld, D J; van Bekkum, T; Cheung, K L; Dirven, R J; Castaman, G; Reitsma, P H; van Vlijmen, B; Eikenboom, J

    BACKGROUND: One of the major determinants of von Willebrand factor (VWF) plasma levels is ABO blood group status, and individuals with blood group O have ~ 25% lower plasma levels. The exact mechanism behind this relationship remains unknown, although effects on clearance have been postulated.

  5. An ELISA for the quantitation of von Willebrand Factor

    DEFF Research Database (Denmark)

    Vinholt, Pernille Just; Overgaard, Martin; Diederichsen, Axel Cosmus Pyndt

    2013-01-01

    for measurement of von Willebrand factor-osteoprotegerin complex (VWF:OPG) in human plasma. Furthermore, the significance of VWF:OPG complex as a marker of cardiovascular disease (CVD) was evaluated. PATIENTS/METHODS: A sandwich ELISA for quantification of VWF:OPG was developed using a polyclonal rabbit anti...... with and without documented coronary calcification (total n=118). RESULTS AND CONCLUSIONS: The assay detected VWF:OPG complexes in human plasma, while no significant signal was observed when testing solutions containing VWF or recombinant OPG alone. Importantly, the ELISA assay was able to detect in vitro formed...

  6. Von Willebrand factor regulation of blood vessel formation.

    Science.gov (United States)

    Randi, Anna M; Smith, Koval E; Castaman, Giancarlo

    2018-06-04

    Several important physiological processes, from permeability to inflammation to haemostasis, take place at the vessel wall and are regulated by endothelial cells (EC). Thus, proteins that have been identified as regulators of one process are increasingly found to be involved in other vascular functions. Such is the case for Von Willebrand Factor (VWF), a large glycoprotein best known for its critical role in haemostasis. In vitro and in vivo studies have shown that lack of VWF causes enhanced vascularisation, both constitutively and following ischemia. This evidence is supported by studies on blood outgrowth endothelial cells (BOEC) from patients with lack of VWF synthesis (type 3 von Willebrand disease [VWD]). The molecular pathways are likely to involve VWF binding partners, such as integrin αvβ3, and components of Weibel Palade bodies (WPB), such as Angiopoietin-2 and Galectin-3, whose storage is regulated by VWF; these converge on the master regulator of angiogenesis and endothelial homeostasis, vascular endothelial growth factor (VEGF) signalling. Recent studies suggest that the roles of VWF may be tissue-specific. The ability of VWF to regulate angiogenesis has clinical implications for a subset of VWD patients with severe, intractable gastrointestinal bleeding due to vascular malformations. In this article, we review the evidence showing that VWF is involved in blood vessel formation, discuss the role of VWF high molecular weight multimers in regulating angiogenesis, and the value of studies on BOEC in developing a precision medicine approach to validate novel treatments for angiodysplasia in congenital VWD and acquired von Willebrand syndrome. Copyright © 2018 American Society of Hematology.

  7. von Willebrand factor, Jedi knight of the bloodstream.

    Science.gov (United States)

    Springer, Timothy A

    2014-08-28

    When blood vessels are cut, the forces in the bloodstream increase and change character. The dark side of these forces causes hemorrhage and death. However, von Willebrand factor (VWF), with help from our circulatory system and platelets, harnesses the same forces to form a hemostatic plug. Force and VWF function are so closely intertwined that, like members of the Jedi Order in the movie Star Wars who learn to use "the Force" to do good, VWF may be considered the Jedi knight of the bloodstream. The long length of VWF enables responsiveness to flow. The shape of VWF is predicted to alter from irregularly coiled to extended thread-like in the transition from shear to elongational flow at sites of hemostasis and thrombosis. Elongational force propagated through the length of VWF in its thread-like shape exposes its monomers for multimeric binding to platelets and subendothelium and likely also increases affinity of the A1 domain for platelets. Specialized domains concatenate and compact VWF during biosynthesis. A2 domain unfolding by hydrodynamic force enables postsecretion regulation of VWF length. Mutations in VWF in von Willebrand disease contribute to and are illuminated by VWF biology. I attempt to integrate classic studies on the physiology of hemostatic plug formation into modern molecular understanding, and point out what remains to be learned. © 2014 by The American Society of Hematology.

  8. [Homocysteine and von Willebrand factor in chronic alcoholism].

    Science.gov (United States)

    Koriakin, A M; Epifantseva, N N; Dadyka, I V; Gorbatovskiĭ, Ia A

    2010-04-01

    The levels of homocysteine (HC) and von Willebrand factor (VWF) as cardiovascular risk factors were studied in patients with Stage II chronic alcoholism. Forty-one men with Stage II chronic alcoholism without clinical signs of somatic and infectious diseases were examined. Their median age was 37 (range 32-40) years; the alcoholization period was 12 (range 8-17) years. Plasma HC and VWF (amount and activity) levels were determined. In 63.4% of chronic alcoholic patients, HC levels was twice as high as in the controls; in 80.6%, both the content and activity of VWF were increased. There was no correlation between the levels of HC and VWF. Vascular endothelial damage concurrent with hyperhomocysteinemia increases a cardiovascular risk in patients with Stage II chronic alcoholism.

  9. Value of Von Willebrand Factor as a Predictor for Osteoporosis Development in Women with Hypothyroidism

    Directory of Open Access Journals (Sweden)

    I.V. Pankiv

    2015-08-01

    Full Text Available The paper presents the study of the value of von Willebrand factor as a marker of endothelial dysfunction for osteoporosis development and for prediction of risk of its formation in women with hypothyroidism. Postmenopausal women with hypothyroidism have significant increase of von Willebrand factor at lumbar osteopenia. High concentrations of von Willebrand factor in women with hypothyroidism follows to consider it as a predictor for osteoporosis development. Increased level of С-reactive protein belongs to the unfavorable prognostic signs in relation to the decline of bone mineral density for patients with primary hypothyroidism.

  10. Characterization of a novel mutation in the von Willebrand factor propeptide in a distinct subtype of recessive von Willebrand disease

    DEFF Research Database (Denmark)

    Lanke, Elsa; Kristoffersson, Ann-Charlotte; Philips, Malou

    2008-01-01

    von Willebrand factor (VWF) is a plasma protein that consists of a series of multimers of which the high-molecular-weight VWF multimers are the most potent in platelet adhesion and aggregation. The propeptide of the VWF (VWFpp) is known to be essential in the process of multimer assembly. Genetic...... mutation in the VWFpp abolishes multimerization of VWF. The mutation probably disrupts the normal configuration of the VWFpp, which is essential for correct orientation of the protomers and ultimately multimerization. The mutant amino acid is located in a region that is highly conserved across several...

  11. Evaluation of von Willebrand factor during pregnancy, lactation and oestrous cycle in bitches affected and unaffected by von Willebrand disease.

    Science.gov (United States)

    Mattoso, C R S; Takahira, R K; Beier, S L; Araujo, J P; Corrente, J E

    2013-06-01

    Plasmatic concentrations of von Willebrand Factor (vWF) increase during pregnancy in humans and dogs; however the mechanism of such increase is still not well defined. The aims of this study were: (i) to evaluate changes in vWF concentration during pregnancy and during the subsequent oestrous cycle in bitches affected and unaffected by von Willebrand Disease (vWD); (ii) to correlate the vWF levels and cortisol levels in both groups. Seven vWD affected (GI) and nine unaffected (GII) bitches were used. The animals were assessed during pregnancy, parturition, lactation and non-gestational oestrous cycle in 11 moments (Pregnancy 1, Pregnancy 2, Parturition, Lactation 1, Lactation 2, Lactation 3, Anestrus, Proestrus, Oestrus, Diestrus 1, and Diestrus 2). The following tests were performed; measurement of von Willebrand factor antigen (vWF:Ag), albumin and cortisol. In both groups, vWF concentration remained stable during the non-gestational oestrous cycle, but increased during pregnancy, with the highest value observed at parturition. Increases of 70% and 124% in vWF were seen in GI and GII, respectively, compared to anestrus. No correlation was found between vWF and cortisol. Values of vWF:Ag changed during pregnancy, with a peak at parturition, both in vWD affected and unaffected animals. Values of vWF were not altered in the different phases of the oestrous cycle following pregnancy in both groups. Evaluation of vWF during pregnancy can cause false negative results for vWD, but assessment can be performed at any point in the oestrous cycle of non-pregnant bitches. © 2012 Blackwell Verlag GmbH.

  12. Association of von Willebrand factor blood levels with exercise hypertension.

    Science.gov (United States)

    Nikolic, Sonja B; Adams, Murray J; Otahal, Petr; Edwards, Lindsay M; Sharman, James E

    2015-05-01

    A hypertensive response to moderate intensity exercise (HRE) is associated with increased cardiovascular risk. The mechanisms of an HRE are unclear, although previous studies suggest this may be due to haemostatic and/or haemodynamic factors. We investigated the relationships between an HRE with haemostatic and hemodynamic indices. Sixty-four participants (57 ± 10 years, 71 % male) with indication for exercise stress testing underwent cardiovascular assessment at rest and during moderate intensity exercise, from which 20 participants developed an HRE (defined as moderate exercise systolic BP ≥ 170 mmHg/men and ≥ 160 mmHg/women). Rest, exercise and post-exercise blood samples were analysed for haemostatic markers, including von Willebrand factor (vWf), and haemodynamic measures of brachial and central blood pressure (BP), aortic stiffness and systemic vascular resistance index (SVRi). HRE participants had higher rest vWf compared with normotensive response to exercise (NRE) participants (1,927 mU/mL, 95 % CI 1,240-2,615, vs. 1,129 mU/mL, 95 % CI 871-1,386; p = 0.016). vWf levels significantly decreased from rest to post-exercise in HRE participants (p = 0.005), whereas vWf levels significantly increased from rest to exercise in NRE participants (p = 0.030). HRE participants also had increased triglycerides, rest BP, aortic stiffness and exercise SVRi (p HRE at moderate intensity.

  13. Modeling Shear Induced Von Willebrand Factor Binding to Collagen

    Science.gov (United States)

    Dong, Chuqiao; Wei, Wei; Morabito, Michael; Webb, Edmund; Oztekin, Alparslan; Zhang, Xiaohui; Cheng, Xuanhong

    2017-11-01

    Von Willebrand factor (vWF) is a blood glycoprotein that binds with platelets and collagen on injured vessel surfaces to form clots. VWF bioactivity is shear flow induced: at low shear, binding between VWF and other biological entities is suppressed; for high shear rate conditions - as are found near arterial injury sites - VWF elongates, activating its binding with platelets and collagen. Based on parameters derived from single molecule force spectroscopy experiments, we developed a coarse-grain molecular model to simulate bond formation probability as a function of shear rate. By introducing a binding criterion that depends on the conformation of a sub-monomer molecular feature of our model, the model predicts shear-induced binding, even for conditions where binding is highly energetically favorable. We further investigate the influence of various model parameters on the ability to predict shear-induced binding (vWF length, collagen site density and distribution, binding energy landscape, and slip/catch bond length) and demonstrate parameter ranges where the model provides good agreement with existing experimental data. Our results may be important for understanding vWF activity and also for achieving targeted drug therapy via biomimetic synthetic molecules. National Science Foundation (NSF),Division of Mathematical Sciences (DMS).

  14. Phenotypic correction of von Willebrand disease type 3 blood-derived endothelial cells with lentiviral vectors expressing von Willebrand factor

    Science.gov (United States)

    De Meyer, Simon F.; Vanhoorelbeke, Karen; Chuah, Marinee K.; Pareyn, Inge; Gillijns, Veerle; Hebbel, Robert P.; Collen, Désiré; Deckmyn, Hans; VandenDriessche, Thierry

    2006-01-01

    Von Willebrand disease (VWD) is an inherited bleeding disorder, caused by quantitative (type 1 and 3) or qualitative (type 2) defects in von Willebrand factor (VWF). Gene therapy is an appealing strategy for treatment of VWD because it is caused by a single gene defect and because VWF is secreted into the circulation, obviating the need for targeting specific organs or tissues. However, development of gene therapy for VWD has been hampered by the considerable length of the VWF cDNA (8.4 kb [kilobase]) and the inherent complexity of the VWF protein that requires extensive posttranslational processing. In this study, a gene-based approach for VWD was developed using lentiviral transduction of blood-outgrowth endothelial cells (BOECs) to express functional VWF. A lentiviral vector encoding complete human VWF was used to transduce BOECs isolated from type 3 VWD dogs resulting in high-transduction efficiencies (95.6% ± 2.2%). Transduced VWD BOECs efficiently expressed functional vector-encoded VWF (4.6 ± 0.4 U/24 hour per 106 cells), with normal binding to GPIbα and collagen and synthesis of a broad range of multimers resulting in phenotypic correction of these cells. These results indicate for the first time that gene therapy of type 3 VWD is feasible and that BOECs are attractive target cells for this purpose. PMID:16478886

  15. Von Willebrand Factor Gene Variants Associate with Herpes simplex Encephalitis.

    Directory of Open Access Journals (Sweden)

    Nada Abdelmagid

    Full Text Available Herpes simplex encephalitis (HSE is a rare complication of Herpes simplex virus type-1 infection. It results in severe parenchymal damage in the brain. Although viral latency in neurons is very common in the population, it remains unclear why certain individuals develop HSE. Here we explore potential host genetic variants predisposing to HSE. In order to investigate this we used a rat HSE model comparing the HSE susceptible SHR (Spontaneously Hypertensive Rats with the asymptomatic infection of BN (Brown Norway. Notably, both strains have HSV-1 spread to the CNS at four days after infection. A genome wide linkage analysis of 29 infected HXB/BXH RILs (recombinant inbred lines-generated from the prior two strains, displayed variable susceptibility to HSE enabling the definition of a significant QTL (quantitative trait locus named Hse6 towards the end of chromosome 4 (160.89-174Mb containing the Vwf (von Willebrand factor gene. This was the only gene in the QTL with both cis-regulation in the brain and included several non-synonymous SNPs (single nucleotide polymorphism. Intriguingly, in human chromosome 12 several SNPs within the intronic region between exon 43 and 44 of the VWF gene were associated with human HSE pathogenesis. In particular, rs917859 is nominally associated with an odds ratio of 1.5 (95% CI 1.11-2.02; p-value = 0.008 after genotyping in 115 HSE cases and 428 controls. Although there are possibly several genetic and environmental factors involved in development of HSE, our study identifies variants of the VWF gene as candidates for susceptibility in experimental and human HSE.

  16. Differential proteolytic activation of factor VIII-von Willebrand factor complex by thrombin

    International Nuclear Information System (INIS)

    Hill-Eubanks, D.C.; Parker, C.G.; Lollar, P.

    1989-01-01

    Blood coagulation factor VIII (fVIII) is a plasma protein that is decreased or absent in hemophilia A. It is isolated as a mixture of heterodimers that contain a variably sized heavy chain and a common light chain. Thrombin catalyzes the activation of fVIII in a reaction that is associated with cleavages in both types of chain. The authors isolated a serine protease from Bothrops jararacussu snake venom that catalyzes thrombin-like heavy-chain cleavage but not light-chain cleavage in porcine fVIII as judged by NaDodSO 4 /PAGE and N-terminal sequence analysis. Using a plasma-free assay of the ability of activated 125 I-fVIII to function as a cofactor in the activation of factor X by factor IXa, they found that fVIII is activated by the venom enzyme. The venom enzyme-activated fVIII was isolated in stable form by cation-exchange HPLC. von Willebrand factor inhibited venom enzyme-activated fVIII but not thrombin-activated fVIII. These results suggest that the binding of fVIII to von Willebrand factor depends on the presence of an intact light chain and that activated fVIII must dissociate from von Willebrand factor to exert its cofactor effect. Thus, proteolytic activation of fVIII-von Willebrand factor complex appears to be differentially regulated by light-chain cleavage to dissociate the complex and heavy-chain cleavage to activate the cofactor function

  17. A study of the effect of ethamsylate (Dicynene) on the bleeding time, von Willebrand factor level and fibrinolysis in patients with von Willebrand's disease.

    Science.gov (United States)

    Hutton, R A; Hales, M; Kernoff, P B

    1988-12-22

    Nine patients with clinically moderate or severe Type I von Willebrand's disease were treated for 2 weeks with ethamsylate (2 g/day in four equal doses) and with a matched placebo in a randomised double-blind trial. Template bleeding time, von Willebrand factor activity (ristocetin co-factor) and antigen, euglobulin lysis time and type I tissue plasminogen activator inhibitor were determined before and at the end of each treatment period. None of these parameters showed any significant change attributable to ethamsylate. Thus, despite the fact that five patients thought subjectively that their bleeding symptoms improved during ethamsylate treatment compared to only one while on placebo, we obtained no evidence that the drug was of benefit to patients with von Willebrand's disease.

  18. Interference from lupus anticoagulant on von Willebrand factor measurement in splenic marginal zone lymphoma

    DEFF Research Database (Denmark)

    Vinholt, Pernille J; Nybo, Mads

    2015-01-01

    We present a case concerning a patient with splenic marginal zone lymphoma (SMZL) and isolated prolonged activated partial thromboplastin time (aPTT) caused by lupus anticoagulant. Von Willebrand factor (VWF) activity and antigen were immeasurable by latex particle immunoturbidimetric assays...

  19. Assembly and activation of alternative complement components on endothelial cell-anchored ultra-large von Willebrand factor links complement and hemostasis-thrombosis.

    Directory of Open Access Journals (Sweden)

    Nancy A Turner

    Full Text Available Vascular endothelial cells (ECs express and release protein components of the complement pathways, as well as secreting and anchoring ultra-large von Willebrand factor (ULVWF multimers in long string-like structures that initiate platelet adhesion during hemostasis and thrombosis. The alternative complement pathway (AP is an important non-antibody-requiring host defense system. Thrombotic microangiopathies can be associated with defective regulation of the AP (atypical hemolytic-uremic syndrome or with inadequate cleavage by ADAMTS-13 of ULVWF multimeric strings secreted by/anchored to ECs (thrombotic thrombocytopenic purpura. Our goal was to determine if EC-anchored ULVWF strings caused the assembly and activation of AP components, thereby linking two essential defense mechanisms.We quantified gene expression of these complement components in cultured human umbilical vein endothelial cells (HUVECs by real-time PCR: C3 and C5; complement factor (CF B, CFD, CFP, CFH and CFI of the AP; and C4 of the classical and lectin (but not alternative complement pathways. We used fluorescent microscopy, monospecific antibodies against complement components, fluorescent secondary antibodies, and the analysis of >150 images to quantify the attachment of HUVEC-released complement proteins to ULVWF strings secreted by, and anchored to, the HUVECs (under conditions of ADAMTS-13 inhibition. We found that HUVEC-released C4 did not attach to ULVWF strings, ruling out activation of the classical and lectin pathways by the strings. In contrast, C3, FB, FD, FP and C5, FH and FI attached to ULVWF strings in quantitative patterns consistent with assembly of the AP components into active complexes. This was verified when non-functional FB blocked the formation of AP C3 convertase complexes (C3bBb on ULVWF strings.AP components are assembled and activated on EC-secreted/anchored ULVWF multimeric strings. Our findings provide one possible molecular mechanism for clinical

  20. Differential effects of the loss of intrachain- versus interchain-disulfide bonds in the cystine-knot domain of von Willebrand factor on the clinical phenotype of von Willebrand disease

    NARCIS (Netherlands)

    Tjernberg, Pernilla; Vos, Hans L.; Spaargaren-van Riel, Caroline C.; Luken, Brenda M.; Voorberg, Jan; Bertina, Rogier M.; Eikenboom, Jeroen C. J.

    2006-01-01

    Von Willebrand factor (VWF) contains a large number of cysteine residues, which all form disulfide bonds. Mutations of cysteines located in the cystine-knot (CK) domain of VWF have been identified in both qualitative type 2A (IID) and quantitative type 3 von Willebrand disease (VWD). Our objective

  1. Worldsheet factorization for twistor-strings

    Energy Technology Data Exchange (ETDEWEB)

    Adamo, Tim [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2014-04-10

    We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions.

  2. Worldsheet factorization for twistor-strings

    International Nuclear Information System (INIS)

    Adamo, Tim

    2014-01-01

    We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions

  3. Dynamics of von Willebrand factor reactivity in sickle cell disease during vaso-occlusive crisis and steady state

    NARCIS (Netherlands)

    Sins, J. W. R.; Schimmel, M.; Luken, B. M.; Nur, E.; Zeerleder, S. S.; van Tuijn, C. F. J.; Brandjes, D. P. M.; Kopatz, W. F.; Urbanus, R. T.; Meijers, J. C. M.; Biemond, B. J.; Fijnvandraat, K.

    2017-01-01

    Background: Endothelial activation plays a central role in the pathophysiology of vaso-occlusion in sickle cell disease (SCD), facilitating adhesive interactions with circulating blood cells. Upon activation, various adhesive molecules are expressed, including von Willebrand factor (VWF). Increased

  4. Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise

    NARCIS (Netherlands)

    J.E. van Loon (Janine ); M.A.H. Sonneveld (Michelle); S.F.E. Praet (Stephan); M.P.M. de Maat (Moniek); F.W.G. Leebeek (Frank)

    2014-01-01

    textabstractBackground: Physical stress triggers the endothelium to release von Willebrand Factor (VWF) from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the

  5. Aging and ABO blood type influence von Willebrand factor and factor VIII levels through interrelated mechanisms.

    Science.gov (United States)

    Albánez, S; Ogiwara, K; Michels, A; Hopman, W; Grabell, J; James, P; Lillicrap, D

    2016-05-01

    Essentials von Willebrand factor (VWF) and factor VIII (FVIII) levels are modulated by age and ABO status. The effect of aging and ABO blood type on VWF and FVIII was assessed in 207 normal individuals. Aging and ABO blood type showed combined and bidirectional influences on VWF and FVIII levels. Aging and ABO blood type influence VWF levels through both secretion and clearance mechanisms. Background The effect of aging and ABO blood type on plasma levels of von Willebrand factor (VWF) and factor VIII (FVIII) have been widely reported; however, a comprehensive analysis of their combined effect has not been performed and the mechanisms responsible for the age-related changes have not been determined. Objectives To assess the influence of aging and ABO blood type on VWF and FVIII levels, and to evaluate the contribution of VWF secretion and clearance to the age-related changes. Methods A cross-sectional observational study was performed in a cohort of 207 normal individuals, whose levels of VWF, FVIII, VWF propeptide (VWFpp), VWFpp/VWF:Ag ratio and blood type A antigen content on VWF (A-VWF) were quantified. Results Aging and ABO blood type exerted interrelated effects on VWF and FVIII plasma levels, because the age-related increase in both proteins was significantly higher in type non-O individuals (β = 0.011 vs. 0.005). This increase with age in non-O subjects drove the differences between blood types in VWF levels, as the mean difference increased from 0.13 U/mL in the young to 0.57 U/mL in the old. Moreover, A-VWF was associated with both VWF antigen (β = 0.29; 95% confidence interval [CI], 0.09, 0.50) and VWF clearance (β = -0.15; 95% CI, -0.25, -0.06). We also documented an effect of ABO blood type on VWF secretion with aging, as old individuals with blood type non-O showed higher levels of VWFpp (mean difference 0.29 U/mL). Conclusions Aging and ABO blood type have an interrelated effect on VWF and FVIII levels, where the effect of one is significantly

  6. Single molecule force spectroscopy data and BD- and MD simulations on the blood protein von Willebrand factor

    Directory of Open Access Journals (Sweden)

    Sandra Posch

    2016-09-01

    Full Text Available We here give information for a deeper understanding of single molecule force spectroscopy (SMFS data through the example of the blood protein von Willebrand factor (VWF. It is also shown, how fitting of rupture forces versus loading rate profiles in the molecular dynamics (MD loading-rate range can be used to demonstrate the qualitative agreement between SMFS and MD simulations. The recently developed model by Bullerjahn, Sturm, and Kroy (BSK was used for this demonstration. Further, Brownian dynamics (BD simulations, which can be utilized to estimate the lifetimes of intramolecular VWF interactions under physiological shear, are described. For interpretation and discussion of the methods and data presented here, we would like to directly point the reader to the related research paper, “Mutual A domain interactions in the force sensing protein von Willebrand Factor” (Posch et al., 2016 [1]. Keywords: Atomic force microscopy, Single molecule force spectroscopy, Molecular dynamics simulation, Brownian dynamics simulation, von Willebrand factor

  7. Profile of von Willebrand factor antigen and von Willebrand factor propeptide in an overall TIA and ischaemic stroke population and amongst subtypes.

    Science.gov (United States)

    Tobin, W O; Kinsella, J A; Kavanagh, G F; O'Donnell, J S; McGrath, R T; Tierney, S; Egan, B; Feeley, T M; Coughlan, T; Collins, D R; O'Neill, D; Murphy, Sjx; Lim, S J; Murphy, R P; McCabe, Djh

    2017-04-15

    Von Willebrand factor propeptide (VWF:Ag II) is proposed to be a more sensitive marker of acute endothelial activation than von Willebrand factor antigen (VWF:Ag). Simultaneous data on VWF:Ag and VWF:Ag II profiles are very limited following TIA and ischaemic stroke. In this prospective, observational, case-control study, plasma VWF:Ag and VWF:Ag II levels were quantified in 164 patients≤4weeks of TIA or ischaemic stroke (baseline), and then ≥14days (14d) and ≥90days (90d) later, and compared with those from 27 healthy controls. TIA and stroke subtyping was performed according to the TOAST classification. The relationship between VWF:Ag and VWF:Ag II levels and platelet activation status was assessed. 'Unadjusted' VWF:Ag and VWF:Ag II levels were higher in patients at baseline, 14d and 90d than in controls (p≤0.03). VWF:Ag levels remained higher in patients than controls at baseline (p≤0.03), but not at 14d or 90d after controlling for differences in age or hypertension, and were higher in patients at baseline and 90d after controlling for smoking status (p≤0.04). 'Adjusted' VWF:Ag II levels were not higher in patients than controls after controlling for age, hypertension or smoking (p≥0.1). Patients with symptomatic carotid stenosis (N=46) had higher VWF:Ag and VWF:Ag II levels than controls at all time-points (p≤0.002). There was no significant correlation between platelet activation status and VWF:Ag or VWF:Ag II levels. VWF:Ag and VWF:Ag II levels are increased in an overall TIA and ischaemic stroke population, especially in patients with recently symptomatic carotid stenosis. VWF:Ag II was not superior to VWF:Ag at detecting acute endothelial activation in this cohort and might reflect timing of blood sampling in our study. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Functional variation in the arginine vasopressin 2 receptor as a modifier of human plasma von Willebrand factor levels

    DEFF Research Database (Denmark)

    Nossent, Anne Yaël; Robben, J H; Deen, P M T

    2010-01-01

    SUMMARY OBJECTIVES: Stimulation of arginine vasopressin 2 receptor (V2R) with arginine vasopressin (AVP) results in a rise in von Willebrand factor (VWF) and factor VIII plasma levels. We hypothesized that gain-of-function variations in the V2R gene (AVPR2) would lead to higher plasma levels of V...

  9. Characterization of Zebrafish von Willebrand Factor Reveals Conservation of Domain Structure, Multimerization, and Intracellular Storage

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    Arunima Ghosh

    2012-01-01

    Full Text Available von Willebrand disease (VWD is the most common inherited human bleeding disorder and is caused by quantitative or qualitative defects in von Willebrand factor (VWF. VWF is a secreted glycoprotein that circulates as large multimers. While reduced VWF is associated with bleeding, elevations in overall level or multimer size are implicated in thrombosis. The zebrafish is a powerful genetic model in which the hemostatic system is well conserved with mammals. The ability of this organism to generate thousands of offspring and its optical transparency make it unique and complementary to mammalian models of hemostasis. Previously, partial clones of zebrafish vwf have been identified, and some functional conservation has been demonstrated. In this paper we clone the complete zebrafish vwf cDNA and show that there is conservation of domain structure. Recombinant zebrafish Vwf forms large multimers and pseudo-Weibel-Palade bodies (WPBs in cell culture. Larval expression is in the pharyngeal arches, yolk sac, and intestinal epithelium. These results provide a foundation for continued study of zebrafish Vwf that may further our understanding of the mechanisms of VWD.

  10. Regulation of plasma von Willebrand factor [version 1; referees: 3 approved

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    Karl C Desch

    2018-01-01

    Full Text Available Von Willebrand factor (VWF is a multimeric plasma glycoprotein that plays a central role in the initiation of blood coagulation. Through interactions between its specific functional domains, the vascular wall, coagulation factor VIII, and platelet receptors, VWF maintains hemostasis by binding to platelets and delivering factor VIII to the sites of vascular injury. In the healthy human population, plasma VWF levels vary widely. The important role of VWF is illustrated by individuals at the extremes of the normal distribution of plasma VWF concentrations where individuals with low VWF levels are more likely to present with mucocutaneous bleeding. Conversely, people with high VWF levels are at higher risk for venous thromboembolic disease, stroke, and coronary artery disease. This report will summarize recent advances in our understanding of environmental influences and the genetic control of VWF plasma variation in healthy and symptomatic populations and will also highlight the unanswered questions that are currently driving this field of study.

  11. Maximal unbordered factors of random strings

    DEFF Research Database (Denmark)

    Cording, Patrick Hagge; Knudsen, Mathias Bæk Tejs

    2016-01-01

    A border of a string is a non-empty prefix of the string that is also a suffix of the string, and a string is unbordered if it has no border. Loptev, Kucherov, and Starikovskaya [CPM 2015] conjectured the following: If we pick a string of length n from a fixed alphabet uniformly at random...

  12. Dynamics of von Willebrand factor reactivity in sickle cell disease during vaso-occlusive crisis and steady state

    NARCIS (Netherlands)

    Sins, J. W.R.; Schimmel, Marein; Luken, Brenda M.; Nur, Erfan; Zeerleder, S.; van Tuijn, Charlotte F. J.; Brandjes, Dees P. M.; Kopatz, W. F.; Urbanus, R. T.; Meijers, Joost C. M.; Biemond, B. J.; Fijnvandraat, K.

    2017-01-01

    Essentials The role of von Willebrand Factor (VWF) in the pathophysiology of sickle cell disease is unclear. We assessed markers of VWF during admission for vaso-occlusive crisis (VOC) and steady state. VWF reactivity was higher during VOC and was associated with inflammation and neutrophil

  13. Expression of von Willebrand factor and caldesmon in the placental tissues of pregnancies complicated with intrauterine growth restriction.

    Science.gov (United States)

    Göksever Çelik, Hale; Uhri, Mehmet; Yildirim, Gökhan

    2017-11-02

    The decreased placental perfusion is the underlying reason for intrauterine growth restriction that in turn leads to reduced placental perfusion and ischemia. However, there are several issues to be understood in the pathophysiology of intrauterine growth restriction. We aimed to study whether any compensatory response in placental vascular bed occur in pregnancies complicated with intrauterine growth restriction by the immunohistochemical staining of von Willebrand factor and caldesmon in placental tissues. A total of 103 pregnant women was enrolled in the study including 50 patients who were complicated with IUGR and 50 uncomplicated control patients. The study was designed in a prospective manner. All placentas were also stained with von Willebrand factor and caldesmon monoclonal kits. The immunohistochemical staining of von Willebrand factor and caldesmon expressions in placental tissues were different between normal and intrauterine growth restriction group. The percentages of 2+ and 3+ von Willebrand factor expression were higher in the intrauterine growth restriction group comparing with the normal group, although the difference was not statistically significant. The intensity of caldesmon expression was significantly lower in the intrauterine growth restriction group in comparison with the normal group (p intrauterine growth restriction which is a hypoxic condition. But newly formed vessels are immature and not strong enough. Our study is important to clarify the pathophysiology and placental compensatory responses in intrauterine growth restriction.

  14. Neutrophil Protease Cleavage of Von Willebrand Factor in Glomeruli – An Anti-thrombotic Mechanism in the Kidney

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    Ramesh Tati

    2017-02-01

    Full Text Available Adequate cleavage of von Willebrand factor (VWF prevents formation of thrombi. ADAMTS13 is the main VWF-cleaving protease and its deficiency results in development of thrombotic microangiopathy. Besides ADAMTS13 other proteases may also possess VWF-cleaving activity, but their physiological importance in preventing thrombus formation is unknown. This study investigated if, and which, proteases could cleave VWF in the glomerulus. The content of the glomerular basement membrane (GBM was studied as a reflection of processes occurring in the subendothelial glomerular space. VWF was incubated with human GBMs and VWF cleavage was assessed by multimer structure analysis, immunoblotting and mass spectrometry. VWF was cleaved into the smallest multimers by the GBM, which contained ADAMTS13 as well as neutrophil proteases, elastase, proteinase 3 (PR3, cathepsin-G and matrix-metalloproteinase 9. The most potent components of the GBM capable of VWF cleavage were in the serine protease or metalloprotease category, but not ADAMTS13. Neutralization of neutrophil serine proteases inhibited GBM-mediated VWF-cleaving activity, demonstrating a marked contribution of elastase and/or PR3. VWF-platelet strings formed on the surface of primary glomerular endothelial cells, in a perfusion system, were cleaved by both elastase and the GBM, a process blocked by elastase inhibitor. Ultramorphological studies of the human kidney demonstrated neutrophils releasing elastase into the GBM. Neutrophil proteases may contribute to VWF cleavage within the subendothelium, adjacent to the GBM, and thus regulate thrombus size. This anti-thrombotic mechanism would protect the normal kidney during inflammation and could also explain why most patients with ADAMTS13 deficiency do not develop severe kidney failure.

  15. Elevated plasma factor VIII enhances venous thrombus formation in rabbits: contribution of factor XI, von Willebrand factor and tissue factor.

    Science.gov (United States)

    Sugita, Chihiro; Yamashita, Atsushi; Matsuura, Yunosuke; Iwakiri, Takashi; Okuyama, Nozomi; Matsuda, Shuntaro; Matsumoto, Tomoko; Inoue, Osamu; Harada, Aya; Kitazawa, Takehisa; Hattori, Kunihiro; Shima, Midori; Asada, Yujiro

    2013-07-01

    Elevated plasma levels of factor VIII (FVIII) are associated with increased risk of deep venous thrombosis. The aim of this study is to elucidate how elevated FVIII levels affect venous thrombus formation and propagation in vivo. We examined rabbit plasma FVIII activity, plasma thrombin generation, whole blood coagulation, platelet aggregation and venous wall thrombogenicity before and one hour after an intravenous infusion of recombinant human FVIII (rFVIII). Venous thrombus induced by the endothelial denudation of rabbit jugular veins was histologically assessed. Thrombus propagation was evaluated as indocyanine green fluorescence intensity. Argatroban, a thrombin inhibitor, and neutralised antibodies for tissue factor (TF), factor XI (FXI), and von Willebrand factor (VWF) were infused before or after thrombus induction to investigate their effects on venous thrombus formation or propagation. Recombinant FVIII (100 IU/kg) increased rabbit plasma FVIII activity two-fold and significantly enhanced whole blood coagulation and total plasma thrombin generation, but did not affect initial thrombin generation time, platelet aggregation and venous wall thrombogenicity. The rFVIII infusion also increased the size of venous thrombus 1 hour after thrombus induction. Argatroban and the antibodies for TF, FXI or VWF inhibited such enhanced thrombus formation and all except TF suppressed thrombus propagation. In conclusion, elevated plasma FVIII levels enhance venous thrombus formation and propagation. Excess thrombin generation by FXI and VWF-mediated FVIII recruitment appear to contribute to the growth of FVIII-driven venous thrombus.

  16. Quality factor improvement of silicon nitride micro string resonators

    DEFF Research Database (Denmark)

    Schmid, Silvan; Malm, Bjarke; Boisen, Anja

    2011-01-01

    Resonant micro and nano strings are of interest for sensor applications due to their extraordinary high quality factors, low mass and tunable resonant frequency. It has been found that the quality factor of strings is usually limited by clamping loss. In this work, clamping loss has been addressed...... by varying the clamping design and string geometry. We present silicon nitride micro strings with quality factors (Q) of up to 4 million in high vacuum achieved by minimizing clamping loss. For applications such as for chemical sensing, strings need to vibrate at atmospheric pressure. Maximal quality factor...

  17. Increased active von Willebrand factor during disease development in the aging diabetic patient population.

    Science.gov (United States)

    Chen, Shuang Feng; Xia, Zuo Li; Han, Ji Ju; Wang, Yi Ting; Wang, Ji Yue; Pan, Shao Dong; Wu, Ya Ping; Zhang, Bin; Li, Guang Yao; Du, Jing Wei; Gao, Hen Qiang; de Groot, Philip G; de Laat, Bas; Hollestelle, Martine J

    2013-02-01

    Type 2 diabetes is known to cause endothelial activation resulting in the secretion of von Willebrand factor (VWF). We have shown that levels of VWF in a glycoprotein Ib-binding conformation are increased in specific clinical settings. The aim of the current study is to investigate whether active VWF levels increase during aging and the development of diabetes within the population of patients suffering from type 2 diabetes. Patients and controls were divided into two groups based on age: older and younger than 60 years of age. VWF antigen, VWF propeptide, VWF activation factor and total active VWF were measured. Patients older than 60 years of age had increased levels of total active VWF, VWF activation factor and VWF propeptide compared to younger patients and controls. All measured VWF parameters were associated with age in diabetic patients. Total active VWF and VWF propeptide correlated with the period of being diagnosed with diabetes. Regression analyses showed that especially the VWF activation factor was strongly associated with diabetes in patients older than 60 years of age. In conclusion, we found that the conformation of VWF could be involved in the disease process of diabetes and that the VWF in a glycoprotein Ib-binding conformation could play a role as risk marker during the development of diabetes in combination with an increase in age. Our study shows that the active quality of VWF was more important than the quantity.

  18. The structure of the TFIIH p34 subunit reveals a von Willebrand factor A like fold.

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    Dominik R Schmitt

    Full Text Available RNA polymerase II dependent transcription and nucleotide excision repair are mediated by a multifaceted interplay of subunits within the general transcription factor II H (TFIIH. A better understanding of the molecular structure of TFIIH is the key to unravel the mechanism of action of this versatile protein complex within these vital cellular processes. The importance of this complex becomes further evident in the context of severe diseases like xeroderma pigmentosum, Cockayne's syndrome and trichothiodystrophy, that arise from single point mutations in TFIIH subunits. Here we describe the structure of the p34 subunit of the TFIIH complex from the eukaryotic thermophilic fungus Chaetomium thermophilum. The structure revealed that p34 contains a von Willebrand Factor A (vWA like domain, a fold which is generally known to be involved in protein-protein interactions. Within TFIIH p34 strongly interacts with p44, a positive regulator of the helicase XPD. Putative protein-protein interfaces are analyzed and possible binding sites for the p34-p44 interaction suggested.

  19. PROTEOLYTIC PROCESSING OF VON WILLEBRAND FACTOR BY ADAMTS13 AND LEUKOCYTE PROTEASES

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    Stefano Lancellotti

    2013-09-01

    Full Text Available ADAMTS13 is a 190 kDa zinc protease encoded by a gene located on chromosome 9q34.   This protease specifically hydrolyzes von Willebrand factor (VWF multimers, thus causing VWF size reduction. ADAMTS13 belongs to the A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS family, involved in proteolytic processing of many matrix proteins. ADAMTS13 consists of numerous domains including a metalloprotease domain, a disintegrin domain, several thrombospondin type 1 (TSP1 repeats, a cysteine-rich domain, a spacer domain and 2 CUB (Complement c1r/c1s, sea Urchin epidermal growth factor, and Bone morphogenetic protein domains. ADAMTS13 cleaves a single peptide bond (Tyr1605-Met1606 in the central A2 domain of the VWF molecule. This proteolytic cleavage is essential to reduce the size of ultra-large VWF polymers, which, when exposed to high shear stress in the microcirculation, are prone to form with platelets clumps, which cause severe syndromes called thrombotic microangiopathies (TMAs. In this review, we a discuss the current knowledge of structure-function aspects of ADAMTS13 and its involvement in the pathogenesis of TMAs, b address the recent findings concerning proteolytic processing of VWF multimers by different proteases, such as the leukocyte-derived serine and metallo-proteases and c indicate the direction of future investigations

  20. Taq I polymorphism in the 5' region of the von Willebrand Factor (vWF) gene

    Energy Technology Data Exchange (ETDEWEB)

    Lavergne, J M; Bahnak, B R; Assouline, Z; Pietu, G; Kerbiriou-Nabias, D; Meulien, P; Pavirani, A; Meyer, D

    1988-03-25

    pvWFIPC8 is a 2.28 Kb partial cDNA clone for human von Willebrand factor (vWF) isolated from a human lung cDNA library and inserted into the EcoRI site of pUC9. The sequence includes the last 1330 nucleotides that encode for vWF propeptide and 950 nucleotides that encode for mature vWF. Taq I (TCGA) identifies plural invariant bands and two variant bands with alleles at 2.3 (Al) and 1.0 (A2). The frequency was determined in 33 unrelated European and North American caucasians. The extreme 3' region of pvWFIPC8 corresponds to the 5' boundary of an area that could possibly hybridize with similar sequences on human chromosome 22. The 5' 1.74 Kb portion of pvWFIPC8 generated by Bam HI digestion that corresponds to sequences only on chromosome 12 also demonstrates the polymorphism. Co-dominant segregation was demonstrated in 6 families of 48 individuals.

  1. Von Willebrand Factor as a Novel Player in Valvular Heart Disease: From Bench to Valve Replacement.

    Science.gov (United States)

    Gragnano, Felice; Crisci, Mario; Bigazzi, Maurizio Cappelli; Bianchi, Renatomaria; Sperlongano, Simona; Natale, Francesco; Fimiani, Fabio; Concilio, Claudia; Cesaro, Arturo; Pariggiano, Ivana; Diana, Vincenzo; Limongelli, Giuseppe; Cirillo, Plinio; Russo, Mariagiovanna; Golia, Enrica; Calabrò, Paolo

    2018-02-01

    von Willebrand Factor (vWF) is a well-known mediator of hemostasis and vascular inflammation. Its dynamic modulation in the bloodstream, according to hemodynamic conditions, makes it an appealing biomarker in patients with valvular heart disease (VHD). Recent studies highlight the close connection between vWF and VHD, with possible implications in the pathogenesis of VHD, promoting valve aging and calcification or favoring the development of infective endocarditis. Moreover, vWF has been recently proposed as a new diagnostic and prognostic tool in patients with valve stenosis or regurgitation, showing a strict correlation with severity of valve disease, outcome, and bleeding (Heyde syndrome). A novel role for vWF is also emerging in patients undergoing percutaneous or surgical valve repair/replacement to select and stratify patients, evaluate periprocedural bleeding risk, and detect procedural complications. We also report our single-center experience, suggesting, for the first time, possible clinical implications for vWF in percutaneous mitral valve repair (MitraClip). This review summarizes recent advances in the role of vWF in VHD with an updated overview going from bench to operating room.

  2. Pattern of von Willebrand factor in hypertensive patients in Lagos, Nigeria

    Directory of Open Access Journals (Sweden)

    Ann Abiola Ogbenna

    2018-01-01

    Full Text Available Background and Objective: Hypertension alone accounts for 50% of death from stroke. Its ability to induce endothelial dysfunction leads to the release of von Willebrand factor (vWF, a prothrombotic glycoprotein. The increase secretion of vWF may account for increased risk of stroke in hypertensive disorders. This study aimed to determine the vWF:antigen (Ag levels among hypertensives and assess its relationship with blood pressure and occurrence of stroke in hypertensives. Subjects and Methods: The study included 66 hypertensives, 33 with stroke (HS and 33 without stroke (HWS, and 33 controls matched for age and sex. Structured questionnaires were used to obtain biodata and clinical information. Blood pressure was taken after 15 min rest. Four milliliters of blood was collected into 0.1 ml of 3.2% trisodium citrate for vWF:Ag assay and 4 ml into K-ethylenediaminetetraacetic acid anticoagulant bottles for blood grouping and erythrocyte sedimentation rate. Data were analyzed with SPSS version 21. Confidence interval was set at 95%. Results: Mean vWF:Ag levels were significantly higher in hypertensives compared with nonhypertensives (P = 0.005, but no statistically significant difference was observed between HS and HWS (P = 0.874. A positive correlation of vWF with systolic blood pressure was observed (r = 0.335, P = 0.001. Conclusion: Our study suggests that higher systolic blood pressure is associated with higher levels of endothelial activation and release of vWF.

  3. Thrombomodulin and von Willebrand factor as markers of radiation-induced endothelial injury

    International Nuclear Information System (INIS)

    Zhou Quansheng; Zhao Yimin; Li Peixia; Bai Xia; Ruan Changgeng

    1992-02-01

    Cultured confluent human umbilical vein endothelial cells were irradiated in vitro by 60 Co-gamma ray at doses from 0 to 50 Gy. After irradiation Thrombomodulin in the supernatants of endothelial cell culture medium, on the surface of the cells and within the cells was measured at different times over six days. At twenty-four hours after irradiation, an increase in the release of Thrombomodulin and von Willebrand factor from irradiated endothelial cells and an increase in the number of molecules and the activity of Thrombomodulin on the surface of the cells were observed, which were radiation-dose dependent. The capacity of the cells to produce and release Thrombomodulin was decreased from two to six days after exposure to 60 Co-gamma ray. Our data indicate that radiation can injure endothelial cells and that Thrombomodulin may be as a marker of radiation-induced endothelial cell injury. The relationship between dysfunction of irradiated endothelial cells and the pathological mechanisms of acute radiation sickness are discussed

  4. Neuropeptide delivery to the brain: a von Willebrand factor signal peptide to direct neuropeptide secretion

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    de Backer Marijke WA

    2010-08-01

    Full Text Available Abstract Background Multiple neuropeptides, sometimes with opposing functions, can be produced from one precursor gene. To study the roles of the different neuropeptides encoded by one large precursor we developed a method to overexpress minigenes and establish local secretion. Results We fused the signal peptide from the Von Willebrand Factor (VWF to a furin site followed by a processed form of the Agouti related protein (AgRP, AgRP83-132 or α-melanocyte stimulating hormone. In vitro, these minigenes were secreted and biologically active. Additionally, the proteins of the minigenes were not transported into projections of primary neurons, thereby ensuring local release. In vivo administration of VWF-AgRP83-132 , using an adeno-associated viral vector as a delivery vehicle, into the paraventricular hypothalamus increased body weight and food intake of these rats compared to rats which received a control vector. Conclusions This study demonstrated that removal of the N-terminal part of full length AgRP and addition of a VWF signal peptide is a successful strategy to deliver neuropeptide minigenes to the brain and establish local neuropeptide secretion.

  5. Detection of von Willebrand factor and tissue factor in platelets-fibrin rich coronary thrombi in acute myocardial infarction.

    Science.gov (United States)

    Yamashita, Atsushi; Sumi, Takahiro; Goto, Shinya; Hoshiba, Yasunari; Nishihira, Kensaku; Kawamoto, Riichirou; Hatakeyama, Kinta; Date, Haruhiko; Imamura, Takuroh; Ogawa, Hisao; Asada, Yujiro

    2006-01-01

    The rapid closure of coronary arteries due to occlusive thrombi is the major cause of acute myocardial infarction. However, the mechanisms of coronary thrombus formation have not been elucidated. We immunohistochemically assessed the localizations and their changes over time of glycoprotein IIb/IIIa, fibrin, von Willebrand factor (vWF), and tissue factor (TF), after the onset of chest pain (platelets, fibrin, vWF, and TF from the early phase of onset, and glycoprotein IIb/IIIa and fibrin were closely associated with vWF and TF, respectively. vWF and/or TF may contribute to occlusive thrombus formation and be novel therapeutic candidates for treating patients with coronary thrombosis.

  6. Complex changes in von Willebrand factor-associated parameters are acquired during uncomplicated pregnancy.

    Directory of Open Access Journals (Sweden)

    Danielle N Drury-Stewart

    Full Text Available The coagulation protein von Willebrand Factor (VWF is known to be elevated in pregnancy. However, the timing and nature of changes in VWF and associated parameters throughout pregnancy are not well understood.To better understand the changes in VWF provoked by pregnancy, we studied VWF-associated parameters in samples collected over the course of healthy pregnancies.We measured VWF antigen (VWF:Ag, VWF propeptide (VWFpp, Factor VIII (FVIII, and ADAMTS13 activity in samples collected from 46 women during pregnancy and at non-pregnant baseline. We also characterized pregnant vs. non-pregnant VWF multimer structure in 21 pregnancies, and performed isoelectric focusing (IEF of VWF in two pregnancies which had samples from multiple trimesters.VWF:Ag and FVIII levels were significantly increased during pregnancy. ADAMTS13 activity was unchanged. VWFpp levels increased much later in pregnancy than VWF:Ag, resulting in a progressive decrease in VWFpp:Ag ratios. FVIII:VWF ratios also decreased in pregnancy. Most pregnancies exhibited a clear loss of larger VWF multimers and altered VWF triplet structure. Further evidence of acquired VWF qualitative changes in pregnancy was found in progressive, reversible shifts in VWF IEF patterns over gestation.These data support a new view of pregnancy in which VWF can acquire qualitative changes associated with advancing gestational age. Modeling supports a scenario in which both increased VWF production and doubling of the VWF half-life would account for the data observed. We propose that gestation induces a prolongation in VWF survival, which likely contributes to increased total VWF levels and altered VWF structure.

  7. Unconjugated Bilirubin Inhibits Proteolytic Cleavage of von Willebrand Factor by ADAMTS13 Protease

    Science.gov (United States)

    Lu, Rui-Nan; Yang, Shangbin; Wu, Haifeng M.; Zheng, X. Long

    2015-01-01

    Summary Background Bilirubin is a yellow breakdown product of heme catabolism. Increased serum levels of unconjugated bilirubin are conditions commonly seen in premature neonates and adults with acute hemolysis including thrombotic microangiopathy. Previous studies have shown that unconjugated bilirubin lowers plasma ADAMTS13 activity, but the mechanism is not fully understood. Objectives The study is to determine whether unconjugated bilirubin directly inhibits the cleavage of von Willebrand factor (VWF) and its analogs by ADAMTS13. Methods Fluorogenic, SELDI-TOF mass spectrometric assay, and Western blotting analyses were employed to address this question. Results Unconjugated bilirubin inhibits the cleavage of F485-rVWF73-H, D633-rVWF73-H, and GST-rVWF71-11K by ADAMTS13 in a concentration-dependent manner with a half-maximal inhibitory concentration (IC50) of ~13 μM, ~70 μM, and ~17 μM, respectively. Unconjugated bilirubin also dose-dependently inhibits the cleavage of multimeric VWF by ADAMTS13 under denaturing conditions. The inhibitory activity of bilirubin on the cleavage of D633-rVWF73-H and multimeric VWF, but not F485-rVWF73-H, was eliminated after incubation with bilirubin oxidase that converts bilirubin to biliverdin. Furthermore, plasma ADAMTS13 activity in patients with hyperbilirubinemia is lower prior to than after treatment with bilirubin oxidase. Conclusions unconjugated bilirubin directly inhibits ADAMTS13’s ability to cleave both peptidyl and native VWF substrates in addition to its interference with certain fluorogenic assays. Our findings may help proper interpretation of ADAMTS13 results under pathological conditions. Whether elevated serum unconjugated bilirubin has an adverse effect in vivo remains to be determined in our future study. PMID:25782102

  8. Increased metastatic potential of tumor cells in von Willebrand factor-deficient mice.

    Science.gov (United States)

    Terraube, V; Pendu, R; Baruch, D; Gebbink, M F B G; Meyer, D; Lenting, P J; Denis, C V

    2006-03-01

    The key role played by von Willebrand factor (VWF) in platelet adhesion suggests a potential implication in various pathologies, where this process is involved. In cancer metastasis development, tumor cells interact with platelets and the vessel wall to extravasate from the circulation. As a potential mediator of platelet-tumor cell interactions, VWF could influence this early step of tumor spread and therefore play a role in cancer metastasis. To investigate whether VWF is involved in metastasis development. In a first step, we characterized the interaction between murine melanoma cells B16-BL6 and VWF in vitro. In a second step, an experimental metastasis model was used to compare the formation of pulmonary metastatic foci in C57BL/6 wild-type and VWF-null mice following the injection of B16-BL6 cells or Lewis lung carcinoma cells. In vitro adhesion assays revealed that VWF is able to promote a dose-dependent adhesion of B16-BL6 cells via its Arg-Gly-Asp (RGD) sequence. In the experimental metastasis model, we found a significant increase in the number of pulmonary metastatic foci in VWF-null mice compared with the wild-type mice, a phenotype that could be corrected by restoring VWF plasma levels. We also showed that increased survival of the tumor cells in the lungs during the first 24 h in the absence of VWF was the cause of this increased metastasis. These findings suggest that VWF plays a protective role against tumor cell dissemination in vivo. Underlying mechanisms remain to be investigated.

  9. Plasmatic ADAMTS-13 metalloprotease and von Willebrand factor in children with cyanotic congenital heart disease

    Energy Technology Data Exchange (ETDEWEB)

    Soares, R.P.S. [Fundação Pró-Sangue Hemocentro de São Paulo, São Paulo, SP (Brazil); Bydlowski, S.P.; Nascimento, N.M. [Laboratório de Investigação Médica-31, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP (Brazil); Thomaz, A.M.; Bastos, E.N.M.; Lopes, A.A. [Faculdade de Medicina, Instituto do Coração, Universidade de São Paulo, São Paulo, SP (Brazil)

    2013-04-05

    Changes in plasma von Willebrand factor concentration (VWF:Ag) and ADAMTS-13 activity (the metalloprotease that cleaves VWF physiologically) have been reported in several cardiovascular disorders with prognostic implications. We therefore determined the level of these proteins in the plasma of children with cyanotic congenital heart disease (CCHD) undergoing surgical treatment. Forty-eight children were enrolled (age 0.83 to 7.58 years). Measurements were performed at baseline and 48 h after surgery. ELISA, collagen-binding assays and Western blotting were used to estimate antigenic and biological activities, and proteolysis of VWF multimers. Preoperatively, VWF:Ag and ADAMTS-13 activity were decreased (65 and 71% of normal levels considered as 113 (105-129) U/dL and 91 ± 24% respectively, P < 0.003) and correlated (r = 0.39, P = 0.0064). High molecular weight VWF multimers were not related, suggesting an interaction of VWF with cell membranes, followed by proteolytic cleavage. A low preoperative ADAMTS-13 activity, a longer activated partial thromboplastin time and the need for cardiopulmonary bypass correlated with postoperative bleeding (P < 0.05). Postoperatively, ADAMTS-13 activity increased but less extensively than VWF:Ag (respectively, 2.23 and 2.83 times baseline, P < 0.0001), resulting in an increased VWF:Ag/ADAMTS-13 activity ratio (1.20 to 1.54, respectively, pre- and postoperative median values, P = 0.0029). ADAMTS-13 consumption was further confirmed by decreased ADAMTS-13 antigenic concentration (0.91 ± 0.30 to 0.70 ± 0.25 µg/mL, P < 0.0001) and persistent proteolysis of VWF multimers. We conclude that, in pediatric CCHD, changes in circulating ADAMTS-13 suggest enzyme consumption, associated with abnormal structure and function of VWF.

  10. Multiple functions of the von Willebrand Factor A domain in matrilins: secretion, assembly, and proteolysis

    Directory of Open Access Journals (Sweden)

    Kanbe Katsuaki

    2008-06-01

    Full Text Available Abstract The von Willebrand Factor A (vWF A domain is one of the most widely distributed structural modules in cell-matrix adhesive molecules such as intergrins and extracellular matrix proteins. Mutations in the vWF A domain of matrilin-3 cause multiple epiphyseal dysplasia (MED, however the pathological mechanism remains to be determined. Previously we showed that the vWF A domain in matrilin-1 mediates formation of a filamentous matrix network through metal-ion dependent adhesion sites in the domain. Here we show two new functions of the vWF A domain in cartilage-specific matrilins (1 and 3. First, vWF A domain regulates oligomerization of matrilins. Insertion of a vWF A domain into matrilin-3 converts the formation of a mixture of matrilin-3 tetramer, trimer, and dimer into a tetramer only, while deletion of a vWF A domain from matrilin-1 converts the formation of the native matrilin-1 trimer into a mixture of trimer and dimer. Second, the vWF A domain protects matrilin-1 from proteolysis. We identified a latent proteolytic site next to the vWF A2 domain in matrilin-1, which is sensitive to the inhibitors of matrix proteases. Deletion of the abutting vWF A domain results in degradation of matrilin-1, presumably by exposing the adjacent proteolytic site. In addition, we also confirmed the vWF A domain is vital for the secretion of matrilin-3. Secretion of the mutant matrilin-3 harbouring a point mutation within the vWF A domain, as occurred in MED patients, is markedly reduced and delayed, resulting from intracellular retention of the mutant matrilin-3. Taken together, our data suggest that different mutations/deletions of the vWF A domain in matrilins may lead to distinct pathological mechanisms due to the multiple functions of the vWF A domain.

  11. Exercise-induced shear stress is associated with changes in plasma von Willebrand factor in older humans

    OpenAIRE

    Gonzales, Joaquin U.; Thistlethwaite, John R.; Thompson, Benjamin C.; Scheuermann, Barry W.

    2009-01-01

    Shear stress is the frictional force of blood against the endothelium, a stimulus for endothelial activation and the release of von Willebrand factor (vWF). This study tested the hypothesis that the increase in shear stress associated with exercise correlates with plasma vWF. Young (n = 14, 25.7 ± 5.4 y) and older (n = 13, 65.6 ± 10.7 y) individuals participated in 30 min of dynamic handgrip exercise at a moderate intensity. Brachial artery diameter and blood flow were measured using ultrasou...

  12. Fluid-phase immunoradiometric assay for the detection of qualitative abnormalities of factor VIII/von Willebrand factor in variants of von Willebrand's disease

    International Nuclear Information System (INIS)

    Girma, J.P.; Ardaillou, N.; Meyer, D.; Lavergne, J.M.; Larrieu, M.J.

    1979-01-01

    Antigenic reactivity of F.VIII/WF in variants of von Willebrand's disease (vWd) was studied with both fluid-phase and solid-phase immunoradiometric assays. Two different (rabbit and goat) 125 I-labeled specific antibodies against purified F.VIII/WF were used in both their divalent (lgG) and their monovalent (Fab fragment) forms. Dose-response curves obtained by reacting a constant amount of antibody with serial dilutions of plasmas from normal or homozygous vWd demonstrated the specificity of the test. The accuracy was significantly higher with 125 I-Fab fragments of goat anti-F.VIII/WF antiserum than intact goat lgG or rabbit lgG or Fab fragments. The significant decrease of the slope of the dose-response curves obtained with plasma from variants of vWd has been interpreted as due to the presence of abnormal F.VIII/WF molecules with decreased antigenic reactivity. A similar anomaly was found in cryosupernatant prepared from normal plasma, paralleling similarities demonstrated between variants of vWd and cryosupernatant. Results of experiments performed by reacting constant plasma dilutions from control or variants of vWd and varying concentrations of anti-F.VIII/WF Fab fragments (rabbit or goat) confirmed the decreased antigenic reactivity of variant F.VIII/WF

  13. Comparative analysis of von Willebrand factor profiles after implantation of left ventricular assist device and total artificial heart.

    Science.gov (United States)

    Reich, H J; Morgan, J; Arabia, F; Czer, L; Moriguchi, J; Ramzy, D; Esmailian, F; Lam, L; Dunhill, J; Volod, O

    2017-08-01

    Essentials Bleeding is a major source of morbidity during mechanical circulatory support. von Willebrand factor (VWF) multimer loss may contribute to bleeding. Different patterns of VWF multimer loss were seen with the two device types. This is the first report of total artificial heart associated VWF multimer loss. Background Bleeding remains a challenge during mechanical circulatory support and underlying mechanisms are incompletely understood. Functional von Willebrand factor (VWF) impairment because of loss of high-molecular-weight multimers (MWMs) produces acquired von Willebrand disease (VWD) after left ventricular assist device (LVAD). Little is known about VWF multimers with total artificial hearts (TAHs). Here, VWF profiles with LVADs and TAHs are compared using a VWD panel. Methods VWD evaluations for patients with LVAD or TAH (2013-14) were retrospectively analyzed and included: VWF activity (ristocetin cofactor, VWF:RCo), VWF antigen (VWF:Ag), ratio of VWF:RCo to VWF:Ag, and quantitative VWF multimeric analysis. Results Twelve patients with LVADs and 12 with TAHs underwent VWD evaluation. All had either normal (47.8%) or elevated (52.2%) VWF:RCo, normal (26.1%) or elevated (73.9%) VWF:Ag and 50.0% were disproportional (ratio ≤ 0.7). Multimeric analysis showed abnormal patterns in all patients with LVADs: seven with high MWM loss; five with highest MWM loss. With TAH, 10/12 patients had abnormal patterns: all with highest MWM loss. High MWM loss correlated with presence of LVAD and highest MWM loss with TAH. Increased low MWMs were detected in 22/24. Conclusion Using VWF multimeric analysis, abnormalities after LVAD or TAH were detected that would be missed with measurements of VWF level alone: loss of high MWM predominantly in LVAD, loss of highest MWM in TAH, and elevated levels of low MWM in both. This is the first study to describe TAH-associated highest MWM loss, which may contribute to bleeding. © 2017 International Society on Thrombosis and

  14. String-theoretic deformation of the Parke-Taylor factor

    Science.gov (United States)

    Mizera, Sebastian; Zhang, Guojun

    2017-09-01

    Scattering amplitudes in a range of quantum field theories can be computed using the Cachazo-He-Yuan (CHY) formalism. In theories with color ordering, the key ingredient is the so-called Parke-Taylor factor. In this paper we give a fully SL (2 ,C )-covariant definition and study the properties of a new integrand called the "string Parke-Taylor" factor. It has an α' expansion whose leading coefficient is the field-theoretic Parke-Taylor factor. Its main application is that it leads to a CHY formulation of open string tree-level amplitudes. In fact, the definition of the string Parke-Taylor factor was motivated by trying to extend the compact formula for the first α' correction found by He and Zhang, while the main ingredient in its definition is a determinant of a matrix introduced in the context of string theory by Stieberger and Taylor.

  15. Insulin resistance is accompanied by increased von Willebrand factor levels in nondiabetic women: a study of offspring of type 2 diabetic subjects compared to offspring of nondiabetic subjects

    DEFF Research Database (Denmark)

    Foss, Anne-Catherine; Vestbo, Else; Frøland, Anders

    2002-01-01

    OBJECTIVES: To examine whether levels of von Willebrand factor (vWF), fibrinogen and fibronectin are related to a parental history of type 2 diabetes and to determine possible explanatory factors for high versus low vWF and fibrinogen. DESIGN: Cross-sectional study. SUBJECTS, MAIN OUTCOME MEASURE...

  16. Relationship between ABO blood groups and von Willebrand factor, ADAMTS13 and factor VIII in patients undergoing hemodialysis.

    Science.gov (United States)

    Rios, Danyelle R A; Fernandes, Ana Paula; Figueiredo, Roberta C; Guimarães, Daniela A M; Ferreira, Cláudia N; Simões E Silva, Ana C; Carvalho, Maria G; Gomes, Karina B; Dusse, Luci Maria Sant' Ana

    2012-05-01

    Several studies have demonstrated that non-O blood groups subjects present an increased VTE risk as compared to those carrying O blood group. The aim of this study was to investigate the ABO blood groups influence on factor VIII (FVIII) activity, von Willebrand factor (VWF), and ADAMTS13 plasma levels in patients undergoing hemodialysis (HD). Patients undergoing HD (N=195) and 80 healthy subjects (control group) were eligible for this cross-sectional study. The ABO blood group phenotyping was performed by the reverse technique. FVIII activity was measured through coagulometric method, and VWF and ADAMTS13 antigens were assessed by ELISA. FVIII activity and VWF levels were significantly higher and ADAMTS13 levels was decreased in HD patients, as compared to healthy subjects (P blood groups showed a significant increase in FVIII activity (P = 0.001) and VWF levels (P blood group. However, no significant difference was observed in ADAMTS13 levels (P = 0.767). In the control group, increased in FVIII activity (P = 0.001) and VWF levels (P = 0.002) and decreased in ADAMTS13 levels (P = 0.005) were observed in subjects carrying non-O blood groups as compared to carriers of O blood group.Our data confirmed that ABO blood group is an important risk factor for increased procoagulant factors in plasma, as FVIII and VWF. Admitting the possible role of kidneys in ADAMTS13 synthesis or on its metabolism, HD patients were not able to increase ADAMTS13 levels in order to compensate the increase of VWF levels mediated by ABO blood groups. Considering that non-O blood groups constitute a risk factor for thrombosis, it is reasonable to admit that A, B and AB HD patients need a careful and continuous follow-up in order to minimize thrombotic events.

  17. Association of ABO blood groups with von Willebrand factor, factor VIII and ADAMTS-13 in patients with lung cancer.

    Science.gov (United States)

    Liu, Xia; Chen, Xiaogang; Yang, Jiezuan; Guo, Renyong

    2017-09-01

    Coagulative and fibrinolytic disorders appear to be associated with the development of lung cancer. The aim of the present study was to determine plasma levels of von Willebrand factor (VWF) and a disintegrin and metalloproteinase with a thrombospondin type 1 motif 13 (ADAMTS-13), and factor VIII (FVIII) activity, in association with O and non-O blood groups in patients with lung cancer. Plasma levels of VWF and ADAMTS-13, and FVIII activity were measured in 115 patients with lung cancer and 98 healthy subjects. Phenotyping of the ABO blood groups was also performed for the two groups. Significantly increased VWF levels and FVIII activity, as well as significantly decreased ADAMTS-13 levels, were observed in patients with distant metastasis as compared with those without distant metastasis and the healthy controls. Plasma VWF levels and FVIII activity were significantly increased in subjects with non-O type blood compared with those with type O blood in the two groups. However, a significant decrease in ADAMTS-13 levels was observed only in the control group among those with non-O type blood, compared with those with type O blood. The results of the present study indicate that increased VWF and decreased ADAMTS-13 levels facilitate the invasiveness and metastasis of lung cancer. Non-O blood groups constitute a risk factor for increased VWF and FVIII in plasma. Continued monitoring of VWF and ADAMTS-13 levels, and of FVIII activity in patients with lung cancer with distinct blood groups may help to minimize the incidence of thrombotic events and improve assessment of disease progression.

  18. An immunoradiometric assay for procoagulant factor VIII antigen: results in haemophilia, von Willebrand's disease and fetal plasma and serum

    International Nuclear Information System (INIS)

    Peake, I.R.; Bloom, A.L.; Giddings, J.C.; Ludlam, C.A.

    1979-01-01

    An immunoradiometric assay (IRMA) has been developed based on the inhibitor which arose in a polytransfused severe haemophiliac. The two-site IRMA measured antigens closely associated with the procoagulant parts of the factor VIII complex, which are termed FVIIIC antigens or FVIIICAG. FVIIICAG was present in normal plasma and also, at a slightly lower concentration, in normal serum. In 37 patients with haemophilia A, 36 had FVIIICAG levels of less than 10% of the normal plasma pool. In patients with von Willebrand's disease the levels of FVIIIC and FVIIICAG were in good agreement, both before and after treatment with cryoprecipitate or DDAVP. FVIIICAG was relatively stable in plasma at 37 0 C and could also be detected in cord and fetal serum. The assay is of potential value for detecting reduced levels of factor VIII, for carrier detection and for the prenatal diagnosis of haemophilia. (author)

  19. Von willebrand factor cleaving protease activity in the physiopathology of microangiopathic disorders Detección de la actividad de la proteasa que cliva al factor von Willebrand en la patofisiología de las microangiopatías

    Directory of Open Access Journals (Sweden)

    M. M. Amaral

    2003-04-01

    Full Text Available The von Willebrand factor cleaving protease (VWFCP modulates the von Willebrand factor (VWF multimeric size in normal plasma. VWFCP activity levels are decreased in different physiological and pathologic situations. Different techniques have been developed to unfold the purified VWF (perfusion at high shear rate, dialysis against urea in nitrocellulose filters, to detect the VWFCP activity on it (multimeric analysis of VWF, collagen binding to VWF assay and to use the patient plasma both as the source of the enzyme and substrate. In this paper we compared the above mentioned methods with new ones: normal plasma dialyzed on membranes instead of purified VWF, dialysis of the samples against urea in tubing instead of nitrocellulose filters, and sonicated plasma to remove the endogenous VWF. The perfusion assay and detection by multimeric analysis showed a limit of detection (25% of VWFCP activity. Dialysis against urea in both supports and detection by multimeric analysis, showed a better limit of detection (3%, but the recovery of the samples was not as efficient in nitrocellulose filters as it was in tubing. The detection by collagen binding to VWF has more advantages because it allows to analyze more samples than the multimeric analysis does in the same assay. The dialysis of plasma by membranes to obtain the source of exogenous VWF requires no complex equipment. The method, which uses patient plasma as the source of the enzyme and substrate, was inapplicable in our experience because the values could not be interpolated in the reference curve.La proteasa que cliva al factor von Willebrand (VWFCP controla el tamaño multimérico del factor von Willebrand (VWF en plasma normal. Sus niveles se encuentran disminuidos en diferentes situaciones fisiológicas y patológicas. Diferentes técnicas se desarrollaron para desplegar al VWF purificado (perfusión a alta fuerza de cizallamiento, diálisis contra urea en filtros de nitrocelulosa, para detectar

  20. Dogs with hearth diseases causing turbulent high-velocity blood flow have changes in patelet function and von Willebrand factor multimer distribution

    DEFF Research Database (Denmark)

    Tarnow, Inge; Kristensen, Annemarie Thuri; Olsen, Lisbeth Høier

    2005-01-01

    The purpose of this prospective study was to investigate platelet function using in vitro tests based on both high and low shear rates and von Willebrand factor (vWf) multimeric composition in dogs with cardiac disease and turbulent high-velocity blood flow. Client-owned asymptomatic, untreated d...

  1. The impact of statin therapy on plasma levels of von Willebrand factor antigen. Systematic review and meta-analysis of randomised placebo-controlled trials

    NARCIS (Netherlands)

    Sahebkar, Amirhossein; Serban, Corina; Ursoniu, Sorin; Mikhailidis, Dimitri P.; Undas, Anetta; Lip, Gregory Y. H.; Bittner, Vera; Ray, Kausik; Watts, Gerald F.; Hovingh, G. Kees; Rysz, Jacek; Kastelein, John J. P.; Banach, Maciej

    2016-01-01

    Increased plasma levels of von Willebrand factor antigen (vWF:Ag) are associated with high risk of coronary artery disease. The effect of statin therapy on vWF:Ag levels remains uncertain. Therefore the aim of this meta-analysis was to evaluate the effect of statin therapy on vWF:Ag Levels. A

  2. Binding of von Willebrand factor to collagen type III: role of specific amino acids in the collagen binding domain of vWF and effects of neighboring domains

    NARCIS (Netherlands)

    van der Plas, R. M.; Gomes, L.; Marquart, J. A.; Vink, T.; Meijers, J. C.; de Groot, P. G.; Sixma, J. J.; Huizinga, E. G.

    2000-01-01

    Binding of von Willebrand Factor (vWF) to sites of vascular injury is the first step of hemostasis. Collagen types I and III are important binding sites for vWF. We have previously determined the three-dimensional structure of the collagen binding A3 domain of vWF (Huizinga et al., Structure 1997;

  3. Von Willebrand disease protects against arterial thrombosis

    NARCIS (Netherlands)

    Sanders, Y.V.; Eikenboom, J.C.; De Wee, E.M.; Van Der Bom, J.G.; Cnossen, M.H.; Degenaar-Dujardin, M.E.; Fijnvandraat, K.; Kamphuisen, P.W.; Laros-Van Gorkum, B.A.; Meijer, K.; Mauser -Bunschoten, E.P.; Leebee k, F.W.

    Background and Aims: Von Willebrand disease (VWD) is caused by reduced levels of or dysfunctional von Willebrand factor (VWF) and is characterized by a bleeding tendency. It is well known that individuals with high VWF levels have a higher risk for arterial thrombosis. Although it has never been

  4. Storage of factor VIII variants with impaired von Willebrand factor binding in Weibel-Palade bodies in endothelial cells.

    Directory of Open Access Journals (Sweden)

    Maartje van den Biggelaar

    Full Text Available BACKGROUND: Point mutations resulting in reduced factor VIII (FVIII binding to von Willebrand factor (VWF are an important cause of mild/moderate hemophilia A. Treatment includes desmopressin infusion, which concomitantly increases VWF and FVIII plasma levels, apparently from storage pools containing both proteins. The source of these VWF/FVIII co-storage pools and the mechanism of granule biogenesis are not fully understood. METHODOLOGY/PRINCIPAL FINDINGS: We studied intracellular trafficking of FVIII variants implicated in mild/moderate hemophilia A together with VWF in HEK293 cells and primary endothelial cells. The role of VWF binding was addressed using FVIII variants displaying reduced VWF interaction. Binding studies using purified FVIII proteins revealed moderate (Arg2150His, Del2201, Pro2300Ser to severe (Tyr1680Phe, Ser2119Tyr VWF binding defects. Expression studies in HEK293 cells and primary endothelial cells revealed that all FVIII variants were present within VWF-containing organelles. Quantitative studies showed that the relative amount of FVIII storage was independent of various mutations. Substantial amounts of FVIII variants are co-stored in VWF-containing storage organelles, presumably by virtue of their ability to interact with VWF at low pH. CONCLUSIONS: Our data suggest that the potential of FVIII co-storage with VWF is not affected in mild/moderate hemophilia A caused by reduced FVIII/VWF interaction in the circulation. These data support the hypothesis that Weibel-Palade bodies comprise the desmopressin-releasable FVIII storage pool in vivo.

  5. Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise.

    Science.gov (United States)

    van Loon, Janine E; Sonneveld, Michelle A H; Praet, Stephan F E; de Maat, Moniek P M; Leebeek, Frank W G

    2014-01-01

    Physical stress triggers the endothelium to release von Willebrand Factor (VWF) from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the main mediators of the VWF increase by exhaustive physical exercise. 105 healthy individuals (18-35 years) were included in this study. Each participant performed an incremental exhaustive exercise test on a cycle ergometer. Respiratory gas exchange measurements were obtained while cardiac function was continuously monitored. Blood was collected at baseline and directly after exhaustion. VWF antigen (VWF:Ag) levels, VWF collagen binding (VWF:CB) levels, ADAMTS13 activity and common variations in Syntaxin Binding Protein-5 (STXBP5, rs1039084 and rs9399599), Syntaxin-2 (STX2, rs7978987) and VWF (promoter, rs7965413) were determined. The median VWF:Ag level at baseline was 0.94 IU/mL [IQR 0.8-1.1] and increased with 47% [IQR 25-73] after exhaustive exercise to a median maximum VWF:Ag of 1.38 IU/mL [IQR 1.1-1.8] (pexercise (median increase 43% and 12%, both pexercise (females 1.2 IU/mL; males 1.7 IU/mL, p = 0.001), which was associated by a difference in performance. Genetic variations in STXBP5, STX2 and the VWF promoter were not associated with VWF:Ag levels at baseline nor with the VWF:Ag increase. VWF:Ag levels strongly increase upon exhaustive exercise and this increase is strongly determined by physical fitness level and the intensity of the exercise, while there is no clear effect of genetic variation in STXBP5, STX2 and the VWF promoter.

  6. Testosterone and acute stress are associated with fibrinogen and von Willebrand factor in African men: the SABPA study.

    Science.gov (United States)

    Malan, Nicolaas T; von Känel, Roland; Schutte, Alta E; Huisman, Hugo W; Schutte, Rudolph; Smith, Wayne; Mels, Carina M; Kruger, Ruan; Meiring, Muriel; van Rooyen, Johannes M; Malan, Leoné

    2013-10-12

    Low testosterone, acute and chronic stress and hypercoagulation are all associated with hypertension and hypertension-related diseases. The interaction between these factors and future risk for coronary artery disease in Africans has not been fully elucidated. In this study, associations of testosterone, acute cardiovascular and coagulation stress responses with fibrinogen and von Willebrand factor in African and Caucasian men in a South African cohort were investigated. Cardiovascular variables were studied by means of beat-to-beat and ambulatory blood pressure monitoring. Fasting serum-, salivary testosterone and citrate coagulation markers were obtained from venous blood samples. Acute mental stress responses were evoked with the Stroop test. The African group demonstrated a higher cardiovascular risk compared to Caucasian men with elevated blood pressure, low-grade inflammation, chronic hyperglycemia (HbA1c), lower testosterone levels, and elevated von Willebrand factor (VWF) and fibrinogen levels. Blunted testosterone acute mental stress responses were demonstrated in African males. In multiple regression analyses, higher circulating levels of fibrinogen and VWF in Africans were associated with a low T environment (R(2) 0.24-0.28; p≤0.01), but only circulating fibrinogen in Caucasians. Regarding endothelial function, a low testosterone environment and a profile of augmented α-adrenergic acute mental stress responses (diastolic BP, D-dimer and testosterone) were associated with circulating VWF levels in Africans (Adj R(2) 0.24; pstress, salivary testosterone, D-dimer and vascular responses existed in African males in their association with circulating VWF but no interdependence of the independent variables occurred with fibrinogen levels. © 2013.

  7. Factor VIII and von Willebrand factor co-delivery by endothelial cells

    NARCIS (Netherlands)

    Bouwens, E.A.M.|info:eu-repo/dai/nl/314061894

    2011-01-01

    A defect in coagulation factor VIII (FVIII) results in the inherited bleeding disorder hemophilia A. Current treatment of hemophilia A is hampered by the need of frequent administration of costly FVIII products. Therefore gene therapy is an attractive alternative for protein replacement to treat

  8. Establishment and characterization of a new and stable collagen-binding assay for the assessment of von Willebrand factor activity

    Science.gov (United States)

    Ni, Y; Nesrallah, J; Agnew, M; Geske, F J; Favaloro, E J

    2013-01-01

    Introduction Laboratory diagnosis of von Willebrand disease (VWD) requires determination of both von Willebrand factor (VWF) protein levels and activity. Current VWF activity tests include the ristocetin cofactor assay and the collagen-binding assay (VWF:CB). The goal of this investigation is to characterize a new collagen-binding assay and to determine its effectiveness in identifying VWD. Methods Analytical studies were carried out to characterize the performance of a new VWF:CB ELISA. Additionally, samples from a normal population were tested as were well-characterized type 1 and type 2 VWD samples. Results Repeatability and within-laboratory precision studies resulted in coefficients of variation (CVs) of ≤11%. A linear range of 1–354% (0.01–3.54 IU/mL) was determined, along with a limit of detection and a lower limit of quantitation of 1.6% and 4.0% (0.016 and 0.04 IU/mL), respectively. Samples tested from apparently healthy individuals resulted in a normal range of 54–217% (0.54–2.17 IU/mL). Known VWD type 1 and type 2 samples were also analyzed by the ELISA, with 99% of samples having VWF:CB below the normal reference range and an estimated 96% sensitivity and 87% specificity using a VWF collagen-binding/antigen cutoff ratio of 0.50. Conclusion This new VWF:CB ELISA provides an accurate measure of collagen-binding activity that aids in the diagnosis and differentiation of type 1 from type 2 VWD. PMID:23107512

  9. Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise.

    Directory of Open Access Journals (Sweden)

    Janine E van Loon

    Full Text Available Physical stress triggers the endothelium to release von Willebrand Factor (VWF from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the main mediators of the VWF increase by exhaustive physical exercise.105 healthy individuals (18-35 years were included in this study. Each participant performed an incremental exhaustive exercise test on a cycle ergometer. Respiratory gas exchange measurements were obtained while cardiac function was continuously monitored. Blood was collected at baseline and directly after exhaustion. VWF antigen (VWF:Ag levels, VWF collagen binding (VWF:CB levels, ADAMTS13 activity and common variations in Syntaxin Binding Protein-5 (STXBP5, rs1039084 and rs9399599, Syntaxin-2 (STX2, rs7978987 and VWF (promoter, rs7965413 were determined.The median VWF:Ag level at baseline was 0.94 IU/mL [IQR 0.8-1.1] and increased with 47% [IQR 25-73] after exhaustive exercise to a median maximum VWF:Ag of 1.38 IU/mL [IQR 1.1-1.8] (p<0.0001. VWF:CB levels and ADAMTS13 activity both also increased after exhaustive exercise (median increase 43% and 12%, both p<0.0001. The strongest determinants of the VWF:Ag level increase are performance related (p<0.0001. We observed a gender difference in VWF:Ag response to exercise (females 1.2 IU/mL; males 1.7 IU/mL, p = 0.001, which was associated by a difference in performance. Genetic variations in STXBP5, STX2 and the VWF promoter were not associated with VWF:Ag levels at baseline nor with the VWF:Ag increase.VWF:Ag levels strongly increase upon exhaustive exercise and this increase is strongly determined by physical fitness level and the intensity of the exercise, while there is no clear effect of genetic variation in STXBP5, STX2 and the VWF promoter.

  10. The thrombospondin-1 N700S polymorphism is associated with early myocardial infarction without altering von Willebrand factor multimer size.

    Science.gov (United States)

    Zwicker, Jeffrey I; Peyvandi, Flora; Palla, Roberta; Lombardi, Rossana; Canciani, Maria Teresa; Cairo, Andrea; Ardissino, Diego; Bernardinelli, Luisa; Bauer, Kenneth A; Lawler, Jack; Mannucci, Pier

    2006-08-15

    The N700S polymorphism of thrombospondin-1 (TSP-1) has been identified as a potential genetic risk factor for myocardial infarction (MI). In a large case-control study of 1425 individuals who survived a myocardial infarction prior to age 45, the N700S polymorphism was a significant risk factor for myocardial infarction in both homozygous (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.1-3.3, P = .01) and heterozygous carriers of the S700 allele (OR 1.4, 95% CI 1.1-3.3, P = .01). TSP-1 has been shown to reduce von Willebrand factor (VWF) multimer size, and the domain responsible for VWF-reducing activity has been localized to the calcium-binding C-terminal sequence. As the N700S polymorphism was previously shown to alter the function of this domain, we investigated whether the altered VWF-reducing activity of TSP-1 underlies the observed prothrombotic phenotype. The TSP1 N700S polymorphism did not influence VWF multimer size in patients homozygous for either allele nor was there a significant reduction of VWF multimer size following incubation with recombinant N700S fragments or platelet-derived TSP-1.

  11. Elevated Factor VIII and von Willebrand Factor Levels Predict Unfavorable Outcome in Stroke Patients Treated with Intravenous Thrombolysis

    Directory of Open Access Journals (Sweden)

    Noémi Klára Tóth

    2018-01-01

    Full Text Available IntroductionPlasma factor VIII (FVIII and von Willebrand factor (VWF levels have been associated with the rate and severity of arterial thrombus formation and have been linked to outcomes following thrombolytic therapy in acute myocardial infarction patients. Here, we aimed to investigate FVIII and VWF levels during the course of thrombolysis in acute ischemic stroke (AIS patients and to find out whether they predict long-term outcomes.Materials and methodsStudy population included 131 consecutive AIS patients (median age: 69 years, 60.3% men who underwent i.v. thrombolysis with recombinant tissue plasminogen activator (rt-PA. Blood samples were taken on admission, 1 and 24 h after rt-PA administration to measure FVIII activity and VWF antigen levels. Neurological deficit of patients was determined according to the National Institutes of Health Stroke Scale (NIHSS. ASPECT scores were assessed using computer tomography images taken before and 24 h after thrombolysis. Intracranial hemorrhage was classified according to the European Cooperative Acute Stroke Study (ECASS II criteria. Long-term functional outcome was determined at 90 days after the event by the modified Rankin scale (mRS.ResultsVWF levels on admission were significantly elevated in case of more severe AIS [median and IQR values: NIHSS <6:189.6% (151.9–233.2%; NIHSS 6–16: 199.6% (176.4–250.8%; NIHSS >16: 247.8% (199.9–353.8%, p = 0.013]; similar, but non-significant trend was observed for FVIII levels. FVIII and VWF levels correlated well on admission (r = 0.748, p < 0.001 but no significant correlation was found immediately after thrombolysis (r = 0.093, p = 0.299, most probably due to plasmin-mediated FVIII degradation. VWF levels at all investigated occasions and FVIII activity before and 24 h after thrombolysis were associated with worse 24 h post-lysis ASPECT scores. In a binary backward logistic regression analysis including age, gender

  12. Analysis of von Willebrand factor A domain-related protein (WARP polymorphism in temperate and tropical Plasmodium vivax field isolates

    Directory of Open Access Journals (Sweden)

    Zakeri Sedigheh

    2009-06-01

    Full Text Available Abstract Background The identification of key molecules is crucial for designing transmission-blocking vaccines (TBVs, among those ookinete micronemal proteins are candidate as a general class of malaria transmission-blocking targets. Here, the sequence analysis of an extra-cellular malaria protein expressed in ookinetes, named von Willebrand factor A domain-related protein (WARP, is reported in 91 Plasmodium vivax isolates circulating in different regions of Iran. Methods Clinical isolates were collected from north temperate and southern tropical regions in Iran. Primers have been designed based on P. vivax sequence (ctg_6991 which amplified a fragment of about 1044 bp with no size variation. Direct sequencing of PCR products was used to determine polymorphism and further bioinformatics analysis in P. vivax sexual stage antigen, pvwarp. Results Amplified pvwarp gene showed 886 bp in size, with no intron. BLAST analysis showed a similarity of 98–100% to P. vivax Sal-I strain; however, Iranian isolates had 2 bp mismatches in 247 and 531 positions that were non-synonymous substitution [T (ACT to A (GCT and R (AGA to S (AGT] in comparison with the Sal-I sequence. Conclusion This study presents the first large-scale survey on pvwarp polymorphism in the world, which provides baseline data for developing WARP-based TBV against both temperate and tropical P. vivax isolates.

  13. Molecular cloning of the human gene for von Willebrand factor and identification of the transcription initiation site

    International Nuclear Information System (INIS)

    Collins, C.J.; Underdahl, J.P.; Levene, R.B.; Ravera, C.P.; Morin, M.J.; Dombalagian, M.J.; Ricca, G.; Livingston, D.M.; Lynch, D.C.

    1987-01-01

    A series of overlapping cosmid genomic clones have been isolated that contain the entire coding unit of the human gene for van Willebrand factor (vWf), a major component of the hemostatic system. The cloned segments span ≅ 175 kilobases of human DNA sequence, and hybridization analysis suggest that the vWf coding unit is ≅150 kilobases in length. Within one of these clones, the vWF transcription initiation site has been mapped and a portion of the vWf promoter region has been sequenced, revealing a typical TATA box, a downstream CCAAT box, and a perfect downstream repeat of the 8 base pairs containing the transcription start site. Sequencing of a segment of another genomic clone has revealed the vWF translation termination codon. Where tested, comparative restriction analysis of cloned and chromosomal DNA segments strongly suggests that no major alterations occurred during cloning and that there is only one complete copy of the vWf gene in the human haploid genome. Similar analyses of DNA from vWf-producing endothelial cells and nonexpressing leukocytes suggest that vWf gene expression is not accompanied by gross genomic rearrangements. In addition, there is significant homology of C-terminal coding sequences among the vWf genes of several vertebrate species

  14. Exercise-induced shear stress is associated with changes in plasma von Willebrand factor in older humans.

    Science.gov (United States)

    Gonzales, Joaquin U; Thistlethwaite, John R; Thompson, Benjamin C; Scheuermann, Barry W

    2009-07-01

    Shear stress is the frictional force of blood against the endothelium, a stimulus for endothelial activation and the release of von Willebrand factor (vWF). This study tested the hypothesis that the increase in shear stress associated with exercise correlates with plasma vWF. Young (n = 14, 25.7 +/- 5.4 years) and older (n = 13, 65.6 +/- 10.7 years) individuals participated in 30 min of dynamic handgrip exercise at a moderate intensity. Brachial artery diameter and blood flow were measured using ultrasound Doppler and blood samples were collected before, immediately after, and following 30 min of recovery from exercise with plasma levels of vWF. Plasma levels of vWF increased (P exercise. The change in plasma vWF was linearly correlated with the increase in shear stress during exercise in older individuals (post-exercise: r = 0.78, 30 min recovery: r = 0.77, P < 0.01), but no association was found in the young individuals. These changes in plasma levels of vWF in humans suggest that aging influences endothelial activation and hemostasis.

  15. Space and Time Resolved Detection of Platelet Activation and von Willebrand Factor Conformational Changes in Deep Suspensions.

    Science.gov (United States)

    Biasetti, Jacopo; Sampath, Kaushik; Cortez, Angel; Azhir, Alaleh; Gilad, Assaf A; Kickler, Thomas S; Obser, Tobias; Ruggeri, Zaverio M; Katz, Joseph

    2017-01-01

    Tracking cells and proteins' phenotypic changes in deep suspensions is critical for the direct imaging of blood-related phenomena in in vitro replica of cardiovascular systems and blood-handling devices. This paper introduces fluorescence imaging techniques for space and time resolved detection of platelet activation, von Willebrand factor (VWF) conformational changes, and VWF-platelet interaction in deep suspensions. Labeled VWF, platelets, and VWF-platelet strands are suspended in deep cuvettes, illuminated, and imaged with a high-sensitivity EM-CCD camera, allowing detection using an exposure time of 1 ms. In-house postprocessing algorithms identify and track the moving signals. Recombinant VWF-eGFP (rVWF-eGFP) and VWF labeled with an FITC-conjugated polyclonal antibody are employed. Anti-P-Selectin FITC-conjugated antibodies and the calcium-sensitive probe Indo-1 are used to detect activated platelets. A positive correlation between the mean number of platelets detected per image and the percentage of activated platelets determined through flow cytometry is obtained, validating the technique. An increase in the number of rVWF-eGFP signals upon exposure to shear stress demonstrates the technique's ability to detect breakup of self-aggregates. VWF globular and unfolded conformations and self-aggregation are also observed. The ability to track the size and shape of VWF-platelet strands in space and time provides means to detect pro- and antithrombotic processes.

  16. von Willebrand factor as a novel noninvasive predictor of portal hypertension and esophageal varices in hepatitis B patients with cirrhosis.

    Science.gov (United States)

    Wu, Hao; Yan, Shiping; Wang, Guangchuan; Cui, Shaobo; Zhang, Chunqing; Zhu, Qiang

    2015-01-01

    At present, there is no perfect noninvasive method to assess portal hypertension and esophageal varices. Early predicting esophageal varices can provide evidence for managing cirrhotic patients. We aimed to further investigate von Willebrand factor (vWF) as a noninvasive predictor of portal hypertension, especially of esophageal varices. A total of 60 hepatitis B patients with cirrhosis and 45 healthy subjects were enrolled in this study. Levels of six markers were examined. All patients underwent hepatic venous pressure gradient (HVPG) and esophagogastroduodenoscopy. We evaluated the performance of six factors for diagnosis of portal hypertension and esophageal varices. The vWF levels in liver tissues were observed by immunohistochemistry. Correlations between the level of vWF in liver tissues and HVPG and between levels of vWF in tissues and plasma were examined. Cutoff values of plasma vWF (1510.5 mU/mL and 1701 mU/mL) showed high positive predictive value (PPV, 90.2% and 87.5%) in predicting clinically significant portal hypertension and severe portal hypertension. Cutoff values of vWF (1414 mU/ml and 1990 mU/mL, PPV 90.3% and 86.3%, respectively) were provided to detect the presence and degree of esophageal varices. Linear correlations were observed between levels of vWF in liver tissues and HVPG (r(2) = 0.552, p portal hypertension and esophageal varices in hepatitis B patients with cirrhosis. Increased levels of vWF in liver tissues may induce the elevated plasma vWF levels, but molecular mechanism is needed for further study.

  17. Von Willebrand factor indicates bacterial translocation, inflammation, and procoagulant imbalance and predicts complications independently of portal hypertension severity.

    Science.gov (United States)

    Mandorfer, M; Schwabl, P; Paternostro, R; Pomej, K; Bauer, D; Thaler, J; Ay, C; Quehenberger, P; Fritzer-Szekeres, M; Peck-Radosavljevic, M; Trauner, M; Reiberger, T; Ferlitsch, A

    2018-04-01

    Elevated plasma von Willebrand factor antigen (vWF) has been shown to indicate the presence of clinically significant portal hypertension, and thus, predicts the development of clinical events in patients with cirrhosis. To investigate the impact of bacterial translocation and inflammation on vWF, as well as the association between vWF and procoagulant imbalance. Moreover, we assessed whether vWF predicts complications of cirrhosis, independent of the severity of portal hypertension. Our study population comprised 225 patients with hepatic venous pressure gradient (HVPG) ≥ 10 mm Hg without active bacterial infections or hepatocellular carcinoma. vWF correlated with markers of bacterial translocation (lipopolysaccharide-binding protein [LBP; ρ = 0.201; P = 0.021]), inflammation (interleukin 6 [IL-6; ρ = 0.426; P protein [CRP; ρ = 0.249; P protein C ratio; ρ = 0.507; P model for transplant-free mortality. Finally, the independent prognostic value of vWF/CRP groups for mortality was confirmed by competing risk analysis. Our results demonstrate that vWF is not only a marker of portal hypertension but also independently linked to bacterial translocation, inflammation and procoagulant imbalance, which might explain its HVPG-independent association with most clinical events. Prognostic groups based on vWF/CRP efficiently discriminate between patients with a poor 5-year survival and patients with a favourable prognosis. © 2018 John Wiley & Sons Ltd.

  18. A pilot study of homocyst(e)ine levels in essential hypertension: relationship to von Willebrand factor, an index of endothelial damage.

    Science.gov (United States)

    Lip, G Y; Edmunds, E; Martin, S C; Jones, A F; Blann, A D; Beevers, D G

    2001-07-01

    An interaction between homocyst(e)ine and the endothelium in hypertensive patients may promote thrombogenesis and atherogenesis, leading to adverse cardiovascular events. We hypothesized that homocyst(e)ine levels are abnormal in patients with essential hypertension, and that this may be related to an adverse effect on the vascular endothelium. Accordingly, we compared plasma levels of homocyst(e)ine and von Willebrand factor (marking endothelial damage) in 83 patients (43 men; mean age 54 +/- standard deviation 15.9 years) with essential hypertension (> 160/90 mm Hg), with levels in 25 healthy normotensive controls (13 men; mean age 56+/-11.8 years). Baseline levels of the markers and other clinical indices were then related to adverse cardiovascular events at follow-up. Plasma homocyst(e)ine (P = .0001) and von Willebrand factor (P = .031) levels were significantly higher in hypertensives compared to controls. After a mean follow-up of 76 patients for 45 months (range, 1 to 66 months), 17 subjects experienced an end point of either cardiovascular death (n = 10) or adverse cardiovascular event (n = 7). Comparing these 17 with the 59 free of an end point, the former were older (P = .0002) and had a longer duration of known hypertension (P = .018). There was a nonsignificant trend toward higher median plasma homocyst(e)ine levels in the patients sustaining a vascular end point (P = .07). In this pilot study, we suggest that essential hypertension may be associated with increased plasma homocyst(e)ine levels, but that this amino acid is unrelated to endothelial damage (von Willebrand factor), clinical indices, or prognosis.

  19. Elevated levels of plasma von Willebrand factor and the risk of macro- and microvascular disease in type 2 diabetic patients with microalbuminuria

    DEFF Research Database (Denmark)

    Gaede, P; Vedel, P; Parving, H H

    2001-01-01

    BACKGROUND: The purpose of this study was to examine the concept suggesting that microalbuminuria in combination with high levels of plasma von Willebrand factor is a stronger predictor for cardiovascular disease and microvascular complications than microalbuminuria alone in type 2 diabetic...... patients. METHODS: One hundred and sixty patients with type 2 diabetes mellitus and persistent microalbuminuria were followed for an average of 3.8 (SD 0.3) years. 70% of the patients were treated with angiotensin converting enzyme (ACE)-inhibitors. Patients in this subanalysis were divided into two groups...... nephropathy or progression in diabetic retinopathy than microalbuminuria alone in patients with type 2 diabetes and persistent microalbuminuria....

  20. Associations Between Diabetic Retinopathy and Plasma Levels of High-sensitive C-reactive Protein or Von Willebrand Factor in Long-term Type 1 Diabetic Patients

    DEFF Research Database (Denmark)

    Laursen, Jonas Vejvad Nørskov; Hoffmann, Stine Skovbo; Green, Anders

    2013-01-01

    .27 IU/ml (0.79-2.07 IU/ml), respectively. No or minimal DR (ETDRS-levels 10-20) was found in 16.4%, mild DR (ETDRS-level 35) in 19.4%, moderate DR (ETDRS-levels 43-47) in 11.0%, and 53.2% had proliferative diabetic retinopathy (PDR) corresponding to ETDRS-level 60 or more. In an age- and sex......Purpose: To evaluate high-sensitive C-reactive protein (hs-CRP) and von Willebrand factor as possible plasma markers of diabetic retinopathy in a population-based cohort of type 1 diabetic patients. Materials and Methods: This was a cross-sectional study of 201 type 1 diabetic patients from...... a population-based cohort from Fyn County, Denmark. Plasma levels of hs-CRP and von Willebrand factor antigen were measured and related to the level of diabetic retinopathy (DR) as evaluated by dilated nine-field 45 degree monoscopic fundus photos captured by Topcon TRC-NWS6 and graded according to the Early...

  1. von Willebrand Factor Test

    Science.gov (United States)

    ... with infections, inflammation, trauma, and with physical and emotional stressors. They are also increased with pregnancy and with the use of estrogen medications such as oral contraceptives. Is there anything else I should know? A ...

  2. Influences of ABO blood group, age and gender on plasma coagulation factor VIII, fibrinogen, von Willebrand factor and ADAMTS13 levels in a Chinese population.

    Science.gov (United States)

    Wang, Zongkui; Dou, Miaomiao; Du, Xi; Ma, Li; Sun, Pan; Cao, Haijun; Ye, Shengliang; Jiang, Peng; Liu, Fengjuan; Lin, Fangzhao; Zhang, Rong; Li, Changqing

    2017-01-01

    ABO blood group is a hereditary factor of plasma levels of coagulation factor VIII (FVIII) and von Willebrand factor (VWF). Age and gender have been shown to influence FVIII, VWF, fibrinogen (Fbg), and ADAMTS13 (A disintegrin and metalloprotease with thrombospondin type 1 motif, 13). We investigated the effects of ABO type, age, and gender on plasma levels of FVIII, Fbg, VWF, and ADAMTS13 in a Chinese population. A total of 290 healthy volunteers were eligible for this study. ABO blood group was determined by indirect technique. FVIII:C and Fbg were measured by clotting assays. VWF antigen (VWF:Ag), collagen-binding activity (VWF:CBA), and ADAMTS13 antigen were assessed by ELISA, whereas VWF ristocetin cofactor activity (VWF:Rcof) was performed by agglutination of platelets with ristocetin. Mean FVIII:C and VWF levels (VWF:Ag, VWF:CBA, and VWF:Rcof) were significantly higher in non-O than in O type subjects ( p  blood group, age, and gender showed different effects on plasma levels of FVIII:C, Fbg, VWF:Ag, VWF:CBA, VWF:Rcof, and ADAMTS13 antigen. These new data on a Chinese population are quite helpful to compare with other ethnic groups.

  3. Use of routine histopathology and factor VIII-related antigen/von Willebrand factor immunohistochemistry to differentiate primary hemangiosarcoma of bone from telangiectatic osteosarcoma in 54 dogs.

    Science.gov (United States)

    Giuffrida, M A; Bacon, N J; Kamstock, D A

    2017-12-01

    Hemangiosarcoma (HSA) of bone and telangiectatic osteosarcoma (tOSA) can appear similar histologically, but differ in histogenesis (malignant endothelial cells versus osteoblasts), and may warrant different treatments. Immunohistochemistry (IHC) for endothelial cell marker factor VIII-related antigen/von Willebrand factor (FVIII-RAg/vWF) is a well-documented ancillary test to confirm HSA diagnoses in soft tissues, but its use in osseous HSA is rarely described. Archived samples of 54 primary appendicular bone tumours previously diagnosed as HSA or tOSA were evaluated using combination routine histopathology (RHP) and IHC. Approximately 20% of tumours were reclassified on the basis of FVIII-RAg/vWF immunoreactivity, typically from an original diagnosis of tOSA to a reclassified diagnosis of HSA. No sample with tumour osteoid clearly identified on RHP was immunopositive for FVIII-RAg/vWF. RHP alone was specific but not sensitive for diagnosis of HSA, compared with combination RHP and IHC. Routine histopathological evaluation in combination with FVIII-RAg/vWF IHC can help differentiate canine primary appendicular HSA from tOSA. © 2016 John Wiley & Sons Ltd.

  4. Doença de von Willebrand e anestesia Enfermedad de von Willebrand y anestesia Von Willebrand's disease and anesthesia

    Directory of Open Access Journals (Sweden)

    Fabiano Timbó Barbosa

    2007-06-01

    Full Text Available JUSTIFICATIVA E OBJETIVOS: A doença de von Willebrand ocorre devido à mutação no cromossomo 12 e é caracterizada por deficiência qualitativa ou quantitativa do fator de von Willebrand. A diversidade de mutações leva ao aparecimento das mais variadas manifestações clínicas possibilitando a divisão dos pacientes em vários tipos e subtipos clínicos. A coagulopatia se manifesta basicamente através da disfunção plaquetária associada à diminuição dos níveis séricos do fator VIII coagulante. O objetivo dessa revisão foi mostrar os cuidados relacionados aos pacientes portadores da doença de von Willebrand durante o período perioperatório. CONTEÚDO: Foram definidas as características da doença de von Willebrand quanto à fisiopatologia, à classificação, ao diagnóstico laboratorial, ao tratamento atual e aos cuidados com o manuseio do paciente no período perioperatório. CONCLUSÕES: A doença de von Willebrand é o distúrbio hemorrágico hereditário mais comum, porém ela é subdiagnosticada pela complexidade da própria doença. A correta classificação do paciente, o uso apropriado da desmopressina e a transfusão do fator de von Willebrand são medidas fundamentais para a realização do procedimento anestésico bem-sucedido.JUSTIFICATIVA Y OBJETIVOS: La enfermedad de von Willebrand ocurre debido a la mutación en el cromosoma 12 y se caracteriza por la deficiencia cualitativa o cuantitativa del factor de von Willebrand. La diversidad de mutaciones conlleva al aparecimiento de las más variadas manifestaciones clínicas posibilitando la división de los pacientes en varios tipos y subtipos clínicos. La coagulopatía se manifiesta básicamente a través de la disfunción plaquetaria asociada con la disminución de los niveles séricos del factor VIII coagulante. El objetivo de esa revisión fue mostrar los cuidados relacionados con las pacientes portadoras de la enfermedad de von Willebrand durante el per

  5. Endothelial markers in malignant vascular tumours of the liver: superiority of QB-END/10 over von Willebrand factor and Ulex europaeus agglutinin 1.

    Science.gov (United States)

    Anthony, P P; Ramani, P

    1991-01-01

    A new monoclonal antibody, QB-END/10, raised against the CD34 antigen in human endothelial cell membranes and haemopoietic progenitor cells, was studied for its usefulness as a marker of neoplastic vascular cells in 21 angiosarcomas and seven malignant haemangioendotheliomas of the liver. QB-END/10 was both more sensitive and more specific than Von Willebrand factor (VWF) and Ulex europaeus 1 agglutinin (UEA-1) in labelling endothelial cells and it did not cross react with epithelia as UEA-1 often does. Staining was uniformly strong and clear in all histological variants of these two tumours. QB-END/10 should prove particularly useful in the differential diagnosis of malignant vascular tumours of the liver.

  6. Analysis of expression of von Willebrand factor, endothelin-1, vascular endothelial growth factor in Budd-Chiari syndrome with membranous obstruction

    International Nuclear Information System (INIS)

    Han Xinqiang; Zu Maoheng

    2011-01-01

    Objective: To investigate whether the injured vascular endothelial plays an important role in the membranous formation of the inferior vena cava (IVC). Methods: There were 40 cases of membranous obstruction of inferior vena cava (MOVC) in the experimental group and 40 arrhythmic inpatients in the control group from affiliated hospital. There were 23 males and 17 females in experimental group while 21 males and 19 females in control group, and the age were (41.8±8.1) yrs and (43.2± 7.6) yrs respectively. All of them had no anti-coagulation (clotting) drug history and smoking history, no hypertension, no pulmonary artery hypertension, no coronary heart disease, no valvular disease, no myocardial disease, no blood disease, no diabetes, no connective tissue disease and malignancy, and liver and renal function must be normal. And then the serum concentrations of von Willebrand factor (vWF), endothelin-l (ET-1), vascular endothelial growth factor (VEGF) were defined by enzyme-linked immunosorbent assay (ELISA). The results were analyzed with independent sample t-test. Results: In MOVC patients, the serum concentrations of vWF, ET-1 and VEGF [(37.8±6.6) μg/L, (31.9± 6.0) ng/L, (20.84±5.78) μg/L] were higher than those in the control group [(3.3±1.3) μg/L, (5.3±1.8) ng/L, (4.2±1.2) μg/L. t=32.65, 26.70, 17.85, P<0.01, respectively]. Conclusions: The injury of vascular endothelium is related to the formation of membrane in the IVC. (authors)

  7. Diagnosis and management of von Willebrand disease: guidelines for primary care.

    Science.gov (United States)

    Yawn, Barbara; Nichols, William L; Rick, Margaret E

    2009-12-01

    Von Willebrand disease is an inherited condition characterized by deficiency of von Willebrand factor, which is essential in hemostasis. The National Heart, Lung, and Blood Institute has released new evidence-based guidelines for the diagnosis and management of the disease. There are three major subtypes of von Willebrand disease, classified as partial quantitative deficiency (low levels) of von Willebrand factor (type 1), qualitative deficiency (type 2), or virtually complete deficiency (type 3). Diagnosis is usually made by reviewing the patient's personal and family history of bleeding and by clinical evaluation for more common reasons for bleeding, supplemented with laboratory tests. Assessment may be used to determine bleeding risk before surgery and other invasive procedures, and to diagnose reasons for unexplained hemorrhaging. Von Willebrand factor levels of 30 IU per dL or lower are required for the definite diagnosis of inherited von Willebrand disease. Persons with levels of 30 to 50 IU per dL may not have the disease, but may need agents to increase von Willebrand factor levels during invasive procedures or childbirth. Treatment is tailored to the subtype of the disease: increasing plasma concentration of von Willebrand factor by releasing endogenous stores with desmopressin or replacing nonexistent or ineffective von Willebrand factor by using human plasma-derived, viral-inactivated concentrates; treatment is often combined with hemostatic agents that have mechanisms other than increasing von Willebrand factor. Regular prophylaxis is seldom required, and treatment is initiated before planned invasive procedures or in response to bleeding.

  8. Descripción de un inmunoensayo enzimático que reconoce anticuerpos anti-factor VIII/von Willebrand obtenidos a partir de hibridomas múridos Description of an enzime immunoassay that recognizes anti-factor VIII/von Willebrand antibodies obtained from murine hybridomas

    Directory of Open Access Journals (Sweden)

    Renée González Sampedro

    1999-04-01

    Full Text Available Se describe un inmunoensayo enzimático (ELISA que detecta anticuerpos anti-Factor-VIII/von Willebrand (FVIII/vW, con una relación de enlace > 5, que permite reconocer dichos anticuerpos tempranamente en los cultivos de hibridomas múridos. Para la adsorción de las placas del inmunoensayo se utilizaron preparados semipurificados de FVIII/vW obtenidos en Cuba. Se inmunizaron ratones Balb/c con la finalidad de generar los anticuerpos monoclonales detectados por este ELISA. Se obtuvo un clon con crecimiento estable y varios subclones positivos por el ELISA con actividad biológica específica de anticuerpos inhibidores de FVIIIAn enzime immunoassay (ELISA that detects anti-Factor VIII/von Willebrand (FVIII/vw antibodies with a binding relationship > 5 that allows the early recognition of such antibodies in the cultures of murine hybridomas is described. Semipurified preparations of FVIII/vw obtained in Cuba were used for the adsorption of the immunoassay plates. Balb/c mice were immunized in order to generate the monoclonal antibodies detected by this ELISA. A clone with stable growth and several positive subclones were obtained by ELISA with specific biological activity of FVIII-inhibiting antibodies

  9. Labor management in a patient with on willebrand

    International Nuclear Information System (INIS)

    Saaqib, S.

    2007-01-01

    von Willebrand disease (VWD) is an inherited bleeding disorder involving a deficiency or abnormal function of a blood clotting protein called von Willebrand factor (VWF). Deficiency of VWF, therefore, shows primarily in organs with small blood vessels such as the skin, the gastrointestinal tract and the uterus. This case report describes management of a patient presenting with type II von Willebrand disease in labor. She had history of lifethreatening hemorrhage from an operation for deviated nasal septum and had a risk of severe postpartum hemorrhage (PPH) within 48 hours of delivery, which was avoided by appropriate planning and timely management. (author)

  10. D-dimer, factor VIII and von Willebrand factor predict a non-dipping pattern of blood pressure in hypertensive patients.

    Science.gov (United States)

    Agorasti, Athanasia; Trivellas, Theodoros; Mourvati, Efthimia; Papadopoulos, Vasilios; Tsatalas, Konstantinos; Vargemezis, Vasilios; Passadakis, Ploumis

    2013-06-01

    The aim of this study is to assess whether the haemostatic markers D-dimer, factor VIII (FVIII) and von Willebrand factor (VWF) are predictive of non-dipping status in treated hypertensive patients; so, as easy available laboratory data can predict non-dipping pattern and help with the selection of the patients whom circadian blood pressure should be re-examined. Forty treated hypertensive patients with essential hypertension were included in the study. Twenty-four-hour ambulatory blood pressure monitoring was performed in all patients. Daytime and nocturnal average systolic, diastolic and mean blood pressures were calculated. Patients were characterised as "non-dippers" on the basis of a less than 10 % decline in nocturnal blood pressure (BP); either systolic or diastolic or mean (MAP). D-dimer as marker of fibrinolytic function, FVIII activity and VWF antigen as marker of endothelial dysfunction were measured on plasma. The predictive efficiency was analysed by receiver operating characteristic (ROC) curves. Youden index was used for the estimation of the cut-off points and the associated values for sensitivity and 1-specificity. Plasma levels of D-dimer, FVIII and VWF were significantly higher in non-dippers as compared with dippers, irrespective of the classification used (BP index); all P AUC(ROC) = 0.697, 0.715 and 0.774), FVIII (AUC(ROC) = 0.714, 0.692 and 0.755) and VWF (AUC(ROC) = 0.706, 0.740 and 0.708) in distinguishing non-dipping pattern (systolic, diastolic or mean) in the study population; all P 168 ng/ml (sensitivity/1-specificity for systolic BP non-dippers of 0.789/0.381, for diastolic BP non-dippers 0.923/0.444 and for MAP non-dippers 0.875/0.375). In conclusion, D-dimer has a good predictive value for non-dipping pattern and the decision for the 24-h ambulatory blood pressure re-monitoring among dippers could rely on its values.

  11. Comparative study on collagen-binding enzyme-linked immunosorbent assay and ristocetin cofactor activity assays for detection of functional activity of von Willebrand factor.

    Science.gov (United States)

    Turecek, Peter L; Siekmann, Jürgen; Schwarz, Hans Peter

    2002-04-01

    For more than two decades, the ristocetin cofactor (RCo) assay, which measures the von Willebrand factor (vWF)-mediated agglutination of platelets in the presence of the antibiotic ristocetin, has been the most common method for measuring the functional activity of vWF. There is, however, general agreement among clinical analysts that this method has major practical disadvantages in performance and reproducibility. Today, collagen-binding assays (CBA) based on the enzyme-linked immunosorbent assay (ELISA) technique that measure the interaction of vWF and collagen are an alternative analytic procedure based on a more physiological function than that of the RCo procedure. We used both assay systems in a comparative study to assess the functional activity of vWF in plasma as well as in therapeutic preparations. We measured RCo activities of plasma from healthy donors and patients with different types of von Willebrand disease (vWD) and of vWF as a drug substance in factor (F) VIII/vWF concentrates using both the aggregometric and the macroscopic methods. In addition, we measured collagen-binding activity (vWF:CB) using a recently developed commercially available CBA system. To investigate the relation between the structure and the functional activity of vWF, we isolated vWF species with different numbers of multimers from FVIII/vWF concentrates by affinity chromatography on immobilized heparin. The vWF:RCo and vWF:CB of the different fractions were measured, and the multimeric structure of vWF was analyzed by sodium dodecyl sulfate (SDS) agarose gel electrophoresis. (vWF:CB and vWF:RCo are part of the nomenclature proposed by the International Society on Thrombosis and Hemostasis Scientific and Standardization Committee [ISTH SSC] subcommittee on von Willebrand factor, in Maastricht, Germany, June 16, 2000.) Measurement of functional vWF activity by CBA can be carried out with substantially higher interassay reproducibility than can measurement of RCo. Both assay

  12. The Molecular Genetics of von Willebrand Disease

    Directory of Open Access Journals (Sweden)

    Ergül Berber

    2012-12-01

    Full Text Available Quantitative and/or qualitative deficiency of von Willebrand factor (vWF is associated with the most common inherited bleeding disease von Willebrand disease (vWD. vWD is a complex disease with clinical and genetic heterogeneity. Incomplete penetrance and variable expression due to genetic and environmental factors contribute to its complexity. vWD also has a complex molecular pathogenesis. Some vWF gene mutations are associated with the affected vWF biosynthesis and multimerization, whereas others are associated with increased clearance and functional impairment. Moreover, in addition to a particular mutation, type O blood may result in the more severe phenotype. The present review aimed to provide a summary of the current literature on the molecular genetics of vWD.

  13. The molecular genetics of von Willebrand disease.

    Science.gov (United States)

    Berber, Ergül

    2012-12-01

    Quantitative and/or qualitative deficiency of von Willebrand factor (vWF) is associated with the most common inherited bleeding disease von Willebrand disease (vWD). vWD is a complex disease with clinical and genetic heterogeneity. Incomplete penetrance and variable expression due to genetic and environmental factors contribute to its complexity. vWD also has a complex molecular pathogenesis. Some vWF gene mutations are associated with the affected vWF biosynthesis and multimerization, whereas others are associated with increased clearance and functional impairment. Moreover, in addition to a particular mutation, type O blood may result in the more severe phenotype. The present review aimed to provide a summary of the current literature on the molecular genetics of vWD. None declared.

  14. Elevated levels of von Willebrand factor and high mobility group box 1 (HMGB1) are associated with disease severity and clinical outcome of scrub typhus.

    Science.gov (United States)

    Chen, Hongliu; Ning, Zong; Qiu, Ying; Liao, Yuanli; Chang, Haihua; Ai, Yuanyuan; Wei, Yinghua; Deng, Yiming; Shen, Ying

    2017-08-01

    This study aimed to investigate whether von Willebrand factor (vWF) and high mobility group box 1 (HMGB1) are associated with the severity and clinical outcome of scrub typhus and to seek novel biomarkers for surveillance and prediction of the prognosis of this infection. Serum concentrations of vWF and HMGB1 were measured twice by ELISA for scrub typhus patients (n=103), once prior to doxycycline therapy and then on day 7 of doxycycline therapy; concentrations were measured once for healthy controls (n=32). Among the total 103 patients enrolled, 38 had disease complicated by multiple organ dysfunction syndrome (MODS). Serum concentrations of vWF and HMGB1 were significantly higher in all the patients than in the healthy controls, both prior to doxycycline treatment and on day 7 of doxycycline treatment (pscrub typhus (area under the curve (AUC)=0.864, p=0.001, and AUC=0.862, p=0.001, respectively). Elevated levels of vWF and HMGB1 are associated with the severity and clinical outcome of scrub typhus. These represent possible new biomarkers for use in the assessment and prognostic prediction of this infection. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  15. Thrombomodulin, von Willebrand factor and E-selectin as plasma markers of endothelial damage/dysfunction and activation in pregnancy induced hypertension.

    Science.gov (United States)

    Nadar, Sunil K; Al Yemeni, Eman; Blann, Andrew D; Lip, Gregory Y H

    2004-01-01

    Endothelial disturbance (whether activation, dysfunction or damage) is a likely pathogenic mechanism in pre-eclampsia and pregnancy-induced hypertension (PIH). We set out to determine which of three plasma markers of endothelial disturbance, indicating endothelial activation (E-selectin) or damage/dysfunction (von Willebrand factor (vWf), soluble thrombomodulin), would provide the best discriminator of PIH compared to normotensive pregnancy. Cross-sectional study of 36 consecutive women with PIH (age 31+/-6 years) and 36 consecutive women with normotensive pregnancies (age 29+/-5 years) of similar parity. Plasma levels of vWf, E-selectin and thrombomodulin were measured using ELISA. As expected, women with PIH had significantly higher levels of plasma vWf (by 19%, p=0.003), E-selectin (by 40%, p<0.001) and thrombomodulin (by 61%, p=0.01) than normotensive women. However, on stepwise multiple regression analysis, only thrombomodulin was an independent significant predictor of the presence of PIH (p=0.023). We conclude that although vWf, E-selectin and thrombomodulin are all raised in PIH, only thrombomodulin was independently associated with PIH. This molecule could potentially be useful in monitoring and in providing clues in aetiology and pathophysiology, and may have implications for the clinical complications associated with PIH.

  16. Characterization of an entomopathogenic fungi target integument protein, Bombyx mori single domain von Willebrand factor type C, in the silkworm, Bombyx mori.

    Science.gov (United States)

    Han, F; Lu, A; Yuan, Y; Huang, W; Beerntsen, B T; Huang, J; Ling, E

    2017-06-01

    The insect cuticle works as the first line of defence to protect insects from pathogenic infections and water evaporation. However, the old cuticle must be shed in order to enter the next developmental stage. During each ecdysis, moulting fluids are produced and secreted into the area among the old and new cuticles. In a previous study, the protein Bombyx mori single domain von Willebrand factor type C (BmSVWC; BGIBMGA011399) was identified in the moulting fluids of Bo. mori and demonstrated to regulate ecdysis. In this study we show that in Bo. mori larvae, BmSVWC primarily locates to the integument (epidermal cells and cuticle), wing discs and head. During the moulting stage, BmSVWC is released into the moulting fluids, and is then produced again by epidermal cells after ecdysis. Fungal infection was shown to decrease the amount of BmSVWC in the cuticle, which indicates that BmSVWC is a target protein of entomopathogenic fungi. Thus, BmSVWC is mainly involved in maintaining the integrity of the integument structure, which serves to protect insects from physical damage and pathogenic infection. © 2017 The Royal Entomological Society.

  17. One-pot preparation of conducting composite containing abundant amino groups on electrode surface for electrochemical detection of von willebrand factor

    Science.gov (United States)

    Wang, Wen; Ma, Chao; Li, Yi; Liu, Baihui; Tan, Liang

    2018-03-01

    A one-pot protocol based on cyclic voltammetric scan was employed to prepare new conducting composite that was abundant in amino groups. The scanning electron microscope, atomic force microscope, X-ray photoelectron spectroscopy and infrared spectrum characterization demonstrate that poly(azure A), gold nanoparticles, chitosan and cysteine were immobilized simultaneously on glassy carbon electrode surface. Von Willebrand factor (vWF) antibody (Ab) was subsequently assembled by using glutaraldehyde to construct the Ab/composite-modified electrode. The capture of vWF could inhibit the charge transfer between the ferri-/ferrocyanide probe and the electrode and exert the negative effect on the electrochemical response of the dye polymer in the conducting composite due to the strong steric hindrance effect. The DPV peak current change before and after the immunoreaction was found to be proportional to the logarithm of the vWF concentration from 0.001 to 100 μg mL-1 with a detection limit of 0.4 ng mL-1. The proposed label-free electrochemical method was employed in the investigation on the release of vWF by oxidation-injured vascular endothelial cells. The experimental results exhibit that the vWF content in growth medium was increased when the oxidation injury of the cells was intensified in the presence of H2O2.

  18. von Willebrand factor and its cleaving protease ADAMTS13 balance in coronary artery vessels: Lessons learned from thrombotic thrombocytopenic purpura. A narrative review.

    Science.gov (United States)

    Morici, Nuccia; Cantoni, Silvia; Panzeri, Francesco; Sacco, Alice; Rusconi, Chiara; Stucchi, Miriam; Oliva, Fabrizio; Cattaneo, Marco

    2017-07-01

    Deficiency of the von Willebrand factor-cleaving protease ADAMTS13 is central to the pathophysiology of thrombotic thrombocytopenic purpura (TTP), a microangiopathic syndrome that presents as an acute medical emergency. In this review we will explore the evidence of a two-way relationship between TTP and ACS. Moreover, we will review the evidence emerged from epidemiological studies of an inverse relationship between the plasma levels of ADAMTS13 and the risk of ACS. Pubmed, MEDLINE and EMBASE, CINHAL, COCHRANE and Google Scholar databases were searched from inception to January 2017. The search yielded 43 studies representing 23 unique patient cases, 5 case series, 5 cohort studies and 10 case-control studies. Most ACS cases developing in the setting of TTP resolved with standard treatment of the underlying microangiopathy, with only a few requiring coronary invasive management. Antiplatelet therapy was not usually prescribed and all of the currently used P2Y 12 were felt to be a potential trigger for a TTP-like syndrome, although our review revealed that the occurrence of TTP in patients treated with new P2Y 12 antagonists is rare. Most studies confirmed the inverse association among ADAMTS13 levels and ACS. The heart is a definite target organ in TTP. The clinical spectrum of its involvement is probably influenced by local factors that add on to the systemic deficiency characteristic of TTP. It follows that patients with TTP should be carefully monitored for ACS events, especially when multiple risk factors for coronary disease exist. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Cloning of the cDNA for murine von Willebrand factor and identification of orthologous genes reveals the extent of conservation among diverse species.

    Science.gov (United States)

    Chitta, Mohan S; Duhé, Roy J; Kermode, John C

    2007-05-01

    Interaction of von Willebrand factor (VWF) with circulating platelets promotes hemostasis when a blood vessel is injured. The A1 domain of VWF is responsible for the initial interaction with platelets and is well conserved among species. Knowledge of the cDNA and genomic DNA sequences for human VWF allowed us to predict the cDNA sequence for murine VWF in silico and amplify its entire coding region by RT-PCR. The murine VWF cDNA has an open reading frame of 8,442 bp, encoding a protein of 2,813 amino acid residues with 83% identity to human pre-pro-VWF. The same strategy was used to predict in silico the cDNA sequence for the ortholog of VWF in a further six species. Many of these predictions diverged substantially from the putative Reference Sequences derived by ab initio methods. Our predicted sequences indicated that the VWF gene has a conserved structure of 52 exons in all seven mammalian species examined, as well as in the chicken. There is a minor structural variation in the pufferfish Takifugu rubripes insofar as the VWF gene in this species has 53 exons. Comparison of the translated amino acid sequences also revealed a high degree of conservation. In particular, the cysteine residues are conserved precisely throughout both the pro-peptide and the mature VWF sequence in all species, with a minor exception in the pufferfish VWF ortholog where two adjacent cysteine residues are omitted. The marked conservation of cysteine residues emphasizes the importance of the intricate pattern of disulfide bonds in governing the structure of pro-VWF and regulating the function of the mature VWF protein. It should also be emphasized that many of the conserved features of the VWF gene and protein were obscured when the comparison among species was based on the putative Reference Sequences instead of our predicted cDNA sequences.

  20. Influence of atrial fibrillation on plasma von willebrand factor, soluble E-selectin, and N-terminal pro B-type natriuretic peptide levels in systolic heart failure.

    Science.gov (United States)

    Freestone, Bethan; Gustafsson, Finn; Chong, Aun Yeong; Corell, Pernille; Kistorp, Caroline; Hildebrandt, Per; Lip, Gregory Y H

    2008-05-01

    Endothelial dysfunction is present in patients with heart failure (HF) due to left ventricular systolic dysfunction, as well as in patients with atrial fibrillation (AF) who have normal cardiac function. It is unknown whether AF influences the degree of endothelial dysfunction in patients with systolic HF. We measured levels of plasma von Willebrand factor (vWF) and E-selectin (as indexes of endothelial damage/dysfunction and endothelial activation, respectively; both enzyme-linked immunosorbent assay) in patients with AF and HF (AF-HF), who were compared to patients with sinus rhythm and HF (SR-HF), as well as in age-matched, healthy, control subjects. We also assessed the relationship of vWF and E-selectin to plasma N-terminal pro B-type natriuretic peptide (NTpro-BNP), a marker for HF severity and prognosis. One hundred ninety patients (73% men; mean age, 69.0 +/- 10.1 years [+/- SD]) with systolic HF were studied, who were compared to 117 healthy control subjects: 52 subjects (27%) were in AF, while 138 subjects (73%) were in sinus rhythm. AF-HF patients were older than SR-HF patients (p = 0.046), but left ventricular ejection fraction and New York Heart Association class were similar. There were significant differences in NT-proBNP (p NT-proBNP (p NT-proBNP levels (Spearman r = 0.139; p = 0.017). There is evidence of greater endothelial damage/dysfunction in AF-HF patients when compared to SR-HF patients. The clinical significance of this is unclear but may have prognostic value.

  1. The important role of von Willebrand factor in platelet-derived FVIII gene therapy for murine hemophilia A in the presence of inhibitory antibodies.

    Science.gov (United States)

    Shi, Q; Schroeder, J A; Kuether, E L; Montgomery, R R

    2015-07-01

    Our previous studies have demonstrated that targeting FVIII expression to platelets results in FVIII storage together with von Willebrand factor (VWF) in platelet α-granules and that platelet-derived FVIII (2bF8) corrects the murine hemophilia A phenotype even in the presence of high-titer anti-FVIII inhibitory antibodies (inhibitors). To explore how VWF has an impact on platelet gene therapy for hemophilia A with inhibitors. 2bF8 transgenic mice in the FVIII(-/-) background (2bF8(tg+/-) F8(-/-) ) with varying VWF phenotypes were used in this study. Animals were analyzed by VWF ELISA, FVIII activity assay, Bethesda assay and tail clip survival test. Only 18% of 2bF8(tg+/-) F8(-/-) VWF(-/-) animals, in which VWF was deficient, survived the tail clip challenge with inhibitor titers of 3-8000 BU mL(-1) . In contrast, 82% of 2bF8(tg+/-) F8(-/-) VWF(+/+) mice, which had normal VWF levels, survived tail clipping with inhibitor titers of 10-50,000 BU mL(-1) . All 2bF8(tg+/-) F8(-/-) VWF(-/-) mice without inhibitors survived tail clipping and no VWF(-/-) F8(-/-) mice survived this challenge. Because VWF is synthesized by endothelial cells and megakaryocytes and is distributed in both plasma and platelets in peripheral blood, we further investigated the effect of each compartment of VWF on platelet-FVIII gene therapy for hemophilia A with inhibitors. In the presence of inhibitors, 42% of animals survived tail clipping in the group with plasma-VWF and 50% survived in the platelet-VWF group. VWF is essential for platelet gene therapy for hemophilia A with inhibitors. Both platelet-VWF and plasma-VWF are required for optimal platelet-derived FVIII gene therapy for hemophilia A in the presence of inhibitors. © 2015 International Society on Thrombosis and Haemostasis.

  2. Acquired von Willebrand syndrome: A rare disorder of heterogeneous etiology

    Directory of Open Access Journals (Sweden)

    P Kasatkar

    2013-01-01

    Full Text Available Context: Acquired von Willebrand syndrome (AVWS is a rare bleeding disorder that mimics the inherited form of von Willebrand disease (VWD in terms of laboratory findings and clinical presentation. Aims: To study the etiology of acquired VWD. Settings and Design: The patients referred from various hospitals in and out of Mumbai were included in the study. Materials and Methods: Six patients with AVWS diagnosed at this center over the last 10 years were analyzed against 171 patients with inherited VWD. The differential diagnosis of AVWS was made based on reduced levels of von Willebrand antigen and von Willebrand ristocetin cofactor, decrease in ristocetin induced platelet aggregation, absence of correction in mixing studies with no prior history of bleeding problems and a negative family history for bleeding disorders. Results: In three patients, the disease was associated with systematic lupus erythematosus, out of which one was also associated with Kikuchi lymphadenitis and second with autoimmune hemolytic anemia. Fourth case was associated with hypothyroidism and fifth was a case of dermatitis and vitiligo. The last patient was a case of hemophilia A with Burkitts lymphoma, who developed autoantibodies to von Willebrand factor. Except two patients, all other patients responded to immune suppressive therapy with corticosteroids, while the patient with hypothyroidism responded to oral thyroxine. Conclusion: AVWS is a rare condition and may often be missed or diagnosed as inherited disease associated with heterogeneous disease conditions.

  3. Relationship between ADAMTS13 activity, von Willebrand factor antigen levels and platelet function in the early and late phases after TIA or ischaemic stroke.

    Science.gov (United States)

    McCabe, Dominick J H; Murphy, Stephen J X; Starke, Richard; Harrison, Paul; Brown, Martin M; Sidhu, Paul S; Mackie, Ian J; Scully, Marie; Machin, Samuel J

    2015-01-15

    Reduced ADAMTS13 activity is seen in thrombotic thrombocytopenic purpura (TTP), and may lead to accumulation of prothrombotic ultra-large von Willebrand factor (ULVWF) multimers in vivo. ADAMTS13 activity and its relationship with VWF antigen (VWF:Ag) levels and platelet function in 'non-TTP related' TIA or ischaemic stroke has not been comprehensively studied. In this prospective pilot observational analytical case-control study, ADAMTS13 activity and VWF:Ag levels were quantified in platelet poor plasma in 53 patients in the early phase (≤ 4 weeks) and 34 of these patients in the late phase (≥ 3 months) after TIA or ischaemic stroke on aspirin. Data were compared with those from 22 controls not on aspirin. The impact of ADAMTS13 on platelet function in whole blood was quantified by measuring Collagen-ADP (C-ADP) and Collagen-Epinephrine closure times on a platelet function analyser (PFA-100(®)). Median ADAMTS13 activity was significantly reduced in the early phase (71.96% vs. 95.5%, P TIA or stroke compared with controls (86.3% vs. 95.5%, P=0.19). There was a significant inverse relationship between ADAMTS13 activity and VWF:Ag levels in the early phase (r=-0.31; P=0.024), but not in the late phase after TIA or stroke (P=0.74). There was a positive correlation between ADAMTS13 activity and C-ADP closure times in early phase patients only, likely mediated via VWF:Ag levels. ADAMTS13 activity is reduced and VWF:Ag expression is increased within 4 weeks of TIA or ischaemic stroke onset, and can promote enhanced platelet adhesion and aggregation in response to stimulation with collagen and ADP via VWF-mediated pathways. These data improve our understanding of the dynamic haemostatic and thrombotic profiles of ischaemic cerebrovascular disease (CVD) patients, and are important in view of the potential future role that ADAMTS13 may have to play as an anti-thrombotic agent in CVD. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. General rotating black holes in string theory: Greybody factors and event horizons

    International Nuclear Information System (INIS)

    Cvetic, M.; Larsen, F.

    1997-01-01

    We derive the wave equation for a minimally coupled scalar field in the background of a general rotating five-dimensional black hole. It is written in a form that involves two types of thermodynamic variables, defined at the inner and outer event horizon, respectively. We model the microscopic structure as an effective string theory, with the thermodynamic properties of the left- and right-moving excitations related to those of the horizons. Previously known solutions to the wave equation are generalized to the rotating case, and their regime of validity is sharpened. We calculate the greybody factors and interpret the resulting Hawking emission spectrum microscopically in several limits. We find a U-duality-invariant expression for the effective string length that does not assume a hierarchy between the charges. It accounts for the universal low-energy absorption cross section in the general nonextremal case. copyright 1997 The American Physical Society

  5. Greybody factor of scalar fields from black strings

    Science.gov (United States)

    Ahmed, Jamil; Saifullah, K.

    2017-12-01

    The greybody factor of massless, uncharged scalar fields is studied in the background of cylindrically symmetric spacetimes, in the low-energy approximation. We discuss two cases. In the first case we derive analytical expression for the absorption probability when the spacetime is kinetically coupled with the Einstein tensor. In the second case we do the analysis in the absence of the coupling constant. For this purpose we analyze the wave equation which is obtained from Klein-Gordon equation. The radial part of the wave equation is solved in the form of the hypergeometric function in the near horizon region, whereas in the far region the solution is of the form of Bessel's function. Finally, considering continuity of the wave function we smoothly match the two solutions in the low-energy approximation to get the formula for the absorption probability.

  6. Greybody factor of scalar fields from black strings

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Jamil [Quaid-i-Azam University, Department of Mathematics, Islamabad (Pakistan); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Saifullah, K. [Quaid-i-Azam University, Department of Mathematics, Islamabad (Pakistan); Harvard University, Center for the Fundamental Laws of Nature, Cambridge, MA (United States)

    2017-12-15

    The greybody factor of massless, uncharged scalar fields is studied in the background of cylindrically symmetric spacetimes, in the low-energy approximation. We discuss two cases. In the first case we derive analytical expression for the absorption probability when the spacetime is kinetically coupled with the Einstein tensor. In the second case we do the analysis in the absence of the coupling constant. For this purpose we analyze the wave equation which is obtained from Klein-Gordon equation. The radial part of the wave equation is solved in the form of the hypergeometric function in the near horizon region, whereas in the far region the solution is of the form of Bessel's function. Finally, considering continuity of the wave function we smoothly match the two solutions in the low-energy approximation to get the formula for the absorption probability. (orig.)

  7. Translational Medicine Advances in von Willebrand Disease

    Science.gov (United States)

    Lillicrap, David

    2014-01-01

    Following the recognition of von Willebrand disease (VWD) in 1926 and the cloning of the gene for von Willebrand factor (VWF) in 1985, significant advances have been made in our fundamental knowledge of both the disease and the protein. Some of this new knowledge has also begun to impact the clinical management of VWD. First, the progressive increase in our understanding of the molecular genetic basis of VWD has resulted in rational applications of molecular testing to complement the current range of phenotypic tests for VWD. These molecular genetic strategies are most effectively directed at the prenatal diagnosis of type 3 VWD and confirmatory testing for types 2B and 2N disease. In contrast, the use of molecular testing to clarify the diagnosis of type 1 VWD is of marginal benefit, at best. In terms of VWD therapies, a new recombinant VWF concentrate has recently completed successful clinical trials and is now awaiting more widespread application. There have even been some pre-clinical successes with VWF gene transfer although the clinical rationale for this therapeutic strategy needs careful consideration. Much more remains to be learnt about the biology of VWF and further translational advances for the enhancement of VWD care will inevitably be realized. PMID:23809112

  8. A method for the automated processing and analysis of images of ULVWF-platelet strings.

    Science.gov (United States)

    Reeve, Scott R; Abbitt, Katherine B; Cruise, Thomas D; Hose, D Rodney; Lawford, Patricia V

    2013-01-01

    We present a method for identifying and analysing unusually large von Willebrand factor (ULVWF)-platelet strings in noisy low-quality images. The method requires relatively inexpensive, non-specialist equipment and allows multiple users to be employed in the capture of images. Images are subsequently enhanced and analysed, using custom-written software to perform the processing tasks. The formation and properties of ULVWF-platelet strings released in in vitro flow-based assays have recently become a popular research area. Endothelial cells are incorporated into a flow chamber, chemically stimulated to induce ULVWF release and perfused with isolated platelets which are able to bind to the ULVWF to form strings. The numbers and lengths of the strings released are related to characteristics of the flow. ULVWF-platelet strings are routinely identified by eye from video recordings captured during experiments and analysed manually using basic NIH image software to determine the number of strings and their lengths. This is a laborious, time-consuming task and a single experiment, often consisting of data from four to six dishes of endothelial cells, can take 2 or more days to analyse. The method described here allows analysis of the strings to provide data such as the number and length of strings, number of platelets per string and the distance between each platelet to be found. The software reduces analysis time, and more importantly removes user subjectivity, producing highly reproducible results with an error of less than 2% when compared with detailed manual analysis.

  9. DEEP VEIN THROMBOSIS IN PATIENT WITH VON WILLEBRAND DISEASE

    Directory of Open Access Journals (Sweden)

    V. A. Elykomov

    2016-01-01

    Full Text Available Objective: to identify the possible factors of thrombogenic risk and ways of its prevention in patients with von Willebrand disease.Case description. Patient X., 42 years old, who suffers from von Willebrand disease type 3 with 5-years of age. Asked on reception to the traumatologist in the polyclinic of the Regional Hospital with pain in the left hip joint. Recommended planned operative treatment in the Altai Regional Clinical Hospital. Preoperative preparation included the infusion of concentrate of von Willebrand factor and coagulation factor VIII. Operation – cement total arthroplasty of the left hip joint. In the postoperative period analgesic treatment, elastic compression of the lower extremities, iron supplements, also conducted infusion of concentrate of von Willebrand factor and coagulation factor VIII for 20 days and thromboprophylactic with dabigatran. On the 3rd day after the operation the patient revealed deep vein thrombosis of the femoral segment (floating clot.Results. The patient was operated for emergency indications in the Department of endovascular surgery – installation of venous cava filter “Volan”. Dabigatran is cancelled, appointed clexane for 3 months. In our clinical example the patient lacked risk factors of pulmonary embolism as obesity, age, smoking, prolonged immobilization, estrogen therapy. Overdose of factor VIII were not observed – the level of factor did not exceed 135 % on transfusions. At the same time, the patient was found polymorphisms in the genes ITGA2, FGB, MTHFR, MTR – heterozygote, MTRR – mutant homozygote, which may indicate the genetic factors of thrombogenic risk. Also a significant risk factor was massive surgical intervention (total hip replacement. Despite preventive measures (elastic compression, thromboprophylactic dabigatran, early activation we cannot to avoid thrombotic complications.Conclusion. This article presents a case demonstrating a thrombotic complication in patients

  10. Nordic Haemophilia Council's practical guidelines on diagnosis and management of von Willebrand disease

    DEFF Research Database (Denmark)

    Lassila, Riitta; Holme, Pål André; Landorph, Andrea

    2011-01-01

    Von Willebrand disease (VWD) is the most common inherited bleeding disorder characterized by spontaneous or tissue injury-related, mostly mucocutaneous, bleeding events. VWD affects both males and females and is caused by quantitative or qualitative deficiency of Von Willebrand factor. The diagno......Von Willebrand disease (VWD) is the most common inherited bleeding disorder characterized by spontaneous or tissue injury-related, mostly mucocutaneous, bleeding events. VWD affects both males and females and is caused by quantitative or qualitative deficiency of Von Willebrand factor...... subtyping may also be problematic. This article summarizes the guidelines of the Nordic Haemophilia Council (NHC), which are intended to serve as a practical tool and provide the standards for diagnosing and treating VWD patients. The complete Nordic Guidelines on VWD are available at the NHC Web site (http://nordhemophilia.org)....

  11. Von Willebrand's disease in the German shepherd dog : clinical communication

    Directory of Open Access Journals (Sweden)

    R.G. Lobetti

    2000-07-01

    Full Text Available Two litters of Germanshepherd dogs were evaluated for a haemorrhagic tendency that was characterised by excessive bleeding from the umbilicus at birth, haemorrhage and haematoma formation at vaccination, excessive bruising, and lameness due to haemarthrosis. Platelet counts, clotting times and Von Willebrand's factor (VWF assays were assessed in all dogs. Factor VIII determination was performed in 1 puppy and its parents. Based on the clotting times and VWF assay, 6 puppies (4 male and 2 female showed type I Von Willebrand's disease (VWD, 5 (4 male and 1 female possible type II VWD, and 4 were unaffected. One puppy with possible type II VWD had very low factor VIII activity; its sire had a normal factor activity, whereas the dam was in the low-normal range. This article reports type I and possible type II VWD in 2 related litters of German shepherd dogs, the latter being rare in German shepherd dogs.

  12. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor, a cardiovascular risk marker: results from a randomized, double-blind, placebo-controlled, multicenter North American clinical trial

    Directory of Open Access Journals (Sweden)

    Jensen GS

    2016-10-01

    Full Text Available Gitte S Jensen,1 Miki Lenninger,1 Michael P Ero,2 Kathleen F Benson,1 1NIS Labs, Klamath Falls, OR, 2Machaon Diagnostics, Inc., Oakland, CA, USA Objective: The objective of this study is to evaluate the effects of consumption of nattokinase on hypertension in a North American hypertensive population with associated genetic, dietary, and lifestyle factors. This is in extension of, and contrast to, previous studies on Asian populations.Materials and methods: A randomized, double-blind, placebo-controlled, parallel-arm clinical study was performed to evaluate nattokinase (NSK-SD, a fermented soy extract nattō from which vitamin K2 has been removed. Based on the results from previous studies on Asian populations, 79 subjects were enrolled upon screening for elevated blood pressure (BP; systolic BP ≥130 or diastolic BP ≥90 mmHg who consumed placebo or 100 mg nattokinase/d for the 8-week study duration. Blood collections were performed at baseline and 8 weeks for testing plasma renin activity, von Willebrand factor (vWF, and platelet factor-4. Seventy-four people completed the study with good compliance.Results: Consumption of nattokinase was associated with a reduction in both systolic and diastolic BP. The reduction in systolic BP was seen for both sexes but was more robust in males consuming nattokinase. The average reduction in diastolic BP in the nattokinase group from 87 mmHg to 84 mmHg was statistically significant when compared to that in the group consuming placebo, where the average diastolic BP remained constant at 87 mmHg (P<0.05, and reached a high level of significance for males consuming nattokinase, where the average diastolic BP dropped from 86 mmHg to 81 mmHg (P<0.006. A decrease in vWF was seen in the female population consuming nattokinase (P<0.1. In the subpopulation with low plasma renin activity levels at baseline (<0.29 ng/mL/h, an increase was seen for 66% of the people after 8-week consumption of nattokinase (P

  13. Von Willebrand's disease: case report and review of literature.

    Science.gov (United States)

    Echahdi, Hanae; El Hasbaoui, Brahim; El Khorassani, Mohamed; Agadr, Aomar; Khattab, Mohamed

    2017-01-01

    Von Willebrand Disease (VWD) is the most common human inherited bleeding disorder due to a defect of Von Willebrand Factor (VWF), which a glycoprotein crucial for platelet adhesion to the subendothelium after vascular injury. VWD include quantitative defects of VWF, either partial (type 1 with VWF levels < 50 IU/dL) or virtually total (type 3 with undetectable VWF levels) and also qualitative defects of VWF (type 2 variants with discrepant antigenic and functional VWF levels). The most bleeding forms of VWD usually do not concern type 1 patients with the mildest VWF defects (VWF levels between 30 and 50IU/dL). Von willebrand factor is a complex multimeric protein with two functions: it forms a bridge between the platelets and areas of vascular damage and it binds to and stabilizes factor VIII, which is necessary for the clotting cascade. By taking a clinical history of bleeding (mucocutaneous bleeding symptoms suggestive of a primary haemostatic disorder, a quantitative or qualitative abnormality of VWF is possible) it is important to think about VWD and to make the appropriate diagnosis. If the VWD is suspected diagnostic tests should include an activated partial thromboplastin time, bleeding time, factor VIII: C Ristocetin cofactor and vWF antigen. Additional testing of ristocetin induced plattlet adhesion (RIPA) the multimeric structure and collagen binding test and genanalysis allow diagnosing the different types of von. Willebrand Disease. The treatment of choice in mild forms is the synthetic agent desmopressin. In patients with severe type 1, type 2B, 2N and type 3 or in people who do not response to desmopressin, the appropriate treatment is a factor VIII concentrate that is rich of VWF. We report a case of infant in 27-month-old boy who had been referred due to haemorrhagic shock. His birth histories, his familie's social history and developmental milestones were unremarkable. He was born at full term with no antenatal or perinatal complications. Prior to

  14. Optimal Packed String Matching

    DEFF Research Database (Denmark)

    Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany

    2011-01-01

    In the packed string matching problem, each machine word accommodates – characters, thus an n-character text occupies n/– memory words. We extend the Crochemore-Perrin constantspace O(n)-time string matching algorithm to run in optimal O(n/–) time and even in real-time, achieving a factor – speed...

  15. String field theory solution for any open string background

    Czech Academy of Sciences Publication Activity Database

    Erler, T.; Maccaferri, Carlo

    2014-01-01

    Roč. 10, Oct (2014), 1-37 ISSN 1029-8479 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : tachyon condensation * string field theory * conformal field models in string theory * bosonic strings Subject RIV: BE - Theoretical Physics Impact factor: 6.111, year: 2014

  16. Coulomb string tension, asymptotic string tension, and the gluon chain

    OpenAIRE

    Greensite, Jeff; Szczepaniak, Adam P.

    2014-01-01

    We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

  17. String theory

    International Nuclear Information System (INIS)

    Chan Hongmo.

    1987-10-01

    The paper traces the development of the String Theory, and was presented at Professor Sir Rudolf Peierls' 80sup(th) Birthday Symposium. The String theory is discussed with respect to the interaction of strings, the inclusion of both gauge theory and gravitation, inconsistencies in the theory, and the role of space-time. The physical principles underlying string theory are also outlined. (U.K.)

  18. Open string model building

    International Nuclear Information System (INIS)

    Ishibashi, Nobuyuki; Onogi, Tetsuya

    1989-01-01

    Consistency conditions of open string theories, which can be a powerful tool in open string model building, are proposed. By making use of these conditions and assuming a simple prescription for the Chan-Paton factors, open string theories in several backgrounds are studied. We show that 1. there exist a large number of consistent bosonic open string theories on Z 2 orbifolds, 2. SO(32) type I superstring is the unique consistent model among fermionic string theories on the ten-dimensional flat Minkowski space, and 3. with our prescription for the Chan-Paton factors, there exist no consistent open superstring theories on (six-dimensional Minkowski space-time) x (Z 2 orbifold). (orig.)

  19. Von Willebrand protein binds to extracellular matrices independently of collagen.

    OpenAIRE

    Wagner, D D; Urban-Pickering, M; Marder, V J

    1984-01-01

    Von Willebrand protein is present in the extracellular matrix of endothelial cells where it codistributes with fibronectin and types IV and V collagen. Bacterial collagenase digestion of endothelial cells removed fibrillar collagen, but the pattern of fibronectin and of von Willebrand protein remained undisturbed. Exogenous von Willebrand protein bound to matrices of different cells, whether rich or poor in collagen. von Willebrand protein also decorated the matrix of cells grown in the prese...

  20. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor, a cardiovascular risk marker: results from a randomized, double-blind, placebo-controlled, multicenter North American clinical trial.

    Science.gov (United States)

    Jensen, Gitte S; Lenninger, Miki; Ero, Michael P; Benson, Kathleen F

    2016-01-01

    The objective of this study is to evaluate the effects of consumption of nattokinase on hypertension in a North American hypertensive population with associated genetic, dietary, and lifestyle factors. This is in extension of, and contrast to, previous studies on Asian populations. A randomized, double-blind, placebo-controlled, parallel-arm clinical study was performed to evaluate nattokinase (NSK-SD), a fermented soy extract nattō from which vitamin K2 has been removed. Based on the results from previous studies on Asian populations, 79 subjects were enrolled upon screening for elevated blood pressure (BP; systolic BP ≥130 or diastolic BP ≥90 mmHg) who consumed placebo or 100 mg nattokinase/d for the 8-week study duration. Blood collections were performed at baseline and 8 weeks for testing plasma renin activity, von Willebrand factor (vWF), and platelet factor-4. Seventy-four people completed the study with good compliance. Consumption of nattokinase was associated with a reduction in both systolic and diastolic BP. The reduction in systolic BP was seen for both sexes but was more robust in males consuming nattokinase. The average reduction in diastolic BP in the nattokinase group from 87 mmHg to 84 mmHg was statistically significant when compared to that in the group consuming placebo, where the average diastolic BP remained constant at 87 mmHg ( P nattokinase, where the average diastolic BP dropped from 86 mmHg to 81 mmHg ( P nattokinase ( P nattokinase ( P nattokinase consumption in a North American population is associated with beneficial changes to BP in a hypertensive population, indicating sex-specific mechanisms of action of nattokinase's effect on vWF and hypertension.

  1. Changes in bleeding patterns in von Willebrand disease after institution of long-term replacement therapy : results from the von Willebrand Disease Prophylaxis Network

    NARCIS (Netherlands)

    Holm, Elena; Abshire, Thomas C; Bowen, Joel; Álvarez, M Teresa; Bolton-Maggs, Paula; Carcao, Manuel; Federici, Augusto B; Gill, Joan Cox; Halimeh, Susan; Kempton, Christine; Key, Nigel S; Kouides, Peter; Lail, Alice; Landorph, Andrea; Leebeek, Frank; Makris, Michael; Mannucci, Pier; Mauser-Bunschoten, Eveline P; Nugent, Diane; Valentino, Leonard A; Winikoff, Rochelle; Berntorp, Erik

    Clinically, the leading symptom in von Willebrand disease (VWD) is bleeding, chiefly of mucosal type, for example, epistaxis, gingival, or gastrointestinal bleeding, and menorrhagia. In severe forms of VWD with secondary deficiency of factor VIII, spontaneous joint bleeding, resembling that observed

  2. Hyperbolic strings

    International Nuclear Information System (INIS)

    Popov, A.D.

    1991-01-01

    We introduce hyperbolic strings as closed bosonic strings with the target space R d-1,1 xT q+1,1 which has an additional time-like dimension in the internal space. The Fock spaces of the q-parametric family of standard bosonic, fermionic and heterotic strings with the target spaces of dimension n≤d+q are shown to be embedded into the Fock space of hyperbolic strings. The condition of the absence of anomaly fixes d and q for all three types of strings written in a bosonized form. (orig.)

  3. The metal-ion-dependent adhesion site in the Von Willebrand factor-A domain of α2δ subunits is key to trafficking voltage-gated Ca2+ channels

    Science.gov (United States)

    Cantí, C.; Nieto-Rostro, M.; Foucault, I.; Heblich, F.; Wratten, J.; Richards, M. W.; Hendrich, J.; Douglas, L.; Page, K. M.; Davies, A.; Dolphin, A. C.

    2005-01-01

    All auxiliary α2δ subunits of voltage-gated Ca2+ (CaV) channels contain an extracellular Von Willebrand factor-A (VWA) domain that, in α2δ-1 and -2, has a perfect metal-ion-dependent adhesion site (MIDAS). Modeling of the α2δ-2 VWA domain shows it to be highly likely to bind a divalent cation. Mutating the three key MIDAS residues responsible for divalent cation binding resulted in a MIDAS mutant α2δ-2 subunit that was still processed and trafficked normally when it was expressed alone. However, unlike WT α2δ-2, the MIDAS mutant α2δ-2 subunit did not enhance and, in some cases, further diminished CaV1.2, -2.1, and -2.2 currents coexpressed with β1b by using either Ba2+ or Na+ as a permeant ion. Furthermore, expression of the MIDAS mutant α2δ-2 reduced surface expression and strongly increased the perinuclear retention of CaVα1 subunits at the earliest time at which expression was observed in both Cos-7 and NG108–15 cells. Despite the presence of endogenous α2δ subunits, heterologous expression of α2δ-2 in differentiated NG108–15 cells further enhanced the endogenous high-threshold Ca2+ currents, whereas this enhancement was prevented by the MIDAS mutations. Our results indicate that α2δ subunits normally interact with the CaVα1 subunit early in their maturation, before the appearance of functional plasma membrane channels, and an intact MIDAS motif in the α2δ subunit is required to promote trafficking of the α1 subunit to the plasma membrane by an integrin-like switch. This finding provides evidence for a primary role of a VWA domain in intracellular trafficking of a multimeric complex, in contrast to the more usual roles in binding extracellular ligands in other exofacial VWA domains. PMID:16061813

  4. Von-Willebrand Disease Presenting as Intractable Epistaxis after Nasal Polypectomy

    Directory of Open Access Journals (Sweden)

    Jeong Jin Park

    2014-01-01

    Full Text Available Von-Willebrand disease (VWD is one of the platelet dysfunction disorders that results from a deficiency of Von-Willebrand factor, which is essential for hemostasis. VWD patients typically have normal laboratory results on screening for bleeding disorders. To suspect and diagnose VWD, a careful review of past medical history and laboratory tests is critical. A 59-year-old male patient presented with intractable nasal bleeding after nasal polypectomy. The bleeding was controlled by platelet transfusion, and he was later diagnosed with VWD.

  5. Bowed Strings

    Science.gov (United States)

    Rossing, Thomas D.; Hanson, Roger J.

    In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.

  6. Bosonic strings

    CERN Document Server

    Jost, Jürgen

    2007-01-01

    This book presents a mathematical treatment of Bosonic string theory from the point of view of global geometry. As motivation, Jost presents the theory of point particles and Feynman path integrals. He provides detailed background material, including the geometry of Teichmüller space, the conformal and complex geometry of Riemann surfaces, and the subtleties of boundary regularity questions. The high point is the description of the partition function for Bosonic strings as a finite-dimensional integral over a moduli space of Riemann surfaces. Jost concludes with some topics related to open and closed strings and D-branes. Bosonic Strings is suitable for graduate students and researchers interested in the mathematics underlying string theory.

  7. N1421K mutation in the glycoprotein Ib binding domain impairs ristocetin- and botrocetin-mediated binding of von Willebrand factor to platelets

    DEFF Research Database (Denmark)

    Lanke, E.; Kristoffersson, A.C.; Isaksson, C.

    2008-01-01

    , moderately decreased plasma factor VIII (FVIII) and VWF levels, and disproportionately low-plasma VWF:RCo levels. The patients were found to be heterozygous for the novel N1421K mutation, caused by a 4263C > G transversion in exon 28 of the VWF gene coding for the A1 domain. Botrocetin- and ristocetin-mediated...... binding of plasma VWF to GPIb were reduced in the patients. In vitro mutagenesis and expression in COS-7 cells confirmed the impairment of the mutant in botrocetin- and ristocetin-mediated VWF binding to GPIb. VWF collagen binding capacity was unaffected in plasma from the heterozygous individuals as well...

  8. Activation of pathways involved in HUVEC apoptosis and proliferation. Sex hormones agonist related. Effect of hormones on von Willebrand factor and ADAMTS 13 release

    OpenAIRE

    Powazniak, Yanina

    2008-01-01

    El VWF es una glicoproteína adhesiva, sintetizada en las CE y megacariocitos. Se sintetiza en forma monomérica, luego se organiza en dímeros y se multimeriza. El VWF media la adhesión de plaquetas al subendotelio vascular dañado y lel transporte del factor FVIII. La ADAMTS13, proteasa que cliva al VWF, pertenece a la familia de metaloproteasas ADAMTS, llamadas así por la combinación característica de una desintegrina y una metaloproteasa con motivos trombospondina tipo 1. La ADAMTS13 es sinte...

  9. Is playing string or wind musical instruments a risk factor for temporomandibular dysfunction? A Systematic Review.

    Directory of Open Access Journals (Sweden)

    Alessandro Leite Cavalcanti

    2017-11-01

    Full Text Available Aim. Medical problems specifically affecting professional musicians are commonly mentioned in the literature. The present study is aimed to evaluate, through a systematic review, the possible association between the practice of string with bow and wind musical instruments and the occurrence of Temporomandibular Dysfunction (TMD. Methods. The search for articles was conducted in PubMed/Medline, Web of Science, Scopus, Lilacs, Cochrane Library, and Open Gray databases, and there was no restriction on language or date of publication. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA guidelines were followed. The MeSH terms used were: “music”; “temporomandibular joint”; “temporomandibular joint disorders”; “temporomandibular joint dysfunction syndrome”; and “occupational diseases”. Cross-sectional studies, case-control, cohort and clinical trials were included that involved the practice of string with bow and wind musical instruments and the occurrence of Temporomandibular Dysfunction (TMD. Articles were previously selected by title and abstract. Qualitative evaluation was done through the Newcastle-Ottawa Scale. Results. The literature search identified 732 studies, of which 10 met the inclusion criteria, nine of them cross-sectional studies and one a clinical intervention study. The TMD prevalence ranged from 47.0% to 89.0%. Recruitment of participants took place in professional schools and orchestras, and in bands of professional musicians. All studies reported associations between TMD and the practice of musical instruments, and violinists presented higher prevalence rates when compared to other instrument groups. Conclusion. All studies pointed to a possible association between TMD and the practice of string and wind musical instruments. More longitudinal and clinical trials studies are needed to verify any possible interrelationship.

  10. Multiquark strings

    International Nuclear Information System (INIS)

    Wang, F.; Chun, W.

    1985-01-01

    The use of basis states described as hadronic (or hadron-hadron) or hidden-colour (or colour-colour) for a system of quarks does not necessarily imply that connected exotic multiquark hadrons do exist. Antisymmetrization of quark wave functions tends to make these descriptions ill defined. It appears necessary to have stable collective structures called strings or bags to provide the physical connections required by quark confinement. The masses of multiquark hadrons can then be estimated by using semplified string, bag and NR potential models. The results turn out to be qualitatively similar in all these models. The stability problem for multiquark strings is briefly discussed

  11. Cosmic strings

    International Nuclear Information System (INIS)

    Bennett, D.P.

    1988-07-01

    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

  12. Magnetic strings

    International Nuclear Information System (INIS)

    Chaves, Max

    2006-01-01

    The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

  13. Lattice strings

    International Nuclear Information System (INIS)

    Thorn, C.B.

    1988-01-01

    The possibility of studying non-perturbative effects in string theory using a world sheet lattice is discussed. The light-cone lattice string model of Giles and Thorn is studied numerically to assess the accuracy of ''coarse lattice'' approximations. For free strings a 5 by 15 lattice seems sufficient to obtain better than 10% accuracy for the bosonic string tachyon mass squared. In addition a crude lattice model simulating string like interactions is studied to find out how easily a coarse lattice calculation can pick out effects such as bound states which would qualitatively alter the spectrum of the free theory. The role of the critical dimension in obtaining a finite continuum limit is discussed. Instead of the ''gaussian'' lattice model one could use one of the vertex models, whose continuum limit is the same as a gaussian model on a torus of any radius. Indeed, any critical 2 dimensional statistical system will have a stringy continuum limit in the absence of string interactions. 8 refs., 1 fig. , 9 tabs

  14. Splitting strings on integrable backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Vicedo, Benoit

    2011-05-15

    We use integrability to construct the general classical splitting string solution on R x S{sup 3}. Namely, given any incoming string solution satisfying a necessary self-intersection property at some given instant in time, we use the integrability of the worldsheet {sigma}-model to construct the pair of outgoing strings resulting from a split. The solution for each outgoing string is expressed recursively through a sequence of dressing transformations, the parameters of which are determined by the solutions to Birkhoff factorization problems in an appropriate real form of the loop group of SL{sub 2}(C). (orig.)

  15. Pseudo (Platelet-type von Willebrand disease in pregnancy: a case report

    Directory of Open Access Journals (Sweden)

    Grover Neetu

    2013-01-01

    Full Text Available Abstract Background Pseudo (platelet-type-von Willebrand disease is a rare autosomal dominant bleeding disorder caused by an abnormal function of the glycoprotein lb protein; the receptor for von Willebrand factor. This leads to an increased removal of VWF multimers from the circulation as well as platelets and this results in a bleeding diathesis. Worldwide, less than 50 patients are reported with platelet type von Willebrand disease (PT-VWD. Case presentation We describe the management of platelet type von Willebrand disease in pregnancy of a 26 year old Caucasian primigravida. The initial diagnosis was made earlier following a significant haemorrhage post tonsillectomy several years prior to pregnancy. The patient was managed under a multidisciplinary team which included obstetricians, haematologists, anaesthetists and neonatologists. Care plans were made for the ante- natal, intra-partum and post-partum periods in partnership with the patient. The patient’s platelet count levels dropped significantly during the antenatal period. This necessitated the active exclusion of other causes of thrombocytopenia in pregnancy. A vaginal delivery was desired and plans were made for induction of labour at 38 weeks of gestation with platelet cover in view of the progressive fall of the platelet count. The patient however went into spontaneous labour on the day of induction. She was transfused two units of platelets before delivery. She had an unassisted vaginal delivery of a healthy baby. The successful antenatal counselling has encouraged the diagnosis of the same condition in her mother and sister. We found this to be a particularly interesting case as well as challenging to manage due to its rarity. Psuedo von Willebrand disease in pregnancy can be confused with a number of other differential diagnoses, such as gestational thrombocutopenia, idiopathatic thrombocytopenia, thrombotic thrombocytopenic purpura and pre-eclampsia; all need consideration

  16. N-loop string amplitude

    International Nuclear Information System (INIS)

    Mandelstam, S.

    1986-06-01

    Work on the derivation of an explicit perturbation series for string and superstring amplitudes is reviewed. The light-cone approach is emphasized, but some work on the Polyakov approach is also mentioned, and the two methods are compared. The calculation of the measure factor is outlined in the interacting-string picture

  17. Clinical and laboratory diagnosis of von Willebrand disease: A synopsis of the 2008 NHLBI/NIH guidelines

    Science.gov (United States)

    Nichols, William L.; Rick, Margaret E.; Ortel, Thomas L.; Montgomery, Robert R.; Sadler, J. Evan; Yawn, Barbara P.; James, Andra H.; Hultin, Mae B.; Manco-Johnson, Marilyn J.; Weinstein, Mark

    2017-01-01

    Von Willebrand factor (VWF) mediates blood platelet adhesion and accumulation at sites of blood vessel injury, and also carries coagulation factor VIII (FVIII) that is important for generating procoagulant activity. Von Willebrand disease (VWD), the most common inherited bleeding disorder, affects males and females, and reflects deficiency or defects of VWF that may also cause decreased FVIII. It may also occur less commonly as an acquired disorder (acquired von Willebrand syndrome). This article briefly summarizes selected features of the March 2008 evidence-based clinical and laboratory diagnostic recommendations from the National Heart, Lung, and Blood Institute (NHLBI) Expert Panel for assessment for VWD or other bleeding disorders or risks. Management of VWD is also addressed in the NHLBI guidelines, but is not summarized here. The VWD guidelines are available at the NHLBI Web site (http://www.nhlbi.nih.gov/guidelines/vwd). PMID:19415721

  18. Singleton strings

    International Nuclear Information System (INIS)

    Engquist, J.; Sundell, P.; Tamassia, L.

    2007-01-01

    The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)

  19. Matrix string partition function

    CERN Document Server

    Kostov, Ivan K; Kostov, Ivan K.; Vanhove, Pierre

    1998-01-01

    We evaluate quasiclassically the Ramond partition function of Euclidean D=10 U(N) super Yang-Mills theory reduced to a two-dimensional torus. The result can be interpreted in terms of free strings wrapping the space-time torus, as expected from the point of view of Matrix string theory. We demonstrate that, when extrapolated to the ultraviolet limit (small area of the torus), the quasiclassical expressions reproduce exactly the recently obtained expression for the partition of the completely reduced SYM theory, including the overall numerical factor. This is an evidence that our quasiclassical calculation might be exact.

  20. Transverse structure of the QCD string

    International Nuclear Information System (INIS)

    Meyer, Harvey B.

    2010-01-01

    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 β defined from the slope of its gravitational form factor, is given by (d-1/2πσ)log(β/4r 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-1/2πσ)log(r/r 0 ). We also obtain predictions for transition form factors among closed-string states.

  1. String phenomenology

    CERN Document Server

    Ibáñez, Luis E

    2015-01-01

    This chapter reviews a number of topics in the field of string phenomenology, focusing on orientifold/F-theory models yielding semirealistic low-energy physics. The emphasis is on the extraction of the low-energy effective action and possible tests of specific models at the LHC.

  2. String GUTs

    International Nuclear Information System (INIS)

    Aldazabal, G.; Ibanez, L.E.; Uranga, A.M.

    1995-01-01

    Standard SUSY-GUTs such as those based on SU(5) or SO(10) lead to predictions for the values of α s and sin 2 θ W in amazing agreement with experiment. In this article we investigate how these models may be obtained from string theory, thus bringing them into the only known consistent framework for quantum gravity. String models with matter in standard GUT representations require the realization of affine Lie algebras at higher levels. We start by describing some methods to build level k=2 symmetric orbifold string models with gauge groups SU(5) or SO(10). We present several examples and identify generic features of the type of models constructed. Chiral fields appropriate to break the symmetry down to the standard model generically appear in the massless spectrum. However, unlike in standard SUSY-GUTs, they often behave as string moduli, i.e., they do not have self-couplings. We also discuss briefly the doublet-triplet Higgs splitting. We find that, in some models, built-in sliding-singlet type of couplings exist. (orig.)

  3. Worldsheet geometries of ambitwistor string

    Energy Technology Data Exchange (ETDEWEB)

    Ohmori, Kantaro [Department of Physics, the University of Tokyo,Hongo, Bunkyo-ku, Tokyo 133-0022 (Japan)

    2015-06-12

    Mason and Skinner proposed the ambitwistor string theory which directly reproduces the formulas for the amplitudes of massless particles proposed by Cachazo, He and Yuan. In this paper we discuss geometries of the moduli space of worldsheets associated to the bosonic or the RNS ambitwistor string. Further, we investigate the factorization properties of the amplitudes when an internal momentum is near on-shell in the abstract CFT language. Along the way, we propose the existence of the ambitwistor strings with three or four fermionic worldsheet currents.

  4. A string theory which isn't about strings

    Science.gov (United States)

    Lee, Kanghoon; Rey, Soo-Jong; Rosabal, J. A.

    2017-11-01

    Quantization of closed string proceeds with a suitable choice of worldsheet vacuum. A priori, the vacuum may be chosen independently for left-moving and right-moving sectors. We construct ab initio quantized bosonic string theory with left-right asymmetric worldsheet vacuum and explore its consequences and implications. We critically examine the validity of new vacuum and carry out first-quantization using standard operator formalism. Remarkably, the string spectrum consists only of a finite number of degrees of freedom: string gravity (massless spin-two, Kalb-Ramond and dilaton fields) and two massive spin-two Fierz-Pauli fields. The massive spin-two fields have negative norm, opposite mass-squared, and provides a Lee-Wick type extension of string gravity. We compute two physical observables: tree-level scattering amplitudes and one-loop cosmological constant. Scattering amplitude of four dilatons is shown to be a rational function of kinematic invariants, and in D = 26 factorizes into contributions of massless spin-two and a pair of massive spin-two fields. The string one loop partition function is shown to perfectly agree with one loop Feynman diagram of string gravity and two massive spin-two fields. In particular, it does not exhibit modular invariance. We critically compare our construction with recent studies and contrast differences.

  5. Multi-branes boundary states with open string interactions

    International Nuclear Information System (INIS)

    Pesando, Igor

    2008-01-01

    We derive boundary states which describe configurations of multiple parallel branes with arbitrary open string states interactions in bosonic string theory. This is obtained by a careful discussion of the factorization of open/closed string states amplitudes taking care of cycles needed by ensuring vertices commutativity: in particular the discussion reveals that already at the tree level open string knows of the existence of closed string

  6. Prophylaxis escalation in severe von Willebrand disease: A prospective study from the von Willebrand Disease Prophylaxis Network

    NARCIS (Netherlands)

    T.C. Abshire (Thomas Calvin); J. Cox-Gill; C.L. Kempton; F.W.G. Leebeek (Frank); M. Carcao (M.); P. Kouides (P.); S. Donfield (S.); E. Berntorp

    2015-01-01

    textabstractBackground: Treatment of mucosal bleeding (epistaxis, gastrointestinal bleeding, and menorrhagia) and joint bleeding remains problematic in clinically severe von Willebrand disease (VWD). Patients are often unresponsive to treatment (e.g. desmopressin or antifibrinolytic therapy) and may

  7. String Gas Cosmology

    OpenAIRE

    Brandenberger, Robert H.

    2008-01-01

    String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

  8. Universal character and large N factorization in topological gauge/string theory

    International Nuclear Information System (INIS)

    Kanno, Hiroaki

    2006-01-01

    We establish a formula of the large N factorization of the modular S-matrix for the coupled representations in U(N) Chern-Simons theory. The formula was proposed by Aganagic, Neitzke and Vafa, based on computations involving the conifold transition. We present a more rigorous proof that relies on the universal character for rational representations and an expression of the modular S-matrix in terms of the specialization of characters

  9. Closed string field theory

    International Nuclear Information System (INIS)

    Strominger, A.

    1987-01-01

    A gauge invariant cubic action describing bosonic closed string field theory is constructed. The gauge symmetries include local spacetime diffeomorphisms. The conventional closed string spectrum and trilinear couplings are reproduced after spontaneous symmetry breaking. The action S is constructed from the usual ''open string'' field of ghost number minus one half. It is given by the associator of the string field product which is non-vanishing because of associativity anomalies. S does not describe open string propagation because open string states associate and can thereby be shifted away. A field theory of closed and open strings can be obtained by adding to S the cubic open string action. (orig.)

  10. String Formation Beyond Leading Colour

    CERN Document Server

    Christiansen, Jesper R.

    2015-08-03

    We present a new model for the hadronisation of multi-parton systems, in which colour correlations beyond leading $N_C$ are allowed to influence the formation of confining potentials (strings). The multiplet structure of $SU(3)$ is combined with a minimisation of the string potential energy, to decide between which partons strings should form, allowing also for "baryonic" configurations (e.g., two colours can combine coherently to form an anticolour). In $e^+e^-$collisions, modifications to the leading-colour picture are small, suppressed by both colour and kinematics factors. But in $pp$ collisions, multi-parton interactions increase the number of possible subleading connections, counteracting their naive $1/N_C^2$ suppression. Moreover, those that reduce the overall string lengths are kinematically favoured. The model, which we have implemented in the PYTHIA 8 generator, is capable of reaching agreement not only with the important $\\left(n_\\mathrm{charged})$ distribution but also with measured rates (and ra...

  11. Remarks on entanglement entropy in string theory

    Science.gov (United States)

    Balasubramanian, Vijay; Parrikar, Onkar

    2018-03-01

    Entanglement entropy for spatial subregions is difficult to define in string theory because of the extended nature of strings. Here we propose a definition for bosonic open strings using the framework of string field theory. The key difference (compared to ordinary quantum field theory) is that the subregion is chosen inside a Cauchy surface in the "space of open string configurations." We first present a simple calculation of this entanglement entropy in free light-cone string field theory, ignoring subtleties related to the factorization of the Hilbert space. We reproduce the answer expected from an effective field theory point of view, namely a sum over the one-loop entanglement entropies corresponding to all the particle-excitations of the string, and further show that the full string theory regulates ultraviolet divergences in the entanglement entropy. We then revisit the question of factorization of the Hilbert space by analyzing the covariant phase-space associated with a subregion in Witten's covariant string field theory. We show that the pure gauge (i.e., BRST exact) modes in the string field become dynamical at the entanglement cut. Thus, a proper definition of the entropy must involve an extended Hilbert space, with new stringy edge modes localized at the entanglement cut.

  12. Cosmic global strings

    International Nuclear Information System (INIS)

    Sikivie, P.

    1991-01-01

    The topics are: global strings; the gravitational field of a straight global string; how do global strings behave?; the axion cosmological energy density; computer simulations of the motion and decay of global strings; electromagnetic radiation from the conversion of Nambu-Goldstone bosons in astrophysical magnetic fields. (orig.)

  13. Evidence for string substructure

    International Nuclear Information System (INIS)

    Bergman, O.

    1996-06-01

    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

  14. String driven inflation

    International Nuclear Information System (INIS)

    Turok, N.

    1987-11-01

    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

  15. Hot String Soup

    OpenAIRE

    Lowe, D. A.; Thorlacius, L.

    1994-01-01

    Above the Hagedorn energy density closed fundamental strings form a long string phase. The dynamics of weakly interacting long strings is described by a simple Boltzmann equation which can be solved explicitly for equilibrium distributions. The average total number of long strings grows logarithmically with total energy in the microcanonical ensemble. This is consistent with calculations of the free single string density of states provided the thermodynamic limit is carefully defined. If the ...

  16. String-driven inflation

    International Nuclear Information System (INIS)

    Turok, N.

    1988-01-01

    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. The heterotic string

    International Nuclear Information System (INIS)

    Gross, D.J.

    1986-01-01

    Traditional string theories, either bosonic or supersymmetric, came in two varieties, closed string theories and open string theories. Closed string are neutral objects which describe at low energies gravity or supergravity. Open strings have geometrically invariant ends to which charge can be attached, thereby obtaining, in addition to gravity, Yang-Mills gauge interactions. Recently a new kind of string theory was discovered--the heterotic string, which is a chiral hybrid of the closed superstring and the closed bosonic string, and which produces by an internal dynamical mechanism gauge interactions of a totally specified kind. Although this theory is found in an attempt to produce a superstring theory which would yield a low energy E/sub 8/xE/sub 8/ supersymmetric, anomaly free, gauge theory, as suggested by the anomaly cancellation mechanism of Green and Schwarz, it fits naturally into the general framework of consistent string theories

  18. String field representation of the Virasoro algebra

    Czech Academy of Sciences Publication Activity Database

    Mertes, N.; Schnabl, Martin

    2016-01-01

    Roč. 2016, č. 12 (2016), 1-14, č. článku 151. ISSN 1029-8479 R&D Projects: GA ČR(CZ) GA14-31689S Institutional support: RVO:68378271 Keywords : String Held Theory * Conformal Field Models in String Theory Subject RIV: BE - Theoretical Physics Impact factor: 6.063, year: 2016

  19. Relativistic classical strings. II

    International Nuclear Information System (INIS)

    Galvao, C.A.P.

    1985-01-01

    The interactions of strings with electromagnetic and gravitational fields are extensively discussed. Some concepts of differential geometry are reviewed. Strings in Kaluza-Klein manifolds are studied. (L.C.) [pt

  20. Inflationary string theory?

    Indian Academy of Sciences (India)

    strongly motivate a detailed search for inflation within string theory, although it has ... between string theory and observations provides a strong incentive for ..... sonably be expected to arise for any system having very many degrees of freedom.

  1. Strings in the Sun?

    International Nuclear Information System (INIS)

    Chudnovsky, E.; Vilenkin, A.

    1988-01-01

    If light superconducting strings were formed in the early Universe, then it is very likely that now they exist in abundance in the interstellar plasma and in stars. The dynamics of such strings can be dominated by friction, so that they are ''frozen'' into the plasma. Turbulence of the plasma twists and stretches the strings, forming a stochastic string network. Such networks must generate particles and magnetic fields, and may play an important role in the physics of stars and of the Galaxy

  2. Why string theory?

    CERN Document Server

    Conlon, Joseph

    2016-01-01

    Is string theory a fraud or one of the great scientific advances? Why do so many physicists work on string theory if it cannot be tested? This book provides insight into why such a theory, with little direct experimental support, plays such a prominent role in theoretical physics. The book gives a modern and accurate account of string theory and science, explaining what string theory is, why it is regarded as so promising, and why it is hard to test.

  3. Non-critical Poincare invariant bosonic string backgrounds and closed string tachyons

    International Nuclear Information System (INIS)

    Alvarez, Enrique; Gomez, Cesar; Hernandez, Lorenzo

    2001-01-01

    A new family of non critical bosonic string backgrounds in arbitrary space-time dimension D and with ISO(1,D-2) Poincare 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 -T 2 e -T , is suggested

  4. Introduction to string theory and string compactifications

    International Nuclear Information System (INIS)

    GarcIa-Compean, Hugo

    2005-01-01

    Basics of some topics on perturbative and non-perturbative string theory are reviewed. After a mathematical survey of the Standard Model of particle physics and GUTs, the bosonic string kinematics for the free case and with interaction is described. The effective action of the bosonic string and the spectrum is also discussed. T-duality in closed and open strings and the definition of D-brane are surveyed. Five perturbative superstring theories and their spectra is briefly outlined. Calabi-Yau three-fold compactifications of heterotic strings and their relation to some four-dimensional physics are given. Finally, non-perturbative issues like S-duality, M-theory and F-theory are also reviewed

  5. Beneficial Effects of High-Density Lipoproteins on Acquired von Willebrand Syndrome in Aortic Valve Stenosis.

    Science.gov (United States)

    Gebhard, C; Maafi, F; Stähli, B E; Bonnefoy, A; Gebhard, C E; Nachar, W; de Oliveira Moraes, A Benjamim; Mecteau, M; Mihalache-Avram, T; Lavoie, V; Kernaleguen, A E; Shi, Y; Busseuil, D; Chabot-Blanchet, M; Perrault, L P; Rhainds, D; Rhéaume, E; Tardif, J C

    2018-02-01

     Infusions of apolipoprotein A-I (apoA-I), the major protein component of high-density lipoproteins (HDL), result in aortic valve stenosis (AVS) regression in experimental models. Severe AVS can be complicated by acquired von Willebrand syndrome, a haemorrhagic disorder associated with loss of high-molecular-weight von Willebrand factor (vWF) multimers (HMWM), the latter being a consequence of increased shear stress and enhanced vWF-cleaving protease (ADAMTS-13) activity. Although antithrombotic actions of HDL have been described, its effects on ADAMTS-13 and vWF in AVS are unknown.  We assessed ADAMTS-13 activity in plasma derived from a rabbit model of AVS ( n  = 29) as well as in plasma collected from 64 patients with severe AVS (age 65.0 ± 10.4 years, 44 males) undergoing aortic valve replacement (AVR). In both human and rabbit AVS plasma, ADAMTS-13 activity was higher than that in controls ( p  AVS patients had less HMWM than controls (66.3 ± 27.2% vs. 97.2 ± 24.1%, p  AVS rabbits as compared with the placebo group (2.0 ± 0.5 RFU/sec vs. 3.8 ± 0.4 RFU/sec, p  AVS ( r  = -0.3, p  = 0.045).  Our data indicate that HDL levels are associated with reduced ADAMTS-13 activity and increased HMWM. HDL-based therapies may reduce the haematologic abnormalities of the acquired von Willebrand syndrome in AVS. Schattauer GmbH Stuttgart.

  6. Random surfaces and strings

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1987-08-01

    The theory of strings is the theory of random surfaces. I review the present attempts to regularize the world sheet of the string by triangulation. The corresponding statistical theory of triangulated random surfaces has a surprising rich structure, but the connection to conventional string theory seems non-trivial. (orig.)

  7. Dynamics of Carroll strings

    Energy Technology Data Exchange (ETDEWEB)

    Cardona, Biel [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Gomis, Joaquim [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Department of Physics, Faculty of Science, Chulalongkorn University,Bangkok 10330 (Thailand); Pons, Josep M. [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

    2016-07-11

    We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.

  8. String Math 2017

    CERN Document Server

    The series of String-Math conferences has developed into a central event on the interface between mathematics and physics related to string theory, quantum field theory and neighboring subjects. The conference will take place from July 24-28 in the main building of Hamburg university. The String-Math conference is organised by the University of Hamburg jointly with DESY Hamburg.

  9. Diagnosis and management of von Willebrand disease: a developing country perspective.

    Science.gov (United States)

    Nair, Sukesh Chandran; Viswabandya, Auro; Srivastava, Alok

    2011-07-01

    Special challenges exist in the management of patients with von Willebrand disease (VWD) because of limitations in diagnostic facilities and therapeutic options. However, even within these limitations, it is possible to establish comprehensive services for this condition. Our data show that among 202 patients with VWD, 107 were type 3, 62 were type 1, and the others different categories of type 2. Basic tests such as bleeding time and activated partial thromboplastin time with factor (F)VIII coagulant are able to diagnose most of those with severe disease. We have been able to adapt the specific tests such as von Willebrand factor (VWF) ristocetin cofactor and VWF antigen from the tedious batched manual methods to cost-effective automated methods on advanced coagulometers. Discriminatory tests such as VWF collagen binding, VWF:FVIIIB, ristocetin-induced platelet agglutination (RIPA) are done in batches. Therapeutic options and for the treatment of bleeding include desmopressin, cryoprecipitate, and intermediate purity VWF-containing clotting factor concentrates. Tranexamic acid is also widely used as well as hormonal therapy for menorrhagia. We have also shown that modest doses of intermediate purity FVIII (Koate DVI; Talecris Biotherapeutics, Raleigh, NC, USA) at 35 IU/kg preoperatively and 10 to 20 IU/kg after that are sufficient for surgical hemostasis in these patients. © Thieme Medical Publishers.

  10. String theory and cosmological singularities

    Indian Academy of Sciences (India)

    recent times, string theory is providing new perspectives of such singularities which .... holes appear as stacks of a large number of D-branes wrapped in internal .... results into a well-known measure factor which makes the wave function into a.

  11. Topics in string theory

    Science.gov (United States)

    Gorbatov, Elie

    In the first part of the dissertation we study noncommutative field theories at finite temperature. We find evidence for winding states and observe the existence of a transition to a new phase where there is a reduction of the degrees of freedom in the non-planar sector of the theory. We emphasize that such a transition is generic and insensitive to the particulars of the UV definition of the theory. In the second part we investigate some aspects of M-theory compactifications on orbifolds. The heterotic E8 x E 8 string compactified on T4/ ZN has gauge group G x G˜ with massless states in the twisted sector charged under both factors. In the dual M-theory description on T4/ ZN x S1/Z 2 the two groups do not communicate with each other since they reside on the boundary of the eleven dimensional spacetime. This leads to a conundrum for the twisted states of the perturbative heterotic string for there does not seem to be local degrees of freedom which carry charges under both G and G˜. We propose a resolution of this apparent paradox by nonperturbative states in M-theory. In support of our argument we review the consideration of six-dimensional gauge couplings and verify the local anomaly cancellation. In order to understand the dynamical properties of these states we deform the orbifold geometry, find an equivalent string theory background, and brane engineer the low energy six-dimensional field theories. In the process we encounter many exotic and surprising phenomena which are intrinsically M-theoretic and completely invisible to the perturbative observer.

  12. Cosmic strings and inflation

    International Nuclear Information System (INIS)

    Vishniac, E.T.

    1987-01-01

    We examine the compatibility of inflation with the cosmic string theory for galaxy formation. There is a general conflict between having sufficient string tension to effect galaxy formation, and reheating after inflation to a high enough temperature that strings may form in a thermal phase transition. To escape this conflict, we propose a class of models where the inflation is coupled to the string-producing field. The strings are formed late in inflation as the inflaton rolls towards its zero-temperature value. A large subset of these models have a novel large-scale distribution of galaxies that is fractal, displays biasing without dynamics or feedback mechanisms, and contains voids. (orig.)

  13. Minimal open strings

    International Nuclear Information System (INIS)

    Hosomichi, Kazuo

    2008-01-01

    We study FZZT-branes and open string amplitudes in (p, q) minimal string theory. We focus on the simplest boundary changing operators in two-matrix models, and identify the corresponding operators in worldsheet theory through the comparison of amplitudes. Along the way, we find a novel linear relation among FZZT boundary states in minimal string theory. We also show that the boundary ground ring is realized on physical open string operators in a very simple manner, and discuss its use for perturbative computation of higher open string amplitudes.

  14. Towards personalised therapy for von Willebrand disease: a future role for recombinant products.

    Science.gov (United States)

    Favaloro, Emmanuel J

    2016-05-01

    von Willebrand disease (VWD) is reportedly the most common bleeding disorder and is caused by deficiencies and/or defects in the adhesive plasma protein von Willebrand factor (VWF). Functionally, normal VWF prevents bleeding by promoting both primary and secondary haemostasis. In respect to primary haemostasis, VWF binds to both platelets and sub-endothelial matrix components, especially collagen, to anchor platelets to damaged vascular tissue and promote thrombus formation. VWF also stabilises and protects factor VIII in the circulation, delivering FVIII to the site of injury, which then facilitates secondary haemostasis and fibrin formation/thrombus stabilisation. As a result of this, patients with VWD suffer a bleeding diathesis reflective of a primary defect caused by defective/deficient VWF, which in some patients is compounded by a reduction in FVIII. Management of VWD, therefore, chiefly entails replacement of VWF, and sometimes also FVIII, to protect against bleeding. The current report principally focuses on the future potential for "personalised" management of VWD, given the emerging options in recombinant therapies. Recombinant VWF has been developed and is undergoing clinical trials, and this promising therapy may soon change the way in which VWD is managed. In particular, we can envisage a personalised treatment approach using recombinant VWF, with or without recombinant FVIII, depending on the type of VWD, the extent of deficiencies, and the period and duration of treatment.

  15. Closed Strings From Nothing

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, Albion

    2001-07-25

    We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order {alpha}' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting.

  16. Closed Strings From Nothing

    International Nuclear Information System (INIS)

    Lawrence, Albion

    2001-01-01

    We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order α' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting

  17. The arithmetic of strings

    International Nuclear Information System (INIS)

    Freund, P.G.O.

    1988-01-01

    According to the author nobody has succeeded as yet in extracting any new numbers from string theory. This paper discusses how if one cannot get new numbers from string theory, maybe one can get new strings out of number theory. Number theory is generally regarded as the purest form of mathematics. So how can it conceivably make contact with physics which aims at describing nature? The author discusses how the connecting link of these two disciplines is provided by the compact Riemann surfaces. These appear as world sheets of interacting strings. For instance, string-string scattering at the three-loop level involves the four external strings attaching themselves to a genus three compact surface

  18. Hemophilia and von Willebrand's disease: 1. Diagnosis, comprehensive care and assessment. Association of Hemophilia Clinic Directors of Canada.

    Science.gov (United States)

    1995-07-01

    To present current strategies for the assessment and comprehensive care of patients with hemophilia and von Willebrand's disease. Hospital care, home care, single-provider care and multidisciplinary care. Morbidity and quality of life associated with bleeding and treatment. Relevant clinical studies and reports published from 1974 to 1994 were examined. A search was conducted of own reprint files, MEDLINE, citations in the articles reviewed and references provided by colleagues. In the MEDLINE search the following terms were used singly or in combination: "hemophilia," "von Willebrand's disease," "Factor VIII," "Factor IX," "von Willebrand factor," "diagnosis," "management," "home care," "comprehensive care," "inhibitor," "AIDS," "hepatitis," "life expectancy," "complications," "practice guidelines," "consensus statement" and "controlled trial." The in-depth review included only articles written in English from North America and Europe that were relevant to human disease and to a predetermined outline. The availability of treatment products in Canada was also considered. Minimizing morbidity and maximizing functional status and quality of life were given a high value. The optimal use of treatment procedures and home care offers patients the advantages of minimized disability, improved survival and financial benefit. It is also cost effective. Potential harm, including the risk of hepatitis B, hepatitis C and HIV infection, has now been minimized through viral inactivation of plasma-derived coagulation-factor concentrates and through the use of recombinant clotting factor concentrates and other non-plasma-derived hemostatic agents. Patients with hemophilia and severe von Willebrand's disease should be followed in comprehensive care centres that offer expertise in the diagnosis, assessment and management of bleeding and complications and that can meet the educational and counselling needs of patients, family members and health care providers. Eligible patients should

  19. Electromagnetic form factors for nucleons and pions at positive and negative q2 in the model of quark-gluon strings

    International Nuclear Information System (INIS)

    Kaidalov, A.B.; Kondratyuk, L.A.; Tchekin, D.V.

    2000-01-01

    The electromagnetic form factors for pions and nucleons are considered within the model of quark-gluon strings, where the momentum-transfer dependence of hadronic form factors is determined by the intercepts of the corresponding Regge trajectories and by the Sudakov form factor. Analytic expressions found for form factors in the timelike region admit an analytic continuation to the spacelike region. The resulting form factors for pions and nucleons comply well with experimental data both for positive and for negative values of the squared momentum transfer q 2 . It is shown that the distinctions between the absolute values of the pion and nucleon form factors F π (q 2 ), G m (q 2 ), and F 2 (q 2 ) at positive values of q 2 and those at negative values of this variable are associated with the analytic properties of the double-logarithmic term in the exponent of the Sudakov form factor. The spin structure of the amplitudes for quark transitions into hadrons that is proposed in the present study makes it possible to describe fairly well available experimental data on the Pauli form factor F 2 and on the ratio G e /G m

  20. Statistical sums of strings on hyperellyptic surfaces

    International Nuclear Information System (INIS)

    Lebedev, D.; Morozov, A.

    1987-01-01

    Contributions of hyperellyptic surfaces to statistical sums of string theories are presented. Available results on hyperellyptic surface give the apportunity to check factorization of three-loop statsum. Some remarks on the vanishing statistical sum are presented

  1. BRST invariant mixed string vertex for the bosonic string

    International Nuclear Information System (INIS)

    Clarizia, A.; Pezzella, F.

    1987-09-01

    We construct a BRST invariant (N+M)-string vertex including both open and closed string states. When we saturate it with N open string and M closed string physical states it reproduces their corresponding scattering amplitude. As a particular case we obtain BRST invariant vertex for the open-closed string transition. (orig.)

  2. Open-closed string correspondence in open string field theory

    International Nuclear Information System (INIS)

    Baumgartl, M.; Sachs, I.

    2008-01-01

    We address the problem of describing different closed string backgrounds in background independent open string field theory: A shift in the closed string background corresponds to a collective excitation of open strings. As an illustration we apply the formalism to the case where the closed string background is a group manifold. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  3. Percutaneous coronary intervention and the management of acute coronary syndromes in patients with von Willebrand disease.

    Science.gov (United States)

    Rathore, Sulaiman; Deleon, Dexter; Akram, Hafsa; Sane, David; Ball, Timothy

    2013-04-01

    Von Willebrand disease (vWD) results from quantitative or qualitative deficiency of von Willebrand factor (vWF). The occurrence of myocardial infarction is very rare in patients with vWD. A few case reports of acute coronary syndrome (ACS) in vWD patients are present in the literature, but no definite management recommendations are available for such patients. We report a case of successful percutaneous coronary intervention (PCI) with bare-metal stent (BMS) implantation in a 46-year-old woman with type 1 vWD and history of coronary artery disease (CAD). She received periprocedural dual-antiplatelet therapy for 2 weeks and then continued aspirin without any bleeding complications. The optimal management of patients with vWD and ACS is complex and presents a therapeutic challenge. We propose that dual-antiplatelet therapy can be used safely in most vWD patients presenting with ACS as most of them are type 1 vWD. PCI with BMS can be done safely. Long-term management of these patients requires a systemic approach including hematological consultation, ascertaining vWF levels, as well as patient education and close outpatient follow-up.

  4. Strings, texture, and inflation

    International Nuclear Information System (INIS)

    Hodges, H.M.; Primack, J.R.

    1991-01-01

    We examine mechanisms, several of which are proposed here, to generate structure formation, or to just add large-scale features, through either gauged or global cosmic strings or global texture, within the framework of inflation. We first explore the possibility that strings or texture form if there is no coupling between the topological theory and the inflaton or spacetime curvature, via (1) quantum creation, and (2) a sufficiently high reheat temperature. In addition, we examine the prospects for the inflaton field itself to generate strings or texture. Then, models with the string/texture field coupled to the curvature, and an equivalent model with coupling to the inflaton field, are considered in detail. The requirement that inflationary density fluctuations are not so large as to conflict with observations leads to a number of constraints on model parameters. We find that strings of relevance for structure formation can form in the absence of coupling to the inflaton or curvature through the process of quantum creation, but only if the strings are strongly type I, or if they are global strings. If formed after reheating, naturalness suggests that gauged cosmic strings correspond to a type-I superconductor. Similarly, gauged strings formed during inflation via conformal coupling ξ=1/6 to the spacetime curvature (in a model suggested by Yokoyama in order to evade the millisecond pulsar constraint on cosmic strings) are expected to be strongly type I

  5. Von Willebrand's Disease in Two Families of Doberman Pinschers

    OpenAIRE

    Johnstone, I. B.; Crane, S.

    1981-01-01

    The history, clinical symptoms and laboratory results in two families of Doberman pinschers with von Willebrand's disease are described. The affected animals illustrate the rather nonspecific bleeding problems that may be encountered in mild and moderate forms of this disease. In both families a bleeding diathesis was suspected when one member of the family underwent surgery with serious postoperative bleeding complications. These cases illustrate the importance of a thorough presurgical hist...

  6. Topics in string theory

    International Nuclear Information System (INIS)

    Neveu, A.

    1986-01-01

    There exist several string models. In the first lecture, the simplest one, the open bosonic string, which turns out to live most naturally in 26 dimensions will be described in some detail. In the second lecture, the closed bosonic strings, and the open and closed 10-dimensional strings (superstrings) are reviewed. In the third lecture, various compactification schemes which have been proposed to deal with the extra space dimensions, from 4 to 10 or 26 are dealt with; in particular, the Frenkel-Kac construction which builds non-Abelian internal symmetry groups out of the compactified dimensions, and the resulting heterotic string are described. Finally, in the fourth lecture, the important problem of the second quantization of string theories, and of the underlying gauge invariance which is responsible for the possibility of dealing, in a consistent fashion, with interacting high-spin states without negative metric is addressed. 41 references, 8 figures

  7. Strings and quantum gravity

    International Nuclear Information System (INIS)

    Vega, H.J. de

    1990-01-01

    One of the main challenges in theoretical physics today is the unification of all interactions including gravity. At present, string theories appear as the most promising candidates to achieve such a unification. However, gravity has not completely been incorporated in string theory, many technical and conceptual problems remain and a full quantum theory of gravity is still non-existent. Our aim is to properly understand strings in the context of quantum gravity. Attempts towards this are reviewed. (author)

  8. 6d string chains

    Science.gov (United States)

    Gadde, Abhijit; Haghighat, Babak; Kim, Joonho; Kim, Seok; Lockhart, Guglielmo; Vafa, Cumrun

    2018-02-01

    We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E 8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.

  9. QCD and string theories

    International Nuclear Information System (INIS)

    Cohen-Tannoudji, G.

    1990-01-01

    This paper is devoted to a review of the connections between quantumchromodynamics (QCD) and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality

  10. Thermodynamics of quantum strings

    CERN Document Server

    Morgan, M J

    1994-01-01

    A statistical mechanical analysis of an ideal gas of non-relativistic quantum strings is presented, in which the thermodynamic properties of the string gas are calculated from a canonical partition function. This toy model enables students to gain insight into the thermodynamics of a simple 'quantum field' theory, and provides a useful pedagogical introduction to the more complicated relativistic string theories. A review is also given of the thermodynamics of the open bosonic string gas and the type I (open) superstring gas. (author)

  11. Interpolating string field theories

    International Nuclear Information System (INIS)

    Zwiebach, B.

    1992-01-01

    This paper reports that a minimal area problem imposing different length conditions on open and closed curves is shown to define a one-parameter family of covariant open-closed quantum string field theories. These interpolate from a recently proposed factorizable open-closed theory up to an extended version of Witten's open string field theory capable of incorporating on shell closed strings. The string diagrams of the latter define a new decomposition of the moduli spaces of Riemann surfaces with punctures and boundaries based on quadratic differentials with both first order and second order poles

  12. Heterotic cosmic strings

    International Nuclear Information System (INIS)

    Becker, Katrin; Becker, Melanie; Krause, Axel

    2006-01-01

    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

  13. Stretching cosmic strings

    International Nuclear Information System (INIS)

    Turok, N.; Bhattacharjee, P.

    1984-01-01

    The evolution of a network of strings produced at a grand-unification phase transition in an expanding universe is discussed, with particular reference to the processes of energy exchange between the strings and the rest of the universe. This is supported by numerical calculations simulating the behavior of strings in an expanding universe. It is found that in order that the energy density of the strings does not come to dominate the total energy density there must be an efficient mechanism for energy loss: the only plausible one being the production of closed loops and their subsequent decay via gravitational radiation

  14. QCD and hadronic strings

    International Nuclear Information System (INIS)

    Cohen-Tannoudji, G.

    1989-01-01

    This series of lectures is devoted to review ot he connections between QCD and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality.(author)

  15. String formation beyond leading colour

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, Jesper R. [Department of Astronomy and Theoretical Physics, Lund University,Sölvegatan 14, Lund (Sweden); Theoretical Physics, CERN,CH-1211, Geneva 23 (Switzerland); Skands, Peter Z. [Theoretical Physics, CERN,CH-1211, Geneva 23 (Switzerland); School of Physics and Astronomy, Monash University,VIC-3800 (Australia)

    2015-08-03

    We present a new model for the hadronisation of multi-parton systems, in which colour correlations beyond leading N{sub C} are allowed to influence the formation of confining potentials (strings). The multiplet structure of SU(3) is combined with a minimisation of the string potential energy, to decide between which partons strings should form, allowing also for “baryonic” configurations (e.g., two colours can combine coherently to form an anticolour). In e{sup +}e{sup −}collisions, modifications to the leading-colour picture are small, suppressed by both colour and kinematics factors. But in pp collisions, multi-parton interactions increase the number of possible subleading connections, counteracting their naive 1/N{sub C}{sup 2} suppression. Moreover, those that reduce the overall string lengths are kinematically favoured. The model, which we have implemented in the PYTHIA 8 generator, is capable of reaching agreement not only with the important 〈p{sub ⊥}〉(n{sub charged}) distribution but also with measured rates (and ratios) of kaons and hyperons, in both ee and pp collisions. Nonetheless, the shape of their p{sub ⊥} spectra remains challenging to explain.

  16. The design of steel string crane with lifting capacity 10 tons

    International Nuclear Information System (INIS)

    Syamsurrijal Ramdja

    2007-01-01

    The steel string (sling) used for lift Crane of type of Overhead Travelling Crane, with capacities lifting 10 ton are designed. If compared to other string type, string of steel have some excellence. At this design, election of type of string become primary and the factor of safety become prima facie matter with pursuant to up to date standard. From made of design, is hence got by specification and age of steel string. (author)

  17. Sa’Unine String Orchestra, Orkes Geseknya Indonesia

    Directory of Open Access Journals (Sweden)

    Ranti - Rachmawanti

    2012-04-01

    Full Text Available ABSTRACT   This article explains the result of Sa’Unine String Orchestra as one of Indonesian orchestras in popular culture. Main idea of this research is to uncover and describe the characteristic, func- tion, and role of Sa’Unine String Orchestra within the popular culture in Indonesia. This research used qualitative method with ethnographical approaches to identify all facts that discovered during research. The conclusions of this research show that Sa’Unine String Orchestra moves in two ways, there are; the idealism which had a vision to create a real Indonesian string orchestra and a part of music industry. At the end, these two ways are connected to each other because of the earnings of those. Music industry becomes a support factor which create the idealism of Sa’Unine String Or- chestra to be an Indonesian String Orchestra.   Keywords: String Orchestra, Music, Popular Culture.

  18. Gauge and general covariance of string interactions

    International Nuclear Information System (INIS)

    Das, S.R.

    1986-01-01

    All fundamental interactions at observable energies seem to arise out of local symmetries - gauge invariances and general coordinate invariance. In usual field theories of point particles these invariances are postulated a priori: the idea is to deduce everything else from the symmetry group and the representation content of the matter fields. In string theories, the situation is rather different. Here the basic principle is reparametrization invariance on the world sheet swept out by the string. The authors consider the simplest string models-those defined on flat Minkowski space-time. The transverse oscillations of the string lead to an infinite tower of modes which may be thought of as the ''particles'' constituting the string. The interacting string theory is defined, in the first quantized formulation, by specifying the interaction of these modes with the string. These interaction vertices must satisfy a basic requirement: when any dual amplitude is factorized only physical states (i.e. those satisfying the Virasoro conditions) must occur as on-mass-shell intermediate states. This means that the vertices respect the reparametrization invariance of the world sheet, since it is this symmetry which eliminates ghost states by virtue of Virasoro conditions

  19. Semilocal and electroweak strings

    NARCIS (Netherlands)

    Achucarro, A; Vachaspati, T

    We review a class of non-topological defects in the standard electroweak model, and their implications. Starting with the semilocal string, which provides a counterexample to many well-known properties of topological vortices, we discuss electroweak strings and their stability with and without

  20. Disordered chaotic strings

    DEFF Research Database (Denmark)

    Schäfer, Mirko; Greiner, Martin

    2011-01-01

    to chaotic strings. Inhomogeneous coupling weights as well as small-world perturbations of the ring-network structure are discussed. It is found that certain combinations of coupling and network disorder preserve the empirical relationship between chaotic strings and the weak and strong sector...

  1. A rotating string

    International Nuclear Information System (INIS)

    Jensen, B.

    1993-06-01

    The author presents a global solution of Einstein's equations which represents a rotating cosmic string with a finite coreradius. The importance of pressure for the generation of closed timelike curves outside the coreregion of such strings is clearly displayed in this model due to the simplicity of the source. 10 refs

  2. Derandomizing from random strings

    NARCIS (Netherlands)

    Buhrman, H.; Fortnow, L.; Koucký, M.; Loff, B.

    2010-01-01

    In this paper we show that BPP is truth-table reducible to the set of Kolmogorov random strings R(K). It was previously known that PSPACE, and hence BPP is Turing-reducible to R(K). The earlier proof relied on the adaptivity of the Turing-reduction to find a Kolmogorov-random string of polynomial

  3. Unification of string dualities

    International Nuclear Information System (INIS)

    Sen, A.

    1997-01-01

    We argue that all conjectured dualities involving various string, M- and F-theory compactifications can be 'derived' from the conjectured duality between type I and SO(32) heterotic string theory, T-dualities and the definition of M-and F-theories. (orig.)

  4. Introduction to string theory

    CERN Multimedia

    CERN. Geneva. Audiovisual Unit

    2002-01-01

    I will present a simple and non-technical overview of string theory, aimed for non-experts who like to get some idea what string theory is about. Besides introductory material, I intend to cover also some of the more recent developments.

  5. StringForce

    DEFF Research Database (Denmark)

    Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva

    2017-01-01

    In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play String......Force two or four physically collocated tablets are required. These tablets are connected to form one large shared game area. The game can only be played by collaborating. StringForce extends previous work, both technologically and regarding social-emotional training. We believe String......Force to be an interesting demo for the IDC community, as it intertwines several relevant research fields, such as mobile interaction and collaborative gaming in the special education context....

  6. String-Math 2015

    CERN Document Server

    2015-01-01

    Welcome to String-Math 2015 at Sanya. The conference will be opened in December 31, 2015- January 4, 2016. String theory plays a central role in theoretical physics as a candidate for the quantum theory unifying gravity with other interactions. It has profound connections with broad branches of modern mathematics ever since the birth. In the last decades, the prosperous interaction, built upon the joint efforts from both mathematicians and physicists, has given rise to marvelous deep results in supersymmetric gauge theory, topological string, M-theory and duality on the physics side as well as in algebraic geometry, differential geometry, algebraic topology, representation theory and number theory on the mathematics side. The interplay is two-fold. The mathematics has provided powerful tools to fulfill the physical interconnection of ideas and clarify physical structures to understand the nature of string theory. On the other hand, ideas from string theory and quantum field theory have been a source of sign...

  7. Paciente portadora de doença de von Willebrand submetida a cirurgia da valva mitral: uma estratégia para o controle da coagulopatia Patient with von Willebrand disease undergoing mitral valve repair: a strategy for the control of the coagulopathy

    Directory of Open Access Journals (Sweden)

    Ally Nader Roquetti Saroute

    2007-01-01

    Full Text Available Relatamos o caso de uma mulher de 60 anos portadora da doença de von Willebrand tipo I, submetida a cirurgia da valva mitral. A paciente necessitou de cuidados especiais em razão da coagulopatia e foi necessária a utilização de concentrado de fator VIII (VIIIf e fator de von Willebrand (vWf antes, durante e depois da cirurgia. Não houve complicações durante e após a cirurgia. Nove meses depois, a paciente encontra-se assintomática. A correção para valores adequados de VIIIf e vWf permitiu a realização da cirurgia com segurança.We report a case of a 60 year-old woman with von Willebrand disease type I that was submitted to a mitral valve repair. The patient needed special care due coagulopathy and needed VIII factor (VIIIf and von Willebrand factor (vWf, before, during and after surgery. There was no complication during or after surgery. Patient is asymptomatic nine months postoperatively. The correction of VIIIf and vWf allowed the realization of a safety surgery.

  8. A reduced covariant string model for the extrinsic string

    International Nuclear Information System (INIS)

    Botelho, L.C.L.

    1989-01-01

    It is studied a reduced covariant string model for the extrinsic string by using Polyakov's path integral formalism. On the basis of this reduced model it is suggested that the extrinsic string has its critical dimension given by 13. Additionally, it is calculated in a simple way Poliakov's renormalization group law for the string rigidity coupling constants. (A.C.A.S.) [pt

  9. Van Willebrand's disease in the Western Cape

    African Journals Online (AJOL)

    agglutinate normal platelets but does not have an effect on platelets from patients with VWD. The ristocetin co-factor. (RiCo~ assay measures the ability of plasma to agglutinate fixed platelets and is therefore regarded as an indirect measure of VWF activity. Qualitative analysis of VWF antigen. 0JWF-Ag) is required for ...

  10. String field theory

    International Nuclear Information System (INIS)

    Kaku, M.

    1987-01-01

    In this article, the authors summarize the rapid progress in constructing string field theory actions, such as the development of the covariant BRST theory. They 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 they 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). The geometric formulation places superstring theory on the same rigorous group theoretical level as general relativity and gauge theory

  11. Duality relation between charged elastic strings and superconducting cosmic strings

    International Nuclear Information System (INIS)

    Carter, B.

    1989-01-01

    The mechanical properties of macroscopic electromagnetically coupled string models in a flat or curved background are treated using a covariant formalism allowing the construction of a duality transformation that relates the category of uniform ''electric'' string models, constructed as the (nonconducting) charged generalisation of ordinary uncoupled (violin type) elastic strings, to a category of ''magnetic'' string models comprising recently discussed varieties of ''superconducting cosmic strings''. (orig.)

  12. Lattice gravity and strings

    International Nuclear Information System (INIS)

    Jevicki, A.; Ninomiya, M.

    1985-01-01

    We are concerned with applications of the simplicial discretization method (Regge calculus) to two-dimensional quantum gravity with emphasis on the physically relevant string model. Beginning with the discretization of gravity and matter we exhibit a discrete version of the conformal trace anomaly. Proceeding to the string problem we show how the direct approach of (finite difference) discretization based on Nambu action corresponds to unsatisfactory treatment of gravitational degrees. Based on the Regge approach we then propose a discretization corresponding to the Polyakov string. In this context we are led to a natural geometric version of the associated Liouville model and two-dimensional gravity. (orig.)

  13. Superconducting cosmic strings

    International Nuclear Information System (INIS)

    Chudnovsky, E.M.; Field, G.B.; Spergel, D.N.; Vilenkin, A.

    1986-01-01

    Superconducting loops of string formed in the early Universe, if they are relatively light, can be an important source of relativistic particles in the Galaxy. They can be observed as sources of synchrotron radiation at centimeter wavelengths. We propose a string model for two recently discovered radio sources, the ''thread'' in the galactic center and the source G357.7-0.1, and predict that the filaments in these sources should move at relativistic speeds. We also consider superheavy superconducting strings, and the possibility that they be observed as extragalactic radio sources

  14. Final Report: "Strings 2014"

    Energy Technology Data Exchange (ETDEWEB)

    Witten, Edward

    2015-10-21

    The Strings 2014 meeting was held at Princeton University June 23-27, 2014, co-sponsored by Princeton University and the Institute for Advanced Study. The goal of the meeting was to provide a stimulating and up-to-date overview of research in string theory and its relations to other areas of physics and mathematics, ranging from geometry to quantum field theory, condensed matter physics, and more. This brief report lists committee members and speakers but contains no scientific information. Note that the talks at Strings 2014 were videotaped and are available on the conference website: http://physics.princeton.edustrings2014/Talk_titles.shtml.

  15. A disintegrating cosmic string

    International Nuclear Information System (INIS)

    Griffiths, J B; Docherty, P

    2002-01-01

    We present a simple sandwich gravitational wave of the Robinson-Trautman family. This is interpreted as representing a shock wave with a spherical wavefront which propagates into a Minkowski background minus a wedge (i.e. the background contains a cosmic string). The deficit angle (the tension) of the string decreases through the gravitational wave, which then ceases. This leaves an expanding spherical region of Minkowski space behind it. The decay of the cosmic string over a finite interval of retarded time may be considered to generate the gravitational wave. (letter to the editor)

  16. Baryon string model

    International Nuclear Information System (INIS)

    Klimenko, S.V.; Kochin, V.N.; Plyushchaj, M.S.; Pron'ko, G.P.; Razumov, A.V.; Samarin, A.V.

    1985-01-01

    Partial solutions to classical equations of three-string motion are considered. Simplest solutions, when three-string center moving with high velocity, are co nsidered. Single-mode solutions are studied. Explicit form of their parametrization is obtained and three-string dynamics visualization is made. Means of graphic packet ''Atom'' were used for visualization. A set of processes for graphic representation of multiparametric functions is developed. Peculiarity of these processes is a wide class of functions, which are represented by parametric, coordinate and functional isolines

  17. Exceptional groups from open strings

    International Nuclear Information System (INIS)

    Gaberdiel, M.R.; Zwiebach, B.

    1998-01-01

    We consider type IIB theory compactified on a two-sphere in the presence of mutually non-local 7-branes. The BPS states associated with the gauge vectors of exceptional groups are seen to arise from open strings connecting the 7-branes, and multi-pronged open strings capable of ending on more than two 7-branes. These multi-pronged strings are built from open string junctions that arise naturally when strings cross 7-branes. The different string configurations can be multiplied as traditional open strings, and are shown to generate the structure of exceptional groups. (orig.)

  18. Erythrocytes and von Willebrand factor in venous thrombosis

    NARCIS (Netherlands)

    Smeets, M.W.J.

    2018-01-01

    Venous thromboembolism represents the third leading vascular disease after myocardial infarction and stroke. Erythrocytes, the most abundant cells in venous thrombi, were thought to be innocent bystanders that become tangled up in the fibrin mesh of venous thrombi. However, this thesis describes

  19. Molecular characterization of exon 28 of von Willebrand's factor ...

    African Journals Online (AJOL)

    2016-05-12

    May 12, 2016 ... were mostly among individuals with Arab ancestry.[3] In. Zimbabwe ... bleeding symptoms are epistaxis, menorrhagia (in women), easy bruising, oral cavity ... North American, British, and Japanese populations. rs1800383 ...

  20. Cosmic strings and cosmic structure

    International Nuclear Information System (INIS)

    Albrecht, A.; Brandenberger, R.; Turok, N.

    1987-01-01

    The paper concerns the application of the theory of cosmic strings to explain the structure of the Universe. The formation of cosmic strings in the early Universe is outlined, along with the Big Bang theory, Grand Unified theories, and the first three minutes after the Big Bang. A description is given of the shaping of the Universe by cosmic strings, including the evolution of the string. The possibility for direct observation of cosmic strings is discussed. (U.K.)

  1. International conference on string theory

    CERN Document Server

    2017-01-01

    The Strings 2017 conference is part of the "Strings" series of annual conferences, that bring the entire string theory community together. It will include reviews of major developments in the field, and specialized talks on specific topics. There will also be several public lectures given by conference participants, a pre-Strings school at the Technion, and a post-Strings workshop at the Weizmann Institute.

  2. Mechanical Properties of Nylon Harp Strings

    Science.gov (United States)

    Lynch-Aird, Nicolas; Woodhouse, Jim

    2017-01-01

    Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings. PMID:28772858

  3. Mechanical Properties of Nylon Harp Strings

    Directory of Open Access Journals (Sweden)

    Nicolas Lynch-Aird

    2017-05-01

    Full Text Available Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings.

  4. String-math 2012

    CERN Document Server

    Katz, Sheldon; Klemm, Albrecht; Morrison, David R

    2015-01-01

    This volume contains the proceedings of the conference String-Math 2012, which was held July 16-21, 2012, at the Hausdorff Center for Mathematics, Universitat Bonn. This was the second in a series of annual large meetings devoted to the interface of mathematics and string theory. These meetings have rapidly become the flagship conferences in the field. Topics include super Riemann surfaces and their super moduli, generalized moonshine and K3 surfaces, the latest developments in supersymmetric and topological field theory, localization techniques, applications to knot theory, and many more. The contributors include many leaders in the field, such as Sergio Cecotti, Matthias Gaberdiel, Rahul Pandharipande, Albert Schwarz, Anne Taormina, Johannes Walcher, Katrin Wendland, and Edward Witten. This book will be essential reading for researchers and students in this area and for all mathematicians and string theorists who want to update themselves on developments in the math-string interface.

  5. Hydroball string sensing system

    International Nuclear Information System (INIS)

    Hurwitz, M.J.; Ekeroth, D.E.; Squarer, D.

    1991-01-01

    This patent describes a hydroball string sensing system for a nuclear reactor having a core containing a fluid at a fluid pressure. It comprises a tube connectable to the nuclear reactor so that the fluid can flow within the tube at a fluid pressure that is substantially the same as the fluid pressure of the nuclear reactor core; a hydroball string including - a string member having objects positioned therealong with a specified spacing, the object including a plurality of hydroballs, and bullet members positioned at opposing ends of the string member; first sensor means, positioned outside a first segment of the tube, for sensing one of the objects being positioned within the first segment, and for providing a sensing signal responsive to the sensing of the first sensing means

  6. The QCD Effective String

    International Nuclear Information System (INIS)

    Espriu, D.

    2003-01-01

    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. (author)

  7. Field theory of strings

    International Nuclear Information System (INIS)

    Ramond, P.

    1987-01-01

    We review the construction of the free equations of motion for open and closed strings in 26 dimensions, using the methods of the Florida Group. Differing from previous treatments, we argue that the constraint L 0 -anti L 0 =0 should not be imposed on all the fields of the closed string in the gauge invariant formalism; we show that it can be incorporated in the gauge invariant formalism at the price of being unable to extract the equations of motion from a Langrangian. We then describe our purely algebraic method to introduce interactions, which works equally well for open and closed strings. Quartic interactions are absent except in the Physical Gauge. Finally, we speculate on the role of the measure of the open string path functional. (orig.)

  8. String Theory Rocks!

    CERN Multimedia

    2008-01-01

    String Theory supporters argue that the universe we live in has eleven dimensions, out of which three spacial dimensions and a temporal one, which define the void and the space-time environment we experience daily.

  9. Nonrelativistic closed string theory

    International Nuclear Information System (INIS)

    Gomis, Jaume; Ooguri, Hirosi

    2001-01-01

    We construct a Galilean invariant nongravitational closed string theory whose excitations satisfy a nonrelativistic dispersion relation. This theory can be obtained by taking a consistent low energy limit of any of the conventional string theories, including the heterotic string. We give a finite first order worldsheet Hamiltonian for this theory and show that this string theory has a sensible perturbative expansion, interesting high energy behavior of scattering amplitudes and a Hagedorn transition of the thermal ensemble. The strong coupling duals of the Galilean superstring theories are considered and are shown to be described by an eleven-dimensional Galilean invariant theory of light membrane fluctuations. A new class of Galilean invariant nongravitational theories of light-brane excitations are obtained. We exhibit dual formulations of the strong coupling limits of these Galilean invariant theories and show that they exhibit many of the conventional dualities of M theory in a nonrelativistic setting

  10. String theory compactifications

    CERN Document Server

    Graña, Mariana

    2017-01-01

    The lectures in this book provide graduate students and non-specialist researchers with a concise introduction to the concepts and formalism required to reduce the ten-dimensional string theories to the observable four-dimensional space-time - a procedure called string compactification. The text starts with a very brief introduction to string theory, first working out its massless spectrum and showing how the condition on the number of dimensions arises. It then dwells on the different possible internal manifolds, from the simplest to the most relevant phenomenologically, thereby showing that the most elegant description is through an extension of ordinary Riemannian geometry termed generalized geometry, which was first introduced by Hitchin. Last but not least, the authors review open problems in string phenomenology, such as the embedding of the Standard Model and obtaining de Sitter solutions.

  11. Technological advances in diagnostic testing for von Willebrand disease: new approaches and challenges.

    Science.gov (United States)

    Hayward, C P M; Moffat, K A; Graf, L

    2014-06-01

    Diagnostic tests for von Willebrand disease (VWD) are important for the assessment of VWD, which is a commonly encountered bleeding disorder worldwide. Technical innovations have been applied to improve the precision and lower limit of detection of von Willebrand factor (VWF) assays, including the ristocetin cofactor activity assay (VWF:RCo) that uses the antibiotic ristocetin to induce plasma VWF binding to glycoprotein (GP) IbIXV on target platelets. VWF-collagen-binding assays, depending on the type of collagen used, can improve the detection of forms of VWD with high molecular weight VWF multimer loss, although the best method is debatable. A number of innovations have been applied to VWF:RCo (which is commonly performed on an aggregometer), including replacing the target platelets with immobilized GPIbα, and quantification by an enzyme-linked immunosorbent assay (ELISA), immunoturbidimetric, or chemiluminescent end-point. Some common polymorphisms in the VWF gene that do not cause bleeding are associated with falsely low VWF activity by ristocetin-dependent methods. To overcome the need for ristocetin, some new VWF activity assays use gain-of-function GPIbα mutants that bind VWF without the need for ristocetin, with an improved precision and lower limit of detection than measuring VWF:RCo by aggregometry. ELISA of VWF binding to mutated GPIbα shows promise as a method to identify gain-of-function defects from type 2B VWD. The performance characteristics of many new VWF activity assays suggest that the detection of VWD, and monitoring of VWD therapy, by clinical laboratories could be improved through adopting newer generation VWF assays. © 2014 John Wiley & Sons Ltd.

  12. Heterotic string construction

    International Nuclear Information System (INIS)

    Schellekens, A.N.

    1989-01-01

    In this paper an elementary introduction to the principles of four-dimensional string construction will be given. Although the emphasis is on lattice constructions, almost all results have further, and often quite straightforward generalizations to other constructions. Since heterotic strings look phenomenologically more promising than type-II theories the authors only consider the former, although everything can easily be generalized to type-II theories. Some additional aspects of lattice constructions are discussed, and an extensive review can be found

  13. Confusing the heterotic string

    International Nuclear Information System (INIS)

    Benett, D.L.; Mizrachi, L.

    1986-01-01

    A confusion mechanism is proposed as a global modification of the heterotic string model. It envolves a confusion hypersurface across which the two E 8 's of the heterotic string are permuted. A remarkable numerical coincidence is found which prevents an inconsistency in the model. The low energy limit of this theory (after compactification) is typically invariant under one E 8 only, thereby removing the shadow world from the original model. (orig.)

  14. Confusing the heterotic string

    Science.gov (United States)

    Benett, D.; Brene, N.; Mizrachi, Leah; Nielsen, H. B.

    1986-10-01

    A confusion mechanism is proposed as a global modification of the heterotic string model. It envolves a confusion hypersurface across which the two E 8's of the heterotic string are permuted. A remarkable numerical coincidence is found which prevents an inconsistency in the model. The low energy limit of this theory (after compactification) is typically invariant under one E 8 only, thereby removing the shadow world from the original model.

  15. Confusing the heterotic string

    Energy Technology Data Exchange (ETDEWEB)

    Benett, D.L.; Brene, N.; Nielsen, H.B.; Mizrachi, L.

    1986-10-02

    A confusion mechanism is proposed as a global modification of the heterotic string model. It envolves a confusion hypersurface across which the two E/sub 8/'s of the heterotic string are permuted. A remarkable numerical coincidence is found which prevents an inconsistency in the model. The low energy limit of this theory (after compactification) is typically invariant under one E/sub 8/ only, thereby removing the shadow world from the original model.

  16. Lectures on string theory

    International Nuclear Information System (INIS)

    Thorn, C.B.

    1988-01-01

    Several topics are discussed in string theory presented as three lectures to the Spring School on Superstrings at the ICTP at Trieste, Italy, in April, 1988. The first lecture is devoted to some general aspects of conformal invariance and duality. The second sketches methods for carrying out perturbative calculations in string field theory. The final lecture presents an alternative lattice approach to a nonperturbative formulation of the sum over world surfaces. 35 refs., 12 figs

  17. String dynamics in QCD

    International Nuclear Information System (INIS)

    Gervais, J.L.; Neveu, A.

    1980-01-01

    Recent works of the authors on string interpretation of the Wilson loop operators in QCD are reviewed in a self-contained fashion. Although most of the results habe already appeared in print, some new material is presented in renormalization of the Wilson loop operator and on the use of light-cone expansion to derive a linear string-like equation in light-cone formalism. (orig.)

  18. Matrix String Theory

    CERN Document Server

    Dijkgraaf, R; Verlinde, Herman L

    1997-01-01

    Via compactification on a circle, the matrix model of M-theory proposed by Banks et al 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 appearance of D-particle and D-membrane states.

  19. Manipulating Strings in Python

    Directory of Open Access Journals (Sweden)

    William J. Turkel

    2012-07-01

    Full Text Available This lesson is a brief introduction to string manipulation techniques in Python. Knowing how to manipulate strings plays a crucial role in most text processing tasks. If you’d like to experiment with the following lessons, you can write and execute short programs as we’ve been doing, or you can open up a Python shell / Terminal to try them out on the command line.

  20. String Theory - The Physics of String-Bending and Other Electric Guitar Techniques

    Science.gov (United States)

    Grimes, David Robert

    2014-01-01

    Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed. PMID:25054880

  1. String theory--the physics of string-bending and other electric guitar techniques.

    Directory of Open Access Journals (Sweden)

    David Robert Grimes

    Full Text Available Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

  2. String theory--the physics of string-bending and other electric guitar techniques.

    Science.gov (United States)

    Grimes, David Robert

    2014-01-01

    Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

  3. Deterministic indexing for packed strings

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Skjoldjensen, Frederik Rye

    2017-01-01

    Given a string S of length n, the classic string indexing problem is to preprocess S into a compact data structure that supports efficient subsequent pattern queries. In the deterministic variant the goal is to solve the string indexing problem without any randomization (at preprocessing time...... or query time). In the packed variant the strings are stored with several character in a single word, giving us the opportunity to read multiple characters simultaneously. Our main result is a new string index in the deterministic and packed setting. Given a packed string S of length n over an alphabet σ...

  4. The identity string field and the sliver frame level expansion

    Czech Academy of Sciences Publication Activity Database

    Erler, Theodore

    2012-01-01

    Roč. 2012, č. 11 (2012), s. 1-25 ISSN 1126-6708 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : tachyon condensation, bosonic strings , String Field Theory Subject RIV: BE - Theoretical Physics Impact factor: 5.618, year: 2012

  5. New variations on two old themes - String Theory and Baryonium

    International Nuclear Information System (INIS)

    Chan Hong-Mo.

    1989-07-01

    A trace factor introduced twenty years ago to incorporate internal symmetry into String Theory is generalised to include also string dynamics, while some new spectroscopic data are examined in relation to a ten year old model of exotic qq-q-barq-bar mesons. (author)

  6. Cesariana em paciente com doença de von Willebrand associada à infecção pelo HIV: relato de caso Cesárea en paciente con enfermedad de von Willebrand asociada a la infección por el HIV: relato de caso Anesthesia for cesarean section in patient with von Willebrand's disease and HIV infection: case report

    Directory of Open Access Journals (Sweden)

    Vanessa Rezende Balle

    2004-12-01

    Willebrand y HIV positiva sometida a cesárea. RELATO DEL CASO: Paciente de 24 años, portadora de anemia microcítica, enfermedad de von Willebrand y HIV, llegó a la emergencia obstétrica en inicio de trabajo de alumbramiento. No realizó prenatal. Fue indicada cesárea a fin de disminuir los riesgos de transmisión vertical en paciente con carga vírica de HIV desconocida. Presentaba hematomas por el cuerpo e historia de hematoma de pared abdominal en cesárea anterior. Los tests de coagulación estaban un poco alterados. Después de infusión de concentrado de factor VIII fue realizada anestesia general. Madre y recién nacido presentaron evolución satisfactoria. CONCLUSIONES: La evaluación de manifestaciones clínicas en pacientes con coagulopatia es fundamental en la decisión del tipo de anestesia que será indicada para cada paciente. La evaluación debe ser individualizada, considerando los riesgos y beneficios de la técnica escogida. En estas pacientes, se debe siempre restringir al máximo la indicación de interrupción de la gestación por vía alta, optándose siempre por los métodos menos invasivos. La terapia con concentrado de factor VIII es actualmente la mejor opción de tratamiento, corrigiendo la deficiencia específica y dismunuyendo los riesgos de transmisión vírica.BACKGROUND AND OBJECTIVES: Von Willebrand's disease is the most common hereditary coagulation disorder in young women. The incidence of HIV infection among women has been progressively increasing, and vertical transmission may account for 25% of cases. This report aimed at describing the case of an HIV-positive patient with von Willebrand's disease scheduled for cesarean section. CASE REPORT: Female HIV-positive patient, 24 years old, with microcytic anemia and von Willebrand's disease, admitted to the emergency room in early labor. She had no pre-natal care. Cesarean section was indicated to lower vertical transmission risks since HIV viral count was unknown. Patient had hematomas

  7. Windings of twisted strings

    Science.gov (United States)

    Casali, Eduardo; Tourkine, Piotr

    2018-03-01

    Twistor string models have been known for more than a decade now but have come back under the spotlight recently with the advent of the scattering equation formalism which has greatly generalized the scope of these models. A striking ubiquitous feature of these models has always been that, contrary to usual string theory, they do not admit vibrational modes and thus describe only conventional field theory. In this paper we report on the surprising discovery of a whole new sector of one of these theories which we call "twisted strings," when spacetime has compact directions. We find that the spectrum is enhanced from a finite number of states to an infinite number of interacting higher spin massive states. We describe both bosonic and world sheet supersymmetric models, their spectra and scattering amplitudes. These models have distinctive features of both string and field theory, for example they are invariant under stringy T-duality but have the high energy behavior typical of field theory. Therefore they describe a new kind of field theories in target space, sitting on their own halfway between string and field theory.

  8. Strings and fundamental physics

    International Nuclear Information System (INIS)

    Baumgartl, Marco; Brunner, Ilka; Haack, Michael

    2012-01-01

    The basic idea, simple and revolutionary at the same time, to replace the concept of a point particle with a one-dimensional string, has opened up a whole new field of research. Even today, four decades later, its multifaceted consequences are still not fully conceivable. Up to now string theory has offered a new way to view particles as different excitations of the same fundamental object. It has celebrated success in discovering the graviton in its spectrum, and it has naturally led scientists to posit space-times with more than four dimensions - which in turn has triggered numerous interesting developments in fields as varied as condensed matter physics and pure mathematics. This book collects pedagogical lectures by leading experts in string theory, introducing the non-specialist reader to some of the newest developments in the field. The carefully selected topics are at the cutting edge of research in string theory and include new developments in topological strings, AdS/CFT dualities, as well as newly emerging subfields such as doubled field theory and holography in the hydrodynamic regime. The contributions to this book have been selected and arranged in such a way as to form a self-contained, graduate level textbook. (orig.)

  9. Strings and fundamental physics

    Energy Technology Data Exchange (ETDEWEB)

    Baumgartl, Marco [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Brunner, Ilka; Haack, Michael (eds.) [Muenchen Univ. (Germany). Fakultaet fuer Physik

    2012-07-01

    The basic idea, simple and revolutionary at the same time, to replace the concept of a point particle with a one-dimensional string, has opened up a whole new field of research. Even today, four decades later, its multifaceted consequences are still not fully conceivable. Up to now string theory has offered a new way to view particles as different excitations of the same fundamental object. It has celebrated success in discovering the graviton in its spectrum, and it has naturally led scientists to posit space-times with more than four dimensions - which in turn has triggered numerous interesting developments in fields as varied as condensed matter physics and pure mathematics. This book collects pedagogical lectures by leading experts in string theory, introducing the non-specialist reader to some of the newest developments in the field. The carefully selected topics are at the cutting edge of research in string theory and include new developments in topological strings, AdS/CFT dualities, as well as newly emerging subfields such as doubled field theory and holography in the hydrodynamic regime. The contributions to this book have been selected and arranged in such a way as to form a self-contained, graduate level textbook. (orig.)

  10. Perspectives on string phenomenology

    CERN Document Server

    Kane, Gordon; Kumar, Piyush

    2015-01-01

    The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M Theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model. This book contains perspectives on stri...

  11. String Chopping and Time-ordered Products of Linear String-localized Quantum Fields

    Science.gov (United States)

    Cardoso, Lucas T.; Mund, Jens; Várilly, Joseph C.

    2018-03-01

    For a renormalizability proof of perturbative models in the Epstein-Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).

  12. Open Wilson lines as states of closed string

    International Nuclear Information System (INIS)

    Murakami, Koichi; Nakatsu, Toshio

    2003-01-01

    A system of a D-brane in bosonic string theory on a constant B field background is studied in order to obtain further insight into the bulk-boundary duality. Boundary states which describe arbitrary numbers of open-string tachyons and gluons are given. The UV behavior of field theories on the non-commutative world-volume is investigated by using these states. We take the zero-slope limits of the generating functions of one-loop amplitudes of gluons (and open-string tachyons) in which the region of the small open-string proper time is magnified. The existence of a B field allows the limits to be slightly different from the standard field theory limits of a closed-string. These limits enable us to obtained world-volume theories at a trans-string scale. In this limit the generating functions are shown to be factorized into two curved open Wilson lines (and their analogues) and become integrals on the space of paths with a Gaussian distribution around straight lines. These facts indicate the possibility that field theories on the non-commutative world-volume are topological at such a trans-string scale. We also give a proof of the Dhar-Kitazawa conjecture by determining an explicit correspondence between the closed-string states and the paths. Momentum eigenstates of closed-string or momentum loops also play an important role in these analyses. (author)

  13. Improved algorithms for approximate string matching (extended abstract

    Directory of Open Access Journals (Sweden)

    Papamichail Georgios

    2009-01-01

    Full Text Available Abstract Background The problem of approximate string matching is important in many different areas such as computational biology, text processing and pattern recognition. A great effort has been made to design efficient algorithms addressing several variants of the problem, including comparison of two strings, approximate pattern identification in a string or calculation of the longest common subsequence that two strings share. Results We designed an output sensitive algorithm solving the edit distance problem between two strings of lengths n and m respectively in time O((s - |n - m|·min(m, n, s + m + n and linear space, where s is the edit distance between the two strings. This worst-case time bound sets the quadratic factor of the algorithm independent of the longest string length and improves existing theoretical bounds for this problem. The implementation of our algorithm also excels in practice, especially in cases where the two strings compared differ significantly in length. Conclusion We have provided the design, analysis and implementation of a new algorithm for calculating the edit distance of two strings with both theoretical and practical implications. Source code of our algorithm is available online.

  14. Interacting-string picture of the fermionic string

    International Nuclear Information System (INIS)

    Mandelstam, S.

    1986-01-01

    This report gives a review of the interacting-string picture of the Bose string. In the present lecture, the author outlines a similar treatment of the Fermionic string. The quantization of the free Fermionic string is carried out to the degrees of freedom x, representing the displacement of the string. Also presented are Grassman degrees of freedom S distributed along the string. The report pictures the fermionic string as a string of dipoles. The general picture of the interaction of such strings by joining and splitting is the same as for the Bose string. The author does not at present have the simplest formula for fermion string scattering amplitudes. A less detailed treatment is given than for the Bose string. The report sets up the functional-integration formalism, derives the analog mode, and indicates in general, terms how the conformal transformation to the z-plane may be performed. The paper concludes by stating without proof the formula for the N-article tree amplitude in the manifestly supersymmetric formalism

  15. Are Stopped Strings Preferred in Sad Music?

    OpenAIRE

    David Huron; Caitlyn Trevor

    2017-01-01

    String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut) or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard). Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifica...

  16. Strings for quantumchromodynamics

    International Nuclear Information System (INIS)

    Schomerus, V.

    2007-04-01

    During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

  17. The confining trailing string

    CERN Document Server

    Kiritsis, E; Nitti, F

    2014-01-01

    We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

  18. Strings for quantumchromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Schomerus, V.

    2007-04-15

    During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

  19. Quark potential of spontaneous strings

    International Nuclear Information System (INIS)

    German, G.; Kleinert, H.

    1989-01-01

    The authors present some recent developments in string models with an extrinsic curvature term in action. Particular emphasis is placed upon the static quark potential and on the thermal deconfinement properties of spontaneous strings

  20. Cosmic strings and galaxy formation

    International Nuclear Information System (INIS)

    Bertschinger, E.

    1989-01-01

    Cosmic strings have become increasingly popular candidates as seeds for the formation of structure in the universe. This scenario, remains a serious cosmogonical model despite close scrutiny. In constrast, magnetic monopoles and domain walls - relic topological defects as are cosmic strings - are disastrous for cosmology if they are left over from the early universe. The production of heavy cosmic strings is speculative, as it depends on the details of ultrahigh energy physics. Fortunately, speculation about cosmic strings is not entirely idle because, if they exist and are heavy enough to seed galaxy formation, cosmic strings can be detected astronomically. Failure to detect cosmic strings would impose some constraints on grand unified theories (GUTs); their discovery would have exciting consequences for high energy physics and cosmology. This article reviews the basic physics of nonsuperconducting cosmic strings, highlighting the field theory aspects, and provides a progress report on calculations of structure formation with cosmic strings

  1. STRING v10

    DEFF Research Database (Denmark)

    Szklarczyk, Damian; Franceschini, Andrea; Wyder, Stefan

    2015-01-01

    , and the available data exhibit notable differences in terms of quality and completeness. The STRING database (http://string-db.org) aims to provide a critical assessment and integration of protein-protein interactions, including direct (physical) as well as indirect (functional) associations. The new version 10...... into families at various levels of phylogenetic resolution. Further improvements in version 10.0 include a completely redesigned prediction pipeline for inferring protein-protein associations from co-expression data, an API interface for the R computing environment and improved statistical analysis...

  2. Proceedings of strings, 89

    International Nuclear Information System (INIS)

    Arnowitt, R.; Bryan, R.; Duff, M.J.; Nanopoulos, D.; Pope, C.N.

    1990-01-01

    Does string theory provide us with a consistent quantum theory of gravity? Is it that Holy Grail of elementary particle physics, a Theory of Everything with embraces all the forces and particles of Nature? Even if it is, can we extract concrete predictions about our low-energy world that can be tested experimentally at the SSC and other particle accelerators? What does it have to say about the origin of the Universe and the thorny problem of the cosmological constant? Are superstring theories unique, or might the eleven-dimensional supermembrane prove equally consistent? These are just some of the question posed and debated at Strings '89

  3. Strings draw theorists together

    International Nuclear Information System (INIS)

    Green, Michael

    2000-01-01

    Theorists are confident that they are closer than ever to finding a quantum theory that unites gravity with the three other fundamental forces in nature. Many of the leading figures in the world of string theory met at the California Institute of Technology in January to discuss recent progress in the field and to reflect on the state of the theory. The enthusiastic mood of the gathering was based on the fact that string theory provides an elegant framework for a unified theory of all the forces and particles in nature, and also gives a consistent quantum-mechanical description of general relativity. String theory, and more precisely superstring theory, describes the assortment of elementary particles such as quarks and leptons, and the gauge bosons responsible for mediating forces in a unified manner as different modes of vibration of a single extended string. This version of the theory also embodies supersymmetry a conjectured symmetry that unifies fermions and bosons. Furthermore, the fact that the string has a fundamental length scale - the ''string length'' - apparently cures the short-distance problems of uniting general relativity with quantum theory. The main problem with the early formulations of superstring theory was that they emphasized the ''perturbative'' point of view, an approximation that describes string-like quantum-mechanical particles moving through classical (that is non quantum-mechanical) space-time. However, very general arguments require that any quantum theory of gravity should also describe space-time geometry in a quantum-mechanical manner. The classical geometry of space-time should then emerge as an approximate description at distance scales much larger than the so-called Planck scale of 10 -33 m. This requires an understanding of the theory beyond the perturbative approximation. It is the quest for this more fundamental description of string theory that has provided the main challenge for string theorists over the past decade. Much

  4. Introduction to string theory

    International Nuclear Information System (INIS)

    Randjbar-Daemi, S.; Strathdee, J.

    1987-10-01

    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. (author). 15 refs

  5. Deriving the four-string and open-closed string interactions from geometric string field theory

    International Nuclear Information System (INIS)

    Kaku, M.

    1990-01-01

    One of the questions concerning the covariant open string field theory is why there are two distinct BRST theories and why the four-string interaction appears in one version but not the other. The authors solve this mystery by showing that both theories are gauge-fixed versions of a higher gauge theory, called the geometric string field theory, with a new field, a string verbein e μσ νρ , which allows us to gauge the string length and σ parametrization. By fixing the gauge, the authors can derive the endpoint gauge (the covariantized light cone gauge), the midpoint gauge of Witten, or the interpolating gauge with arbitrary string length. The authors show explicitly that the four-string interaction is a gauge artifact of the geometric theory (the counterpart of the four-fermion instantaneous Coulomb term of QED). By choosing the interpolating gauge, they produce a new class of four-string interactions which smoothly interpolate between the endpoint gauge and the midpoint gauge (where it vanishes). Similarly, they can extract the closed string as a bound state of the open string, which appears in the endpoint gauge but vanishes in the midpoint gauge. Thus, the four-string and open-closed string interactions do not have to be added to the action as long as the string vierbein is included

  6. Racetrack inflation and cosmic strings

    Energy Technology Data Exchange (ETDEWEB)

    Brax, P. [CEA-Saclay, Gif sur Yvette (France). CEA/DSM/SPhT, Unite de Recherche Associee au CNRS, Service de Physique Theorique; Bruck, C. van de [Sheffield Univ. (United Kingdom). Dept. of Applied Mathematics; Davis, A.C.; Davis, S.C. [Cambridge Univ. (United Kingdom). DAMTP, Centre for Mathematical Sciences; Jeannerot, R. [Instituut-Lorentz for Theoretical Physics, Leiden (Netherlands); Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)

    2008-05-15

    We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

  7. String theory in four dimensions

    International Nuclear Information System (INIS)

    Dine, M.

    1988-01-01

    A representative sample of current ideas about how one might develop a string phenomenology is presented. Some of the obstacles which lie in between string theory and contact with experiment are described. It is hoped that this volume will provide the reader with ways of thinking about string theory in four dimensions and provide tools for asking questions about string theory and ordinary physics. 102 refs

  8. The STRING database in 2011

    DEFF Research Database (Denmark)

    Szklarczyk, Damian; Franceschini, Andrea; Kuhn, Michael

    2011-01-01

    present an update on the online database resource Search Tool for the Retrieval of Interacting Genes (STRING); it provides uniquely comprehensive coverage and ease of access to both experimental as well as predicted interaction information. Interactions in STRING are provided with a confidence score...... models, extensive data updates and strongly improved connectivity and integration with third-party resources. Version 9.0 of STRING covers more than 1100 completely sequenced organisms; the resource can be reached at http://string-db.org....

  9. Instability of colliding metastable strings

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-04-15

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  10. Cosmic strings and galaxy formation

    Science.gov (United States)

    Bertschinger, Edmund

    1989-01-01

    The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

  11. Instability of colliding metastable strings

    International Nuclear Information System (INIS)

    Hiramatsu, Takashi; Kobayashi, Tatsuo; Ookouchi, Yutaka; Kyoto Univ.

    2013-04-01

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  12. Racetrack inflation and cosmic strings

    International Nuclear Information System (INIS)

    Brax, P.; Postma, M.

    2008-05-01

    We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

  13. Continuing between closed and open strings

    International Nuclear Information System (INIS)

    Green, M.B.; Thorn, C.B.

    1991-01-01

    A family of dual models is defined that interpolates between the tree diagrams of non-orientable bosonic closed-string theory (which has a massless spin-2 state) and the open-string theory with no internal symmetry (in which the lowest-mass spin-2 state is massive). These models are parametrized by the intercept, Δ, of the leading Regge pole. The only models that have an infinite-dimensional conformal invariance and are consequently free of ghosts are the two familiar string theories with Δ=2 (closed strings) and Δ=1 (open strings with no internal symmetry). For arbitrary Δ the models are invariant under the finite dimensional conformal group, SO(Δ,2), which guarantees the crossing symmetry and consistent factorization of tree amplitudes. The spectrum of the level-two states is exhibited explicitly as Δ varies from 2 to 1 in order to illustrate the manner in which the graviton (the lowest-mass spin-2 state) acquires a mass. The scalar ghost generically associated with massive gravity cancels with the 'dilaton' precisely at Δ=1. (orig.)

  14. Supergravity duals of matrix string theory

    International Nuclear Information System (INIS)

    Morales, Jose F.; Samtleben, Henning

    2002-01-01

    We study holographic duals of type II and heterotic matrix string theories described by warped AdS 3 supergravities. By explicitly solving the linearized equations of motion around near horizon D-string geometries, we determine the spectrum of Kaluza-Klein primaries for type I, II supergravities on warped AdS 3 xS 7 . The results match those coming from the dual two-dimensional gauge theories living on the D-string worldvolumes. We briefly discuss the connections with the N=(8,8), N=(8,0) orbifold superconformal field theories to which type IIB/heterotic matrix strings flow in the infrared. In particular, we associate the dimension (h,h-bar) (32,32) twisted operator which brings the matrix string theories out from the conformal point (R; 8 ) N /S N with the dilaton profile in the supergravity background. The familiar dictionary between masses and 'scaling' dimensions of field and operators are modified by the presence of non-trivial warp factors and running dilatons. These modifications are worked out for the general case of domain wall/QFT correspondences between supergravities on warped AdS d+1 xS q geometries and super Yang-Mills theories with 16 supercharges. (author)

  15. String theory and quark confinement

    International Nuclear Information System (INIS)

    Polyakov, A.M.

    1998-01-01

    This article is based on a talk given at the ''Strings '97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed. (orig.)

  16. String theory in four dimensions

    CERN Document Server

    1988-01-01

    ``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

  17. String necklaces and primordial black holes from type IIB strings

    International Nuclear Information System (INIS)

    Lake, Matthew; Thomas, Steve; Ward, John

    2009-01-01

    We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.

  18. Suspensions with reduced violin string modes

    International Nuclear Information System (INIS)

    Lee, B H; Ju, L; Blair, D G

    2006-01-01

    We discuss the possibility of significantly reducing the number and Q-factor of violin string modes in the mirror suspension. Simulations of a bar-flexure suspension and an orthogonal ribbon have shown a reduction in the number of violin string modes when compared to a normal ribbon suspension. By calculating the expected suspension thermal noise, we find that the orthogonal ribbon provides a promising suspension alternative. A lower number of violin modes oscillating in the direction of the laser and a reduction in violin mode peak values of at least 23dB can be achieved with a slight increase in thermal noise above 40Hz

  19. Suspensions with reduced violin string modes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B H; Ju, L; Blair, D G [School of Physics, University of Western Australia, Crawley 6009, WA (Australia)

    2006-03-02

    We discuss the possibility of significantly reducing the number and Q-factor of violin string modes in the mirror suspension. Simulations of a bar-flexure suspension and an orthogonal ribbon have shown a reduction in the number of violin string modes when compared to a normal ribbon suspension. By calculating the expected suspension thermal noise, we find that the orthogonal ribbon provides a promising suspension alternative. A lower number of violin modes oscillating in the direction of the laser and a reduction in violin mode peak values of at least 23dB can be achieved with a slight increase in thermal noise above 40Hz.

  20. The bispectrum of matter perturbations from cosmic strings

    Energy Technology Data Exchange (ETDEWEB)

    Regan, Donough; Hindmarsh, Mark, E-mail: d.regan@sussex.ac.uk, E-mail: m.b.hindmarsh@sussex.ac.uk [Astronomy Centre, University of Sussex, Falmer, Brighton, BN1 9QH (United Kingdom)

    2015-03-01

    We present the first calculation of the bispectrum of the matter perturbations induced by cosmic strings. The calculation is performed in two different ways: the first uses the unequal time correlators (UETCs) of the string network - computed using a Gaussian model previously employed for cosmic string power spectra. The second approach uses the wake model, where string density perturbations are concentrated in sheet-like structures whose surface density grows with time. The qualitative and quantitative agreement of the two gives confidence to the results. An essential ingredient in the UETC approach is the inclusion of compensation factors in the integration with the Green's function of the matter and radiation fluids, and we show that these compensation factors must be included in the wake model also. We also present a comparison of the UETCs computed in the Gaussian model, and those computed in the unconnected segment model (USM) used by the standard cosmic string perturbation package CMBACT. We compare numerical estimates for the bispectrum of cosmic strings to those produced by perturbations from an inflationary era, and discover that, despite the intrinsically non-Gaussian nature of string-induced perturbations, the matter bispectrum is unlikely to produce competitive constraints on a population of cosmic strings.

  1. Kahler stabilized, modular invariant heterotic string models

    International Nuclear Information System (INIS)

    Gaillard, Mary K.; Gaillard, Mary K.; Nelson, Brent D.

    2007-01-01

    We review the theory and phenomenology of effective supergravity theories based on orbifold compactifications of the weakly-coupled heterotic string. In particular, we consider theories in which the four-dimensional theory displays target space modular invariance and where the dilatonic mode undergoes Kahler stabilization. A self-contained exposition of effective Lagrangian approaches to gaugino condensation and heterotic string theory is presented, leading to the development of the models of Bintruy, Gaillard and Wu. Various aspects of the phenomenology of this class of models are considered. These include issues of supersymmetry breaking and superpartner spectra, the role of anomalous U(1) factors, issues of flavor and R-parity conservation, collider signatures, axion physics, and early universe cosmology. For the vast majority of phenomenological considerations the theories reviewed here compare quite favorably to other string-derived models in the literature. Theoretical objections to the framework and directions for further research are identified and discussed

  2. SUPERCOLLIDER: String test success

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    On 14 August at the Superconducting Supercollider (SSC) Laboratory in Ellis County, Texas, the Accelerator Systems String Test (ASST) successfully met its objective by operating a half-cell of five collider dipole magnets, one quadrupole magnet, and two spool pieces at the design current of 6500 amperes

  3. Help from the strings

    CERN Multimedia

    2007-01-01

    "How can the nature of basic particles be defined beyond the mechanisms presiding over their creation? Besides the standard model of particle physics - resulting from the postulations of quantum mechanics - contemporary science has pinned its hopes on the totally new unifying notion provided by the highly mathematical string theory."(2 pages)

  4. New Z3 strings

    Directory of Open Access Journals (Sweden)

    Marco A.C. Kneipp

    2016-12-01

    Full Text Available We consider a Yang–Mills–Higgs theory with the gauge group SU(3 broken to its center Z3 by two scalar fields in the adjoint representation and obtain new Z3 strings asymptotic configurations with the gauge field and magnetic field in the direction of the step operators.

  5. On exceptional instanton strings

    NARCIS (Netherlands)

    Del Zotto, M.; Lockhart, G.

    According to a recent classification of 6d (1, 0) theories within F-theory there are only six “pure” 6d gauge theories which have a UV superconformal fixed point. The corresponding gauge groups are SU(3), SO(8), F4, E6, E7, and E8. These exceptional models have BPS strings which are also instantons

  6. String perturbation theory diverges

    International Nuclear Information System (INIS)

    Gross, D.J.; Periwal, V.

    1988-01-01

    We prove that perturbation theory for the bosonic string diverges for arbitrary values of the coupling constant and is not Borel summable. This divergence is independent of the existence of the infinities that occur in the theory due to the presence of tachyons and dilaton tadpoles. We discuss the physical implications of such a divergence

  7. Transversally extended string

    International Nuclear Information System (INIS)

    Akama, Keiichi

    1988-01-01

    Starting with the space-time action of the transversally extended string, we derive its world-sheet action, which is that of a gravitational and gauge theory with matter fields on the world-sheet, with additional effects of the second fundamental quantity. (author)

  8. Lectures on strings and dualities

    International Nuclear Information System (INIS)

    Vafa, C.

    1997-01-01

    In this set of lectures I review recent developments in string theory emphasizing their non-perturbative aspects and their recently discovered duality symmetries. The goal of the lectures is to make the recent exciting developments in string theory accessible to those with no previous background in string theory who wish to join the research effort in this area. Topics covered include a brief review of string theory, its compactifications, solitons and D-branes, black hole entropy and wed of string dualities. (author)

  9. Macroscopic fundamental strings in cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Aharonov, Y; Englert, F; Orloff, J

    1987-12-24

    We show that, when D greater than or equal to 4, theories of closed strings of closed strings in D, non-compact space-time dimensions exhibit a phase transition. The high-temperature phase is characterized by a condensate of arbitrarily long strings with Hausdorff dimension two (area filling curves). We suggest that this stringy phase is the ancestor of the adiabatic era. Fundamental strings could then both drive the inflation and seed, in a way reminiscent of the cosmic string mechanism, the large structures in the universe.

  10. Strings draw theorists together

    Energy Technology Data Exchange (ETDEWEB)

    Green, Michael [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge (United Kingdom)

    2000-03-01

    Theorists are confident that they are closer than ever to finding a quantum theory that unites gravity with the three other fundamental forces in nature. Many of the leading figures in the world of string theory met at the California Institute of Technology in January to discuss recent progress in the field and to reflect on the state of the theory. The enthusiastic mood of the gathering was based on the fact that string theory provides an elegant framework for a unified theory of all the forces and particles in nature, and also gives a consistent quantum-mechanical description of general relativity. String theory, and more precisely superstring theory, describes the assortment of elementary particles such as quarks and leptons, and the gauge bosons responsible for mediating forces in a unified manner as different modes of vibration of a single extended string. This version of the theory also embodies supersymmetry a conjectured symmetry that unifies fermions and bosons. Furthermore, the fact that the string has a fundamental length scale - the ''string length'' - apparently cures the short-distance problems of uniting general relativity with quantum theory. The main problem with the early formulations of superstring theory was that they emphasized the ''perturbative'' point of view, an approximation that describes string-like quantum-mechanical particles moving through classical (that is non quantum-mechanical) space-time. However, very general arguments require that any quantum theory of gravity should also describe space-time geometry in a quantum-mechanical manner. The classical geometry of space-time should then emerge as an approximate description at distance scales much larger than the so-called Planck scale of 10{sup -33} m. This requires an understanding of the theory beyond the perturbative approximation. It is the quest for this more fundamental description of string theory that has provided the main challenge for

  11. Gravitational effects of global strings

    International Nuclear Information System (INIS)

    Aryal, M.; Everett, A.E.

    1986-01-01

    We have obtained the gravitational field, in the weak-field approximation, of cosmic strings formed in a phase transition in which a global symmetry is broken (global strings). The effect of this field on light rays passing a global string is found, and the resulting formation of double images and production of discontinuities in the microwave background temperature compared with the corresponding results for gauge strings. There are some differences in the case of global strings, reflecting the fact that the space surrounding such strings is not purely conical. However, the differences between gauge and global strings with masses suitable to explain galaxy formation are small, and the task of distinguishing them observationally appears difficult at best

  12. Device for balancing parallel strings

    Science.gov (United States)

    Mashikian, Matthew S.

    1985-01-01

    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.

  13. Stringing physics along

    Energy Technology Data Exchange (ETDEWEB)

    Riordan, M. [Stanford University and the University of California, Santa Cruz (United States)]. E-mail: mriordan@ucsc.edu

    2007-02-15

    In the last few decades, however, physical theory has drifted away from the professional norms advocated by Newton and other enlightenment philosophers. A vast outpouring of hypotheses has occurred under the umbrella of what is widely called string theory. But string theory is not really a 'theory' at all - at least not in the strict sense that scientists generally use the term. It is instead a dense, weedy thicket of hypotheses and conjectures badly in need of pruning. That pruning, however, can come only from observation and experiment, to which string theory (a phrase I will grudgingly continue using) is largely inaccessible. String theory was invented in the 1970s in the wake of the Standard Model of particle physics. Encouraged by the success of gauge theories of the strong, weak and electromagnetic forces, theorists tried to extend similar ideas to energy and distance scales that are orders of magnitude beyond what can be readily observed or measured. The normal, healthy intercourse between theory and experiment - which had led to the Standard Model - has broken down, and fundamental physics now finds itself in a state of crisis. So it is refreshing to hear from a theorist - one who was deeply involved with string theory and championed it in his previous book, Three Roads to Quantum Gravity - that all is not well in this closeted realm. Smolin argues from the outset that viable hypotheses must lead to observable consequences by which they can be tested and judged. String theory by its very nature does not allow for such probing, according to Smolin, and therefore it must be considered as an unprovable conjecture. Towards the end of his book, Smolin suggests other directions fundamental physics can take, particularly in the realm of quantum gravity, to resolve its crisis and reconnect with the observable world. From my perspective, he leans a bit too heavily towards highly speculative ideas such as doubly special relativity, modified Newtonian

  14. Light-like tachyon condensation in open string field theory

    Czech Academy of Sciences Publication Activity Database

    Hellerman, S.; Schnabl, Martin

    2013-01-01

    Roč. 2013, č. 4 (2013), s. 1-34 ISSN 1126-6708 Institutional support: RVO:68378271 Keywords : string field theory * tachyon condensation Subject RIV: BE - Theoretical Physics Impact factor: 5.618, year: 2012

  15. Real topological string amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Narain, K.S. [The Abdus Salam International Centre for Theoretical Physics (ICTP),Strada Costiera 11, Trieste, 34151 (Italy); Piazzalunga, N. [Simons Center for Geometry and Physics, State University of New York,Stony Brook, NY, 11794-3636 (United States); International School for Advanced Studies (SISSA) and INFN, Sez. di Trieste,via Bonomea 265, Trieste, 34136 (Italy); Tanzini, A. [International School for Advanced Studies (SISSA) and INFN, Sez. di Trieste,via Bonomea 265, Trieste, 34136 (Italy)

    2017-03-15

    We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G{sub χ}, at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g{sup ′}=−χ+1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F{sub g}.

  16. Open spinning strings

    International Nuclear Information System (INIS)

    Stefanski, B. Jr.

    2004-01-01

    We find classical open string solutions in the AdS 5 x S 5 /Z 2 orientifold with angular momenta along the five-sphere. The energy of these solutions has an expansion in integral powers of λ with sigma-model corrections suppressed by inverse powers of J - the total angular momentum. This gives a prediction for the exact anomalous dimensions of operators in the large N limit of an N = 2 Sp, Super-Yang-Mills theory with matter. We also find a simple map between open and closed string solutions. This gives a prediction for an all-loop planar relationship between the anomalous dimensions of single-trace and two-quark operators in the dual gauge theory. (author)

  17. New Supersymmetric String Compactifications

    Energy Technology Data Exchange (ETDEWEB)

    Kachru, Shamit

    2002-11-25

    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 the (super)potential governing the light fields, which is generated by the fluxes and certain ''twists'' in the geometry. Detailed consideration of an example also gives strong evidence that in some cases, these exotic geometries are related by smooth transitions to standard Calabi-Yau or G2 compactifications of M-theory.

  18. Unified string theories

    International Nuclear Information System (INIS)

    Gross, D.J.

    1985-01-01

    String theories offer a way of realizing the potential of supersymmetry, Kaluza-Klein and much more. They represent a radical departure from ordinary quantum field theory, but in the direction of increased symmetry and structure. They are based on an enormous increase in the number of degrees of freedom, since in addition to fermionic coordinates and extra dimensions, the basic entities are extended one dimensional objects instead of points. Correspondingly the symmetry group is greatly enlarged, in a way that we are only beginning to comprehend. At the very least this extended symmetry contains the largest group of symmetries that can be contemplated within the framework of point field theories-those of ten-dimensional supergravity and super Yang-Mills theory. Types of string theories and the phenomenology to be expected from them are reviewed

  19. Fractional bosonic strings

    Science.gov (United States)

    Diaz, Victor Alfonzo; Giusti, Andrea

    2018-03-01

    The aim of this paper is to present a simple generalization of bosonic string theory in the framework of the theory of fractional variational problems. Specifically, we present a fractional extension of the Polyakov action, for which we compute the general form of the equations of motion and discuss the connection between the new fractional action and a generalization the Nambu-Goto action. Consequently, we analyze the symmetries of the modified Polyakov action and try to fix the gauge, following the classical procedures. Then we solve the equations of motion in a simplified setting. Finally, we present a Hamiltonian description of the classical fractional bosonic string and introduce the fractional light-cone gauge. It is important to remark that, throughout the whole paper, we thoroughly discuss how to recover the known results as an "integer" limit of the presented model.

  20. p-adic string

    International Nuclear Information System (INIS)

    Volovich, I.V.

    1987-01-01

    The hypothesis of the possible p-adic structure of spacetime is considered. The p-adic Veneziano amplitude is proposed and the main properties of the p-adic string theory are discussed. The analogous questions on the Galois field are also discussed. In this case the Jacobi sum plays the role of the Veneziano amplitude which can be expressed by means of the I-adic cohomology of the Fermat curves. The corresponding vertex operator is given. (author)

  1. Exactly soluble dynamics of (p,q) string near macroscopic fundamental strings

    International Nuclear Information System (INIS)

    Bak, Dongsu; Rey, Soojong; Yee, Houng

    2004-01-01

    We study dynamics of type-IIB bound-state of a Dirichlet string and n fundamental strings in the background of N fundamental strings. Because of supergravity potential, the bound-state string is pulled to the background fundamental strings, whose motion is described by open string rolling radion field. The string coupling can be made controllably weak and, in the limit 1 2 st n 2 st N, the bound-state energy involved is small compared to the string scale. We thus propose rolling dynamics of open string radion in this system as an exactly solvable analog for rolling dynamics of open string tachyon in decaying D-brane. The dynamics bears a novel feature that the worldsheet electric field increases monotonically to the critical value as the bound-state string falls into the background string. Close to the background string, D string constituent inside the bound-state string decouples from fundamental string constituents. (author)

  2. The theta-structure in string theories - 1: bosonic strings

    International Nuclear Information System (INIS)

    Li Miao.

    1985-09-01

    We explored the theta-structures in bosonic string theories which are similar to those in gauge field theories. The theta-structure of string is due to the multiply connected spatial compact subspace of space-time. The work of this paper shows that there is an energy band E(theta) in the string theory and one may move the tachyon out in theory by choosing some proper theta parameters. (author)

  3. Clinical Significance of von Willebrand Factor and Antithrombin in Diabetes Mellitus with Retinopathy%血管性血友病因子与抗凝血酶在糖尿病视网膜病变中的临床意义

    Institute of Scientific and Technical Information of China (English)

    张鹏; 汤荣华

    2012-01-01

    目的 探讨糖尿病微血管视网膜病变患者血管性血友病因子(vWF)、抗凝血酶(AT)的变化及临床意义.方法 将100例2型糖尿病患者分为两组,糖尿病无微血管视网膜病变并发症组53例,糖尿病微血管视网膜病变并发症组47例,设健康人群对照组50例.所有人群入院或体检时即采集静脉血,进行vWF:Ag、AT:A检测.结果 2型糖尿病无微血管视网膜病变并发症组患者血浆vWF:Ag含量较正常对照组增高(P<0.05),2型糖尿病微血管视网膜病变并发症组患者血浆vWF:Ag含量与2型糖尿病无微血管视网膜病变并发症组及正常对照组相比有显著性差异(P<0.05);且2型糖尿病微血管视网膜病变并发症组中背景性病变和增殖性病变患者血浆vWF:Ag含量比较有显著性差异(P<0.05).2型糖尿病无微血管视网膜病变并发症组患者血浆AT活性与正常对照组相比无显著性差异(P>0.05),2型糖尿病微血管视网膜病变并发症组患者血浆AT活性与2型糖尿病无微血管视网膜病变并发症组及正常对照组相比有显著性差异(P<0.05);且2型糖尿病微血管视网膜病变并发症组中背景性病变和增殖性病变患者血浆AT活性比较有显著性差异(P<0.05).结论 血浆vWF:Ag、AT:A的变化与糖尿病微血管视网膜病变的发生、发展有密切关系,监测其水平与活性对糖尿病微血管并发症的治疗和预防有重要的临床意义.%Objective To explore the changes of von Willebrand factor(vWF) and antithrombin(AT) in diabetic patients with retinopathy and its clinical implications. Methods 100 type 2 diabetes mellitus (T2DM) patients were divided into 2 groups,one group included 53 T2DM patients without retinopathy,another group included 47 T2DM patients with retinopathy, 50 healthy peoples were enrolled as control group. Venous blood was collected from all groups and vWF:Ag, AT; A were determined. Results The level of vWF;Ag in T2DM

  4. An invariant string propagator

    International Nuclear Information System (INIS)

    Cohen, A.; Moore, G.; Nelson, P.; Polchinski, J.

    1986-01-01

    The authors show that the Polyakov path integral is used to define off-shell quantities in string theory. The path integral of Polyakov gives an elegant description of strings and their interactions. However, its use has been limited to obtaining the Koba-Nielsen expressions for S-matrix elements. It is not yet clear what quantities make sense in string theory. This study shows that the path integral can be used to define off-shell quantities as well. In particular it defines a natural n-point function in loop space as the sum of all world surfaces bounded by n specific spacetime curves. The reader is referred for more detail. The report first outlines general evaluation then discusses the additional features added by boundaries. Locally, the three gauge freedoms ξ/sup a/ and δphi can be used to take g/sub ab/ (σ) to the unit matrix. Globally, this is not quite possible. In general the researchers choose a family of fiducial metrics g/sub ab/ (σ,tau), depending on a finite number of Teichmuller parameters tau, and every metric is gauge equivalent to one of these

  5. Thermodynamical string fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Nadine [Theoretical Particle Physics, Department of Astronomy and Theoretical Physics, Lund University,Sölvegatan 14A, Lund, SE-223 62 (Sweden); School of Physics and Astronomy, Monash University,Wellington Road, Clayton, VIC-3800 (Australia); Sjöstrand, Torbjörn [Theoretical Particle Physics, Department of Astronomy and Theoretical Physics, Lund University,Sölvegatan 14A, Lund, SE-223 62 (Sweden)

    2017-01-31

    The observation of heavy-ion-like behaviour in pp collisions at the LHC suggests that more physics mechanisms are at play than traditionally assumed. The introduction e.g. of quark-gluon plasma or colour rope formation can describe several of the observations, but as of yet there is no established paradigm. In this article we study a few possible modifications to the Pythia event generator, which describes a wealth of data but fails for a number of recent observations. Firstly, we present a new model for generating the transverse momentum of hadrons during the string fragmentation process, inspired by thermodynamics, where heavier hadrons naturally are suppressed in rate but obtain a higher average transverse momentum. Secondly, close-packing of strings is taken into account by making the temperature or string tension environment-dependent. Thirdly, a simple model for hadron rescattering is added. The effect of these modifications is studied, individually and taken together, and compared with data mainly from the LHC. While some improvements can be noted, it turns out to be nontrivial to obtain effects as big as required, and further work is called for.

  6. Building GUTs from strings

    International Nuclear Information System (INIS)

    Aldazabal, G.; Ibanez, L.E.; Uranga, A.M.

    1996-01-01

    We study in detail the structure of Grand Unified Theories derived as the low-energy limit of orbifold four-dimensional strings. To this aim, new techniques for building level-two symmetric orbifold theories are presented. New classes of GUTs in the context of symmetric orbifolds are then constructed. The method of permutation modding is further explored and SO(10) GUTs with both 45- or 54-plets are obtained. SU(5) models are also found through this method. It is shown that, in the context of symmetric orbifold SO(10) GUTs, only a single GUT Higgs, either a 54 or a 45, can be present and it always resides in an order-two untwisted sector. Very restrictive results also hold in the case of SU(5). General properties and selection rules for string GUTs are described. Some of these selection rules forbid the presence of some particular GUT-Higgs couplings which are sometimes used in SUSY-GUT model building. Some semi-realistic string GUT examples are presented and their properties briefly discussed. (orig.)

  7. Fingerprints in Compressed Strings

    DEFF Research Database (Denmark)

    Bille, Philip; Cording, Patrick Hagge; Gørtz, Inge Li

    2013-01-01

    The Karp-Rabin fingerprint of a string is a type of hash value that due to its strong properties has been used in many string algorithms. In this paper we show how to construct a data structure for a string S of size N compressed by a context-free grammar of size n that answers fingerprint queries...... derivative that captures LZ78 compression and its variations) we get O(loglogN) query time. Hence, our data structures has the same time and space complexity as for random access in SLPs. We utilize the fingerprint data structures to solve the longest common extension problem in query time O(logNlogℓ) and O....... That is, given indices i and j, the answer to a query is the fingerprint of the substring S[i,j]. We present the first O(n) space data structures that answer fingerprint queries without decompressing any characters. For Straight Line Programs (SLP) we get O(logN) query time, and for Linear SLPs (an SLP...

  8. Successful Ultrasound-Guided Femoral Nerve Blockade and Catheterization in a Patient with Von Willebrand Disease

    Directory of Open Access Journals (Sweden)

    Youmna E. DiStefano

    2015-01-01

    Full Text Available Peripheral nerve blockade (PNB is superior to neuraxial anesthesia and/or opioid therapy for perioperative analgesia in total knee replacement (TKR. Evidence on the safety of PNB in patients with coagulopathy is lacking. We describe the first documented account of continuous femoral PNB for perioperative analgesia in a patient with Von Willebrand Disease (vWD. Given her history of opioid tolerance and after an informative discussion, a continuous femoral PNB was planned for in this 34-year-old female undergoing TKR. A Humate-P intravenous infusion was started and the patient was positioned supinely. Using sterile technique with ultrasound guidance, a Contiplex 18 Gauge Tuohy needle was advanced in plane through the fascia iliaca towards the femoral nerve. A nerve catheter was threaded through the needle and secured without complications. Postoperatively, a levobupivacaine femoral catheter infusion was maintained, and twice daily Humate-P intravenous infusions were administered for 48 hours; enoxaparin thromboprophylaxis was initiated thereafter. The patient was discharged uneventfully on postoperative day 4. Given documentation of delayed, unheralded bleeding from PNB in coagulopathic patients, we recommend individualized PNB in vWD patients. Multidisciplinary team involvement is required to guide factor supplementation and thromboprophylaxis, as is close follow-up to elicit signs of bleeding throughout the delayed postoperative period.

  9. How to simulate global cosmic strings with large string tension

    Energy Technology Data Exchange (ETDEWEB)

    Klaer, Vincent B.; Moore, Guy D., E-mail: vklaer@theorie.ikp.physik.tu-darmstadt.de, E-mail: guy.moore@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstraße 2, Darmstadt, D-64289 Germany (Germany)

    2017-10-01

    Global string networks may be relevant in axion production in the early Universe, as well as other cosmological scenarios. Such networks contain a large hierarchy of scales between the string core scale and the Hubble scale, ln( f {sub a} / H ) ∼ 70, which influences the network dynamics by giving the strings large tensions T ≅ π f {sub a} {sup 2} ln( f {sub a} / H ). We present a new numerical approach to simulate such global string networks, capturing the tension without an exponentially large lattice.

  10. Dynamics of chaotic strings

    International Nuclear Information System (INIS)

    Schaefer, Mirko

    2011-01-01

    The main topic of this thesis is the investigation of dynamical properties of coupled Tchebycheff map networks. The results give insights into the chaotic string model and its network generalization from a dynamical point of view. As a first approach, discrete symmetry transformations of the model are studied. These transformations are formulated in a general way in order to be also applicable to similar dynamics on bipartite network structures. The dynamics is studied numerically via Lyapunov measures, spatial correlations, and ergodic properties. It is shown that the zeros of the interaction energy are distinguished only with respect to this specific observable, but not by a more general dynamical principle. The original chaotic string model is defined on a one-dimensional lattice (ring-network) as the underlying network topology. This thesis studies a modification of the model based on the introduction of tunable disorder. The effects of inhomogeneous coupling weights as well as small-world perturbations of the ring-network structure on the interaction energy are discussed. Synchronization properties of the chaotic string model and its network generalization are studied in later chapters of this thesis. The analysis is based on the master stability formalism, which relates the stability of the synchronized state to the spectral properties of the network. Apart from complete synchronization, where the dynamics at all nodes of the network coincide, also two-cluster synchronization on bipartite networks is studied. For both types of synchronization it is shown that depending on the type of coupling the synchronized dynamics can display chaotic as well as periodic or quasi-periodic behaviour. The semi-analytical calculations reveal that the respective synchronized states are often stable for a wide range of coupling values even for the ring-network, although the respective basins of attraction may inhabit only a small fraction of the phase space. To provide

  11. Quantum backreaction in string theory

    International Nuclear Information System (INIS)

    Evnin, O.

    2012-01-01

    There are situations in string theory when a finite number of string quanta induce a significant backreaction upon the background and render the perturbation theory infrared-divergent. The simplest example is D0-brane recoil under an impact by closed strings. A more physically interesting case is backreaction on the evolution of a totally compact universe due to closed string gas. Such situations necessitate qualitative amendments to the traditional formulation of string theory in a fixed classical background. In this contribution to the proceedings of the XVII European Workshop on String Theory in Padua, I review solved problems and current investigations in relation to this kind of quantum backreaction effects. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Fast Searching in Packed Strings

    DEFF Research Database (Denmark)

    Bille, Philip

    2009-01-01

    Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time....... However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m...... word-RAM with logarithmic word size we present an algorithm using time O(n/log(sigma) n + m + occ) Here occ is the number of occurrences of P in Q. For m = o(n) this improves the O(n) bound...

  13. Comparing double string theory actions

    International Nuclear Information System (INIS)

    De Angelis, L.; Gionti, S.J.G.; Marotta, R.; Pezzella, F.

    2014-01-01

    Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed

  14. Comparing double string theory actions

    Energy Technology Data Exchange (ETDEWEB)

    De Angelis, L. [Dipartimento di Fisica, Università degli Studi “Federico II” di Napoli,Complesso Universitario Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy); Gionti, S.J.G. [Specola Vaticana, Vatican City, V-00120, Vatican City State and Vatican Observatory Research Group, Steward Observatory, The University Of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 (United States); Marotta, R.; Pezzella, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli,Complesso Universitario di Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy)

    2014-04-28

    Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed.

  15. Regularized strings with extrinsic curvature

    International Nuclear Information System (INIS)

    Ambjoern, J.; Durhuus, B.

    1987-07-01

    We analyze models of discretized string theories, where the path integral over world sheet variables is regularized by summing over triangulated surfaces. The inclusion of curvature in the action is a necessity for the scaling of the string tension. We discuss the physical properties of models with extrinsic curvature terms in the action and show that the string tension vanishes at the critical point where the bare extrinsic curvature coupling tends to infinity. Similar results are derived for models with intrinsic curvature. (orig.)

  16. Classical theory of radiating strings

    Science.gov (United States)

    Copeland, Edmund J.; Haws, D.; Hindmarsh, M.

    1990-01-01

    The divergent part of the self force of a radiating string coupled to gravity, an antisymmetric tensor and a dilaton in four dimensions are calculated to first order in classical perturbation theory. While this divergence can be absorbed into a renormalization of the string tension, demanding that both it and the divergence in the energy momentum tensor vanish forces the string to have the couplings of compactified N = 1 D = 10 supergravity. In effect, supersymmetry cures the classical infinities.

  17. Cosmic string induced CMB maps

    International Nuclear Information System (INIS)

    Landriau, M.; Shellard, E. P. S.

    2011-01-01

    We compute maps of CMB temperature fluctuations seeded by cosmic strings using high resolution simulations of cosmic strings in a Friedmann-Robertson-Walker universe. We create full-sky, 18 deg. and 3 deg. CMB maps, including the relevant string contribution at each resolution from before recombination to today. We extract the angular power spectrum from these maps, demonstrating the importance of recombination effects. We briefly discuss the probability density function of the pixel temperatures, their skewness, and kurtosis.

  18. Introduction to strings and superstrings

    International Nuclear Information System (INIS)

    Traubenberg, M.R. de.

    1988-01-01

    We discuss the main features on the formulation of string theory that, in a primitive level, describe the hadronic phenomenon of duality. We also study an extension of the models of closed and strings with spin. Then, by using supersymmetry, it is formulated the theory of superstrings and heterotic strings with the aim of unify the fundamental interactions and matter. (M.W.O.) [pt

  19. Experimenting with string musical instruments

    Science.gov (United States)

    LoPresto, Michael C.

    2012-03-01

    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.

  20. On multibrane solutions in open string field theory

    Czech Academy of Sciences Publication Activity Database

    Murata, Masaki; Schnabl, Martin

    2011-01-01

    Roč. 2011, č. 188 (2011), s. 50-55 ISSN 0375-9687. [International Conference on String Field Theory and Related Aspects (SFT2010). Kyoto, 18.10.2010-22.10.2010] Grant - others:EUROHORC and ESF(XE) EYI/07/E010 Institutional research plan: CEZ:AV0Z10100502 Keywords : string field theory * D-branes * open strings Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 1.063, year: 2011 http://ptp.ipap.jp/link?PTPS/188/50/

  1. From maximal to minimal supersymmetry in string loop amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Marcus; Buchberger, Igor [Department of Physics, Karlstad University,651 88 Karlstad (Sweden); Schlotterer, Oliver [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut,14476 Potsdam (Germany)

    2017-04-28

    We calculate one-loop string amplitudes of open and closed strings with N=1,2,4 supersymmetry in four and six dimensions, by compactification on Calabi-Yau and K3 orbifolds. In particular, we develop a method to combine contributions from all spin structures for arbitrary number of legs at minimal supersymmetry. Each amplitude is cast into a compact form by reorganizing the kinematic building blocks and casting the worldsheet integrals in a basis. Infrared regularization plays an important role to exhibit the expected factorization limits. We comment on implications for the one-loop string effective action.

  2. String breaking with Wilson loops?

    CERN Document Server

    Kratochvila, S; Kratochvila, Slavo; Forcrand, Philippe de

    2003-01-01

    A convincing, uncontroversial observation of string breaking, when the static potential is extracted from Wilson loops only, is still missing. This failure can be understood if the overlap of the Wilson loop with the broken string is exponentially small. In that case, the broken string ground state will only be seen if the Wilson loop is long enough. Our preliminary results show string breaking in the context of the 3d SU(2) adjoint static potential, using the L\\"uscher-Weisz exponential variance reduction approach. As a by-product, we measure the fundamental SU(2) static potential with improved accuracy and see clear deviations from Casimir scaling.

  3. A primer on string theory

    CERN Document Server

    Schomerus, Volker

    2017-01-01

    Since its conception in the 1960s, string theory has been hailed as one of the most promising routes we have to unify quantum mechanics and general relativity. This book provides a concise introduction to string theory explaining central concepts, mathematical tools and covering recent developments in physics including compactifications and gauge/string dualities. With string theory being a multidisciplinary field interfacing with high energy physics, mathematics and quantum field theory, this book is ideal for both students with no previous knowledge of the field and scholars from other disciplines who are looking for an introduction to basic concepts.

  4. Open problems in string cosmology

    International Nuclear Information System (INIS)

    Toumbas, N.

    2010-01-01

    Some of the open problems in string cosmology are highlighted within the context of the recently constructed thermal and quantum superstring cosmological solutions. Emphasis is given on the high temperature cosmological regime, where it is argued that thermal string vacua in the presence of gravito-magnetic fluxes can be used to bypass the Hagedorn instabilities of string gas cosmology. This article is based on a talk given at the workshop on ''Cosmology and Strings'', Corfu, September 6-13, 2009. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  5. Multiflavor string-net models

    Science.gov (United States)

    Lin, Chien-Hung

    2017-05-01

    We generalize the string-net construction to multiple flavors of strings, each of which is labeled by the elements of an Abelian group Gi. The same flavor of strings can branch, while different flavors of strings can cross one another and thus they form intersecting string nets. We systematically construct the exactly soluble lattice Hamiltonians and the ground-state wave functions for the intersecting string-net condensed phases. We analyze the braiding statistics of the low-energy quasiparticle excitations and find that our model can realize all the topological phases as the string-net model with group G =∏iGi . In this respect, our construction provides various ways of building lattice models which realize topological order G , corresponding to different partitions of G and thus different flavors of string nets. In fact, our construction concretely demonstrates the Künneth formula by constructing various lattice models with the same topological order. As an example, we construct the G =Z2×Z2×Z2 string-net model which realizes a non-Abelian topological phase by properly intersecting three copies of toric codes.

  6. The ABCDEFG of Little Strings

    OpenAIRE

    Haouzi, Nathan; Kozçaz, Can

    2017-01-01

    Starting from type IIB string theory on an $ADE$ singularity, the (2,0) little string arises when one takes the string coupling $g_s$ to 0. In this setup, we give a unified description of the codimension-two defects of the little string, for any simple Lie algebra ${\\mathfrak{g}}$. Geometrically, these are D5 branes wrapping 2-cycles of the singularity. Equivalently, the defects are specified by a certain set of weights of $^L {\\mathfrak{g}}$, the Langlands dual of ${\\mathfrak{g}}$. As a firs...

  7. String Theory in a Nutshell

    CERN Document Server

    Kiritsis, Elias

    2007-01-01

    This book is the essential new introduction to modern string theory, by one of the world's authorities on the subject. Concise, clearly presented, and up-to-date, String Theory in a Nutshell brings together the best understood and most important aspects of a theory that has been evolving since the early 1980s. A core model of physics that substitutes one-dimensional extended ""strings"" for zero-dimensional point-like particles (as in quantum field theory), string theory has been the leading candidate for a theory that would successfully unify all fundamental forces of nature, includin

  8. Strings and superstrings. Electron linear colliders

    International Nuclear Information System (INIS)

    Alessandrini, V.; Bambade, P.; Binetruy, P.; Kounnas, C.; Le Duff, J.; Schwimmer, A.

    1989-01-01

    Basic string theory; strings in interaction; construction of strings and superstrings in arbitrary space-time dimensions; compactification and phenomenology; linear e+e- colliders; and the Stanford linear collider were discussed [fr

  9. Strings, Branes and Symmetries

    International Nuclear Information System (INIS)

    Westerberg, A.

    1997-01-01

    Recent dramatic progress in the understanding of the non-perturbative structure of superstring theory shows that extended objects of various kinds, collectively referred to as p-branes, are an integral part of the theory. In this thesis, comprising an introductory text and seven appended research papers, we study various aspects of p-branes with relevance for superstring theory. The first part of the introductory text is a brief review of string theory focussing on the role of p-branes. In particular, we consider the so-called D-branes which currently are attracting a considerable amount of attention. The purpose of this part is mainly to put into context the results of paper 4, 5 and 6 concerning action functionals describing the low-energy dynamics of D-branes. The discussion of perturbative string theory given in this part of the introduction is also intended to provide some background to paper 2 which contains an application of the Reggeon-sewing approach to the construction of string vertices. The second part covers a rather different subject, namely higher-dimensional loop algebras and their cohomology, with the aim of facilitating the reading of papers 1, 3 and 7. The relation to p-branes is to be found in paper 1 where we introduce a certain higher-dimensional generalization of the loop algebra and discuss its potential applicability as a symmetry algebra for p-branes. Papers 3 and 7 are mathematically oriented out-growths of this paper addressing the issue of realizing algebras of this kind, known in physics as current algebras, in terms of pseudo differential operators (PSDOs). The main result of paper 3 is a proof of the equivalence between certain Lie-algebra cocycles on the space of second-quantizable PSDOs

  10. Drill string gas data

    Energy Technology Data Exchange (ETDEWEB)

    Siciliano, E.R.

    1998-05-12

    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%.

  11. Transmutations for Strings

    Directory of Open Access Journals (Sweden)

    Amin Boumenir

    2008-07-01

    Full Text Available We investigate the existence and representation of transmutations, also known as transformation operators, for strings. Using measure theory and functional analytic methods we prove their existence and study their representation. We show that in general they are not close to unity since their representation does not involve a Volterra operator but rather the eigenvalue parameter. We also obtain conditions under which the transmutation is either a bounded or a compact operator. Explicit examples show that they cannot be reduced to Volterra type operators.  

  12. Sequestering in string theory

    International Nuclear Information System (INIS)

    Kachru, Shamit; McAllister, Liam; Sundrum, Raman

    2007-01-01

    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

  13. Drilling string lifter

    Energy Technology Data Exchange (ETDEWEB)

    Shakhobalov, A B; Galiopa, A A; Ponomarev, G V; Ushakov, A M

    1981-04-28

    A drilling string lifter is suggested which includes a rotating tower installed on a fixed base, hydraulic cylinder and pipe-clamping assembly connected through a chain gear to the drive motor. In order to simplify the design of the hydraulic lifter, the drive motor is installed on a fixed base so that the axis of the outlet shaft of the drive motor coincides with the axis of rotation of the tower. In addition, the axis of rotation of the tower is made in the form of a tubular element, and the outlet shaft of the drive motor is ranged between the tubular element.

  14. Nuclear fuel string assembly

    International Nuclear Information System (INIS)

    Ip, A.K.; Koyanagi, K.; Tarasuk, W.R.

    1976-01-01

    A method of fabricating rodded fuels suitable for use in pressure tube type reactors and in pressure vessel type reactors is described. Fuel rods are secured as an inner and an outer sub-assembly, each rod attached between mounting rings secured to the rod ends. The two sub-assemblies are telescoped together and positioned by spaced thimbles located between them to provide precise positioning while permittng differential axial movement between the sub-assemblies. Such sub-assemblies are particularly suited for mounting as bundle strings. The method provides particular advantages in the assembly of annular-section fuel pins, which includes booster fuel containing enriched fuel material. (LL)

  15. Ambitwistor strings and reggeon amplitudes in N=4 SYM

    Directory of Open Access Journals (Sweden)

    L.V. Bork

    2017-11-01

    Full Text Available We consider the description of reggeon amplitudes (Wilson lines form factors in N=4 SYM within the framework of four dimensional ambitwistor string theory. The latter is used to derive scattering equations representation for reggeon amplitudes with multiple reggeized gluons present. It is shown, that corresponding tree-level string correlation function correctly reproduces previously obtained Grassmannian integral representation of reggeon amplitudes in N=4 SYM.

  16. Vacuum strings in FRW models

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, C C; Oattes, L M; Starkman, G D

    1988-01-01

    The authors find that vacuum string solutions cannot be embedded in an FRW model in the spirit of the swiss cheese model for inhomogeneities. Since all standard lensing calculations rely implicitly on the Swiss Cheese model, this result indicates that the previous lensing results for the vacuum string may be in error.

  17. Tadpole resummations in string theory

    International Nuclear Information System (INIS)

    Kitazawa, Noriaki

    2008-01-01

    While R-R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS-NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in 'wrong' vacua. In this Letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS-NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open-closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from the tadpole resummation. This result is consistent with the fact that this (unstable) configuration is free from tadpoles of massless closed-string modes, although there is a tadpole of the closed string tachyon. The application of this method to superstring models with broken supersymmetry is also discussed

  18. String theory and water waves

    International Nuclear Information System (INIS)

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

    2011-01-01

    We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain c-hat <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 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.

  19. Cool Runnings For String 2

    CERN Multimedia

    2001-01-01

    String 2 is a series of superconducting magnets that are prototypes of those which will be installed in the LHC. It was cooled down to 1.9 Kelvin on September 14th. On Thursday last week, the dipoles of String 2 were successfully taken to nominal current, 11850 A.

  20. String-localized quantum fields

    International Nuclear Information System (INIS)

    Mund, Jens; Santos, Jose Amancio dos; Silva, Cristhiano Duarte; Oliveira, Erichardson de

    2009-01-01

    Full text. The principles of physics admit (unobservable) quantum fields which are localized not on points, but on strings in the sense of Mandelstam: a string emanates from a point in Minkowski space and extends to infinity in some space-like direction. This type of localization might permit the construction of new models, for various reasons: (a) in general, weaker localization implies better UV behaviour. Therefore, the class of renormalizable interactions in the string-localized has a chance to be larger than in the point-localized case; (b) for certain particle types, there are no point-localized (free) quantum fields - for example Anyons in d = 2 + 1, and Wigner's massless 'infinite spin' particles. For the latter, free string-localized quantum fields have been constructed; (c) in contrast to the point-localized case, string-localization admits covariant vector/tensor potentials for fotons and gravitons in a Hilbert space representation with positive energy. We shall present free string-localized quantum fields for various particle types, and some ideas about the perturbative construction of interacting string-localized fields. A central point will be an analogue of gauge theories, completely within a Hilbert space and without ghosts, trading gauge dependence with dependence on the direction of the localization string. In order to discuss renormalizability (item (a)), methods from microlocal analysis (wave front set and scaling degree) are needed. (author)

  1. A Platonic Sextet for Strings

    Science.gov (United States)

    Schaffer, Karl

    2012-01-01

    The use of traditional string figures by the Dr. Schaffer and Mr. Stern Dance Ensemble led to experimentation with polyhedral string constructions. This article presents a series of polyhedra made with six loops of three colors which sequence through all the Platonic Solids.

  2. Symmetry breaking in string theory

    International Nuclear Information System (INIS)

    Potting, R.

    1998-01-01

    A mechanism for a spontaneous breakdown of CPT symmetry appears in string theory, with possible implications for particle models. A realistic string theory might exhibit CPT violation at levels detectable in current or future experiments. A possible new mechanism for baryogenesis in the early Universe is also discussed

  3. Energy in a String Wave

    Science.gov (United States)

    Ng, Chiu-king

    2010-01-01

    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…

  4. String theory : physics or metaphysics?

    CERN Document Server

    Veneziano, Gabriele

    2010-01-01

    I will give arguments for why the enormous progress made during the last century on understanding elementary particles and their fundamental interactions suggests strings as the truly elementary constituents of Nature. I will then address the issue of whether the string paradigm can in principle be falsified or whether it should be considered as mere metaphysics.

  5. Differential formulation in string theories

    International Nuclear Information System (INIS)

    Guzzo, M.M.

    1987-01-01

    The equations of gauge invariance motion for theories of boson open strings and Neveu-Schwarz and Ramond superstring are derived. A construction for string theories using differential formalism, is introduced. The importance of BRST charge for constructing such theories and the necessity of introduction of auxiliary fields are verified. (M.C.K.) [pt

  6. Deformations of topological open strings

    NARCIS (Netherlands)

    Hofman, C.; Ma, Whee Ky

    Deformations of topological open string theories are described, with an emphasis on their algebraic structure. They are encoded in the mixed bulk-boundary correlators. They constitute the Hochschild complex of the open string algebra - the complex of multilinear maps on the boundary Hilbert space.

  7. Towards optimal packed string matching

    DEFF Research Database (Denmark)

    Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany

    2014-01-01

    -size string-matching instruction wssm is available in contemporary commodity processors. The other word-size maximum-suffix instruction wslm is only required during the pattern pre-processing. Benchmarks show that our solution can be efficiently implemented, unlike some prior theoretical packed string...

  8. Experimenting with String Musical Instruments

    Science.gov (United States)

    LoPresto, Michael C.

    2012-01-01

    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…

  9. Progress in string theory research

    CERN Document Server

    2016-01-01

    At the first look, the String Theory seems just an interesting and non-trivial application of the quantum mechanics and the special relativity to vibrating strings. By itself, the quantization of relativistic strings does not call the attention of the particle physicist as a significant paradigm shift. However, when the string quantization is performed by applying the standard rules of the perturbative Quantum Field Theory, one discovers that the strings in certain states have the same physical properties as the gravity in the flat space-time. Chapter one of this book reviews the construction of the thermal bosonic string and D-brane in the framework of the Thermo Field Dynamics (TFD). It briefly recalls the wellknown light-cone quantization of the bosonic string in the conformal gauge in flat space-time, and gives a bird’s eye view of the fundamental concepts of the TFD. Chapter two examines a visual model inspired by string theory, on the system of interacting anyons. Chapter three investigate the late-ti...

  10. Gauge invariance of string fields

    International Nuclear Information System (INIS)

    Banks, T.; Peskin, M.E.

    1985-10-01

    Some work done to understand the appearance of gauge bosons and gravitons in string theories is reported. An action has been constructed for free (bosonic) string field theory which is invariant under an infinite set of gauge transformations which include Yang-Mills transformations and general coordinate transformations as special cases. 15 refs., 1 tab

  11. Planckian axions in string theory

    International Nuclear Information System (INIS)

    Bachlechner, Thomas C.; Long, Cody; McAllister, Liam

    2015-01-01

    We argue that super-Planckian diameters of axion fundamental domains can arise in Calabi-Yau compactifications of string theory. In a theory with N axions θ i , the fundamental domain is a polytope defined by the periodicities of the axions, via constraints of the form −πfactor >√N. This result is robust in the presence of P>N constraints, while for P=N the diameter is further enhanced by eigenvector delocalization to N 3/2 f N . We directly verify our results in explicit Calabi-Yau compactifications of type IIB string theory. In the classic example with h 1,1 =51 where parametrically controlled moduli stabilization was demonstrated by Denef et al. in http://dx.doi.org/10.4310/ATMP.2005.v9.n6.a1, the largest metric eigenvalue obeys f N ≈0.013M pl . The random matrix analysis then predicts, and we exhibit, axion diameters ≈M pl for the precise vacuum parameters found in http://dx.doi.org/10.4310/ATMP.2005.v9.n6.a1. Our results provide a framework for pursuing large-field axion inflation in well-understood flux vacua.

  12. Protéolyse du facteur Willebrand et cardiopathies à forces de cisaillement élevées : nouvelles approches diagnostiques et thérapeutiques

    OpenAIRE

    Rauch , Antoine

    2014-01-01

    In the first part of the thesis, we describe a novel approach based on antibody-based therapy to prevent the acquired von Willebrand factor (VWF) degradation observed in continuous-flow mechanical circulatory assist device therapy. Via a murine monoclonal antibody directed against VWF D4 domain and thus interfering with VWF-ADAMTS13 binding, a partial inhibition of VWF degradation is observed in whole blood using an ex vivo circulatory assist device model. In the second part of the thesis, we...

  13. String dualities and superpotential

    International Nuclear Information System (INIS)

    Ha, Tae-Won

    2010-09-01

    The main objective of this thesis is the computation of the superpotential induced by D5- branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundlemoduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry amore physical meaning. (orig.)

  14. String dualities and superpotential

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae-Won

    2010-09-15

    The main objective of this thesis is the computation of the superpotential induced by D5- branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundlemoduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry amore physical meaning. (orig.)

  15. Cosmology from string theory

    International Nuclear Information System (INIS)

    Anchordoqui, Luis; Nawata, Satoshi; Goldberg, Haim; Nunez, Carlos

    2007-01-01

    We explore the cosmological content of Salam-Sezgin six-dimensional supergravity, and find a solution to the field equations in qualitative agreement with observation of distant supernovae, primordial nucleosynthesis abundances, and recent measurements of the cosmic microwave background. The carrier of the acceleration in the present de Sitter epoch is a quintessence field slowly rolling down its exponential potential. Intrinsic to this model is a second modulus which is automatically stabilized and acts as a source of cold dark matter, with a mass proportional to an exponential function of the quintessence field (hence realizing varying mass particle models within a string context). However, any attempt to saturate the present cold dark matter component in this manner leads to unacceptable deviations from cosmological data--a numerical study reveals that this source can account for up to about 7% of the total cold dark matter budget. We also show that (1) the model will support a de Sitter energy in agreement with observation at the expense of a miniscule breaking of supersymmetry in the compact space; (2) variations in the fine structure constant are controlled by the stabilized modulus and are negligible; (3) ''fifth'' forces are carried by the stabilized modulus and are short range; (4) the long time behavior of the model in four dimensions is that of a Robertson-Walker universe with a constant expansion rate (w=-1/3). Finally, we present a string theory background by lifting our six-dimensional cosmological solution to ten dimensions

  16. Poisson hierarchy of discrete strings

    International Nuclear Information System (INIS)

    Ioannidou, Theodora; Niemi, Antti J.

    2016-01-01

    The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

  17. Basic Concepts of String Theory

    CERN Document Server

    Blumenhagen, Ralph; Theisen, Stefan

    2013-01-01

    The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

  18. Strings, conformal fields and topology

    International Nuclear Information System (INIS)

    Kaku, Michio

    1991-01-01

    String Theory has advanced at an astonishing pace in the last few years, and this book aims to acquaint the reader with the most active topics of research in the field. Building on the foundations laid in his Introduction to Superstrings, Professor Kaku discusses such topics as the classification of conformal string theories, knot theory, the Yang-Baxter relation, quantum groups, the non-polynominal closed string field theory, matrix models, and topological field theory. Several chapters review the fundamentals of string theory, making the presentation of the material self-contained while keeping overlap with the earlier book to a minimum. The book conveys the vitality of current research in string theory and places readers at its forefront. (orig.) With 40 figs. in 50 parts

  19. Poisson hierarchy of discrete strings

    Energy Technology Data Exchange (ETDEWEB)

    Ioannidou, Theodora, E-mail: ti3@auth.gr [Faculty of Civil Engineering, School of Engineering, Aristotle University of Thessaloniki, 54249, Thessaloniki (Greece); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108, Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200, Tours (France); Department of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081 (China)

    2016-01-28

    The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

  20. Basic concepts of string theory

    International Nuclear Information System (INIS)

    Blumenhagen, Ralph

    2013-01-01

    The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

  1. Testing string theory at LHC?

    CERN Multimedia

    CERN. Geneva

    2002-01-01

    A theory with such mathematical beauty cannot be wrong: this is one of the main arguments in favour of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, nor the space of extra dimensions where they live. However there are good reasons to believe that the 'hidden' dimensions of string theory may be much larger than what we thought in the past and that they may be within experimental reach in the near future - together with the strings themselves. In my talk, I will give an elementary introduction of string theory and describe the main experimental predictions.Organiser(s): Jasper Kirkby / EP DivisionNote: Tea & coffee will be served at 16.00 hrs.

  2. Musculoskeletal problems among string instrumentalists in South Africa

    Directory of Open Access Journals (Sweden)

    Adedayo T. Ajidahun

    2017-02-01

    Full Text Available Background: Musicians who play string instruments are affected more by musculoskeletal injuries when compared to other instrument playing groups. Musculoskeletal problems are commonly found in the upper extremities and trunk. Several risk factors such as gender, practice hours and instrument played are associated with the prevalence and distribution of musculoskeletal problems among string instrumentalists. Objectives: The aim of this study was to determine the prevalence, distribution, severity and risk factors for musculoskeletal problems among string instrumentalists. Method: A cross-sectional study design using both online and paper-based questionnaires were used to collect data from string instrumentalists playing in both amateur and professional orchestras in South Africa. Results: A total of 114 string instrumentalists participated in the study, of which 86 (77% reported problems in one or more anatomic regions while 39 (35% were currently experiencing musculoskeletal problems that affected their performance. The trunk and both shoulders were the most commonly affected body regions. The majority of the participants reported the severity of the complaints as mild to moderate with aching, soreness, tingling and fatigue being the most commonly used descriptors of the symptoms of playing-related musculoskeletal problems. Conclusion: The results of this study showed that the prevalence of musculoskeletal problems that affect performance is high among string instrumentalists in South Africa. An evaluation of associated risk factors with the aim of reducing injuries may be important in improving performance.

  3. Notes on the ambitwistor pure spinor string

    Czech Academy of Sciences Publication Activity Database

    Lipinski Jusinskas, Renann

    2016-01-01

    Roč. 2016, č. 5 (2016), s. 1-12, č. článku 116. ISSN 1029-8479 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : ambitwistor string * pure spinor formalism Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 6.063, year: 2016

  4. A 12.3-kb Duplication Within the VWF Gene in Pigs Affected by Von Willebrand Disease Type 3

    Directory of Open Access Journals (Sweden)

    Stefanie Lehner

    2018-02-01

    Full Text Available Von Willebrand Disease (VWD type 3 is a serious and sometimes fatal hereditary bleeding disorder. In pigs, the disease has been known for decades, and affected animals are used as models for the human disease. Due to the recessive mode of inheritance of VWD type 3, severe bleeding is typically seen in homozygous individuals. We sequenced the complete porcine VWF (Von Willebrand Factor complementary DNA (cDNA and detected a tandem duplication of exons 17 and 18, causing a frameshift and a premature termination codon (p.Val814LeufsTer3 in the affected pig. Subsequent next generation sequencing on genomic DNA proved the existence of a 12.3-kb tandem duplication associated with VWD. This duplication putatively originates from porcine Short Interspersed Nuclear Elements (SINEs located within VWF introns 16 and 18 with high identity. The premature termination truncates the VWF open reading frame by a large part, resulting in an almost entire loss of the mature peptide. It is therefore supposed to account for the severe VWD type 3. Our results further indicate the presence of strong, nonsense-mediated decay in VWF messenger RNA (mRNA containing the duplication, which was supported by the almost complete absence of the complete VWF protein in immunohistochemistry analysis of the VWD-affected pig. In the past, differentiation of wild-type and heterozygous pigs in this VWD colony had to rely on clinical examinations and additional laboratory methods. The present study provides the basis to distinguish both genotypes by performing a rapid and simple genetic analysis.

  5. Epidemiologic features of von Willebrand's disease in Doberman pinschers, Scottish terriers, and Shetland sheepdogs: 260 cases (1984-1988)

    Science.gov (United States)

    Brooks, M; Dodds, W J; Raymond, S L

    1992-04-15

    During a study period from 1985 through 1988, plasma von Willebrand's factor antigen (vWF:Ag) concentration was measured as a marker for prevalence of the von Willebrand's disease (vWD) trait in Doberman Pinschers (doberman, n = 5,554), Scottish Terriers (scottie, n = 1,363), and Shetland Sheepdogs (sheltie, n = 4,279). Significant increase in prevalence of the trait was seen in scotties and shelties during this period. In 1988, 73% of dobermans, 30% of scotties, and 28% of shelties tested had abnormal vWF:Ag concentration (less than 50% vWF:Ag). We found significant differences between breeds with respect to age and vWF:Ag concentration of clinically affected dogs at time of diagnosis. The affected dobermans were older (doberman mean age, 4.6 years; scottie mean age, 1.7 years; sheltie mean age, 1.9 years) and had higher concentration of plasma vWF:Ag (doberman mean vWF:Ag, 15%; scottie mean vWF:Ag, 0%; sheltie mean vWF:Ag, 8%). Bleeding in affected dogs of all 3 breeds was observed predominantly from mucosal surfaces and from cutaneous sites of surgery or trauma. The most common site of mucosal bleeding in scotties and shelties was oral or nasal cavity, and in dobermans was the urogenital tract. Differences in clinical manifestations of vWD in purebred dogs may reflect heterogeneous defects within the vWF gene, causing a variety of abnormalities in production, structure, and function of vWF protein. Analogous to vWD in human beings, acquired deficiencies of vWF may also contribute to the clinical variability of vWD in dogs.

  6. Oriented open-closed string theory revisited

    International Nuclear Information System (INIS)

    Zwiebach, B.

    1998-01-01

    String theory on D-brane backgrounds is open-closed string theory. Given the relevance of this fact, we give details and elaborate upon our earlier construction of oriented open-closed string field theory. In order to incorporate explicitly closed strings, the classical sector of this theory is open strings with a homotopy associative A ∞ algebraic structure. We build a suitable Batalin-Vilkovisky algebra on moduli spaces of bordered Ricmann surfaces, the construction of which involves a few subtleties arising from the open string punctures and cyclicity conditions. All vertices coupling open and closed strings through disks are described explicitly. Subalgebras of the algebra of surfaces with boundaries are used to discuss symmetries of classical open string theory induced by the closed string sector, and to write classical open string field theory on general closed string backgrounds. We give a preliminary analysis of the ghost-dilaton theorem. copyright 1998 Academic Press, Inc

  7. Conformal techniques in string theory and string field theory

    International Nuclear Information System (INIS)

    Giddings, S.B.

    1987-01-01

    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 Feynman diagrams for Witten's string field theory respect modular invariance, and in particular give a triangulation of moduli space. The Polyakov formalism is then used to derive the Feynman rules that should follow from this theory upon gauge-fixing. It should also be possible to apply this derivation to deduce the Feynman rules for other gauge-fixed string field theories. Following this, Riemann surface techniques are turned to the problem of proving the equivalence of the Polyakov and light-cone formalisms. It is first shown that the light-cone diagrams triangulate moduli space. Then the Polyakov measure is worked out for these diagrams, and shown to equal that deduced from the light-cone gauge fixed formalism. Also presented is a short description of the comparison of physical states in the two formalisms. The equivalence of the two formalisms in particular constitutes a proof of the unitarity of the Polyakov framework for the closed bosonic string

  8. Coats' disease, Turner syndrome, and von Willebrand disease in a patient with Wildtype Norrie disease pseudoglioma.

    Science.gov (United States)

    Desai, Rajen U; Saffra, Norman A; Krishna, Rati P; Rosenberg, Steven E

    2011-01-01

    The authors describe a girl diagnosed as having Coats' disease, Turner syndrome (45X karyotype), and type 1 von Willebrand disease. She tested negative for the Norrie disease pseudoglioma (NDP) gene located on the X-chromosome, which has been suspected of contributing to Coats' disease. Copyright 2010, SLACK Incorporated.

  9. A systematic review of the effects of hemophilia and von Willebrand disease on arterial trombosis

    NARCIS (Netherlands)

    Biere-Rafi, Sara; Zwiers, M.; Peters, Marjolein; Van Der Meer, Jan; Rosendaal, Frits R; Buller, Harry R; Kamphuisen, Pieter W

    Background: Patients with hemophilia and von Willebrand disease (VWD) may be protected against arterial thrombosis, through a hy-pocoagulable state or atherosclerosis. We performed a systematic review to assess the association between these clotting disorders, arterial thrombosis and the prevalence

  10. Quantum A∞-structures for open-closed topological strings

    International Nuclear Information System (INIS)

    Herbst, M.

    2006-02-01

    We study factorizations of topological string amplitudes on higher genus Riemann surfaces with multiple boundary components and find quantum A ∞ -relations, which are the higher genus analog of the (classical) A ∞ -relations on the disk. For topological strings with c=3 the quantum A ∞ -relations are trivially satisfied on a single D-brane, whereas in a multiple D-brane configuration they may be used to compute open higher genus amplitudes recursively from disk amplitudes. This can be helpful in open Gromov-Witten theory in order to determine open string higher genus instanton corrections. Finally, we find that the quantum A ∞ -structure cannot quite be recast into a quantum master equation on the open string moduli space. (orig.)

  11. String model of elementary particles

    International Nuclear Information System (INIS)

    Kikkawa, Keiji

    1975-01-01

    Recent development of the models of elementary particles is described. The principal features of elementary particle physics can be expressed by quark model, mass spectrum, the Regge behavior of scattering amplitude, and duality. Venezians showed in 1968 that the B function can express these features. From the analysis of mass spectrum, the string model was introduced. The quantization of the string is performed with the same procedure as the ordinary quantum mechanics. The motion of the string is determined by the Nambu-Goto action integral, and the Schroedinger equation is obtained. Mass spectrum from the string model was same as that from the duality model such as Veneziano model. The interaction between strings can be introduced, and the Lagrangian can be formulated. The relation between the string model and the duality model has been studied. The string model is the first theory of non-local field, and the further development is attractive. The relation between this model and the quark model is still not clear. (Kato, T.)

  12. String bit models for superstring

    International Nuclear Information System (INIS)

    Bergman, O.; Thorn, C.B.

    1995-01-01

    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 - 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D - 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

  13. String bit models for superstring

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, O.; Thorn, C.B.

    1995-12-31

    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.

  14. Fermions on the electroweak string

    CERN Document Server

    Moreno, J M; Quirós, Mariano; Moreno, J M; Oaknin, D H; Quiros, M

    1995-01-01

    We construct a simple class of exact solutions of the electroweak theory including the naked Z--string and fermion fields. It consists in the Z--string configuration (\\phi,Z_\\theta), the {\\it time} and z components of the neutral gauge bosons (Z_{0,3},A_{0,3}) and a fermion condensate (lepton or quark) zero mode. The Z--string is not altered (no feed back from the rest of fields on the Z--string) while fermion condensates are zero modes of the Dirac equation in the presence of the Z--string background (no feed back from the {\\it time} and z components of the neutral gauge bosons on the fermion fields). For the case of the n--vortex Z--string the number of zero modes found for charged leptons and quarks is (according to previous results by Jackiw and Rossi) equal to |n|, while for (massless) neutrinos is |n|-1. The presence of fermion fields in its core make the obtained configuration a superconducting string, but their presence (as well as that of Z_{0,3},A_{0,3}) does not enhance the stability of the Z--stri...

  15. Gravity and strings

    CERN Document Server

    Ortín, Tomás

    2015-01-01

    Self-contained and comprehensive, this definitive new edition of Gravity and Strings is a unique resource for graduate students and researchers in theoretical physics. From basic differential geometry through to the construction and study of black-hole and black-brane solutions in quantum gravity - via all the intermediate stages - this book provides a complete overview of the intersection of gravity, supergravity, and superstrings. Now fully revised, this second edition covers an extensive array of topics, including new material on non-linear electric-magnetic duality, the electric-tensor formalism, matter-coupled supergravity, supersymmetric solutions, the geometries of scalar manifolds appearing in 4- and 5-dimensional supergravities, and much more. Covering reviews of important solutions and numerous solution-generating techniques, and accompanied by an exhaustive index and bibliography, this is an exceptional reference work.

  16. Fingerprints in compressed strings

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Cording, Patrick Hagge

    2017-01-01

    In this paper we show how to construct a data structure for a string S of size N compressed into a context-free grammar of size n that supports efficient Karp–Rabin fingerprint queries to any substring of S. That is, given indices i and j, the answer to a query is the fingerprint of the substring S......[i,j]. We present the first O(n) space data structures that answer fingerprint queries without decompressing any characters. For Straight Line Programs (SLP) we get O(log⁡N) query time, and for Linear SLPs (an SLP derivative that captures LZ78 compression and its variations) we get O(log⁡log⁡N) query time...

  17. Field theory and strings

    International Nuclear Information System (INIS)

    Bonara, L.; Cotta-Ramusino, P.; Rinaldi, M.

    1987-01-01

    It is well-known that type I and heterotic superstring theories have a zero mass spectrum which correspond to the field content of N=1 supergravity theory coupled to supersymmetric Yang-Mills theory in 10-D. The authors study the field theory ''per se'', in the hope that simple consistency requirements will determine the theory completely once one knows the field content inherited from string theory. The simplest consistency requirements are: N=1 supersymmetry; and absence of chiral anomalies. This is what the authors discuss in this paper here leaving undetermined the question of the range of validity of the resulting field theory. As is known, a model of N=1 supergravity (SUGRA) coupled to supersymmetric Yang-Mills (SYM) theory was known in the form given by Chapline and Manton. The coupling of SUGRA to SYM was determined by the definition of the ''field strength'' 3-form H in this paper

  18. Some global issues in string perturbation theory

    International Nuclear Information System (INIS)

    Atick, J.J.; Moore, G.; Sen, Ashoke

    1988-01-01

    Calculations of type II string vacuum amplitude using the picture changing prescription have been shown to lead, in general, to a positive cosmological constant. We show that there is a global obstruction to the choices of gauge slice for super-Teichmueller space that lead to such measures. We discuss the general restrictions on gauge slices appropriate for use in explicit fermionic string calculations. We also discuss the relation of the functional determinant and conformal field theory versions of the path integral measure, and show that, at arbitrary genus and in arbitrary backgrounds preserving tree level N=1 supersymmetry, the measure is an exact differential. We evaluate the boundary integrals of this total derivative at genus two in two ways for target space R 10 to show that the integrals are zero. Finally, we use the factorization hypothesis to show that in appropriate compactified spacetimes the boundary integrals continue to vanish. (orig.)

  19. Dynamical evolution of cosmic strings

    International Nuclear Information System (INIS)

    Bouchet, F.R.

    1988-01-01

    The author have studied by means of numerical simulations the dynamical evolution of a network of cosmic strings, both in the radiation and matter era. Our basic conclusion is that a scaling solution exists, i.e., the string energy density evolves as t -2 . This means that the process by which long strings dump their energy into closed loops (which can gravitationally radiate away) is efficient enough to prevent the string domination over other forms of energy. This conclusion does not depend on the initial string energy density, nor on the various numerical parameters. On the other hand, the generated spectrum of loop sizes does depend on the value of our numerical lower cutoff (i.e., the minimum length of loop we allow to be chopped off the network). Furthermore, the network evolution is very different from what was assumed before), namely the creation of a few horizon sized loops per horizon volume and per hubble time, which subsequently fragment into about 10 smaller daughter loops. Rather, many tiny loops are directly cut from the network of infinite strings, and it appears that the only fundamental scale (the horizon) has been lost. This is probably because a fundamental ingredient had been overlooked, namely the kinks. These kinks are created in pairs at each intercommutation, and very rapidly, the long strings appear to be very kinky. Thus the number of long strings per horizon is still of the order of a few, but their total length is fairly large. Furthermore, a large number of kinks favors the formation of small loops, and their sizes might well be governed by the kink density along the long strings. Finally, we computed the two-point correlation function of the loops and found significant differences from the work of Turok

  20. Casimir energy of a nonuniform string

    Science.gov (United States)

    Hadasz, L.; Lambiase, G.; Nesterenko, V. V.

    2000-07-01

    The Casimir energy of a nonuniform string built up from two pieces with different speeds of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to zeta renormalization.

  1. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    We present a detailed analysis of the motion of test particle in the gravitational field of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.

  2. String Formatting Considered Harmful for Novice Programmers

    Science.gov (United States)

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

    2010-01-01

    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…

  3. M-strings, Elliptic Genera and N=4 String Amplitudes

    CERN Document Server

    Hohenegger, Stefan

    2014-01-01

    We study mass-deformed N=2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of R^4 through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T^2, which we calculate explicitly.

  4. Covariant N-string amplitude

    International Nuclear Information System (INIS)

    Di Vecchia, P.; Sciuto, S.; Nakayama, R.; Petersen, J.L.; Sidenius, J.R.

    1986-11-01

    The BRST-invariant N-Reggeon vertex (for the bosonic string) previously given by us in the operator formulation is considered in more detail. In particular we present a direct derivation from the string path integral. Several crucial symmetry properties found a posteriori before, become a priori clearer in this formulation. A number of delicate points related to zero modes, cut off procedures and normal ordering prescriptions are treated in some detail. The old technique of letting the string field acquire a small dimension ε/2 → 0 + is found especially elegant. (orig.)

  5. Plucked Strings and the Harpsichord

    Science.gov (United States)

    GIORDANO, N.; WINANS, J. P.

    1999-07-01

    The excitation of a harpsichord string when it is set into motion, i.e., plucked, by a plectrum is studied. We find that the amplitude of the resulting string vibration is approximately independent of the velocity with which the key is depressed. This result is in accord with conventional wisdom, but at odds with a recent theoretical model. A more realistic theoretical treatment of the plucking process is then described, and shown to be consistent with our measurements. The experiments reveal several other interesting aspects of the plectrum-string interaction.

  6. Spin chain for quantum strings

    International Nuclear Information System (INIS)

    Beisert, N.

    2005-01-01

    We review and compare the integrable structures in N=4 gauge theory and string theory on AdS 5 x S 5 . Recently, Bethe ansaetze for gauge theory/weak coupling and string theory/strong coupling were proposed to describe scaling dimensions in the su(2) subsector. Here we investigate the Bethe equations for quantum string theory, naively extrapolated to weak coupling. Excitingly, we find a spin chain Hamiltonian similar, but not equal, to the gauge theory dilatation operator. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  7. Geometry, topology, and string theory

    Energy Technology Data Exchange (ETDEWEB)

    Varadarajan, Uday [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    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.

  8. Geometry, topology, and string theory

    International Nuclear Information System (INIS)

    Varadarajan, Uday

    2003-01-01

    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

  9. String cosmology modern string theory concepts from the cosmic structure

    CERN Document Server

    2009-01-01

    The field of string cosmology has matured considerably over the past few years, attracting many new adherents to this multidisciplinary Field. This book fills a critical gap by bringing together strains of current research into one single volume. The resulting collection of selected articles presents the latest, ongoing results from renowned experts currently working in the field. This offers the possibility for practitioners to become conversant with many different aspects of string cosmology

  10. String cosmology. Large-field inflation in string theory

    International Nuclear Information System (INIS)

    Westphal, Alexander

    2014-09-01

    This is a short review of string cosmology. We wish to connect string-scale physics as closely as possible to observables accessible to current or near-future experiments. Our possible best hope to do so is a description of inflation in string theory. The energy scale of inflation can be as high as that of Grand Unification (GUT). If this is the case, this is the closest we can possibly get in energy scales to string-scale physics. Hence, GUT-scale inflation may be our best candidate phenomenon to preserve traces of string-scale dynamics. Our chance to look for such traces is the primordial gravitational wave, or tensor mode signal produced during inflation. For GUT-scale inflation this is strong enough to be potentially visible as a B-mode polarization of the cosmic microwave background (CMB). Moreover, a GUT-scale inflation model has a trans-Planckian excursion of the inflaton scalar field during the observable amount of inflation. Such large-field models of inflation have a clear need for symmetry protection against quantum corrections. This makes them ideal candidates for a description in a candidate fundamental theory like string theory. At the same time the need of large-field inflation models for UV completion makes them particularly susceptible to preserve imprints of their string-scale dynamics in the inflationary observables, the spectral index n s and the fractional tensor mode power r. Hence, we focus this review on axion monodromy inflation as a mechanism of large-field inflation in string theory.

  11. Charting the Landscape of Supercritical String Theory

    International Nuclear Information System (INIS)

    Hellerman, Simeon; Swanson, Ian

    2007-01-01

    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

  12. String and Sticky Tape Experiments.

    Science.gov (United States)

    Edge, R. D., Ed.

    1979-01-01

    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)

  13. String theory or field theory?

    International Nuclear Information System (INIS)

    Marshakov, A.V.

    2002-01-01

    The status of string theory is reviewed, and major recent developments - especially those in going beyond perturbation theory in the string theory and quantum field theory frameworks - are analyzed. This analysis helps better understand the role and place of experimental phenomena, it is emphasized that there are some insurmountable problems inherent in it - notably the impossibility to formulate the quantum theory of gravity on its basis - which prevent it from being a fundamental physical theory of the world of microscopic distances. It is this task, the creation of such a theory, which string theory, currently far from completion, is expected to solve. In spite of its somewhat vague current form, string theory has already led to a number of serious results and greatly contributed to progress in the understanding of quantum field theory. It is these developments, which are our concern in this review [ru

  14. String moduli inflation. An overview

    Energy Technology Data Exchange (ETDEWEB)

    Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quevedo, Fernando [Cambridge Univ. (United Kingdom). DAMTP/CMS; Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)

    2011-06-15

    We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the {eta}-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)

  15. Spin chains and string theory.

    Science.gov (United States)

    Kruczenski, Martin

    2004-10-15

    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.

  16. Pattern recognition and string matching

    CERN Document Server

    Cheng, Xiuzhen

    2002-01-01

    The research and development of pattern recognition have proven to be of importance in science, technology, and human activity. Many useful concepts and tools from different disciplines have been employed in pattern recognition. Among them is string matching, which receives much theoretical and practical attention. String matching is also an important topic in combinatorial optimization. This book is devoted to recent advances in pattern recognition and string matching. It consists of twenty eight chapters written by different authors, addressing a broad range of topics such as those from classifica­ tion, matching, mining, feature selection, and applications. Each chapter is self-contained, and presents either novel methodological approaches or applications of existing theories and techniques. The aim, intent, and motivation for publishing this book is to pro­ vide a reference tool for the increasing number of readers who depend upon pattern recognition or string matching in some way. This includes student...

  17. String moduli inflation. An overview

    International Nuclear Information System (INIS)

    Cicoli, Michele; Quevedo, Fernando

    2011-06-01

    We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the η-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)

  18. Strings in the abelized picture

    International Nuclear Information System (INIS)

    Embacher, F.

    1990-01-01

    The transformation properties of the bosonic string variables under the recently discovered abelizing operator are exhibited. The intimate relation of this operator to the light-cone gauge condition is illustrated for the classical string. As an application of the formalism, the derivation of the BRST cohomology by the method of Freemann and Olive is carried over to the abelized picture, where it takes a particularly simple from. (orig.)

  19. The W3 string spectrum

    International Nuclear Information System (INIS)

    Pope, C.N.; Stelle, K.S.

    1991-08-01

    We study the spectrum of W 3 strings. In particular, we show that for appropriately chosen space-time signature, one of the scalar fields is singled out be the spin-3 constraint and is ''frozen'': no creation operators from it can appear in physical states and the corresponding momentum must assume a specific fixed value. The remaining theory is unitary and resembles an ordinary string theory in d contains 26 with anomalies cancelled by appropriate background charges. (author). 8 refs

  20. Cooldown of superconducting magnet strings

    International Nuclear Information System (INIS)

    Yuecel, A.; Carcagno, R.H.

    1995-01-01

    A numerical model for the cooldown of the superconducting magnet strings in the Accelerator System String Test (ASST) Facility at the Superconducting Super Collider (SSC) Laboratory is presented. Numerical results are compared with experimental data from the ASST test runs. Agreement between the numerical predictions and experiments is very good over the entire range from room temperature to liquid helium temperatures. The model can be readily adapted to predict the cooldown and warmup behavior of other superconducting magnets or cold masses

  1. Strings in the abelized picture

    International Nuclear Information System (INIS)

    Embacher, F.

    1990-01-01

    The transformation properties of the bosonic string variables under the recently discovered abelizing operator are exhibited. The intimate relation of this operator to the light-cone gauge condition is illustrated for the classical string. As an application of the formalism, the derivation of the BRST cohomology by the method of Freeman and Olive is carried over to the abelized picture, where it takes a particulary simple form. 14 refs. (Author)

  2. An introduction to string theory

    OpenAIRE

    West, Peter C

    1989-01-01

    These notes are based on lectures given by Michael Green during Part III of the Mathematics Tripos (the Certificate for Advanced Study in Mathematics) in the Spring of 2003. The course provided an introduction to string theory, focussing on the Bosonic string, but treating the superstring as well. A background in quantum field theory and general relativity is assumed. Some background in particle physics, group theory and conformal field theory is useful, though not essential. A number of appe...

  3. Black strings and classical hair

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Yang, H.

    1997-01-01

    We examine the geometry near the event horizon of a family of black string solutions with traveling waves. It has previously been shown that the metric is continuous there. Contrary to expectations, we find that the geometry is not smooth, and the horizon becomes singular whenever a wave is present. Both five-dimensional and six-dimensional black strings are considered with similar results. copyright 1997 The American Physical Society

  4. On Field Theory of Open Strings, Tachyon Condensation and Closed Strings

    OpenAIRE

    Shatashvili, Samson L.

    2001-01-01

    I review the physical properties of different vacua in the background independent open string field theory. Talk presented at Strings 2001, Mumbai, India, http://theory.theory.tifr.res.in/strings/Proceedings/#sha-s.

  5. Kac-Moody algebras and string theory

    International Nuclear Information System (INIS)

    Cleaver, G.B.

    1993-01-01

    The focus of this thesis is on (1) the role of Kac-Moody algebras in string theory and the development of techniques for systematically building string theory models based on a higher level (K ≥ 2) KM algebras and (2) fractional superstrings, a new class of solutions based on SU(2) K /U(1) conformal field theories. The content of this thesis is as follows. In chapter two they review KM algebras and their role in string theory. In the next chapter they present two results concerning the construction of modular invariant partition functions for conformal field theories build by tensoring together other conformal field theories. First they show how the possible modular invariants for the tensor product theory are constrained if the allowed modular invariants of the individuals conformal field theory factors have been classified. They illustrate the use of these constraints for theories of the type SU(2) KA direct-product SU(2) KB , finding all consistent theories for K A and K B odd. Second they show how known diagonal modular invariants can be used to construct inherently asymmetric invariants where the holomorphic and anti-holomorphic theories do not share the same chiral algebra. Explicit examples are given. Next, in chapter four they investigate some issues relating to recently proposed fractional superstring theories with D critical K/4 K/4 , as source of spacetime fermions, is demonstrated

  6. Fast searching in packed strings

    DEFF Research Database (Denmark)

    Bille, Philip

    2011-01-01

    Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth–Morris–Pratt algorithm [SIAM J. Comput. 6 (2) (1977) 323–350] solves the string matching problem in linear time which is optimal if we can only read one character...... at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation....... Let m⩽n be the lengths P and Q, respectively, and let σ denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using timeO(nlogσn+m+occ). Here occ is the number of occurrences of P in Q. For m=o(n) this improves the O(n) bound of the Knuth...

  7. Experimental observation of Bethe strings

    Science.gov (United States)

    Wang, Zhe; Wu, Jianda; Yang, Wang; Bera, Anup Kumar; Kamenskyi, Dmytro; Islam, A. T. M. Nazmul; Xu, Shenglong; Law, Joseph Matthew; Lake, Bella; Wu, Congjun; Loidl, Alois

    2018-02-01

    Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.

  8. Dynamics of strings between walls

    International Nuclear Information System (INIS)

    Eto, Minoru; Fujimori, Toshiaki; Nagashima, Takayuki; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke

    2009-01-01

    Configurations of vortex strings stretched between or ending on domain walls were previously found to be 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) states in N=2 supersymmetric gauge theories in 3+1 dimensions. 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 end points in the wall effective action. In the first method we explicitly obtain the effective Lagrangian in the strong coupling limit, which is written in terms of hypergeometric functions, and find the 90 deg. scattering for head-on collision. In the second method the domain wall effective action is assumed to be U(1) N gauge theory, and we find a good agreement between two methods for well-separated strings.

  9. Is the string theory doomed?

    International Nuclear Information System (INIS)

    Le Meur, H.; Daninos, F.; Bachas, C.

    2007-01-01

    Since its beginning, in the sixties, the string theory has succeeded in overcoming a lot of theoretical difficulties but now the complete absence of experimental validation entertains doubts about its ability to represent the real world and questions its hegemony in today's theoretical physics. Other space-time theories like the twistors, or the non-commutative geometry, or the loop quantum gravity, or the causal dynamics triangulation might begin receiving more attention. Despite all that, the string theory can be given credit for 4 achievements. First, the string theory has provided a consistent quantum description of gravity. Secondly, the string theory has built a theoretical frame that has allowed the unification of the 4 basic interactions. Thirdly, the string theory applied to astrophysics issues has demonstrated that the evaporation of a black hole does not necessarily lead to a loss of information which comforts the universality of the conservation of the quantity of information in any system and as a consequence put a fatal blow to the so-called paradox observed in black holes. Fourthly, the string theory has given a new and original meaning on the true nature of space-time. (A.C.)

  10. String theory on the edge

    International Nuclear Information System (INIS)

    Thorlacius, L.

    1989-01-01

    Open string vacuum configurations are described in terms of a one-dimensional field theory on the worldsheet boundary. The one-dimensional path integral has direct physical interpretation as a source term for closed string fields. This means that the vacuum divergences (Mobius infinities) of the path integral must be renormalized correctly. The author shows that reparametrization invariance Ward identities, apart from specifying the equations of motion of spacetime background gauge fields, also serve to fix the renormalization scheme of the vacuum divergences. He argues that vacuum configurations of open strings correspond to Caldeira-Leggett models of dissipative quantum mechanics (DQM) evaluated at a delocalization critical point. This connection reveals that critical DQM will manifest reparametrization invariance (inherited from the conformal invariance of string theory) rather than just scale invariance. This connection should open up new ways of constructing analytic and approximate solutions of open string theory (in particular, topological solitons such as monopoles and instantons). Type I superstring theory gives rise to a supersymmetric boundary field theory. Bose-Fermi cancellation eliminates vacuum divergences but the one-loop beta function remains the same as in the bosonic theory. Reparametrization invariance Ward identities dictate a boundary state normalization which yields consistent string-loop corrections to spacetime equations of motion, in both the periodic and anti-periodic fermion sectors

  11. Chern-Simons couplings for dielectric F-strings in matrix string theory

    International Nuclear Information System (INIS)

    Brecher, Dominic; Janssen, Bert; Lozano, Yolanda

    2002-01-01

    We compute the non-abelian couplings in the Chern-Simons action for a set of coinciding fundamental strings in both the type IIA and type IIB Matrix string theories. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  12. New expressions for string loop amplitudes leading to an ultra-simple conception of string dynamics

    International Nuclear Information System (INIS)

    Chan Hongmo; Tsou Sheungtsun; Bordes, J.; Nellen, L.

    1990-11-01

    New expressions are derived for string loop amplitudes as overlap integrals of string wave functionals. They are shown to take the form of exchange terms coming from the Bose-Einstein symmetrisation between string segments. One is thus led to the ultra-simple conception that string theory is basically free, and that 'string interactions' are due merely to the fact that strings are composite objects with Bose-Einstein segments as constituents. (author)

  13. Gravity from strings

    International Nuclear Information System (INIS)

    Deser, S.

    1987-01-01

    We obtain the Einstein action plus quadratic curvature corrections generated by closed bosonic, heterotic and supersymmetric strings by matching the four-graviton amplitude (to first order in the slope parameter and fourth power of momenta) with an effective local gravitational action. The resulting corrections are first shown to be of the Gauss-Bonnet form. It is then noted that, by the very nature of the slope expansion, the field-redefinition theorem applies. Consequently, only the curvature-squared term is determined, while squares of its contractions are explicitly seen not to contribute. This latter property has a generalization to all orders which implies that the effective gravitational action is unavoidably ghost-free. The properties of solutions to these corrected theories are then examined. First neglecting dilatons, we find the explicit 'Schwarzschild' metrics. Both asymptotically flat and de Sitter solutions are present. The latter are however shown to be unstable. The former have horizons and singularities which are respectively smaller and less violent than in Einstein gravity; the correct sign of the slope parameter also ensures absence of naked singularities. When dilatons are included, the cosmological vacua are gratifyingly excluded. (orig.)

  14. Functional integral approach to string theories

    International Nuclear Information System (INIS)

    Sakita, B.

    1987-01-01

    Fermionic string theory can be made supersymmetric: the superstring. It contains among others mass zero gauge fields of spin 1 and 2. The recent revival of interests in string field theories is due to the recognition of the compactified superstring theory as a viable theory of grandunification of all interactions, especially after Green and Schwarz's discovery of the gauge and gravitational anomaly cancellation in 0(32) superstring theory. New developments include string phenomenology, general discussions of compactification, new models, especially the heterotic string. These are either applications or extensions of string field theories. Although these are very exciting developments, the author limits his attention to the basics of the bosonic string theory

  15. String Theory for Pedestrians (1/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  16. String Theory for Pedestrians (2/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  17. String Theory for Pedestrians (3/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  18. Frequency of von willebrand disease in patients of heavy menstrual bleeding

    International Nuclear Information System (INIS)

    Anjum, N.; Shaheen, Z.; Altaf, C.

    2016-01-01

    Objective: To determine the frequency of Von Willebrand disease (vWD) in patients of heavy menstrual bleeding (HMB). Study Design: Hospital based cross sectional study. Place and Duration of Study: Study was conducted at the Gynecology and Obstetrics department, Military Hospital, Rawalpindi in collaboration with Haematology Department of Armed Forces Institute of Pathology (AFIP) Rawalpindi, from Jul to Dec 2015. Material and Methods: Women presenting with HMB were enrolled in the study after informed consent. HMB was defined as cyclical bleeding at normal intervals but patient is using more than 5 pads per day or increase in duration 8/28 or more for at least last 06 months. Venous blood samples were taken and screened for the hemoglobin level (Hb), platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT) and Von Willebrand antigen (vWF:Ag) in addition to bleeding time (BT) at the Armed Forces Institute of Pathology (AFIP). The demographic details (age, age at menarche), clinical features (menstrual history, quantity of bleeding) and laboratory findings were recorded on the study proforma. Results: A total of 200 patients were enrolled in this study with mean age of 32.3 +- 8.5 years. Mean flow of menstrual blood was 9.8 +- 2.5 pads / day. Mean Hb percent was 8.1 +- 1.4 g/dl. Twenty nine (14.5 percent) patients were having low level of vWF:Ag. Conclusion: There is high frequency of von Willebrand disease among females presenting with heavy menstrual bleeding in our set up. Therefore all patients with heavy menstrual bleeding except those with obvious causes like multiple fibroid should be screened for von Willebrand disease. (author)

  19. The Carmat Bioprosthetic Total Artificial Heart Is Associated With Early Hemostatic Recovery and no Acquired von Willebrand Syndrome in Calves.

    Science.gov (United States)

    Smadja, David M; Susen, Sophie; Rauch, Antoine; Cholley, Bernard; Latrémouille, Christian; Duveau, Daniel; Zilberstein, Luca; Méléard, Denis; Boughenou, Marie-Fazia; Belle, Eric Van; Gaussem, Pascale; Capel, Antoine; Jansen, Piet; Carpentier, Alain

    2017-10-01

    To determine hemostasis perturbations, including von Willebrand factor (VWF) multimers, after implantation of a new bioprosthetic and pulsatile total artificial heart (TAH). Preclinical study SETTING: Single-center biosurgical research laboratory. Female Charolais calves, 2-to-6 months old, weighing 102-to-122 kg. Surgical implantation of TAH through a mid-sternotomy approach. Four of 12 calves had a support duration of several days (4, 4, 8, and 10 days), allowing for the exploration of early steps of hemostasis parameters, including prothrombin time; coagulation factor levels (II, V, VII+X, and fibrinogen); and platelet count. Multimeric analysis of VWF was performed to detect a potential loss of high-molecular weight (HMW) multimers, as previously described for continuous flow rotary blood pumps. Despite the absence of anticoagulant treatment administered in the postoperative phase, no signs of coagulation activation were detected. Indeed, after an immediate postsurgery decrease of prothrombin time, platelet count, and coagulation factor levels, most parameters returned to baseline values. HMW multimers of VWF remained stable either after initiation or during days of support. Coagulation parameters and platelet count recovery in the postoperative phase of the Carmat TAH (Camat SA, Velizy Villacoublay Cedex, France) implantation in calves, in the absence of anticoagulant treatment and associated with the absence of decrease in HMW multimers of VWF, is in line with early hemocompatibility that is currently being validated in human clinical studies. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. String Theory in a Nutshell

    International Nuclear Information System (INIS)

    Skenderis, Kostas

    2007-01-01

    The book 'String Theory in a Nutshell' by Elias Kiritsis provides a comprehensive introduction to modern string theory. String theory is the leading candidate for a theory that successfully unifies all fundamental forces of nature, including gravity. The subject has been continuously developing since the early 1970s, with classic textbooks on the subject being those of Green, Schwarz and Witten (1987) and Polchinski (1998). Since the latter was published there have been substantial developments, in particular in understanding black holes and gravity/gauge theory dualities. A textbook treatment of this important material is clearly needed, both by students and researchers in string theory and by mathematicians and physicists working in related fields. This book has a good selection of material, starting from basics and moving into classic and modern topics. In particular, Kiritsis' presentation of the basic material is complementary to that of the earlier textbooks and he includes a number of topics which are not easily found or covered adequately elsewhere, for example, loop corrections to string effective couplings. Overall the book nicely covers the major advances of the last ten years, including (non-perturbative) string dualities, black hole physics, AdS/CFT and matrix models. It provides a concise but fairly complete introduction to these subjects which can be used both by students and by researchers. Moreover the emphasis is on results that are reasonably established, as is appropriate for a textbook; concise summaries are given for subjects which are still in flux, with references to relevant reviews and papers. A positive feature of the book is that the bibliography sections at the end of each chapter provide a comprehensive guide to the literature. The bibliographies point to reviews and pedagogical papers on subjects covered in this book as well as those that were omitted. It is rare for a textbook to contain such a self-contained and detailed guide to

  1. Design and Exploitation Problems of Drill String in Directional Drilling

    Directory of Open Access Journals (Sweden)

    Bednarz Stanislaw

    2004-09-01

    Full Text Available Drill string design for directional drilling requires accounting for a number of factors. First, types and expected values of loads should be determined. Then, elements of the drill string should be so selected as to enable realization of the plan at specified loads. Some of additional factors, e. g. purchase, exploitation cost, geological conditions in the bore-hole, washing of the bore-hole, stability, trajectory, rig parameters, accuracy of gauges, pumps parameters remain in conflict. Drill pipes are made of rolled pipes, upset and welded with tool joints to 9,5 m long; the shorter ones can be made of hot forged rods. Exploitation requirements, being a result of practical experience supported by theoretical and laboratory analyses should be a part of syllabuses of technical staff educational programs. Apart from designing the string, it is also vital to lower the risk of a drilling failure. The significance of these aspects seems to be unquestionable.

  2. String Resonances at Hadron Colliders

    CERN Document Server

    Anchordoqui, Luis A; Dai, De-Chang; Feng, Wan-Zhe; Goldberg, Haim; Huang, Xing; Lust, Dieter; Stojkovic, Dejan; Taylor, Tomasz R

    2014-01-01

    [Abridged] We consider extensions of the standard model based on open strings ending on D-branes. Assuming that the fundamental string mass scale M_s is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (3000 fb^{-1}) with \\sqrt{s} = 14 TeV, and at potential future pp colliders, HE-LHC and VLHC, operating at \\sqrt{s} = 33 and 100 TeV, respectively. In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and \\gamma + jet are completely independent of the details of compactification, and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first (n=1) and second (n=2) resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV), lowest massive Regge exc...

  3. Differential geometry in string models

    International Nuclear Information System (INIS)

    Alvarez, O.

    1986-01-01

    In this article the author reviews the differential geometric approach to the quantization of strings. A seminal paper demonstrates the connection between the trace anomaly and the critical dimension. The role played by the Faddeev-Popov ghosts has been instrumental in much of the subsequent work on the quantization of strings. This paper discusses the differential geometry of two dimensional surfaces and its importance in the quantization of strings. The path integral quantization approach to strings will be carefully analyzed to determine the correct effective measure for string theories. The choice of measure for the path integral is determined by differential geometric considerations. Once the measure is determined, the manifest diffeomorphism invariance of the theory will have to be broken by using the Faddeev-Popov ansatz. The gauge fixed theory is studied in detail with emphasis on the role of conformal and gravitational anomalies. In the analysis, the path integral formulation of the gauge fixed theory requires summing over all the distinct complex structures on the manifold

  4. String theory or field theory?

    International Nuclear Information System (INIS)

    Marshakov, Andrei V

    2002-01-01

    The status of string theory is reviewed, and major recent developments - especially those in going beyond perturbation theory in the string theory and quantum field theory frameworks - are analyzed. This analysis helps better understand the role and place of string theory in the modern picture of the physical world. Even though quantum field theory describes a wide range of experimental phenomena, it is emphasized that there are some insurmountable problems inherent in it - notably the impossibility to formulate the quantum theory of gravity on its basis - which prevent it from being a fundamental physical theory of the world of microscopic distances. It is this task, the creation of such a theory, which string theory, currently far from completion, is expected to solve. In spite of its somewhat vague current form, string theory has already led to a number of serious results and greatly contributed to progress in the understanding of quantum field theory. It is these developments which are our concern in this review. (reviews of topical problems)

  5. Topological strings from quantum mechanics

    International Nuclear Information System (INIS)

    Grassi, Alba; Marino, Marcos; Hatsuda, Yasuyuki

    2014-12-01

    We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized θ function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P 2 , local P 1 x P 1 and local F 1 . In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.

  6. An exact bosonization rule for c = 1 noncritical string theory

    International Nuclear Information System (INIS)

    Ishibashi, Nobuyuki; Yamaguchi, Atsushi

    2007-01-01

    We construct a string field theory for c = 1 noncritical strings using the loop variables as the string field. We show how one can express the nonrelativistic free fermions which describes the theory, in terms of these string fields

  7. Interactions for winding strings in Misner space

    International Nuclear Information System (INIS)

    Hikida, Y.

    2006-06-01

    We compute correlation functions of closed strings in Misner space, a big crunch big bang universe. We develop a general method for correlators with twist fields, which are relevant for the investigation on the condensation of winding tachyon. We propose to compute the correlation functions by performing an analytic continuation of the results in C/Z N Euclidean orbifold. In particular, we obtain a finite result for a general four point function of twist fields, which might be important for the interpretation as the quartic term of the tachyon potential. Three point functions are read off through the factorization, which are consistent with the known results. (Orig.)

  8. A matrix model from string field theory

    Directory of Open Access Journals (Sweden)

    Syoji Zeze

    2016-09-01

    Full Text Available We demonstrate that a Hermitian matrix model can be derived from level truncated open string field theory with Chan-Paton factors. The Hermitian matrix is coupled with a scalar and U(N vectors which are responsible for the D-brane at the tachyon vacuum. Effective potential for the scalar is evaluated both for finite and large N. Increase of potential height is observed in both cases. The large $N$ matrix integral is identified with a system of N ZZ branes and a ghost FZZT brane.

  9. Effective string dynamics in large N QCD

    Energy Technology Data Exchange (ETDEWEB)

    Iroshnikov, G.S. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Moskow Inst. of Physics and Technology, Moscow (Russian Federation)

    1995-05-01

    The semiclassical 1/N expansion in the strong coupling regime for spinor quarks was developed and the form of effective action was obtained. An extremum of the effective action that arises in the calculation of the hadronic correlation functions in the large N limit corresponds to a topologically non-trivial configuration of the gauge field. This configuration forms a chromoelectric Nambu string with additional spinor terms that contain in particular the Polyakov spinor factor. In the case when real quarks forming hadrons are replaced by scalar particles the above correlators yield the standard dual resonance amplitudes. (author). 10 refs, 1 fig.

  10. Violin Pedagogy and the Physics of the Bowed String

    Science.gov (United States)

    McLeod, Alexander Rhodes

    The paper describes the mechanics of violin tone production using non-specialist language, in order to present a scientific understanding of tone production accessible to a broad readership. As well as offering an objective understanding of tone production, this model provides a powerful tool for analyzing the technique of string playing. The interaction between the bow and the string is quite complex. Literature reviewed for this study reveals that scientific investigations have provided important insights into the mechanics of string playing, offering explanations for factors which both contribute to and limit the range of tone colours and dynamics that stringed instruments can produce. Also examined in the literature review are significant works of twentieth century violin pedagogy exploring tone production on the violin, based on the practical experience of generations of teachers and performers. Hermann von Helmholtz described the stick-slip cycle which drives the string in 1863, which replaced earlier ideas about the vibration of violin strings. Later, scientists such as John Schelleng and Lothar Cremer were able to demonstrate how the mechanics of the bow-string interaction can create different tone colours. Recent research by Anders Askenfelt, Knut Guettler, and Erwin Schoonderwaldt have continued to refine earlier research in this area. The writings of Lucien Capet, Leopold Auer, Carl Flesch, Paul Rolland, Kato Havas, Ivan Galamian, and Simon Fischer are examined and analyzed. Each author describes a different approach to tone production on the violin, representing a different understanding of the underlying mechanism. Analyzing these writings within the context of a scientific understanding of tone production makes it possible to compare these approaches more consistently, and to synthesize different concepts drawn from the diverse sources evaluated.

  11. Cosmic strings and black holes

    International Nuclear Information System (INIS)

    Aryal, M.; Ford, L.H.; Vilenkin, A.

    1986-01-01

    The metric for a Schwarzschild black hole with a cosmic string passing through it is discussed. The thermodynamics of such an object is considered, and it is shown that S = (1/4)A, where S is the entropy and A is the horizon area. It is noted that the Schwarzschild mass parameter M, which is the gravitational mass of the system, is no longer identical to its energy. A solution representing a pair of black holes held apart by strings is discussed. It is nearly identical to a static, axially symmetric solution given long ago by Bach and Weyl. It is shown how these solutions, which were formerly a mathematical curiosity, may be given a more physical interpretation in terms of cosmic strings

  12. Cooperative strings and glassy interfaces.

    Science.gov (United States)

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-07

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

  13. Vector superconductivity in cosmic strings

    International Nuclear Information System (INIS)

    Dvali, G.R.; Mahajan, S.M.

    1992-03-01

    We argue that in most realistic cases, the usual Witten-type bosonic superconductivity of the cosmic string is automatically (independent of the existence of superconducting currents) accompanied by the condensation of charged gauge vector bosons in the core giving rise to a new vector type superconductivity. The value of the charged vector condensate is related with the charged scalar expectation value, and vanishes only if the latter goes to zero. The mechanism for the proposed vector superconductivity, differing fundamentally from those in the literature, is delineated using the simplest realistic example of the two Higgs doublet standard model interacting with the extra cosmic string. It is shown that for a wide range of parameters, for which the string becomes scalarly superconducting, W boson condensates (the sources of vector superconductivity) are necessarily excited. (author). 14 refs

  14. QCD string in the baryon

    International Nuclear Information System (INIS)

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

    1997-01-01

    The QCD-motivated constituent string model is extended to consider the baryon. The system of three quarks propagating in the confining background field is studied in the Wilson loop approach, and the effective action is obtained. The resulting Lagrangian at large interquark distances corresponds to the Mercedes Benz string configuration. Assuming the quarks to be heavy enough to allow the adiabatic separation of quark and string junction motion and using the hyperspherical expansion for the quark subsystem we write out and solve the classical equation of motion for the junction. We quantize the motion of the junction and demonstrate that the account of these modes leads to the effective swelling of baryon in comparison with standard potential picture. The effects of finite gluonic correlation length which do not affect the excited states but appear to be substantial for the baryonic ground state, reducing the swelling considerably is discussed

  15. Noncompact symmetries in string theory

    International Nuclear Information System (INIS)

    Maharana, J.; Schwarz, J.H.

    1993-01-01

    Noncompact groups, similar to those that appeared in various supergravity theories in the 1970's have been turning up in recent studies of string theory. First it was discovered that moduli spaces of toroidal compactification are given by noncompact groups modded out by their maximal compact subgroups and discrete duality groups. Then it was found that many other moduli spaces have analogous descriptions. More recently, noncompact group symmetries have turned up in effective actions used to study string cosmology and other classical configurations. This paper explores these noncompact groups in the case of toroidal compactification both from the viewpoint of low-energy effective field theory, using the method of dimensional reduction, and from the viewpoint of the string theory world-sheet. The conclusion is that all these symmetries are intimately related. In particular, we find that Chern-Simons terms in the three-form field strength H μνρ play a crucial role. (orig.)

  16. Introduction to strings and superstrings

    International Nuclear Information System (INIS)

    Rausch de Traubenberg, M.

    1988-01-01

    The string theory is applied in the construction of a theory which allows the coupling of the four fundamental interactions and matter. The original model of the string theory describes the hadronic phenomenon of duality. The model extension, which describes the closed strings and those with a spin, is studied. The supersymmetry and the supersymmetric partner concepts are considered, in order to obtain a superstrings theory. The supersymmetry allows the formulation of a ''supertheory'', including matter, fields and gravitation. In order to explain the mass of the observable particles, the mechanism of symmetry breaking must be taken into account. The scalar state concept, originated from the supersymmetry breaking, is analyzed. This ''supertheory'' is not entirely accepted by the scientific world [fr

  17. STRING v9.1

    DEFF Research Database (Denmark)

    Franceschini, A.; Simonovic, M.; Roth, A.

    2013-01-01

    for certain model organisms and functional systems. Currently, protein interactions and associations are annotated at various levels of detail in online resources, ranging from raw data repositories to highly formalized pathway databases. For many applications, a global view of all the available interaction...... data is desirable, including lower-quality data and/or computational predictions. The STRING database (http://string-db.org/) aims to provide such a global perspective for as many organisms as feasible. Known and predicted associations are scored and integrated, resulting in comprehensive protein...... networks covering >1100 organisms. Here, we describe the update to version 9.1 of STRING, introducing several improvements: (i) we extend the automated mining of scientific texts for interaction information, to now also include full-text articles; (ii) we entirely re-designed the algorithm for transferring...

  18. The NMSSM and string theory

    International Nuclear Information System (INIS)

    Lebedev, Oleg; Ramos-Sanchez, Saul

    2009-12-01

    We study the possibility of constructing the NMSSM from the heterotic string. String derived NMSSMs are much more rare than MSSMs due to the extra requirement that there exist a light singlet which couples to the Higgs pairs. They share the common feature that the singlet self-interactions are typically suppressed, leading to either the ''decoupling'' or to the Peccei-Quinn limit of the NMSSM. In the latter case, the spectrum contains a light pseudoscalar which may be relevant to the MSSM fine-tuning problem.We provide a Z 6 heterotic orbifold example of the NMSSM with approximate Peccei-Quinn symmetry, whose origin lies in the string selection rules combined with our choice of the vacuum configuration. (orig.)

  19. On the string equation at c=1

    International Nuclear Information System (INIS)

    Nakatsu, Toshio.

    1994-07-01

    The analogue of the string equation which specifies the partition function of c=1 string with a compactification radius β is an element of Z ≥1 is described in the framework of Toda lattice hierarchy. (author)

  20. Metastable cosmic strings in realistic models

    International Nuclear Information System (INIS)

    Holman, R.

    1992-01-01

    The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2) L x SU(2) R x U(1) B-L are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed

  1. Covariant amplitudes in Polyakov string theory

    International Nuclear Information System (INIS)

    Aoyama, H.; Dhar, A.; Namazie, M.A.

    1986-01-01

    A manifestly Lorentz-covariant and reparametrization-invariant procedure for computing string amplitudes using Polyakov's formulation is described. Both bosonic and superstring theories are dealt with. The computation of string amplitudes is greatly facilitated by this formalism. (orig.)

  2. Cosmic string induced peculiar velocities

    International Nuclear Information System (INIS)

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

    1987-02-01

    We calculate analytically the probability distribution for peculiar velocities on scales from 10h -1 to 60h -1 Mpc with cosmic string loops as the dominant source of primordial gravitational perturbations. We consider a range of parameters βGμ appropriate for both hot (HDM) and cold (CDM) dark matter scenarios. An Ω = 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 βGμ or the effect of loop fissioning and production details be considerable. Specifically, for optimal CDM string parameters Gμ = 10 -6 , β = 9, h = .5, and scales of 60h -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 βGμ 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

  3. Topics in string theory

    Science.gov (United States)

    Jejjala, Vishnumohan

    2002-01-01

    This Thesis explores aspects of superstring theory on orbifold spaces and applies some of the intuition gleaned from the study of the non-commutative geometry of space-time to understanding the fractional quantum Hall effect. The moduli space of vacua of marginal and relevant deformations of N = 4 super-Yang-Mills gauge theory in four dimensions is interpreted in terms of non-commutative geometry. A formalism for thinking about the algebraic geometry of the moduli space is developed. Within this framework, the representation theory of the algebras studied provides a natural exposition of D-brane fractionation. The non-commutative moduli space of deformations preserving N = 1 supersymmetry is examined in detail through various examples. In string theory, by the AdS/CFT correspondence, deformations of the N = 4 field theory are dual to the near-horizon geometries of D-branes on orbifolds of AdS5 x S 5. The physics of D-branes on the dual AdS backgrounds is explored. Quivers encapsulate the matter content of supersymmetric field theories on the worldvolumes of D-branes at orbifold singularities. New techniques for constructing quivers are presented here. When N is a normal subgroup of a finite group G, the quiver corresponding to fixed points of the orbifold M/G is computed from a G/N action on the quiver corresponding to M/G . These techniques prove useful for constructing non-Abelian quivers and for examining discrete torsion orbifolds. Quivers obtained through our constructions contain interesting low-energy phenomenology. The matter content on a brane at an isolated singularity of the Delta27 orbifold embeds the Standard Model. The symmetries of the quiver require exactly three generations of fields in the particle spectrum. Lepton masses are suppressed relative to quark masses because lepton Yukawa couplings do not appear in the superpotential. Lepton masses are generated through the Kahler potential and are related to the supersymmetry breaking scale. The model

  4. Warped models in string theory

    International Nuclear Information System (INIS)

    Acharya, B.S.; Benini, F.; Valandro, R.

    2006-12-01

    Warped models, originating with the ideas of Randall and Sundrum, provide a fascinating extension of the standard model with interesting consequences for the LHC. We investigate in detail how string theory realises such models, with emphasis on fermion localisation and the computation of Yukawa couplings. We find, in contrast to the 5d models, that fermions can be localised anywhere in the extra dimension, and that there are new mechanisms to generate exponential hierarchies amongst the Yukawa couplings. We also suggest a way to distinguish these string theory models with data from the LHC. (author)

  5. Heterotic strings on homogeneous spaces

    International Nuclear Information System (INIS)

    Israel, D.; Kounnas, C.; Orlando, D.; Petropoulos, P.M.

    2005-01-01

    We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU(2)/U(1)∝S 2 (already described in a previous paper) and the SU(3)/U(1) 2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  6. Precise Analysis of String Expressions

    DEFF Research Database (Denmark)

    Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff

    2003-01-01

    We perform static analysis of Java programs to answer a simple question: which values may occur as results of string expressions? The answers are summarized for each expression by a regular language that is guaranteed to contain all possible values. We present several applications of this analysis...... are automatically produced. We present extensive benchmarks demonstrating that the analysis is efficient and produces results of useful precision......., including statically checking the syntax of dynamically generated expressions, such as SQL queries. Our analysis constructs flow graphs from class files and generates a context-free grammar with a nonterminal for each string expression. The language of this grammar is then widened into a regular language...

  7. New twistor string theories revisited

    International Nuclear Information System (INIS)

    Broedel, Johannes; Wurm, Bernhard

    2009-01-01

    A gauged version of Berkovits twistor string theory featuring the particle content of N=8 supergravity was suggested by Abou-Zeid, Hull and Mason. The equations of motion for a particular multiplet in the modified theory are examined on the level of basic twistor fields and thereby shown to imply the vanishing of the negative helicity graviton on-shell. Additionally, the restrictions emerging from the equation of motion for the new gauge field B-bar reveal the chiral nature of interactions in theories constructed in this manner. Moreover, a particular amplitude in Berkovits open string theory is shown to be in agreement with the corresponding result in Einstein gravity.

  8. Introduction to field theory of strings

    International Nuclear Information System (INIS)

    Kikkawa, K.

    1987-01-01

    The field theory of bosonic string is reviewed. First, theory is treated in a light-cone gauge. After a brief survey of the first quantized theory of free string, the second quantization is discussed. All possible interactions of strings are introduced based on a smoothness condition of work sheets swept out by strings. Perturbation theory is developed. Finally a possible way to the manifest covariant formalism is discussed

  9. Twenty-five questions for string theorists

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-09-01

    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.

  10. Hosotani model in closed string theory

    International Nuclear Information System (INIS)

    Shiraishi, Kiyoshi.

    1988-11-01

    Hosotani mechanism in the closed string theory with current algebra symmetry is described by the (old covariant) operator method. We compare the gauge symmetry breaking mechanism in a string theory which has SU(2) symmetry with the one in an equivalent compactified closed string theory. We also investigate the difference between Hosotani mechanism and Higgs mechanism in closed string theories by calculation of a fourpoint amplitude of 'Higgs' bosons at tree level. (author)

  11. Ambitwistor strings and the scattering equations at one loop

    Energy Technology Data Exchange (ETDEWEB)

    Adamo, Tim; Casali, Eduardo; Skinner, David [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2014-04-15

    Ambitwistor strings are chiral, infinite tension analogues of conventional string theory whose target space is the space of complex null geodesics and whose spectrum consists exclusively of massless states. At genus zero, these strings underpin the Cachazo-He-Yuan formulæ for tree level scattering of gravitons, gluons and scalars. In this paper we extend these formulæ in a number of directions. Firstly, we consider Ramond sector vertex operators and construct simple amplitudes involving space-time fermions. These agree with tree amplitudes in ten dimensional supergravity and super Yang-Mills. We then show that, after the usual GSO projections, the ambitwistor string partition function is modular invariant. We consider the scattering equations at genus one, and calculate one loop scattering amplitudes for NS-NS external states in the Type II ambitwistor string. We conjecture that these give new representations of (the integrand of) one loop supergravity amplitudes and we show that they have the expected behaviour under factorization of the worldsheet in both non-separating and separating degenerations.

  12. Hollow micro string based calorimeter device

    DEFF Research Database (Denmark)

    2014-01-01

    positions so as to form a free released double clamped string in-between said two longitudinally distanced positions said micro-channel string comprising a microfluidic channel having a closed cross section and extending in the longitudinal direction of the hollow string, acoustical means adapted...

  13. String field representation of the Virasoro algebra

    Energy Technology Data Exchange (ETDEWEB)

    Mertes, Nicholas [Institute of Physics AS CR,Na Slovance 2, Prague 8 (Czech Republic); Department of Physics, University of Miami,Coral Gables, FL (United States); Schnabl, Martin [Institute of Physics AS CR,Na Slovance 2, Prague 8 (Czech Republic)

    2016-12-29

    We construct a representation of the zero central charge Virasoro algebra using string fields in Witten’s open bosonic string field theory. This construction is used to explore extensions of the KBc algebra and find novel algebraic solutions of open string field theory.

  14. Regularization of finite temperature string theories

    International Nuclear Information System (INIS)

    Leblanc, Y.; Knecht, M.; Wallet, J.C.

    1990-01-01

    The tachyonic divergences occurring in the free energy of various string theories at finite temperature are eliminated through the use of regularization schemes and analytic continuations. For closed strings, we obtain finite expressions which, however, develop an imaginary part above the Hagedorn temperature, whereas open string theories are still plagued with dilatonic divergences. (orig.)

  15. String loop divergences and effective lagrangians

    International Nuclear Information System (INIS)

    Fischler, W.; Klebanov, I.; Susskind, L.

    1988-01-01

    We isolate logarithmic divergences from bosonic string amplitudes on a disc. These divergences are compared with 'tadpole' divergences in the effective field theory, with a covariant cosmological term implied by the counting of string coupling constants. We find an inconsistency between the two. This might be a problem in eliminating divergences from the bosonic string. (orig.)

  16. The issue of supersymmetry breaking in strings

    International Nuclear Information System (INIS)

    Binetruy, P.

    1989-12-01

    We discuss the central role that supersymmetry plays in string models, both in spacetime and at the level of the string world-sheet. The problems associated with supersymmetry-breaking are reviewed together with some of the attempts to solve them, in the string as well as the field theory approach

  17. String duality and novel theories without gravity

    International Nuclear Information System (INIS)

    Kachru, Shamit

    1998-01-01

    We describe some of the novel 6d quantum field theories which have been discovered in studies of string duality. The role these theories (and their 4d descendants) may play in alleviating the vacuum degeneracy problem in string theory is reviewed. The DLCQ of these field theories is presented as one concrete way of formulating them, independent of string theory

  18. Architectures and representations for string transduction

    NARCIS (Netherlands)

    Chrupala, Grzegorz

    2015-01-01

    String transduction problems are ubiquitous in natural language processing: they include transliteration, grapheme-to-phoneme conversion, text normalization and translation. String transduction can be reduced to the simpler problems of sequence labeling by expressing the target string as a sequence

  19. Symmetries and Interactions in Matrix String Theory

    NARCIS (Netherlands)

    Hacquebord, F.H.

    1999-01-01

    This PhD-thesis reviews matrix string theory and recent developments therein. The emphasis is put on symmetries, interactions and scattering processes in the matrix model. We start with an introduction to matrix string theory and a review of the orbifold model that flows out of matrix string theory

  20. Exotic configurations for gauge theory strings

    International Nuclear Information System (INIS)

    Yajnik, U.A.

    1987-01-01

    This paper discusses a class of string configurations occuring in nonabelian gauge theories, which are such that a component of the charged scalar field responsible for the string has a nonvanishing expectation value in the core of the string. A systematic procedure is given for setting up the ansatz for such configurations. (orig.)

  1. General relativity invariance and string field theory

    International Nuclear Information System (INIS)

    Aref'eva, I.Ya.; Volovich, I.V.

    1987-04-01

    The general covariance principle in the string field theory is considered. The algebraic properties of the string Lie derivative are discussed. The string vielbein and spin connection are introduced and an action invariant under general co-ordinate transformation is proposed. (author). 18 refs

  2. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    Gauge strings have their energy concentrated in a very thin tube, the radius of which is of the order of the symmetry- breaking scale whereas the global strings are such that their energy extends to regions far beyond the central core. Strings have an important astrophysical consequence, namely, the double quasar problem ...

  3. Are Stopped Strings Preferred in Sad Music?

    Directory of Open Access Journals (Sweden)

    David Huron

    2017-01-01

    Full Text Available String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard. Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifically, we compare the proportion of potentially open-to-stopped strings in a sample of slow, minor-mode movements with matched major-mode movements. By way of illustration, a preliminary analysis of Samuel Barber's famous Adagio from his Opus 11 string quartet shows that the selected key (B-flat minor provides the optimum key for minimizing open string tones. However, examination of a broader controlled sample of quartet movements by Haydn, Mozart and Beethoven failed to exhibit the conjectured relationship. Instead, major-mode movements were found to avoid possible open strings more than slow minor-mode movements.

  4. Introduction to the theory of strings

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1985-10-01

    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

  5. Open bosonic string in background electromagnetic field

    International Nuclear Information System (INIS)

    Nesterenko, V.V.

    1987-01-01

    The classical and quantum dynamics of an open string propagating in the D-dimensional space-time in the presence of a background electromagnetic field is investigated. An important point in this consideration is the use of the generalized light-like gauge. There are considered the strings of two types; the neutral strings with charges at their ends obeying the condition q 1 +q 2 =0 and the charged strings having a net charge q 1 +q 2 ≠ 0. The consistency of theory demands that the background electric field does not exceed its critical value. The distance between the mass levels of the neutral open string decreases (1-e 2 ) times in comparison with the free string, where e is the dimensionless strength of the electric field. The magnetic field does not affect this distance. It is shown that at a classical level the squared mass of the neutral open string has a tachyonic contribution due to the motion of the string as a whole in transverse directions. The tachyonic term disappears if one considers, instead of M 2 , the string energy in a special reference frame where the projection of the total canonical momentum of the string onto the electric field vanishes. The contributions due to zero point fluctuations to the energy spectrum of the neutral string and to the Virasoro operators in the theory of charged string are found

  6. 2-Dim. gravity and string theory

    International Nuclear Information System (INIS)

    Narain, K.S.

    1991-01-01

    The role of 2-dim. gravity in string theory is discussed. In particular d=25 string theory coupled to 2-d. gravity is described and shown to give rise to the physics of the usual 26-dim. string theory (where one does not quantise 2-d. gravity. (orig.)

  7. Naturally light hidden photons in LARGE volume string compactifications

    International Nuclear Information System (INIS)

    Goodsell, M.; Jaeckel, J.; Redondo, J.; Ringwald, A.

    2009-09-01

    Extra ''hidden'' U(1) gauge factors are a generic feature of string theory that is of particular phenomenological interest. They can kinetically mix with the Standard Model photon and are thereby accessible to a wide variety of astrophysical and cosmological observations and laboratory experiments. In this paper we investigate the masses and the kinetic mixing of hidden U(1)s in LARGE volume compactifications of string theory. We find that in these scenarios the hidden photons can be naturally light and that their kinetic mixing with the ordinary electromagnetic photon can be of a size interesting for near future experiments and observations. (orig.)

  8. BRS anomaly and the Weyl freedom in string theory

    International Nuclear Information System (INIS)

    Fujikawa, Kazuo; Inagaki, Takeshi; Suzuki, Hiroshi.

    1988-06-01

    It is shown that an anomalous correction to the BRS current ΔJ z = 3/4πδ z 2 c z in bosonic string theory essentially corresponds to the surface term 3/8π∫δ α (c α √gR)d 2 x in the anomalous Jacobian factor. To make this correspondence explicit in the operator level, we present a quantization of a free string at D < 26 which maintains the closure of the BRS symmetry. (author)

  9. Testing effective string models of black holes with fixed scalars

    International Nuclear Information System (INIS)

    Krasnitz, M.; Klebanov, I.R.

    1997-01-01

    We solve the problem of mixing between the fixed scalar and metric fluctuations. First, we derive the decoupled fixed scalar equation for the four-dimensional black hole with two different charges. We proceed to the five-dimensional black hole with different electric (one-brane) and magnetic (five-brane) charges, and derive two decoupled equations satisfied by appropriate mixtures of the original fixed scalar fields. The resulting greybody factors are proportional to those that follow from coupling to dimension (2,2) operators on the effective string. In general, however, the string action also contains couplings to chiral operators of dimension (1,3) and (3,1), which cause disagreements with the semiclassical absorption cross sections. Implications of this for the effective string models are discussed. copyright 1997 The American Physical Society

  10. Solving the open bosonic string in perturbation theory

    International Nuclear Information System (INIS)

    Samuel, S.

    1990-01-01

    The integrand and integration region for the N-point amplitude in the open oriented bosonic string are obtained to all orders in perturbation theory. The result is derived from the Witten covariant string field theory by using on-shell and off-shell conformal methods and Riemann surface mathematics. Although only the off-shell g-loop tachyon amplitudes are computed explicitly, the methods generalize to other external states. We derive the g-loop ghost-Jacobi identity in which the ghost correlation function cancels the jacobian factor in changing from second-quantized to first-quantized variables. Moduli space is discussed from several viewpoints and it is shown that string field theory provides an algorithm for its determination. (orig.)

  11. Confinement and strings in MQCD

    International Nuclear Information System (INIS)

    Hanany, A.; Strassler, M.J.; Zaffaroni, A.

    1998-01-01

    We study aspects of confinement in the M-theory fivebrane version of QCD (MQCD). We show heavy quarks are confined in hadrons (which take the form of membrane-fivebrane bound states) for N=1 and softly broken N=2 SU(N) MQCD. We explore and clarify the transition from the exotic physics of the latter to the standard physics of the former. In particular, the many strings and quark-antiquark mesons found in N=2 field theory by Douglas and Shenker are reproduced. It is seen that in the N=1 limit all but one such meson disappears while all of the strings survive. The strings of softly broken N=2, N=1, and even non-supersymmetric SU(N) MQCD have a common ratio for their tensions as a function of the amount of flux they carry. We also comment on the almost BPS properties of the Douglas-Shenker strings and discuss the brane picture for monopole confinement on N=2 QCD Higgs branches. (orig.)

  12. Monads, strings, and M theory

    NARCIS (Netherlands)

    Hofman, C.; Park, J.-S.

    1997-01-01

    The recent developmen ts in string theory suggest that the space-time coordinates should be generalized to non-comm uting matrices. P ostulating this suggestion as the fun- damen tal geometrical principle, w e form ulate a candidate for covariant second quantized RNS superstrings as a topological

  13. Topological strings and quantum curves

    NARCIS (Netherlands)

    Hollands, L.

    2009-01-01

    This thesis presents several new insights on the interface between mathematics and theoretical physics, with a central role for Riemann surfaces. First of all, the duality between Vafa-Witten theory and WZW models is embedded in string theory. Secondly, this model is generalized to a web of

  14. Probing the string winding sector

    Energy Technology Data Exchange (ETDEWEB)

    Aldazabal, Gerardo; Mayo, Martín [G. Física CAB-CNEA and CONICET, Centro Atómico Bariloche,Av. Bustillo 9500, Bariloche (Argentina); Instituto Balseiro, Centro Atómico Bariloche,Av. Bustillo 9500, Bariloche (Argentina); Nuñez, Carmen [Instituto de Astronomía y Física del Espacio (CONICET-UBA),C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina); Departamento de Física, FCEN, Universidad de Buenos Aires,C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina)

    2017-03-17

    We probe a slice of the massive winding sector of bosonic string theory from toroidal compactifications of Double Field Theory (DFT). This string subsector corresponds to states containing one left and one right moving oscillators. We perform a generalized Kaluza Klein compactification of DFT on generic 2n-dimensional toroidal constant backgrounds and show that, up to third order in fluctuations, the theory coincides with the corresponding effective theory of the bosonic string compactified on n-dimensional toroidal constant backgrounds, obtained from three-point amplitudes. The comparison between both theories is facilitated by noticing that generalized diffeomorphisms in DFT allow to fix generalized harmonic gauge conditions that help in identifying the physical degrees of freedom. These conditions manifest as conformal anomaly cancellation requirements on the string theory side. The explicit expression for the gauge invariant effective action containing the physical massless sector (gravity+antisymmetric+gauge+ scalar fields) coupled to towers of generalized Kaluza Klein massive states (corresponding to compact momentum and winding modes) is found. The action acquires a very compact form when written in terms of fields carrying O(n,n) indices, and is explicitly T-duality invariant. The global algebra associated to the generalized Kaluza Klein compactification is discussed.

  15. Hawking radiation in string theories

    International Nuclear Information System (INIS)

    Sakai, N.

    1986-01-01

    String theories in a uniform gravitational field are studied to examine the Hawking radiation. An upper limit is found for the strength of the possible gravitational field: the corresponding Hawking temperature cannot be larger than the Hagedorn limiting temperature divided by π

  16. The Science of String Instruments

    CERN Document Server

    Rossing, Thomas D

    2010-01-01

    Many performing musicians, as well as instrument builders, are coming to realize the importance of understanding the science of musical instruments. This book explains how string instruments produce sound. It presents basic ideas in simple language, and it also translates some more sophisticated ideas in non-technical language. It should be of interest to performers, researchers, and instrument makers alike.

  17. String theory and cosmological singularities

    Indian Academy of Sciences (India)

    Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics.

  18. Defect branes as Alice strings

    International Nuclear Information System (INIS)

    Okada, Takashi; Sakatani, Yuho

    2015-01-01

    There exist various defect-brane backgrounds in supergravity theories which arise as the low energy limit of string theories. These backgrounds typically have non-trivial monodromies, and if we move a charged probe around the center of a defect, its charge will be changed by the action of the monodromy. During the process, the charge conservation law seems to be violated. In this paper, to resolve this puzzle, we examine a dynamics of the charge changing process and show that the missing charge of the probe is transferred to the background. We then explicitly construct the resultant background after the charge transfer process by utilizing dualities. This background has the same monodromy as the original defect brane, but has an additional charge which does not have any localized source. In the literature, such a charge without localized source is known to appear in the presence of Alice strings. We argue that defect branes can in fact be regarded as a realization of Alice strings in string theory and examine the charge transfer process from that perspective.

  19. Parton fragmentation and string dynamics

    International Nuclear Information System (INIS)

    Andersson, B.; Gustafson, G.; Ingelman, G.; Sjoestrand, T.

    1983-01-01

    While much has been learned recently about quark and gluon interactions in the framework of perturbative Quantum Chromodynamics, the relation between calculated parton properties and observed hadron densities involves models where dynamics and jet empirical rules have to be combined. The purpose of this article is to describe a presently successful approach which is based on a cascade jet model using String dynamics. It can readily lead to Monte Carlo jet programmes of great use when analyzing data. Production processes in an iterative cascade approach, with tunneling in a constant force field, are reviewed. Expected differences between quark and gluon jets are discussed. Low transverse momentum phenomena are also reviewed with emphasis on hyperon polarization. In so far as this approach uses a fragmentation scheme based on String dynamics, it was deemed appropriate to also include under the same cover a special report on the Classical theory of relativistic Strings, seen as the classical limit of the Dual Resonance model. The Equations of motion and interaction among strings are presented. (orig.)

  20. Particles, fields, and now strings

    International Nuclear Information System (INIS)

    Weinberg, S.

    1986-01-01

    The author traces the history of the struggle between two views of the world: a world of particles or a world of fields. These positions were crystallised as quantum field theory and S-matrix theory and now by the reintroduction of string theories. (Auth.)

  1. Modified Steiner functional string action

    International Nuclear Information System (INIS)

    Baillie, C.F.; Johnston, D.A.

    1992-01-01

    It has recently been suggested by Ambartzumian et al. that the modified Steiner functional has desirable properties as an action for random surfaces and hence string world sheets. We perform a simulation of this action on a dynamically triangulated random surface to investigate this claim and find that the surfaces are in a flat phase

  2. String theory in the bathtub

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The presence of the surrounding medium makes their dynamics dramatically different from those of ordinary string-like objects propagating in empty space, leading to quite peculiar phenomena, observed in experiments and simulations. I will argue that the effective theory provides an optimal theoretical framework to understand such phenomena, and to make precise quantitative predictions about them.

  3. Topological Strings and Integrable Hierarchies

    CERN Document Server

    Aganagic, M; Klemm, A D; Marino, M; Vafa, C; Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Marino, Marcos; Vafa, Cumrun

    2006-01-01

    We consider the topological B-model on local Calabi-Yau geometries. We show how one can solve for the amplitudes by using W-algebra symmetries which encodes the symmetries of holomorphic diffeomorphisms of the Calabi-Yau. In the highly effective fermionic/brane formulation this leads to a free fermion description of the amplitudes. Furthermore we argue that topological strings on Calabi-Yau geometries provide a unifying picture connecting non-critical (super)strings, integrable hierarchies, and various matrix models. In particular we show how the ordinary matrix model, the double scaling limit of matrix models, and Kontsevich-like matrix model are all related and arise from studying branes in specific local Calabi-Yau three-folds. We also show how A-model topological string on P^1 and local toric threefolds (and in particular the topological vertex) can be realized and solved as B-model topological string amplitudes on a Calabi-Yau manifold.

  4. LZ-Compressed String Dictionaries

    OpenAIRE

    Arz, Julian; Fischer, Johannes

    2013-01-01

    We show how to compress string dictionaries using the Lempel-Ziv (LZ78) data compression algorithm. Our approach is validated experimentally on dictionaries of up to 1.5 GB of uncompressed text. We achieve compression ratios often outperforming the existing alternatives, especially on dictionaries containing many repeated substrings. Our query times remain competitive.

  5. Defect branes as Alice strings

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Takashi [Theoretical Biology Laboratory, RIKEN,Wako 351-0198 (Japan); Sakatani, Yuho [Department of Physics and Astronomy,Seoul National University, Seoul 151-747 (Korea, Republic of)

    2015-03-25

    There exist various defect-brane backgrounds in supergravity theories which arise as the low energy limit of string theories. These backgrounds typically have non-trivial monodromies, and if we move a charged probe around the center of a defect, its charge will be changed by the action of the monodromy. During the process, the charge conservation law seems to be violated. In this paper, to resolve this puzzle, we examine a dynamics of the charge changing process and show that the missing charge of the probe is transferred to the background. We then explicitly construct the resultant background after the charge transfer process by utilizing dualities. This background has the same monodromy as the original defect brane, but has an additional charge which does not have any localized source. In the literature, such a charge without localized source is known to appear in the presence of Alice strings. We argue that defect branes can in fact be regarded as a realization of Alice strings in string theory and examine the charge transfer process from that perspective.

  6. The super G-string

    International Nuclear Information System (INIS)

    Gates, V.; Kangaroo, E.; Roachcock, M.; Gall, W.C.

    1986-01-01

    The authors describe a string theory which gives all the phenomenology of symmetry breaking. It makes use of higher dimensions, higher derivatives, higher spin, higher twist, and hierarchy. It discusses the problems of renormalizability of gravity, the cosmological constant, grand unification, supersymmetry breaking, and the command cold

  7. Strings, fields and critical phenomena

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1987-07-01

    The connection between field theory and critical phenomena is reviewed. Emphasis is put on the use of Monte Carlo methods in the study of non-perturbative aspects of field theory. String theory is then described as a statistical theory of random surfaces and the critical behaviour is analyzed both by analytical and numerical methods. (orig.)

  8. Large BCFT moduli in open string field theory

    Czech Academy of Sciences Publication Activity Database

    Maccaferri, C.; Schnabl, Martin

    2015-01-01

    Roč. 2015, č. 8 (2015), s. 149 ISSN 1029-8479 R&D Projects: GA ČR(CZ) GA14-31689S Institutional support: RVO:68378271 Keywords : String Field Theory * tachyon condensation * D-branes Subject RIV: BE - Theoretical Physics Impact factor: 6.023, year: 2015

  9. Interacting bosonic strings in subcritical dimensions

    International Nuclear Information System (INIS)

    Hwang, S.; Marnelius, R.

    1988-01-01

    Interaction theory for relativistic bosonic string in spacetime dimensions below the critical value 26 is formulated using BRST techniques with an extra scalar field. One-loop zero-point amplitudes for closed strings are modular invariant. For a free scalar field, vertex operators are constructed leading to, e.g., the old dual N-tachyon tree amplitudes in D < 26. The N-tachyon one-loop expressions contain closed string poles for open strings, and are modular invariant for closed strings. However, the threshold cuts are wrong in D < 25. Only for D=25 to the considered vertex operators lead to consistency. (orig.)

  10. Micro string resonators as temperature sensors

    DEFF Research Database (Denmark)

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

    2013-01-01

    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...... 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....

  11. String Theory and M-Theory

    Science.gov (United States)

    Becker, Katrin; Becker, Melanie; Schwarz, John H.

    String theory is one of the most exciting and challenging areas of modern theoretical physics. This book guides the reader from the basics of string theory to recent developments. It introduces the basics of perturbative string theory, world-sheet supersymmetry, space-time supersymmetry, conformal field theory and the heterotic string, before describing modern developments, including D-branes, string dualities and M-theory. It then covers string geometry and flux compactifications, applications to cosmology and particle physics, black holes in string theory and M-theory, and the microscopic origin of black-hole entropy. It concludes with Matrix theory, the AdS/CFT duality and its generalizations. This book is ideal for graduate students and researchers in modern string theory, and will make an excellent textbook for a one-year course on string theory. It contains over 120 exercises with solutions, and over 200 homework problems with solutions available on a password protected website for lecturers at www.cambridge.org/9780521860697. Comprehensive coverage of topics from basics of string theory to recent developments Ideal textbook for a one-year course in string theory Includes over 100 exercises with solutions Contains over 200 homework problems with solutions available to lecturers on-line

  12. String theory as a Lilliputian world

    International Nuclear Information System (INIS)

    Ambjørn, J.; Makeenko, Y.

    2016-01-01

    Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

  13. String theory as a Lilliputian world

    Energy Technology Data Exchange (ETDEWEB)

    Ambjørn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); IMAPP, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Makeenko, Y., E-mail: makeenko@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)

    2016-05-10

    Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

  14. The Consensus String Problem and the Complexity of Comparing Hidden Markov Models

    DEFF Research Database (Denmark)

    Lyngsø, Rune Bang; Pedersen, Christian Nørgaard Storm

    2002-01-01

    The basic theory of hidden Markov models was developed and applied to problems in speech recognition in the late 1960s, and has since then been applied to numerous problems, e.g. biological sequence analysis. Most applications of hidden Markov models are based on efficient algorithms for computing...... the probability of generating a given string, or computing the most likely path generating a given string. In this paper we consider the problem of computing the most likely string, or consensus string, generated by a given model, and its implications on the complexity of comparing hidden Markov models. We show...... that computing the consensus string, and approximating its probability within any constant factor, is NP-hard, and that the same holds for the closely related labeling problem for class hidden Markov models. Furthermore, we establish the NP-hardness of comparing two hidden Markov models under the L∞- and L1...

  15. Aspects of some dualities in string theory

    Science.gov (United States)

    Kim, Bom Soo

    AdS/CFT correspondence in string theory has changed landscape of the theoretical physics. Through this celebrated duality between gravity theory and field theory, one can investigate analytically strongly coupled gauge theories such as Quantum Chromodynamics (QCD) in terms of weakly coupled string theory such as supergravity theory and vice versa. In the first part of this thesis we used this duality to construct a new type of nonlocal field theory, called Puff Field Theory, in terms of D3 branes in type IIB string theory with a geometric twist. In addition to the strong-weak duality of AdS/CFT, there also exists a weak-weak duality, called Twistor String Theory. Twistor technique is successfully used to calculate the SYM scattering amplitude in an elegant fashion. Yet, the progress in the string theory side was hindered by a non-unitary conformal gravity. We extend the Twistor string theory by introducing mass terms, in the second part of the thesis. A chiral mass term is identified as a vacuum expectation value of a conformal supergravity field and is tied with the breaking of the conformal symmetry of gravity. As a prime candidate for a quantum theory of gravity, string theory revealed many promising successes such as counting the number of microstates in supersymmetric Black Holes thermodynamics and resolution of timelike and null singularities, to name a few. Yet, the fundamental string and M-theroy formulations are not yet available. Various string theories without gravity, such as Non-Commutative Open String (NCOS) and Open Membrane (OM) theories, are very nice playground to investigate the fundamental structure of string and M-theory without the complication of gravity. In the last part of the thesis, simpler Non-Relativistic String Theories are constructed and investigated. One important motivation for those theories is related to the connection between Non-Relativistic String Theories and Non-critical String Theories through the bosonization of betagamma

  16. Open string Regge trajectory and its field theory limit

    International Nuclear Information System (INIS)

    Rojas, Francisco; Thorn, Charles B.

    2011-01-01

    We study the properties of the leading Regge trajectory in open string theory including the open string planar one-loop corrections. With SU(N) Chan-Paton factors, the sum over planar open string multiloop diagrams describes the 't Hooft limit N→∞ with Ng s 2 fixed. Our motivation is to improve the understanding of open string theory at finite α ' as a model of gauge field theories. SU(N) gauge theories in D space-time dimensions are described by requiring open strings to end on a stack of N Dp-branes of space-time dimension D=p+1. The large N leading trajectory α(t)=1+α ' t+Σ(t) can be extracted, through order g 2 , from the s→-∞ limit, at fixed t, of the four open string tree and planar loop diagrams. We analyze the t→0 behavior with the result that Σ(t)∼-Cg 2 (-α ' t) (D-4)/2 /(D-4). This result precisely tracks the 1-loop Reggeized gluon of gauge theory in D>4 space-time dimensions. In particular, for D→4 it reproduces the known infrared divergences of gauge theory in 4 dimensions with a Regge trajectory behaving as -ln(-α ' t). We also study Σ(t) in the limit t→-∞ and show that, when D ' t/(ln(-α ' t)) γ , where γ>0 depends on D and the number of massless scalars. Thus, as long as 4 ' t arbitrarily large. Finally we present the results of numerical calculations of Σ(t) for all negative t.

  17. String Theory Volume 1: An Introduction to the Bosonic String and Volume 2: Superstring Theory and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Carlip, S [Department of Physics, University of California, Davis, CA 95616 (United States)

    2006-10-21

    The early 1980s, when I first learned theory, were desperate times for graduate students. We searched frantically for coherent introductions, passing tattered copies of review articles around like samizdat, struggling over obscure references to ancient models of strong interactions, and flocking to lectures-not least those by Joe Polchinski-that promised to really explain what was going on. If only this book had been around, it would have saved much grief. Volume I, The Bosonic String, offers a clear and well organized introduction to bosonic string theory. Topics range from the 'classical' (spectra, vertex operators, consistency conditions, etc.) to the 'modern' (D-branes first appear in an exercise at the end of chapter 1, noncommutative geometry shows up in chapter 8). Polchinski does not hesitate to discuss sophisticated matters-path integral measures, BRST symmetries, etc.-but his approach is pedagogical, and his writing is lucid, if sometimes a bit terse. Chapters end with problems that are sometimes difficult but never impossible. A very useful annotated bibliography directs readers to resources for further study, and a nearly 30-page glossary provides short but clear definitions of key terms. There is much here that will appeal to relativists. Polchinski uses the covariant Polyakov path integral approach to quantization from early on; he clearly distinguishes Weyl invariance from conformal invariance; he is appropriately careful about using complex coordinates on topologically nontrivial manifolds; he keeps the string world sheet metric explicit at the start instead of immediately hiding it by a gauge choice. Volume II includes an elegant introduction to anticommuting coordinates and superconformal transformations. A few conventions may cause confusion-%, Polchinski's stress-energy tensor, for instance, differs from the standard general relativistic definition by a factor of -2{pi}, and while this is briefly mentioned in the text

  18. String-coupling constant and dilaton vacuum expectation value in string field theory

    International Nuclear Information System (INIS)

    Yoneya, Tamiaki

    1987-01-01

    In the first quantized approaches to strings, it is well known that the string-coupling constant is determined by the vacuum expectation value of the dilaton field. This property, however, has never been demonstrated within the framework of string field theory. An explicit reparametrization of the string field associated with the shifts of the dilaton vacuum expectation value and the string-coupling constant is constructed exhibiting the above property in the light-cone field theory of the closed bosonic string. (orig.)

  19. Power from Random Strings

    Czech Academy of Sciences Publication Activity Database

    Allender, E.; Buhrman, H.; Koucký, Michal; van Melkebeek, D.; Ronneburger, D.

    2006-01-01

    Roč. 35, č. 6 (2006), s. 1467-1493 ISSN 0097-5397 Institutional research plan: CEZ:AV0Z10190503 Keywords : Kolmogorov complexity * completeness * reductions Subject RIV: BA - General Mathematics Impact factor: 1.361, year: 2006

  20. Persistent homology and string vacua

    Energy Technology Data Exchange (ETDEWEB)

    Cirafici, Michele [Center for Mathematical Analysis, Geometry and Dynamical Systems,Instituto Superior Técnico, Universidade de Lisboa,Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Institut des Hautes Études Scientifiques,Le Bois-Marie, 35 route de Chartres, F-91440 Bures-sur-Yvette (France)

    2016-03-08

    We use methods from topological data analysis to study the topological features of certain distributions of string vacua. Topological data analysis is a multi-scale approach used to analyze the topological features of a dataset by identifying which homological characteristics persist over a long range of scales. We apply these techniques in several contexts. We analyze N=2 vacua by focusing on certain distributions of Calabi-Yau varieties and Landau-Ginzburg models. We then turn to flux compactifications and discuss how we can use topological data analysis to extract physical information. Finally we apply these techniques to certain phenomenologically realistic heterotic models. We discuss the possibility of characterizing string vacua using the topological properties of their distributions.