Wilson-'t Hooft operators in four-dimensional gauge theories and S-duality

We study operators in four-dimensional gauge theories which are localized on a straight line, create electric and magnetic flux, and in the UV limit break the conformal invariance in the minimal possible way. We call them Wilson-'t Hooft operators, since in the purely electric case they reduce to the well-known Wilson loops, while in general they may carry 't Hooft magnetic flux. We show that to any such operator one can associate a maximally symmetric boundary condition for gauge fields on AdS^2\times S^2. We show that Wilson-'t Hooft operators are classifed by a pair of weights (electric and magnetic) for the gauge group and its magnetic dual, modulo the action of the Weyl group. If the magnetic weight does not belong to the coroot lattice of the gauge group, the corresponding operator is topologically nontrivial (carries nonvanishing 't Hooft magnetic flux). We explain how the spectrum of Wilson-'t Hooft operators transforms under the shift of the theta-angle by 2\pi. We show that, depending on the gauge group, either SL(2,Z) or one of its congruence subgroups acts in a natural way on the set of Wilson-'t Hooft operators. This can be regarded as evidence for the S-duality of N=4 super-Yang-Mills theory. We also compute the one-point function of the stress-energy tensor in the presence of a Wilson-'t Hooft operator at weak coupling.Comment: 32 pages, latex. v2: references added. v3: numerical factors corrected, other minor change

Non-invasive imaging of hypoxia in tissue engineering

In tissue engineering, cells are grown on biomaterials in vitro and subsequently implanted. A critical parameter in effective proliferation and differentiation is the availability of nutrients. Few tools are currently available to monitor the nutritional status of cells. In this study, we have employed A4-4 cells [1], a Chinese hamster ovary cell line stably transfected with a luciferase gene driven by the hypoxia responsive element (HRE) from the promoter region of the VEGF gene [2, 3]. HRE activity, and thus luciferase activity, directly correlates with decreasing cellular O2 levels.The aim of this study is to investigate whether the HREluciferase construct can be used for non-invasive imaging of hypoxia in tissue engineering

Excess portal venous long-chain fatty acids induce syndrome X via HPA axis and sympathetic activation

We tested the hypothesis that excessive portal venous supply of long-chain fatty acids to the liver contributes to the development of insulin resistance via activation of the hypothalamus-pituitary-adrenal axis (HPA axis) and sympathetic system. Rats received an intraportal infusion of the long-chain fatty acid oleate (150 nmol/min, 24 h), the medium-chain fatty acid caprylate, or the solvent. Corticosterone (Cort) and norepinephrine (NE) were measured as indexes for HPA axis and sympathetic activity, respectively. Insulin sensitivity was assessed by means of an intravenous glucose tolerance test (IVGTT). Oleate infusion induced increases in plasma Cort (Δ = 13.5 ± 3.6 µg/dl; P < 0.05) and NE (Δ = 235 ± 76 ng/l; P < 0.05), whereas caprylate and solvent had no effect. The area under the insulin response curve to the IVGTT was larger in the oleate-treated group than in the caprylate and solvent groups (area = 220 ± 35 vs. 112 ± 13 and 106 ± 8, respectively, P < 0.05). The area under the glucose response curves was comparable [area = 121 ± 13 (oleate) vs. 135 ± 20 (caprylate) and 96 ± 11 (solvent)]. The results are consistent with the concept that increased portal free fatty acid is involved in the induction of visceral obesity-related insulin resistance via activation of the HPA axis and sympathetic system.

Towards a stringy extension of self-dual super Yang-Mills

Motivated by the search for a space-time supersymmetric extension of the N=2 string, we construct a particle model which, upon quantization, describes (abelian) self-dual super Yang-Mills in 2+2 dimensions. The local symmetries of the theory are shown to involve both world-line supersymmetry and kappa symmetry.Comment: 9 pages, version to be published in PL

Solution of N=2 Gauge Theories via Compactification to Three Dimensions

A number of N=2 gauge theories can be realized by brane configurations in Type IIA string theory. One way of solving them involves lifting the brane configuration to M-theory. In this paper we present an alternative way of analyzing a subclass of these theories (elliptic models). We observe that upon compactification on a circle one can use a version of mirror symmetry to map the original brane configuration into one containing only D-branes. Simultaneously the Coulomb branch of the four-dimensional theory is mapped to the Higgs branch of a five-dimensional theory with three-dimensional impurities. The latter does not receive quantum corrections and can be analyzed exactly. The solution is naturally formulated in terms of an integrable system, which is a version of a Hitchin system on a punctured torus.Comment: 20 pages, LaTe

Nonperturbative Tests of Three-Dimensional Dualities

We test several conjectural dualities between strongly coupled superconformal field theories in three dimensions by computing their exact partition functions on a three-sphere as a function of Fayet-Iliopoulos and mass parameters. The calculation is carried out using localization of the path integral and the matrix model previously derived for superconformal N = 2 gauge theories. We verify that the partition functions of quiver theories related by mirror symmetry agree provided the mass parameters and the Fayet-Iliopoulos parameters are exchanged, as predicted. We carry out a similar calculation for the mirror of N = 8 super-Yang-Mills theory and show that its partition function agrees with that of the ABJM theory at unit Chern-Simons level. This provides a nonperturbative test of the conjectural equivalence of the two theories in the conformal limit

The adaptation of Dutch energy policy to emerging area-based energy practices

This paper sheds a light on how local conditions affect renewable energy innovation. As empirical case, we study an energy transition policy regulation in the Netherlands: the zip code-rose regulation (PCR) intended for community energy initiatives. Firstly, we analyse the capacity of the PCR to facilitate the accommodation of renewable energy projects by community energy initiatives. Secondly, we analyse how emerging area-based energy practices are feeding back into the energy policy system. Based on empirical evidence from a desk study and interviews with community energy initiatives and key governance actors we find that the policy does provide a modest incentive for initiatives to develop renewable energy projects under local conditions. Nevertheless, the policy falls short of allowing initiatives to openly seek for locally desired solutions and hence, to increase opportunities at a local level to develop projects based on local conditions. However, current difficulties with the policy are being considered at a national level urging for adaptation of Dutch energy policies

Restoring Lorentz Invariance in Classical N=2 String

We study classical N=2 string within the framework of the N=4 topological formalism by Berkovits and Vafa. Special emphasis is put on the demonstration of a classical equivalence of the theories and the construction of an action for the N=4 topological string. The SO(2,2) Lorentz invariance missing in the conventional Brink--Schwarz action for the N=2 string is restored in the N=4 topological action.Comment: 17 pages, LaTe

Functional relationships in the nephrotic syndrome

Functional relationships in the nephrotic syndrome. An analysis of 70 observations in patients with the nephrotic syndrome (NS) on a low sodium diet is presented. The following parameters were determined: plasma volume, plasma renin activity, plasma aldosterone concentration, serum albumin, urinary sodium and protein excretion, and creatinine clearance. In 41 instances glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined on the basis of 51Cr-EDTA and 125I-hippuran clearances, and the filtration fraction (FF) was calculated. The results in patients with minimal lesions (ML) and those with histological glomerular lesions (HL) were compared to determine whether these groups can be separated on the basis of signs of hypovolemia and primary renal sodium retention. Although a higher proportion of the ML patients showed extreme sodium retention and elevated plasma renin and aldosterone levels, these values tended to overlap and no differences were found for blood volume, blood pressure, and overall renal function between the groups. FF was markedly and equally depressed in both groups: 13.5 ± 1.6% in the ML and 14.2 ± 1.1% SEM in the HL group (NS). Analysis of the within-group relationships between the parameters under study revealed relatively few correlations, which supports the hypothesis that primary impairment of renal water and salt excretion is an important if not overruling factor in patients with the NS.Relations fonctionnelles au cours du syndrome néphrotique. Une analyse de 70 observations de malades atteintes de syndrome néphrotique (NS) en régime pauvre en sodium est présentée. Les paramètres suivants ont été déterminés: volume plasmatique, activité rénine plasmatique, aldostéronémie, albuminémie, natriurèse et protéinurie, et clearance de la créatinine. Dans 41 fois, le débit de filtration glomérulaire (GFR) et le débit plasmatique rénal efficace (ERPF) ont été déterminés par des clearances au 51Cr-EDTA et au 125I-hippuran, et on a calculé la fraction de filtration (FF). Les résultats des groupes de malades atteints de lésions minimes (ML) et de ceux atteints de lésions glomérulaires histologiques (HL) ont été comparés pour savoir s'il est possible de séparer ces groupes sur la base des signes d'hypovolémie et de rétention sodée d'origine rénale. Bien qu'une plus forte proportion de malades ML ait présenté une réntention sodée et une élévation des niveaux de rénine et d'aldostérone plasmatiques extrêmes, ces valeurs tendaient à se chevaucher et il n'a pas été trouvé de différence dans le volume sanguin, la pression artérielle et la fonction rénale globale entre les groupes. FF était diminuée de façon marquée et identique dans les deux groupes: 13,5 ± 1,6% dans le groupe ML et 14,2 ± 1,1% SEM dans le groupe HL (NS). Une analyse des interrelations à l'intérieur des groupes entre les paramètres étudiés a révélé relativement peu de corrélations, ce qui est en faveur de l'hypothèse que l'altération primitive de l'excrétion rénale d'eau et de sel est un facteur important, sinon capital chez les malades atteints de NS

Towards a biomimetic gyroscope inspired by the fly's haltere using microelectromechanical systems technology

Flies use so-called halteres to sense body rotation based on Coriolis forces for supporting equilibrium reflexes. Inspired by these halteres, a biomimetic gimbal-suspended gyroscope has been developed using microelectromechanical systems (MEMS) technology. Design rules for this type of gyroscope are derived, in which the haltere-inspired MEMS gyroscope is geared towards a large measurement bandwidth and a fast response, rather than towards a high responsivity. Measurements for the biomimetic gyroscope indicate a (drive mode) resonance frequency of about 550 Hz and a damping ratio of 0.9. Further, the theoretical performance of the fly's gyroscopic system and the developed MEMS haltere-based gyroscope is assessed and the potential of this MEMS gyroscope is discussed