U-duality (sub-)groups and their topology

We discuss some consequences of the fact that symmetry groups appearing in compactified (super-)gravity may be non-simply connected. The possibility to add fermions to a theory results in a simple criterion to decide whether a 3-dimensional coset sigma model can be interpreted as a dimensional reduction of a higher dimensional theory. Similar criteria exist for higher dimensional sigma models, though less decisive. Careful examination of the topology of symmetry groups rules out certain proposals for M-theory symmetries, which are not ruled out at the level of the algebra's. We conclude with an observation on the relation between the ``generalized holonomy'' proposal, and the actual symmetry groups resulting from E_10 and E_11 conjectures.Comment: LaTeX, 8 pages, 2 tables, 1 figure, uses IOP-style files. Contributed to the proceedings of the RTN-workshop ``The quantum structure of space-time and the geometrical nature of the fundamental interactions,'', Copenhagen, Denmark, september 200

Low-energy spectrum of N = 4 super-Yang-Mills on T^3: flat connections, bound states at threshold, and S-duality

We study (3+1)-dimensional N=4 supersymmetric Yang-Mills theory on a spatial three-torus. The low energy spectrum consists of a number of continua of states of arbitrarily low energies. Although the theory has no mass-gap, it appears that the dimensions and discrete abelian magnetic and electric 't Hooft fluxes of the continua are computable in a semi-classical approximation. The wave-functions of the low-energy states are supported on submanifolds of the moduli space of flat connections, at which various subgroups of the gauge group are left unbroken. The field theory degrees of freedom transverse to such a submanifold are approximated by supersymmetric matrix quantum mechanics with 16 supercharges, based on the semi-simple part of this unbroken group. Conjectures about the number of normalizable bound states at threshold in the latter theory play a crucial role in our analysis. In this way, we compute the low-energy spectra in the cases where the simply connected cover of the gauge group is given by SU(n), Spin(2n+1) or Sp(2n). We then show that the constraints of S-duality are obeyed for unique values of the number of bound states in the matrix quantum mechanics. In the cases based on Spin(2n+1) and Sp(2n), the proof involves surprisingly subtle combinatorial identities, which hint at a rich underlying structure.Comment: 28 pages. v2:reference adde

The topology of U-duality (sub-)groups

We discuss the topology of the symmetry groups appearing in compactified (super-)gravity, and discuss two applications. First, we demonstrate that for 3 dimensional sigma models on a symmetric space G/H with G non-compact and H the maximal compact subgroup of G, the possibility of oxidation to a higher dimensional theory can immediately be deduced from the topology of H. Second, by comparing the actual symmetry groups appearing in maximal supergravities with the subgroups of SL(32,R) and Spin(32), we argue that these groups cannot serve as a local symmetry group for M-theory in a formulation of de Wit-Nicolai type.Comment: 18 pages, LaTeX, 1 figure, 2 table

Directions for national mastitis control programs: experiences from The Netherlands

The general aim of mastitis control programs is to improve udder health on dairy farms. Over the last five years an intensive national mastitis program was executed in the Netherlands with the goal to improve udder health at a national level. Different groups of farmers have different motivations and should be approached differently, and their behaviour is influenced by different advisors. Therefore, as many different groups of advisors as possible should be involved in the program. Most of the veterinary practices in the Netherlands participated as did, in later years, other farm advisors. We experienced that for a successful program it is crucial to have knowledge on motivating factors of dairy farmers. Many advisors are convinced that the only way to change farmers’ behavior is through economics. We found that economics are important, but that other factors are as important in influencing farmers’ behaviour. To have a successful national mastitis program it is advisable to involve professionals on communication in designing the program. Although the technical knowledge on which the program is built should be optimal, that generally is not the bottle-neck in being successful. There often is more to gain in presenting knowledge in such a way that it is actually used, than in increasing the amount of existing knowledge

BPS partition functions in N = 4 Yang-Mills theory on T^4

We consider N = 4 Yang-Mills theory on a flat four-torus with the R-symmetry current coupled to a flat background connection. The partition function depends on the coupling constant of the theory, but when it is expanded in a power series in the R-symmetry connection around the loci at which one of the supersymmetries is unbroken, the constant and linear terms are in fact independent of the coupling constant and can be computed at weak coupling for all non-trivial 't Hooft fluxes. The case of a trivial 't Hooft flux is difficult because of infrared problems, but the corresponding terms in the partition function are uniquely determined by S-duality.Comment: 23 pages, v2 Minor correction

Physical chemistry and engineering of membranes for fat - fatty acid separations

Fatty acids have to be removed from non-mineral oil for several purposes. In the refining of edible oils and fats they have to be removed as a contaminant. In the enzymatic hydrolysis of oils, a high content in fatty acids results in a reduced conversion rate. In order to maintain a sufficiently high reaction rate they will have to be removed, preferably in-line. The conventional separation method is the caustic refining process, in which alkali is added to the fatty acid containing oil, resulting in the formation of the sodium salts of the fatty acids (soapstock). Then the soapsock is separated from the oil by centrifugation. However, this soapstock contains considerable amounts of triglycerides (about 50%), which have to be considered as a loss. For this reason, caustic refining of oils containing high concentrations of fatty acids is not an economical process.In this thesis two alternative processes for the separation of fatty acids from oil are presented, with the common feature that membranes are used in a two-phase environment. It is the aim of this thesis to study the engineering and physico-chemical phenomena that are relevant for the operation of these processes.In the first process, alkali is added to the oil in order to form the sodium salts of the fatty acids. Additionally, 2-propanol is added to solubilize the soapstock thus formed, resulting in a twophase system. The water phase contains the fatty acid salts dissolved in a water/2-propanol mixture and the oil phase merely contains triglycerides and a trace amount of 2-propanol. This two-phase system can be separated into its two phases by a hydrophilic and a hydrophobic membrane in series.In chapter 2 the nature of the two-phase system and the permeation behaviour of the water phase through the hydrophilic membrane have been investigated. It appears, that both the oil and the water phase are present as a continuous phase between 20 and 65% water phase in the dispersion. Above 20% water phase, the flux through the membrane is merely determined by the hydrodynamic membrane resistance, provided that the membrane is entirely wetted by the water phase. Below 20% water phase, the water phase is present as dispersed droplets in oil. At the transition from a continuous into a discrete water phase the permeation flux drops almost stepwise to a value close to zero.When in the system described in chapter 2, a concentrated NaCl solution is circulated at the permeate side of the cellulose membrane, initially a flux reversed to the normal permeation flux is observed. After some time the flux changes direction and becomes 2 to 10 times larger than it would be based on the pressure difference over the membrane. These effects cannot be accounted for using the classical Fickian diffusion theory. In chapter 3 it is shown that the flux changes can be explained qualitatively using the Maxwell-Stefan diffusion theory.It appeared, that commercially available hydrophobic membranes were incapable of separating the oil phase from this dispersion. As the preliminary requirement to solve this problem, chapter 4 describes a method that has been developed to measure hydrophobicities of membranes. When a piece of membrane is submerged in a liquid, air bubbles will adhere to the membrane when the surface tension of the liquid is high. Decreasing the surface tension of the liquid yields a transition from adhesion to non-adhesion. The surface tension of the liquid at which this transition occurs can be compared to the critical surface tension as is commonly used to characterize polymeric surfaces.In chapter 5 the adsorption is measured of a surfactant in water/2-propanol mixtures onto surfaces that vary in hydrophobicity. Adsorption appears to occur in three regions: "tail down" adsorption on hydrophobic surfaces, "head down" adsorption on hydrophilic surfaces, and a very small region in between, where adsorption is absent. A membrane that possesses a hydrophobicity belonging to this region appears to be capable of separating the oil phase from the dispersion selectively.The second system for the removal of fatty acids from oil consists of a membrane extraction step, using 1,2-butanediol as a selective extractant. When water is added to the fatty acid containing 1,2-butanediol, the system demixes in a fatty acid phase dispersed in a 1,2-butanediol/water mixture. After phase separation, water has to be removed from the 1,2-butanediol, which can be reused as extractant. In chapter 6 extraction of fatty acids from oil has been investigated. In order to obtain a stable system, it is necessary to use rather dense membranes. This results in relatively high mass transfer resistances and hence in large surface areas for extraction. Due to the fact that the mass transfer coefficients vary significantly with fatty acid chain length, it appears to be possible to fractionate a fatty acid mixture.In chapter 7 membrane cascades for the separation of binary mixtures have been investigated. Calculations based on a McCabe-Thiele diagram show that, for permeabilities and selectivities commonly found for reverse osmosis membranes, permeability is the parameter on which improvements have to be made when a minimum total membrane surface area is required.Finally, in chapter 8 some implications of the work described in this thesis have been discussed. The two systems descibed for the separation of fatty acids from oil are capable to perform this separation selectively and at mild conditions. Two future implications that require further investigations are discussed. The first one is the separation of emulsions using membranes. Secondly, tailoring membranes for special applications and in order to reduce fouling are possible applications that require further investigations

Willingness to undergo surgery again validated clinically important differences in health-related quality of life after total hip replacement or total knee replacement surgery

AbstractObjectivesTo determine clinically important differences (CIDs) in health-related quality of life (HRQoL) after total hip replacement (THR) or total knee replacement (TKR) surgery, using the Short Form 36 (SF-36).Study Design and SettingSF-36 scores were collected 2 weeks before and at 1.5–6 years after joint replacement in 586 THR and 400 TKR patients in a multicenter cohort study. We calculated distribution-based CIDs (0.8 standard deviations of the preoperative score) for each SF-36 subscale. Responders (patients with an improvement in HRQoL ≥ CID of a particular subscale) were compared with nonresponders using an external validation question: willingness to undergo surgery again.ResultsCIDs for THR/TKR were physical functioning (PF), 17.9/16.7; role-physical (RP), 31.1/33.4; bodily pain (BP), 16.8/16.2; general health, 15.5/15.7; vitality, 17.3/16.7; social functioning (SF), 22.0/19.9; role-emotional, 33.7/33.6; and mental health, 14.8/14.1. CIDs of PF, RP, BP, and SF were validated by the validation question.ConclusionValid and precise CIDs are estimated of PF, RP, BP, and SF, which are relevant in HRQoL subscales for THR and TKR patients. CIDs of all other subscales should be used cautiously

Time-like T-duality algebra

When compactifying M- or type II string-theories on tori of indefinite space-time signature, their low energy theories involve sigma models on E_{n(n)}/H_n, where H_n is a not necessarily compact subgroup of E_{n(n)} whose complexification is identical to the complexification of the maximal compact subgroup of E_{n(n)}. We discuss how to compute the group H_n. For finite dimensional E_{n(n)}, a formula derived from the theory of real forms of E_n algebra's gives the possible groups immediately. A few groups that have not appeared in the literature are found. For n=9,10,11 we compute and describe the relevant real forms of E_n and H_n. A given H_n can correspond to multiple signatures for the compact torus. We compute the groups H_n for all compactifications of M-, M*-, and M'-theories, and type II-, II*- and II'-theories on tori of arbitrary signature, and collect them in tables that outline the dualities between them. In an appendix we list cosets G/H, with G split and H a subgroup of G, that are relevant to timelike toroidal compactifications and oxidation of theories with enhanced symmetries.Comment: LaTeX, 37 pages, 1 eps-figure, uses JHEP.cls; v2. corrected typo's in tables 16 and 17, minor changes to tex

The Moduli Space and M(atrix) Theory of 9d N=1 Backgrounds of M/String Theory

We discuss the moduli space of nine dimensional N=1 supersymmetric compactifications of M theory / string theory with reduced rank (rank 10 or rank 2), exhibiting how all the different theories (including M theory compactified on a Klein bottle and on a Mobius strip, the Dabholkar-Park background, CHL strings and asymmetric orbifolds of type II strings on a circle) fit together, and what are the weakly coupled descriptions in different regions of the moduli space. We argue that there are two disconnected components in the moduli space of theories with rank 2. We analyze in detail the limits of the M theory compactifications on a Klein bottle and on a Mobius strip which naively give type IIA string theory with an uncharged orientifold 8-plane carrying discrete RR flux. In order to consistently describe these limits we conjecture that this orientifold non-perturbatively splits into a D8-brane and an orientifold plane of charge (-1) which sits at infinite coupling. We construct the M(atrix) theory for M theory on a Klein bottle (and the theories related to it), which is given by a 2+1 dimensional gauge theory with a varying gauge coupling compactified on a cylinder with specific boundary conditions. We also clarify the construction of the M(atrix) theory for backgrounds of rank 18, including the heterotic string on a circle.Comment: 43 pages, 7 figures, JHEP format. v3: typos correcte

Modeling of a fixed bed adsorptive drying of chlorine

Abstract only