Resistance to intercompartmental mass transfer limits β2-microglobulin removal by post-dilution hemodiafiltration

Although clearance of β2-microglobulin is greater with hemodiafiltration than with high-flux hemodialysis, β2-microglobulin concentrations after long-term hemodiafiltration are only slightly less than those obtained with high-flux hemodialysis. Resistance to β2-microglobulin transfer between body compartments could explain this observation. β2-Microglobulin kinetics were determined in patients receiving on-line post-dilution hemodiafiltration for 4 h with 18 l of filtration. Plasma β2-microglobulin concentrations were measured during and for 2 h following hemodiafiltration and immediately before the next treatment. The filter clearance of β2-microglobulin was determined from arterial and venous concentrations. The β2-microglobulin generation rate was calculated from the change in the plasma concentration between treatments. The intercompartmental clearance was obtained by fitting the observed concentrations to a two-compartment, variable volume model. The plasma clearance of β2-microglobulin by the filter was 73±2 ml/min. Plasma β2-microglobulin concentrations decreased by 68±2% from pre- to post-treatment (27.1±2.2–8.5±0.7 mg/l), but rebounded by 32±3% over the next 90 min. The generation rate of β2-microglobulin was 0.136±0.008 mg/min. The model fit yielded an intercompartmental clearance of 82±7 ml/min and a volume of distribution of 10.2±0.6 l, corresponding to 14.3±0.7% of body weight. Hemodiafiltration provides a β2-microglobulin clearance of similar magnitude to the intercompartmental clearance within the body. As a result, intercompartmental mass transfer limits β2-microglobulin removal by hemodiafiltration. This finding suggests that alternative strategies, such as increased treatment times or frequency of treatment, are needed to further reduce plasma β2-microglobulin concentrations

New Measurements of Fine-Scale CMB Polarization Power Spectra from CAPMAP at Both 40 and 90 GHz

We present new measurements of the cosmic microwave background (CMB) polarization from the final season of the Cosmic Anisotropy Polarization MAPper (CAPMAP). The data set was obtained in winter 2004-2005 with the 7 m antenna in Crawford Hill, New Jersey, from 12 W-band (84-100 GHz) and 4 Q-band (36-45 GHz) correlation polarimeters with 3.3' and 6.5' beamsizes, respectively. After selection criteria were applied, 956 (939) hours of data survived for analysis of W-band (Q-band) data. Two independent and complementary pipelines produced results in excellent agreement with each other. A broad suite of null tests as well as extensive simulations showed that systematic errors were minimal, and a comparison of the W-band and Q-band sky maps revealed no contamination from galactic foregrounds. We report the E-mode and B-mode power spectra in 7 bands in the range 200 < l < 3000, extending the range of previous measurements to higher l. The E-mode spectrum, which is detected at 11 sigma significance, is in agreement with cosmological predictions and with previous work at other frequencies and angular resolutions. The BB power spectrum provides one of the best limits to date on B-mode power at 4.8 uK^2 (95% confidence).Comment: 19 pages, 17 figures, 2 tables, submitted to Ap

Double Field Theory Formulation of Heterotic Strings

We extend the recently constructed double field theory formulation of the low-energy theory of the closed bosonic string to the heterotic string. The action can be written in terms of a generalized metric that is a covariant tensor under O(D,D+n), where n denotes the number of gauge vectors, and n additional coordinates are introduced together with a covariant constraint that locally removes these new coordinates. For the abelian subsector, the action takes the same structural form as for the bosonic string, but based on the enlarged generalized metric, thereby featuring a global O(D,D+n) symmetry. After turning on non-abelian gauge couplings, this global symmetry is broken, but the action can still be written in a fully O(D,D+n) covariant fashion, in analogy to similar constructions in gauged supergravities.Comment: 28 pages, v2: minor changes, version published in JHE

Action for the eleven dimensional multiple M-wave system

We present the covariant supersymmetric and kappa-symmetric action for a system of N nearly coincident M-waves (multiple M0-brane system) in flat eleven dimensional superspace.Comment: 4+ pages, RevTeX4, no figures. V2: misprints corrected, discussion extended, references added, LaTeX, 10 pages. V3: misprints corrected. V4, extended version, 1+13 pages, to appear in JHE

Six-dimensional Supergravity and Projective Superfields

We propose a superspace formulation of N=(1,0) conformal supergravity in six dimensions. The corresponding superspace constraints are invariant under super-Weyl transformations generated by a real scalar parameter. The known variant Weyl super-multiplet is recovered by coupling the geometry to a super-3-form tensor multiplet. Isotwistor variables are introduced and used to define projective superfields. We formulate a locally supersymmetric and super-Weyl invariant action principle in projective superspace. Some families of dynamical supergravity-matter systems are presented.Comment: 39 pages; v3: some modifications in section 2; equations (2.3), (2.14b), (2.16) and (2.17) correcte

N=8 Superspace Constraints for Three-dimensional Gauge Theories

We present a systematic analysis of the N=8 superspace constraints in three space-time dimensions. The general coupling between vector and scalar supermultiplets is encoded in an SO(8) tensor W_{AB} which is a function of the matter fields and subject to a set of algebraic and super-differential relations. We show how the conformal BLG model as well as three-dimensional super Yang-Mills theory provide solutions to these constraints and can both be formulated in this universal framework.Comment: 34 + 10 pages; added references, minor correction

Six-dimensional (1,0) effective action of F-theory via M-theory on Calabi-Yau threefolds

The six-dimensional effective action of F-theory compactified on a singular elliptically fibred Calabi-Yau threefold is determined by using an M-theory lift. The low-energy data are derived by comparing a circle reduction of a general six-dimensional (1,0) gauged supergravity theory with the effective action of M-theory on the resolved Calabi-Yau threefold. The derivation includes six-dimensional tensor multiplets for which the (anti-) self-duality constraints are imposed on the level of the five-dimensional action. The vector sector of the reduced theory is encoded by a non-standard potential due to the Green-Schwarz term in six dimensions. This Green-Schwarz term also contains higher curvature couplings which are considered to establish the full map between anomaly coefficients and geometry. F-/M-theory duality is exploited by moving to the five-dimensional Coulomb branch after circle reduction and integrating out massive vector multiplets and matter hypermultiplets. The associated fermions then generate additional Chern-Simons couplings at one-loop. Further couplings involving the graviphoton are induced by quantum corrections due to excited Kaluza-Klein modes. On the M-theory side integrating out massive fields corresponds to resolving the singularities of the Calabi-Yau threefold, and yields intriguing relations between six-dimensional anomalies and classical topology.Comment: 55 pages, v2: typos corrected, discussion of loop corrections improve

CMB Polarimetry using Correlation Receivers with the PIQUE and CAPMAP Experiments

The Princeton IQU Experiment (PIQUE) and the Cosmic Anisotropy Polarization MAPper (CAPMAP) are experiments designed to measure the polarization of the Cosmic Microwave Background (CMB) on sub-degree scales in an area within 1 degree of the North Celestial Pole using heterodyne correlation polarimeters and off-axis telescopes located in central New Jersey. PIQUE produced the tightest limit on the CMB polarization prior to its detection by DASI, while CAPMAP has recently detected polarization at l~1000. The experimental methods and instrumentation for these two projects are described in detail with emphasis on the particular challenges involved in measuring the tiny polarized component of the CMB.Comment: 70 pages, 13 tables, 18 figures. Accepted by ApJS; tentative publication ApJS July 2005, v159

Superconformal M2-branes and generalized Jordan triple systems

Three-dimensional conformal theories with six supersymmetries and SU(4) R-symmetry describing stacks of M2-branes are here proposed to be related to generalized Jordan triple systems. Writing the four-index structure constants in an appropriate form, the Chern-Simons part of the action immediately suggests a connection to such triple systems. In contrast to the previously considered three-algebras, the additional structure of a generalized Jordan triple system is associated to a graded Lie algebra, which corresponds to an extension of the gauge group. In this note we show that the whole theory with six manifest supersymmetries can be naturally expressed in terms of such a graded Lie algebra. Also the BLG theory with eight supersymmetries is included as a special case.Comment: 15 pages, v2 and v3: minor corrections and clarifications, references added, v2: section 4 extended, v3: published versio