Macdonald Polynomials and level two Demazure modules for affine sln+1\mathfrak{sl}_{n+1}

We define a family of symmetric polynomials $G_{\nu,\lambda}(z_1,\cdots, z_{n+1},q)$ indexed by a pair of dominant integral weights. The polynomial $G_{\nu,0}(z,q)$ is the specialized Macdonald polynomial and we prove that $G_{0,\lambda}(z,q)$ is the graded character of a level two Demazure module associated to the affine Lie algebra $\widehat{\mathfrak{sl}}_{n+1}$. Under suitable conditions on $(\nu,\lambda)$ (which includes the case when $\nu=0$ or $\lambda=0$) we prove that $G_{\nu,\lambda}(z,q)$ is Schur positive and give explicit formulae for them in terms of Macdonald polynomials

Multiplex giant magnetoresistive biosensor microarrays identify interferon-associated autoantibodies in systemic lupus erythematosus.

High titer, class-switched autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Dysregulation of the interferon (IFN) pathway is observed in individuals with active SLE, although the association of specific autoantibodies with chemokine score, a combined measurement of three IFN-regulated chemokines, is not known. To identify autoantibodies associated with chemokine score, we developed giant magnetoresistive (GMR) biosensor microarrays, which allow the parallel measurement of multiple serum antibodies to autoantigens and peptides. We used the microarrays to analyze serum samples from SLE patients and found individuals with high chemokine scores had significantly greater reactivity to 13 autoantigens than individuals with low chemokine scores. Our findings demonstrate that multiple autoantibodies, including antibodies to U1-70K and modified histone H2B tails, are associated with IFN dysregulation in SLE. Further, they show the microarrays are capable of identifying autoantibodies associated with relevant clinical manifestations of SLE, with potential for use as biomarkers in clinical practice

Subtraction of test mass angular noise in the LISA Technology Package interferometer

We present recent sensitivity measurements of the LISA Technology Package interferometer with articulated mirrors as test masses, actuated by piezo-electric transducers. The required longitudinal displacement resolution of 9 pm/sqrt[Hz] above 3 mHz has been demonstrated with an angular noise that corresponds to the expected in on-orbit operation. The excess noise contribution of this test mass jitter onto the sensitive displacement readout was completely subtracted by fitting the angular interferometric data streams to the longitudinal displacement measurement. Thus, this cross-coupling constitutes no limitation to the required performance of the LISA Technology Package interferometry.Comment: Applied Physics B - Lasers and Optics (2008

Investigation of noise sources in the LTP interferometer S2-AEI-TN-3028

All breadboards for the LTP interferometer showed an extra noise term that was, until recently, not fully understood. In this report that noise term is investigated in detail. It turns out that it is caused by sidebands on the light. In our lab, these sidebands were caused by nonlinear mixing processes in the power amplifiers that drive the AOM, if electromagnetic interference at a frequency near the operating frequency (ca. 80 MHz) is picked up by the power amplifier. The disturbing nearby frequency is the frequency of the other AOM, with a difference of exactly f_het, causing multiple sidebands at integer multiples of f_het from the carrier. They appear as pairs with a phase relationship that corresponds to phase-modulation (PM). Experiments with a very different electrical setup (in Glasgow) also showed sidebands which demonstrates that they are not caused by peculiarities of the Hannover setup. While the effect of a pair of first-order PM sidebands cancels and causes no harm, only one of the second-order sidebands produces noise which cannot be cancelled by its second-order mirror image. Hence the second-order sidebands are the dominant noise source. Various strategies of mitigation are also investigated. The two most important ones, both of which are already implemented as baseline for the LTP interferometer, are (1) to reduce the sidebands by careful EMC design and dedicated testing, and (2) to stabilize the optical pathlength difference (OPD) between the two fibers with a Piezo device. The combination of these two measures will reduce this error term to insignificance. We have also investigated other noise sources such as laser amplitude noise and beam jitter noise. Laser amplitude noise does have an influence on the total performance of the interferometer. Using a laser amplitude stabilization (part of the baseline), its influence can also be sufficiently reduced. Contrary to earlier worries, we did not find a significant noise contribution from beam jitter noise in conjunction with quadrant photodiodes. As part of this investigation we have also developed a mathematical model for the sideband coupling that fully describes their effect and has been experimentally verified. Furthermore we have developed various numerical procedures to find correlations between auxiliary data streams (such as alignment signals) and the main interferometer output. They are useful for diagnostic purposes, but in general too complex to implement on LTP. Using only those procedures that are the baseline for the FM, the noise performance of the LTP EM interferometer in the lab is now well below its specifications at all frequencies, with remaining noise sources mainly driven by ground-based disturbances, such that we are confident that the LTP interferometer will perform well on orbit and will enable the detailed study of the behaviour and noise performance of the inertial sensor and DFACS systems, which indeed is the primary job of the interferometer. Comment of the Author: Version 1.2 2008/07/0

Protein conformational entropy is not slaved to water

Conformational entropy can be an important element of the thermodynamics of protein functions such as the binding of ligands. The observed role for conformational entropy in modulating molecular recognition by proteins is in opposition to an often-invoked theory for the interaction of protein molecules with solvent water. The solvent slaving model predicts that protein motion is strongly coupled to various aspects of water such as bulk solvent viscosity and local hydration shell dynamics. Changes in conformational entropy are manifested in alterations of fast internal side chain motion that is detectable by NMR relaxation. We show here that the fast-internal side chain dynamics of several proteins are unaffected by changes to the hydration layer and bulk water. These observations indicate that the participation of conformational entropy in protein function is not dictated by the interaction of protein molecules and solvent water under the range of conditions normally encountered

LTP interferometer - noise sources and performance

The LISA Technology Package (LTP) uses laser interferometry to measure the changes in relative displacement between two inertial test masses. The goals of the mission require a displacement measuring precision of 10 pm Hz-1/2 at frequencies in the 3–30 mHz band. We report on progress with a prototype LTP interferometer optical bench in which fused silica mirrors and beamsplitters are fixed to a ZERODUR® substrate using hydroxide catalysis bonding to form a rigid interferometer. The couplings to displacement noise of this interferometer of two expected noise sources—laser frequency noise and ambient temperature fluctuations—have been investigated, and an additional, unexpected, noise source has been identified. The additional noise is due to small amounts of signal at the heterodyne frequency arriving at the photodiode preamplifiers with a phase that quasistatically changes with respect to the optical signal. The phase shift is caused by differential changes in the external optical paths the beams travel before they reach the rigid interferometer. Two different external path length stabilization systems have been demonstrated and these allowed the performance of the overall system to meet the LTP displacement noise requirement

The feed-in tariff in the UK : a case study focus on domestic photovoltaic systems

This paper explores the photovoltaic (PV) industry in the United Kingdom (UK) as experienced by those who are working with it directly and with consideration of current standards, module efficiencies and future environmental trends. The government's consultation on the comprehensive review for solar PV tariffs, proposes a reduction of the generation tariff for PV installations in the UK of more than 50%. The introduction of the Feed-In Tariffs scheme (FITs) has rapidly increased deployment of PV technologies at small scale since its introduction in April 2010. The central principle of FIT policies is to offer guaranteed prices for fixed periods to enable greater number of investors. A financial analysis was performed on two real-life installations in Cornwall, UK to determine the impact of proposed cuts to the FIT will make to a typical domestic PV system under 4 kW. The results show that a healthy Return on Investment (ROI) can still be made but that future installations should focus on off-setting electricity required from the national grid as a long term push for true sustainability rather than subsidised schemes. The profitability of future installations will have to be featured within in-service and end-of-service considerations such as the feed-in tariff, module efficiencies and the implications of costs associated with end-of-life disposal

Conformal mechanics inspired by extremal black holes in d=4

A canonical transformation which relates the model of a massive relativistic particle moving near the horizon of an extremal black hole in four dimensions and the conventional conformal mechanics is constructed in two different ways. The first approach makes use of the action-angle variables in the angular sector. The second scheme relies upon integrability of the system in the sense of Liouville.Comment: V2: presentation improved, new material and references added; the version to appear in JHE