RF applications in digital signal processing

Ever higher demands for stability, accuracy, reproducibility, and monitoring capability are being placed on Low-Level Radio Frequency (LLRF) systems of particle accelerators. Meanwhile, continuing rapid advances in digital signal processing technology are being exploited to meet these demands, thus leading to development of digital LLRF systems. The rst part of this course will begin by focusing on some of the important building-blocks of RF signal processing including mixer theory and down-conversion, I/Q (amplitude and phase) detection, digital down-conversion (DDC) and decimation, concluding with a survey of I/Q modulators. The second part of the course will introduce basic concepts of feedback systems, including examples of digital cavity eld and phase control, followed by radial loop architectures. Adaptive feed-forward systems used for the suppression of repetitive beam disturbances will be examined. Finally, applications and principles of system identi cation approaches will be summarized

Bispecific Tau Antibodies with Additional Binding to C1q or Alpha-Synuclein

BACKGROUND: Alzheimer’s disease (AD) and other tauopathies are neurodegenerative disorders characterized by cellular accumulation of aggregated tau protein. Tau pathology within these disorders is accompanied by chronic neuroinflammation, such as activation of the classical complement pathway by complement initiation factor C1q. Additionally, about half of the AD cases present with inclusions composed of aggregated alpha-synuclein called Lewy bodies. Lewy bodies in disorders such as Parkinson’s disease and Lewy body dementia also frequently occur together with tau pathology. OBJECTIVE: Immunotherapy is currently the most promising treatment strategy for tauopathies. However, the presence of multiple pathological processes within tauopathies makes it desirable to simultaneously target more than one disease pathway. METHODS: Herein, we have developed three bispecific antibodies based on published antibody binding region sequences. One bispecific antibody binds to tau plus alpha-synuclein and two bispecific antibodies bind to tau plus C1q. RESULTS: Affinity of the bispecific antibodies to their targets compared to their monospecific counterparts ranged from nearly identical to one order of magnitude lower. All bispecific antibodies retained binding to aggregated protein in patient-derived brain sections. The bispecific antibodies also retained their ability to inhibit aggregation of recombinant tau, regardless of whether the tau binding sites were in IgG or scFv format. Mono- and bispecific antibodies inhibited cellular seeding induced by AD-derived pathological tau with similar efficacy. Finally, both Tau-C1q bispecific antibodies completely inhibited the classical complement pathway. CONCLUSIONS: Bispecific antibodies that bind to multiple pathological targets may therefore present a promising approach to treat tauopathies and other neurodegenerative disorders

K0 form factor at order p^6 of chiral perturbation theory

This paper describes the calculation of the electromagnetic form factor of the K0 meson at order p^6 of chiral perturbation theory which is the next-to-leading order correction to the well-known p^4 result achieved by Gasser and Leutwyler. On the one hand, at order p^6 the chiral expansion contains 1- and 2-loop diagrams which are discussed in detail. Especially, a numerical procedure for calculating the irreducible 2-loop graphs of the sunset topology is presented. On the other hand, the chiral Lagrangian L^6 produces a direct coupling of the K0 current with the electromagnetic field tensor. Due to this coupling one of the unknown parameters of L^6 occurs in the contribution to the K0 charge radius.Comment: 22 pages Latex with 8 figures, Typos corrected, one reference adde

On the asymptotic O(ααS){\cal O}(\alpha \alpha_S) behavior of the electroweak gauge bosons vacuum polarization functions for arbitrary quark masses

We derive the QCD corrections to the electroweak gauge bosons vacuum polarization functions at high and zero--momentum transfer in the case of arbitrary internal quark masses. We then discuss in this general case (i) the connection between the $O(\alpha \alpha_S)$ calculations of the vector bosons self--energies using dimensional regularization and the one performed via a dispersive approach and (ii) the QCD corrections to the $\rho$ parameter for a heavy quark isodoublet.Comment: 14 pages + 2 figures (not included: available by mail from A. Djouadi), Preprint UdeM-LPN-TH-93-156 and NYU-TH-93/05/0

Up and down quark masses from Finite Energy QCD sum rules to five loops

The up and down quark masses are determined from an optimized QCD Finite Energy Sum Rule (FESR) involving the correlator of axial-vector divergences, to five loop order in Perturbative QCD (PQCD), and including leading non-perturbative QCD and higher order quark mass corrections. This FESR is designed to reduce considerably the systematic uncertainties arising from the (unmeasured) hadronic resonance sector, which in this framework contributes less than 3-4% to the quark mass. This is achieved by introducing an integration kernel in the form of a second degree polynomial, restricted to vanish at the peak of the two lowest lying resonances. The driving hadronic contribution is then the pion pole, with parameters well known from experiment. The determination is done in the framework of Contour Improved Perturbation Theory (CIPT), which exhibits a very good convergence, leading to a remarkably stable result in the unusually wide window $s_0 = 1.0 - 4.0 {GeV}^2$, where $s_0$ is the radius of the integration contour in the complex energy (squared) plane. The results are: $m_u(Q= 2 {GeV}) = 2.9 \pm 0.2$ MeV, $m_d(Q= 2 {GeV}) = 5.3 \pm 0.4$ MeV, and $(m_u + m_d)/2 = 4.1 \pm 0.2$ Mev (at a scale Q=2 GeV).Comment: Additional references to lattice QCD results have been adde

Leptonic μ \mu - and τ \tau -decays: mass effects, polarization effects and O(α) O(\alpha) radiative corrections

We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarized $\mu$ into a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analytical results are given for the energy spectrum and the polar angle distribution of the final state electron whose longitudinal and transverse polarization is calculated. We also provide analytical results on the integrated spectrum functions. We analyze the $m_e \to 0$ limit of our general results and investigate the quality of the $m_e \to 0$ approximation. In the $m_e \to 0$ case we discuss in some detail the role of the $O(\alpha)$ anomalous helicity flip contribution of the final electron which survives the $m_e \to 0$ limit. The results presented in this 0203048 also apply to the leptonic decays of polarized $\tau$-leptons for which we provide numerical results.Comment: 39 pages, 11 postscript figures added. Updated version. Four references added. A few text improvements. Final version to appear in Phys.Rev.

Inclusive Semileptonic Decays in QCD Including Lepton Mass Effects

Starting from an Operator Product Expansion in the Heavy Quark Effective Theory up to order 1/m_b^2 we calculate the inclusive semileptonic decays of unpolarized bottom hadrons including lepton mass effects. We calculate the differential decay spectra d\Gamma/(dE_\tau ), and the total decay rate for B meson decays to final states containing a \tau lepton.Comment: 16 pages + 4 figs. appended in uuencoded form, LaTeX, MZ-TH/93-3

Is there evidence for dimension-two corrections in QCD two-point functions?

The ALEPH data on the (non-strange) vector and axial-vector spectral functions, extracted from tau-lepton decays, is used in order to search for evidence for a dimension-two contribution, $C_{2 V,A}$, to the Operator Product Expansion (other than $d=2$ quark mass terms). This is done by means of a dimension-two Finite Energy Sum Rule, which relates QCD to the experimental hadronic information. The average $C_{2} \equiv (C_{2V} + C_{2A})/2$ is remarkably stable against variations in the continuum threshold, but depends rather strongly on $\Lambda_{QCD}$. Given the current wide spread in the values of $\Lambda_{QCD}$, as extracted from different experiments, we would conservatively conclude from our analysis that $C_{2}$ is consistent with zero.Comment: A misprint in Eq. (14) has been corrected. No other changes. Paper to appear in Phys. Rev.