Quantum Symmetries and Marginal Deformations

We study the symmetries of the N=1 exactly marginal deformations of N=4 Super Yang-Mills theory. For generic values of the parameters, these deformations are known to break the SU(3) part of the R-symmetry group down to a discrete subgroup. However, a closer look from the perspective of quantum groups reveals that the Lagrangian is in fact invariant under a certain Hopf algebra which is a non-standard quantum deformation of the algebra of functions on SU(3). Our discussion is motivated by the desire to better understand why these theories have significant differences from N=4 SYM regarding the planar integrability (or rather lack thereof) of the spin chains encoding their spectrum. However, our construction works at the level of the classical Lagrangian, without relying on the language of spin chains. Our approach might eventually provide a better understanding of the finiteness properties of these theories as well as help in the construction of their AdS/CFT duals.Comment: 1+40 pages. v2: minor clarifications and references added. v3: Added an appendix, fixed minor typo

Comb-Based Radio-Frequency Photonic Filters with Rapid Tunability and High Selectivity

Photonic technologies have received considerable attention for enhancement of radio-frequency (RF) electrical systems, including high-frequency analog signal transmission, control of phased arrays, analog-to-digital conversion, and signal processing. Although the potential of radio-frequency photonics for implementation of tunable electrical filters over broad RF bandwidths has been much discussed, realization of programmable filters with highly selective filter lineshapes and rapid reconfigurability has faced significant challenges. A new approach for RF photonic filters based on frequency combs offers a potential route to simultaneous high stopband attenuation, fast tunability, and bandwidth reconfiguration. In one configuration tuning of the RF passband frequency is demonstrated with unprecedented (~40 ns) speed by controlling the optical delay between combs. In a second, fixed filter configuration, cascaded four-wave mixing simultaneously broadens and smoothes comb spectra, resulting in Gaussian RF filter lineshapes exhibiting extremely high (>60 dB) main lobe to sidelobe suppression ratio and (>70 dB) stopband attenuation.Comment: Updated the submission with the most recent version of the pape

A ten-dimensional action for non-geometric fluxes

The NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change of field variables inspired by Generalized Complex Geometry. We obtain a new metric and dilaton, together with an antisymmetric bivector field which leads to a ten-dimensional version of the non-geometric Q-flux. Given the involved global aspects of non-geometric situations, we prescribe to use this new Lagrangian, whose associated action is well-defined in some examples investigated here. This allows us to perform a standard dimensional reduction and to recover the usual contribution of the Q-flux to the four-dimensional scalar potential. An extension of this work to include the R-flux is discussed. The paper also contains a brief review on non-geometry.Comment: 47 pages; v2: minor modifications, references added, version to be published in JHE

Capillary Regeneration in Scleroderma: Stem Cell Therapy Reverses Phenotype?

BACKGROUND. Scleroderma is an autoimmune disease with a characteristic vascular pathology. The vasculopathy associated with scleroderma is one of the major contributors to the clinical manifestations of the disease. METHODOLOGY/PRINCIPAL FINDINGS. We used immunohistochemical and mRNA in situ hybridization techniques to characterize this vasculopathy and showed with morphometry that scleroderma has true capillary rarefaction. We compared skin biopsies from 23 scleroderma patients and 24 normal controls and 7 scleroderma patients who had undergone high dose immunosuppressive therapy followed by autologous hematopoietic cell transplant. Along with the loss of capillaries there was a dramatic change in endothelial phenotype in the residual vessels. The molecules defining this phenotype are: vascular endothelial cadherin, a supposedly universal endothelial marker required for tube formation (lost in the scleroderma tissue), antiangiogenic interferon α (overexpressed in the scleroderma dermis) and RGS5, a signaling molecule whose expression coincides with the end of branching morphogenesis during development and tumor angiogenesis (also overexpressed in scleroderma skin. Following high dose immunosuppressive therapy, patients experienced clinical improvement and 5 of the 7 patients with scleroderma had increased capillary counts. It was also observed in the same 5 patients, that the interferon α and vascular endothelial cadherin had returned to normal as other clinical signs in the skin regressed, and in all 7 patients, RGS5 had returned to normal. CONCLUSION/SIGNIFICANCE. These data provide the first objective evidence for loss of vessels in scleroderma and show that this phenomenon is reversible. Coordinate changes in expression of three molecules already implicated in angiogenesis or anti-angiogenesis suggest that control of expression of these three molecules may be the underlying mechanism for at least the vascular component of this disease. Since rarefaction has been little studied, these data may have implications for other diseases characterized by loss of capillaries including hypertension, congestive heart failure and scar formation.Scleroderma Research Foundatio

Integrable microwave filter based on a photonic crystal delay line

The availability of a tunable delay line with a chip-size footprint is a crucial step towards the full implementation of integrated microwave photonic signal processors. Achieving a large and tunable group delay on a millimetre-sized chip is not trivial. Slow light concepts are an appropriate solution, if propagation losses are kept acceptable. Here we use a low-loss 1.5 mm-long photonic crystal waveguide to demonstrate both notch and band-pass microwave filters that can be tuned over the 0 50-GHz spectral band. The waveguide is capable of generating a controllable delay with limited signal attenuation (total insertion loss below 10 dB when the delay is below 70 ps) and degradation. Owing to the very small footprint of the delay line, a fully integrated device is feasible, also featuring more complex and elaborate filter functions.This work was funded by the European Union under the project GOSPEL (grant 219299) and by the Valencian Government (Prometeo GVA 2008-92). We thank S. Hughes and P. Lalanne for enlightening discussion about the impact of disorder in photonic crystal waveguides.Sancho Durá, J.; Bourderionnet, J.; Lloret Soler, JA.; Combrie, S.; Gasulla Mestre, I.; Xavier, S.; Sales Maicas, S.... (2012). Integrable microwave filter based on a photonic crystal delay line. Nature Communications. 3:1-9. https://doi.org/10.1038/ncomms2092S193Seeds, A. Microwave photonics. IEEE Trans. Microwave Theory Tech. 50, 877–887 (2002).Capmany, J. & Novak, D. Microwave photonics combines two worlds. Nat. Photon 1, 319–330 (2007).Yao, J. P. Microwave photonics. J. Lightwave Technol. 27, 314–335 (2009).See special technology focus on microwave photonics. Nat. Photon 5, 723–736 (2011).Capmany, J., Ortega, B. & Pastor, D. A tutorial on microwave photonic filters. J. Lightwave. Technol. 24, 201–229 (2006).Long, J. et al. A tunable microstrip bandpass filter with two independently adjustable transmission zeros. IEEE Microw. Wireless Compon. Lett. 21, 74–76 (2011).Velez, A. et al. Tunable coplanar waveguide band-stop and band-pass filters based on open split ring resonators and open complementary split ring resonators. IEEE Microw. Antennas Propag. 5, 277–281 (2011).Sekar, V., Armendariz, M. & Entesari, K. A 1.2-1.6-GHz substrate-integrated-waveguide RF MEMS tunable filter. IEEE Trans. Microwave Theory Tech. 59, 866–876 (2011).Rafique, M. R. et al. Miniaturized superconducting microwave filters. Supercond. Sci. Technol. 21, 075004 (2008).Velu, G. et al. A 360° BST phase shifter with moderate bias voltage at 30 GHz. IEEE Trans. Microwave Theory Tech. 55, 438–444 (2007).Koh, K. J. & Rebeiz, G. M. A 6-18 GHz active phase shifter. In Proceedings IEEE Microwave Symposium Digest 792–795 (2010).Capmany, J., Pastor, D. & Ortega, B. New and flexible fiber-optic delay-line filters using chirped Bragg gratings and laser arrays. IEEE Trans. Microwave Theory Tech. 47, 1321–1326 (1999).Minasian, R. A. Photonic signal processing of microwave signals. IEEE Trans. Microwave Theory Tech. 54, 832–846 (2006).Dai, Y. & Yao, J. P. Nonuniformly-spaced photonic microwave delay-line filter. Opt. Express 16, 4713–4718 (2008).Hamidi, E., Leaird, D. E. & Weiner, A. M. Tunable programmable microwave photonic filters based on an optical frequency comb. IEEE Trans. Microwave Theory Tech. 58, 3269–3278 (2010).Chan, E. H. W. & Minasian, R. A. Coherence-free high-resolution RF/microwave photonic bandpass filter with high skirt selectivity and high stopband attenuation. J. Lightwave Technol. 28, 1646–1651 (2010).Norberg, E. J. et al. Programmable photonic microwave filters monolithically integrated in InPinGaAsP. J. Lightwave. Technol. 29, 1611–1619 (2011).Chen, H. W. et al. Integrated microwave photonic filter on a hybrid silicon platform. IEEE Trans. Microwave Theory Tech. 58, 3213–3219 (2010).Dong, P. et al. GHz-bandwidth optical filters based on high-order silicon ring resonators. Opt. Express 18, 23784–23789 (2010).Lloret, J. et al. Tunable complex-valued multi-tap microwave photonic filter based on single silicon-on-insulator microring resonator. Opt. Express 19, 12402–12407 (2011).Notomi, M. et al. Extremely large group-velocity dispersion of line-defect waveguides in photonic crystal slabs. Phys. Rev. Lett. 87, 253902 (2001).Knight, J. C. Photonic crystal fibres. Nature 424, 847–851 (2003).Supradeepa, V. R. et al. Comb-based radiofrequency photonic filters with rapid tunability and high selectivity. Nat. Photon. 6, 186–194 (2012).Capmany, J., Ortega, B., Pastor, D. & Sales, S. Discrete-time optical processing of microwave signals. J. Lightwave Technol. 23, 702–723 (2005).Hunter, D. B. & Minasian, R. A Tunable microwave fiber-optic bandpass filters. IEEE Photon. Tech. Lett. 11, 874–876 (1999).Baba, T. Slow light in photonic crystals. Nat. Photon. 2, 465–473 (2008).Kuramochi, E. et al. Disorder-induced scattering loss of line-defect waveguides in photonic crystal slabs. Phys. Rev B 72, 161318 (2005).Ishikura, N., Baba, T., Kuramochi, E. & Notomi, M. Large tunable fractional delay of slow light pulse and its application to fast optical correlator. Opt. Express 19, 24102–24108 (2011).O'Faolain, L. et al. Loss engineered slow light waveguides. Opt. Express 18, 27627–27638 (2010).Baron, A., Mazoyer, S., Smigaj, W. & Lalanne, P. Attenuation Coefficient of Single-Mode Periodic Waveguides. Phys. Rev. Lett. 107, 153901 (2011).Patterson, M. et al. Disorder-Induced Coherent Scattering in Slow-Light Photonic Crystal Waveguides. Phys. Rev. Lett. 102, 253903 (2009).Mazoyer, S., Hugonin, J. P. & Lalanne, P. Disorder-Induced Multiple Scattering in Photonic-Crystal Waveguides. Phys. Rev. Lett. 103, 063903 (2009).Combrié, S. et al. Time-delay measurement in singlemode, low-loss photonic crystal waveguides. Electron. Lett. 42, 86–87 (2006).Liang, J. et al. Wideband ultraflat slow light with large group index in a W1 photonic crystal waveguide. J. App. Phys. 110, 063103 (2011).Roy, S. Modeling the dispersion of the nonlinearity in slow mode photonic crystal waveguides. IEEE Photonics. Journal 4, 224–233 (2012).Colman, P., Combrié, S. & De Rossi, A. Control of dispersion in photonic crystal waveguides using group symmetry theory. Opt. Express 20, 13108–13114 (2012).Vy Tran, Q., Combrié, S., Colman, P. & De Rossi, A. Photonic crystal membrane waveguides with low insertion losses. Appl. Phys. Lett. 95, 061105 (2009).Bolea, M., Mora, J., Ortega, B. & Capmany, J. Highly chirped single-bandpass microwave photonic filter with reconfiguration capabilities. Opt. Express 19, 4566–4576 (2011).Binetti, P. et al. Indium phosphide integrated circuits for coherent optical links. IEEE J. Quantum Electron. 48, 279–291 (2012).Thomson, D. J. et al. High contrast 40Gbit/s optical modulation in silicon. Opt. Express 19, 11507–11516 (2011).Asghari, M. & Krishnamoorthy, A. V. Energy efficient communication. Nat. Photon. 5, 268–270 (2011).Vivien, L. et al. Zero-bias 40Gbit/s germanium waveguide photodetector on silicon. Opt. Express 20, 1096–1101 (2012).Feng, N. N. et al. 30GHz Ge electro-absorption modulator integrated with 3 μm silicon-on-insulator waveguide. Opt. Express 19, 7062–7067 (2011).Trinh, P. D., Yegnanarayanan, S., Coppinger, F. & Jalali, B. Compact multimode interference couplers in Silicon-on-insulator technology. Conference on Lasers and Electro-Optics CLEO '97CThV4, 441 (Baltimore, USA, 1997).Loayssa, A., Capmany, J., Sagues, M. & Mora, J. Demonstration of incoherent microwave photonic filters with all-optical complex coefficients. IEEE Photon. Tech. Lett. 18, 1744–1746 (2006).Zhang, W. & Minasian, R. A. Widely tunable single-passband microwave photonic filter based on stimulated Brillouin scattering. IEEE Photon. Tech. Lett. 23, 1775–1777 (2011).Xue, W., Sales, S., Mork, J. & Capmany, J. Widely tunable microwave photonic notch filter based on slow and fast light effects. IEEE Photon. Tech. Lett. 21, 167–169 (2009).Norberg, E. J. et al. A monolithic programmable optical filter for RF signal processing. in Proceedings Microwave Photonics Conf. (Montreal, Canada, 2010).Vlasov, Y. A., O'Boyle, M., Hamann, H. F. & McNab, S. J. Active control of slow light on a chip with photonic crystal waveguides. Nature 438, 65–69 (2005).Eckhouse, V. et al. Highly efficient four wave mixing in GaInP photonic crystal waveguides. Opt. Lett. 35, 1440–1442 (2010).Sagues, M. et al. Multi-tap complex-coefficient incoherent microwave photonic filters based on optical single-sideband modulation and narrow band optical filtering. Opt. Express 16, 295–303 (2008).Huang, T. X. H., Yi, X. & Minasian, R. A. Single passband microwave photonic filter using continuous-time impulse response. Opt. Express 19, 6231–6242 (2011).Burla, M. et al. On-chip CMOS compatible reconfigurable optical delay line with separate carrier tuning for microwave photonic signal processing. Opt. Express 19, 21475–21484 (2011)

Diagnostic accuracy of a clinical diagnosis of idiopathic pulmonary fibrosis: An international case-cohort study

We conducted an international study of idiopathic pulmonary fibrosis (IPF) diagnosis among a large group of physicians and compared their diagnostic performance to a panel of IPF experts. A total of 1141 respiratory physicians and 34 IPF experts participated. Participants evaluated 60 cases of interstitial lung disease (ILD) without interdisciplinary consultation. Diagnostic agreement was measured using the weighted kappa coefficient (\u3baw). Prognostic discrimination between IPF and other ILDs was used to validate diagnostic accuracy for first-choice diagnoses of IPF and were compared using the Cindex. A total of 404 physicians completed the study. Agreement for IPF diagnosis was higher among expert physicians (\u3baw=0.65, IQR 0.53-0.72, p20 years of experience (C-index=0.72, IQR 0.0-0.73, p=0.229) and non-university hospital physicians with more than 20 years of experience, attending weekly MDT meetings (C-index=0.72, IQR 0.70-0.72, p=0.052), did not differ significantly (p=0.229 and p=0.052 respectively) from the expert panel (C-index=0.74 IQR 0.72-0.75). Experienced respiratory physicians at university-based institutions diagnose IPF with similar prognostic accuracy to IPF experts. Regular MDT meeting attendance improves the prognostic accuracy of experienced non-university practitioners to levels achieved by IPF experts

Photonic-Assisted Scanning Receivers for Microwave Frequency Measurement

We present a novel technique based on matrix pencil assisted deconvolution to improve the measurement resolution in scanning receiver systems for microwave frequency measurements. By modeling the scanning receiver output as the cross-correlation of the input modulated signal with the filter’s spectral response and applying the matrix pencil algorithm to convolve the detected optical signal at the receiver output, our technique offers precise estimations of both the frequency and power information of microwave signals with an improved measurement resolution. A multi-tone microwave signal measurement based on an optical filter is experimentally demonstrated, showing a significant measurement resolution reduction from 1 GHz to 0.4 GHz for two radio frequency (RF) tones, which is only about 30.2% of the optical filter bandwidth