69 research outputs found

    Vertical-cavity silicon-integrated lasers by bonding and transfer printing

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    We present the design and performance of the first current-driven hybrid-vertical-cavity silicon-integrated laser with in-plane waveguide emission. We also show results from preliminary work on transfer printing for large-scale integration of such light sources on silicon photonic integrated circuits

    Ternary q-Virasoro-Witt Hom-Nambu-Lie algebras

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    In this paper we construct ternary qq-Virasoro-Witt algebras which qq-deform the ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos using su(1,1)su(1,1) enveloping algebra techniques. The ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos depend on a parameter and are not Nambu-Lie algebras for all but finitely many values of this parameter. For the parameter values for which the ternary Virasoro-Witt algebras are Nambu-Lie, the corresponding ternary qq-Virasoro-Witt algebras constructed in this article are also Hom-Nambu-Lie because they are obtained from the ternary Nambu-Lie algebras using the composition method. For other parameter values this composition method does not yield Hom-Nambu Lie algebra structure for qq-Virasoro-Witt algebras. We show however, using a different construction, that the ternary Virasoro-Witt algebras of Curtright, Fairlie and Zachos, as well as the general ternary qq-Virasoro-Witt algebras we construct, carry a structure of ternary Hom-Nambu-Lie algebra for all values of the involved parameters

    Analysis of defect-related optical degradation of VCSILs for photonic integrated circuits

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    Laser diodes are of paramount importance for on-chip telecommunications applications, and a wide range of sensing devices that require near-infrared sources. In this work, the devices under test are vertical-cavity silicon-integrated lasers (VCSILs) designed for operation at 845 nm in photonic integrated circuits (PICs). We focus on the analysis of the degradation of the optical performance during aging. To investigate the reliability of the devices, we carried out several stress tests at constant current, ranging from 3.5 mA to 4.5 mA representing a highly accelerated stress condition. We observed two different degradation modes. In the first part of the experiments, the samples exhibited a worsening of the threshold current, but the sub-threshold emission was unaffected by degradation. We associated this behavior to the diffusion of impurities that, from the p-contact, were crossing the upper mirror implying a worsening of the DBR optical absorption. In the second stage of the stress test, the devices showed a higher degradation rate of the threshold current, whose variation was found to be linearly correlated to the worsening of the sub-threshold emission. We related this second degradation mode to the migration of the same impurities degrading the top DBR that, when reaching the active region of the laser, induced an increase in the non-radiative recombination rate. In addition to that, we related the two degradation modes to the change in series resistance, which was ascribed to the resistivity increment of the top DBR first and of oxide aperture afterwards

    Review on quality assurance along the CFRP value chain - Non-destructive testing of fabrics, preforms and CFRP by HF radio wave techniques

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    Eddy current testing is well established for non-destructive testing of electrical conductive materials [1]. The development of radio frequency (RF) eddy current technology with frequency ranges up to 100 MHz made it possible to extend the classical fields of application even towards less conductive materials like CFRP [2][3](Table 2). It turns out that RF eddy current technology on CFRP generates a growing number of valuable information for comprehensive material diagnostic. Both permittivity and conductivity of CFRP influence the complex impedance measured with RF eddy current devices. The electrical conductivity contains information about fiber texture like orientations, gaps or undulations in a multilayered material. The permittivity characterization influenced by dielectric properties allows the determination of local curing defects on CFRP e.g. hot spots, thermal impacts or polymer degradation. An explanation for that effect is seen in the measurement frequency range and the capacitive structure of the carbon rovings. Using radio wave frequencies for testing, the effect of displacement currents cannot be neglected anymore. The capacitive structures formed by the carbon rovings is supposed to further strengthen the dielectric influences on eddy current measurement signal [3]. This report gives an overview of several realized applications and should be understood as a general introduction of CFRP testing by HF Radio Wave techniques

    Dendritic cells in cancer immunology and immunotherapy

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    Dendritic cells (DCs) are a diverse group of specialized antigen-presenting cells with key roles in the initiation and regulation of innate and adaptive immune responses. As such, there is currently much interest in modulating DC function to improve cancer immunotherapy. Many strategies have been developed to target DCs in cancer, such as the administration of antigens with immunomodulators that mobilize and activate endogenous DCs, as well as the generation of DC-based vaccines. A better understanding of the diversity and functions of DC subsets and of how these are shaped by the tumour microenvironment could lead to improved therapies for cancer. Here we will outline how different DC subsets influence immunity and tolerance in cancer settings and discuss the implications for both established cancer treatments and novel immunotherapy strategies.S.K.W. is supported by a European Molecular Biology Organization Long- Term Fellowship (grant ALTF 438– 2016) and a CNIC–International Postdoctoral Program Fellowship (grant 17230–2016). F.J.C. is the recipient of a PhD ‘La Caixa’ fellowship. Work in the D.S. laboratory is funded by the CNIC, by the European Research Council (ERC Consolidator Grant 2016 725091), by the European Commission (635122-PROCROP H2020), by the Ministerio de Ciencia, Innovación e Universidades (MCNU), Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional (FEDER) (SAF2016-79040-R), by the Comunidad de Madrid (B2017/BMD-3733 Immunothercan- CM), by FIS- Instituto de Salud Carlos III, MCNU and FEDER (RD16/0015/0018-REEM), by Acteria Foundation, by Atresmedia (Constantes y Vitales prize) and by Fundació La Marató de TV3 (201723). The CNIC is supported by the Instituto de Salud Carlos III, the MCNU and the Pro CNIC Foundation, and is a Severo Ochoa Centre of Excellence (SEV-2015-0505).S

    Auff den unverhofften Todesfall Des ... Helden Gustavi Adolphi, Der Schweden Gothen und Wenden Königes/ So Anno 1632. den 6. Septembris Sein Ritterlich Leben ... geendet ...

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    In zwey Stunden Componirt Durch A. Goyvaerts V. F. Dreßden/ Den 23. Decembris

    Universals in Human Language. A Historical Perspective

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    Cooreman A., Goyvaerts D. Universals in Human Language. A Historical Perspective. In: Revue belge de philologie et d'histoire, tome 58, fasc. 3, 1980. Langues et littératures modernes — Moderne taal- en letterkunde. pp. 615-638

    Liftable pairs of functors and initial objects

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    Let A and B be monoidal categories and let R : A -> B be a lax monoidal functor. If R has a left adjoint L, it is well-known that the two adjoints induce functors (R) over bar = Alg(R) : Alg(A) -> Alg(B) and (L) under bar = Coalg(L) : Coalg(B) -> Coalg (A) respectively. The pair (L, R) is called liftable if the functor R has a left adjoint and if the functor (L) under bar has a right adjoint. A pleasing fact is that, when A, B and R are moreover braided, a liftable pair of functors as above gives rise to an adjunction at the level of bialgebras. In this note, sufficient conditions on the category A for (R) over bar to possess a left adjoint, are given. Natively these conditions involve the existence of suitable colimits that we interpret as objects which are simultaneously initial in four distinguished categories (among which the category of epiinduced objects), allowing for an explicit construction of (L) under bar, under the appropriate hypotheses. This is achieved by introducing a relative version of the notion of weakly coreflective subcategory, which turns out to be a useful tool to compare the initial objects in the involved categories. We apply our results to obtain an analogue of Sweedler's finite dual for the category of vector spaces graded by an abelian group G endowed with a bicharacter. When the bicharacter on G is skew-symmetric, a lifted adjunction as mentioned above is explicitly described, inducing an auto-adjunction on the category of bialgebras "colored" by G

    Pre-rigid monoidal categories

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    Liftable pairs of adjoint functors between braided monoidal categories in the sense of [GV1] provide auto-adjunctions between the associated categories of bialgebras. Motivated by finding interesting examples of such pairs, we study general pre-rigid monoidal categories. Roughly speaking, these are monoidal categories in which for every object X, an object X* and a nicely behaving evaluation map from X* circle times X to the unit object exist. A prototypical example is the category of vector spaces over a field, where X* is not a categorical dual if X is not finite-dimensional. We explore the connection with related notions such as right closedness, and present meaningful examples. We also study the categorical frameworks for Turaev's Hopf group-(co)algebras in the light of pre-rigidity and closedness, filling some gaps in literature along the way. Finally, we show that braided pre-rigid monoidal categories indeed provide an appropriate setting for liftability in the sense of loc. cit. and we present an application, varying on the theme of vector spaces, showing how -in favorable cases-the notion of pre-rigidity allows to construct liftable pairs of adjoint functors when right closedness of the category is not available
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