589 research outputs found
From Nonlinear Integrated Optics to Microresonator Frequency Combs
No full textPerhaps one of the most spectacular current applications of nonlinear integrated optics, a field
which was pioneered by George Stegeman more than thirty years ago [1], is that of nonlinear
microresonator based optical frequency comb light sources. Optical frequency comb sources are
characterized by a spectrum comprising many equally spaced components [2], and have a wide
range of scientific and technological applications. Although commercial comb generators are based
on mode-locked lasers and fiber supercontinuum generation, nonlinear integrated optics provides a
low-cost and chip-scale alternative, based on a low-power cw laser coupled into a high-Q
microresonator [3]. So far microresonator frequency combs have exploited the third order “Kerr”
nonlinearity, which permits to generate successive comb lines with a spacing equal to the resonator
free-spectral range via cascaded four-wave mixing [4-5]. Modeling of microresonator frequency
combs can be greatly simplified by a single partial differential equation approach [4-6], analogous
to the case of other coherently driven Kerr spatially diffractive [7] or temporally dispersive [8-9]
nonlinear cavities. In order to lower the threshold power and extend the spectral range of frequency
comb generation, for example into the visible or mid-infrared, while still using near-infrared cw
laser pumps, quadratic nonlinear cavities can be exploited [10]. These quadratic microresonator
frequency comb sources operate close to the phase-matching condition for the underlying quadratic
processes, and not in the cascading regime that reduces the dynamics to the Kerr case [11]. Quite
remarkably, a single time domain partial differential equation with an effective delayed third-order
nonlinearity was derived to describe with excellent accuracy the dynamics of quadratic frequency
comb generation [12-13]. In situations where multiple processes are present, and the frequency
combs generated around the interacting waves over multiple octaves overlap, we carried out
numerical modeling based on a single envelope equation approach [14].
References
[1] G.I. Stegeman, E.M. Wright, N. Finlayson, R. Zanoni, and C.T. Seaton, J. Lightwave Technology 6, 953 (1988).
[2] T. Udem, R. Holzwarth, and T. W. Hänsch, Nature 416, 233 (2002).
[3] P. Del’Haye, A. Schliesser, O. Arcizet, T. Wilken, R. Holzwarth, and T. J. Kippenberg, Nature 450, 1214 (2007).
[4] S. Coen, H. G. Randle, T. Sylvestre, and M. Erkintalo, Opt. Lett. 38, 37 (2013).
[5] T. Hansson, D. Modotto, and S. Wabnitz, Phys. Rev. A 88, 023819 (2013).
[6] T. Hansson, D. Modotto, and S.Wabnitz, Opt. Comm. 312, 134 (2014).
[7] L. A. Lugiato and R. Lefever, Phys. Rev. Lett. 58, 2209 (1987).
[8] M. Haelterman, S. Trillo, and S. Wabnitz, Opt. Commun. 91, 401 (1992).
[9] F. Leo, S. Coen, P. Kockaert, S.-P. Gorza, P. Emplit, and M. Haelterman, Nature Photon. 4, 471 (2010).
[10] I. Ricciardi, S. Mosca, M. Parisi, P. Maddaloni, L. Santamaria, P. De Natale, and M. De Rosa, Phys. Rev. A 91,
063839 (2015).
[11] G. I. Stegeman, D. J. Hagan, and L. Torner, Optical and Quantum Electronics 28, 1691 (1996).
[12] F. Leo, T. Hansson, I. Ricciardi, M. De Rosa, S. Coen, S. Wabnitz, and M. Erkintalo, Phys. Rev. Lett. 116, 033901
(2016).
[13] F. Leo, T. Hansson, I. Ricciardi, M. De Rosa, S. Coen, S. Wabnitz, and M. Erkintalo, Phys. Rev. A 93 (2016).
[14] T. Hansson, F. Leo, M. Erkintalo, J. Anthony, S. Coen, I. Ricciardi, M. De Rosa, and S. Wabnitz, J. Opt. Soc. Am.
B 33, 1207 (2016)
Coen Beeker’s ‘Urban Fields’ for Addis Ababa
No full textCities under rapid urbanization such as Addis Ababa offer a set of challenges for today’s designers and planners. The urgent need for access to affordable and decent living environments presses city administrations, whose primary response tends to be a top-down approach of public housing projects and allocating plots through a bidding process in which only the affluent become beneficiaries. Such socially selective approaches usually segregate urban dwellers into economic classes and fall short of providing affordable housing options. The formal and informal horizontal sprawl of the city has continued unabated since the mid-1970s and has gained even stronger momentum in the past decade. It is important today to consider options that allow integration instead of segregation and to find options for legal and planned urban environments that deal with peripheral urbanisation. Coen Beeker’s ‘step-by-step’ process of urbanization, which allows gradual changes that promote incremental and adaptable formation of ‘urban fields’ in the peripheries of Addis Ababa, illustrates the possibilities. He argues that access to legally tenured plots of land and further urbanization through measured steps is crucial for developing affordable and cohesive communities in these areas. This paper is an analysis of the pertinent challenges faced by the city of Addis Ababa in relation to peripheral urbanisation and an assessment of Coen Beeker’s proposal to deal with these challenges.OLD Woningbou
N MARGINE A UN RECENTE VOLUME SUI DANNI DI GUERRA. UN CONTROLLO ALLA MODERNA "QUESTIONE DELLA STORIA DELL'ARTE
No full texthe essay is basically a review of an important and recently released-book dedicated to the damages that occurred in Italy during the Second World War. Nonetheless, the review is a point of departure. So, the author takes advantage of this theme for a discussion of the role of the art historian today in Italy when compared to those played by historians and architects
Brownlow Cecil, ninth Earl of Exeter, Thomas Jenkins and Nicolas Mosman: Origins, Functions and Aesthetic Guidelines of a Great Drawing Collection in Eighteenth-Century Rome, now at the British Museum
No full textNicolas Mosman, un allievo di Anton Raphael Mengs, è responsabile di un notevole corpus di disegni, oggi custodito e consultabile presso il Prints & Drawings Department del British Museum di Londra. Tali disegni furono commissionati a Mosman da Brownlow Cecil, nono conte di Exeter e grande collezionista d'arte. La maggior parte di questi disegni sono copie di dipinti che si trovavano a Roma ed erano quasi sempre in vendita. Il saggio riprende in mano l'intera questione dei 'Mosman Drawings' e li esamina da una prospettiva diversa, quella appunto del mercato dell'arte. L'ipotesi più probante è che i disegni siano stati concepiti dal conte per tenersi al corrente delle opere che passavano sulla piazza romana ed eventualmente per comprarle: diverse fra le opere copiate a Roma da Mosman sarebbero infatti di lì a poco passate nella collezione del conte. In questo meccanismo abbastanza complesso ebbe un ruolo attivo uno dei più importanti mercanti attivi fra Roma e il Regno Unito, Thomas Jenkins.
L'articolo affronta e approfondisce un tema importante della storia dell'arte, il rapporto fra originale e copia grafica. Il caso di studio sono i cosiddetti Mosman Drawings, un gruppo di disegni oggi al British Museum, che riproducono a disegno alcune centinaia di quadri che passarono sul mercato romano nel corso del XVIII secolo.Nicolas Mosman, a pupil of Anton Raphael Mengs, is the author of a remarkable body of drawings, now kept at the Prints & Drawings Department of the British Museum in London. The drawings were commissioned to Mosman by Brownlow Cecil, ninth Earl of Exeter, a great art collector. Most of these drawings are copies of paintings that were in Rome, very often on sale. The essay picks up the whole issue of the 'Mosman Drawings' and examines them from a different perspective, that of the art market. Most likely the drawings were conceived by the 9th Earl to be kept updated on the paintings on the Roman art market and possibly to buy them: several of the works copied in Rome by Mosman would in fact shortly become part of Cecil's collection and so are still kept at Burghley House. In this rather complex mechanism, one of the most important art dealer who were active between Rome and the United Kingdom, Thomas Jenkins, played an active role
The emerging role of BK virus in kidney transplantation
Get PDFIn summary, the studies in this thesis show that immunosuppression with tacrolimus carries a higher risk of BKPyV reactivation and pathology and that treatment with CsA or an mTOR inhibitor can then be considered. In addition, it is possible to differentiate between BKPyVAN and rejection with FACS and this method can be used to monitor the effectiveness of anti-rejection treatment or BKPyV-related treatment via immune profiles. BKPyV also has the potential to circumvent the immune system via viral miRNA, whereby the viral miRNAs largely follow the amount of viral DNA, but for which more research is needed to better understand complex expression differences of the miRNA during different phases of infection
Wegener's granulomatosis: immunological and microbiological factors involved in disease activation
Get PDFWegener's granulomatosisin its classic form is characterized by necrotizing granulomatous inflammation of especially nasal and paranasal structures and lungs in combination with pauci-immune necrotizing glomerulonephritis and small vessel vasculitis (1,2). Although a clinical presentationin its classical form is not uncommon, a patient with Wegener's granulomatosis may present with a wide variety of clinical problems, even without some or even all classic features (3). In patients with a less typical presentation the physician can easily be mislead and a long diagnosticd elay can occur (4,5).
See: Introduction
The Violence and Necrophilia at Coen Brothers’
No full textW swojej analizie filmów Ethana i Joela Coenów Syska wykorzystuje narzędzia psychoanalizy Ericha Fromma, by pokazać nekrofilską naturę bohaterów ich filmów. Przemoc, jeden z najistotniejszych elementów filmowej rzeczywistości, jest przedmiotem analizy autora. Syska wskazuje na nowe sposoby obrazowania przemocy, podkreślając fizjologiczny charakter aktów przemocy i biologiczną naturę umierania. Sakralna i metafizyczna wartość śmierci zostaje umniejszona, a na pierwszy plan wysuwają się jej fizjologiczne aspekty. Syska stara się udowodnić, że hiperbolizacja przemocy w filmach braci Coen jest nie tylko punktem wyjścia dla postmodernistycznych zabaw z doświadczonym widzem, ale także próbą wciągnięcia go w patologiczny dyskurs, którego istotą jest estetyczna i moralna akceptacja okrucieństwa. Syska udowadnia, że nekrofilia, będąca jedną z najistotniejszych właściwości składających się na ich filmową rzeczywistość, jest również cechą charakterystyczną postmodernizmu.In his analysis of Ethan and Joel Coen’s films Syska makes use of the tools of Erich Fromm’s psychoanalysis to show the necrophyliac nature of their films’ heroes. Violence, one of the most essential components of film reality, is analysed by the author. Syska points out the new ways of depicting violence by stressing the physiological nature of acts of violence and biological nature of dying. The sacred and metaphysical value of death is belittled while prominence is given to its physiological aspects. Syska tries to prove that the hiperbolisation of violence in Coen brothers’ films is the starting point not only for post-modernist plays with experienced spectators but also the attempt to involve them in a pathological discourse whose essence is aesthetic and moral acceptance of cruelty. Syska proves that necrophyliac nature, which is one of the most essential properties making up their film reality, is also a characteristic feature of post-modernism
The regulatory and effector functions of B cells in ANCA-associated vasculitis
Get PDFSystemische auto-immuunziekten waarbij necrotiserende ontstekingen optreden in kleine en middelgrote bloedvaten kunnen gepaard gaan met de aanwezigheid van specifieke auto-antilichamen, ook wel anti-neutrofiele cytoplasmatische antilichamen (ANCA) genoemd. B-cellen spelen waarschijnlijk een belangrijke rol in deze ANCA-geassocieerde vasculitiden (AAV) vanwege hun productie van de ANCA. Weinig is echter bekend over de mechanismen die leiden tot ANCA-productie in B-cellen. In dit proefschrift wordt aangetoond dat interleukine-21 (IL-21) en B cel activerende factor (BAFF) de in vitro productie van ANCA kunnen stimuleren. Bovendien bleek het aantal IL-21 producerende T helper cellen verhoogd in ANCA-positieve patiënten ten opzichte van ANCA-negatieve patiënten en gezonde personen. Deze bevindingen suggereren dat IL-21 bijdraagt aan de productie van ANCA in patiënten met AAV. Hoewel B-cellen bijdragen aan het ontstaan van AAV door hun productie van ANCA, suggereren recente studies dat B-cellen afweerreacties in andere auto-immuunziekten kunnen onderdrukken. Deze onderdrukkende B-cellen, ook wel regulerende B-cellen genoemd, kunnen andere afweercellen remmen middels hun productie van IL-10. In het tweede deel van dit proefschrift wordt aangetoond dat er weliswaar een verstoorde homeostase van B-cellen is in AAV, maar dat de productie van IL-10 in B-cellen niet verstoord is. Bovendien bleken B-cellen van AAV-patiënten geen defecten te vertonen in het vermogen om andere afweercellen, in dit geval monocyten, te remmen. Derhalve werden geen aanwijzingen gevonden dat functionele defecten van regulerende B-cellen ten grondslag liggen aan het ontstaan van AAV. Samenvattend leveren de bevindingen uit dit proefschrift nieuwe inzichten op in de diverse functies van B-cellen in AAV-patiënten.
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are systemic autoimmune diseases characterized by necrotizing inflammation of small- to medium-sized blood vessels. In patients with AAV, B cells are considered pathogenic as they produce autoantibodies (ANCA) that mediate neutrophil activation which leads to vascular injury. Although ANCA play a pathogenic role in AAV, it is unclear what drives ANCA production. The first aim of this thesis was to study the mechanisms and factors that stimulate autoantibody production in patients with AAV. We demonstrated that interleukin (IL)-21 in combination with B cell activating factor (BAFF) stimulates ANCA production in vitro. In agreement, we demonstrated an increased frequency of IL-21-producing T helper cells in ANCA-positive patients when compared with ANCA-negative patients and healthy controls, suggesting that IL-21 might contribute to ANCA production in patients. Besides antibody production, B cells are known to affect immune responses by providing co-stimulatory signals and secretion of cytokines and growth factors. Recently a novel B cell subset, termed regulatory B cells, was described and reported to exert a suppressive effect on other immune cells. Therefore, the second aim was to characterize the circulating B cell subsets and evaluate the suppressive function of B cells in AAV patients. We found disturbed homeostasis of circulating B cells in AAV patients but the capacity of B cells in these patients to produce the anti-inflammatory cytokine IL-10 and suppress monocyte activation was not impaired.
Overall, the data presented in this thesis contribute to the knowledge on the humoral and cellular functions of B cells in AAV.
Improving clinical management in ANCA-associated vasculitis
Get PDFIn ANCA-associated small vessel vasculitis, patients may present with life threatening rapid clinical decline due to single or multiple organ involvement, especially targeting kidney and lungs (1). The sooner the diagnosis is made, the sooner appropriate and efficacious therapy can be installed. In an ideal situation, patient-tailored therapy should be available, optimizing the risk/benefit ratio of treatment, especially since the burden of toxicity of the induction and maintenance agents of choice can be huge. In this view, duration of maintenance therapy is also important and both choices of specific agents as well as the duration of treatment may have implications for the risks of morbidity, mortality and the quality of life. Following the initial treatment phase, there are several known risk factors for relapse and poor long term prognosis. In this thesis, we go into these factors to improve the clinical management and outcome of ANCA-associated vasculitis
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