Slow waves in locally resonant metamaterials line defect waveguides

In the past decades, many efforts have been devoted to the temporal manipulation of waves, especially focusing on slowing down their propagation. In electromagnetism, from microwave to optics, as well as in acoustics or for elastic waves, slow wave propagation indeed largely benefits both applied and fundamental physics. It is for instance essential in analog signal computing through the design of components such as delay lines and buffers, and it is one of the prerequisite for increased wave/matter interactions. Despite the interest of a broad community, researches have mostly been conducted in optics along with the development of wavelength scaled structured composite media, that appear promising candidates for compact slow light components. Yet their minimum structural scale prevents them from being transposed to lower frequencies where wavelengths range from sub-millimeter to meters. In this article, we propose to overcome this limitation thanks to the deep sub-wavelength scale of locally resonant metamaterials. In our approach, implemented here in the microwave regime, we show that introducing coupled resonant defects in such composite media allows the creation of deep sub-wavelength waveguides. We experimentally demonstrate that waves, while propagating in such waveguides, exhibit largely reduced group velocities. We qualitatively explain the mechanism underlying this slow wave propagation and first experimentally demonstrate, then numerically verify, how it can be taken advantage of to tune the velocity, achieving group indices ng as high as 227 over relatively large bandwidths. We conclude by highlighting the three beneficial consequences of our line defect slow wave waveguides in locally resonant metamaterials: the deep sub-wavelength scale, the very large group indices and the fact that slow wave propagation does not occur at the expense of drastic bandwidth reductions

La dimension psychosociologique dans la reussite entrepreneuriale

Les recherches menées dans le domaine de l’entrepreneuriat ont privilégié tout particulièrement les approches  économiques et sociologiques. Nous avons tenté dans cette étude de focaliser notre réflexion sur les facteurs psychologiques en nous basant sur les travaux de: Aldrich et Zimmer, (1986); Keats et Bracker,  (1988), Stevenson et Jarillo, (1990); Gartner, (1988). Notre recherche a porté principalement sur les caractéristiques psychologiques dans la réussite chez les jeunes entrepreneurs ayant crée une activité dans le cadre du dispositif public de soutien à l’emploi des jeunes (ANSEJ). Les résultats obtenus confirment l’apport des facteurs motivationnels et les traits de personnalité dans la création et le maintien de l’activité. Cependant, malgré cet apport motivationnel important, les jeunes sont très vulnérables au plan des  connaissances et compétences qu’ils possèdent lors du lancement de leurs projets. MOTS CLES: Entrepreneur, personnalité, motivation, entrepreneuriat, PMI-PME

Between history and modernity: negotiating subjectivity in the early work of Edgar Degas, c. 1854-1870

This thesis provides a critical reassessment of the early career of Edgar Degas between the years 1854-1870 a period during which the artist had yet to gain any critical recognition or commercial success and was struggling to find the terms of a practice he could pursue with integrity. While Degas' output during these years has, until now, been summarily dismissed by scholars in the field, my dissertation takes this crucial formative period of artistic production seriously. Primacy is given to Degas' historical canvases (together with their related preparatory drawings), which are seen to function as the site upon which the artist negotiated nineteenth-century notions of 'History' and 'Tradition' within the context of an emerging modern self-consciousness. I also examine what is at stake for Degas' own subjectivity here, both in terms of how it is enmeshed within his formal procedures as well as the ways in which it is implicated within the broader historical and artistic transformations taking place at this moment. Notions of the 'in-between' and 'transitional' function as this thesis' overarching conceptual metaphors. Analogous to Degas' artistic travails, they also articulate something critical about the illegibility of the canvases themselves which exist in various states of 'un-finish'. These pictures initiate a series of radical departures from academic precepts of History painting (most notably here its doctrine of Jim). However, they also dramatize something of the precariousness of Degas' subjectivity and artistic identity during these early years at a moment when he was caught between outmoded academic rhetorics and the yet-to-be fully articulated pictorial languages of modernity. Through a detailed exploration of the ways in which Degas' negotiated the terms of his practice amidst the radically shifting parameters of art in the nineteenth century, I seek to reframe what has thus far been understood as a largely frustrated period of productivity in terms of a crucial process of artistic formation

The immunobiology and clinical management of acute graft versus host disease after allogeneic transplant

Alloreactivity between donor cells against disparate host tissue is a natural and normal physiologic phenomenon after engraftment. Consequently, GVHD is a universally expected side effect after allogeneic HSCT. An effective strategy to prevent severe or fatal acute GVHD is require if the transplant is to be successful. The HSCT field has witnessed significant progress in the prevention and treatment of acute GVHD. However, select interventions come at the cost of losing the alloimmune activity that prevents relapse, the GVL effect, as many of the mechanisms which cause GVHD are shared with those responsible for GVL. Current efforts are focused on therapeutic interventions that not only alleviate the burden of acute GVHD but does so in a way that maintains the GVL effect. This review will provide an up-to-date overview of our current understanding of the diagnosis, risk stratification, immunobiology of acute GVHD, summarize efforts to prevent and treat the disease, and provide a perspective on future directions

COVID-19 Industry Guidance: Places of worship and providers of religious services and cultural ceremonies

The guidelines from the California Department of Public Health (CDPH) and Cal/OSHA provide recommendations and strategies for places of worship during the COVID-19 pandemic. The guidelines discuss issues such as in-person services, the use of masks, ceremonies such as funerals, virtual worship, disinfecting, and social distancing. The role of material culture, such as the use of books, pamphlets, and communal water, is also discussed

The chloroethylating anticancer drug ACNU induces FRA1 that is involved in drug resistance of glioma cells

AbstractFRA1 belongs, together with c-Fos and FosB, to the family of Fos proteins that form with members of the ATF and Jun family the transcription factor AP-1 (activator protein 1). Previously we showed that c-Fos protects mouse embryonic fibroblasts against the cytotoxic effects of ultraviolet (UV) light by induction of the endonuclease XPF, leading to enhanced nucleotide excision repair (NER) activity. Here, we analyzed the regulation of FRA1 in glioma cells treated with the anticancer drug nimustine (ACNU) and its role in ACNU-induced toxicity. We show that FRA1 is upregulated in glioblastoma cells following ACNU on mRNA and protein levels. Knockdown of FRA1 by either siRNA or shRNA clearly sensitized glioma cells towards ACNU-induced cell death. Despite decreased AP-1 binding activity upon FRA1 knockdown, this effect is independent on regulation of the AP-1 target genes fasL, ercc1 and xpf. In addition, FRA1 knockdown does not affect DNA repair capacity. However, lack of FRA1 attenuated the ACNU-induced phosphorylation of CHK1 and led to a reduced arrest of cells in G2/M and, thereby, presumably leads to enhanced cell death in the subsequent cell cycle

Modelling and sustainability analysis of biorefineries using sugarcane lignocellulose to produce polyethylene, sorbitol, glucaric acid and levulinic acid at existing South African sugar mills

Thesis (PhD)--Stellenbosch University, 2021.ENGLISH ABSTRACT: The sugar industry in South Africa and the region has been plagued by factors including the low international sugar prices, reduced cane yields due to climate change and competition from new market entrants producing sweeteners. Therefore, to remain relevant and sustainable, this industry seeks to generate extra revenue by producing bio-based chemicals and bio-energy from part of the bagasse and brown leaves in biorefinery complexes, alongside sugar products. Using a rapid screening approach, bio-based chemicals polyethylene, sorbitol, glucaric acid and levulinic acid were shortlisted for possible production in such biorefineries (objective one). Conceptual biorefinery process flow diagrams were designed in Aspen Plus® v 8.6 producing the aforementioned chemicals with electricity cogeneration in combined heat and power plants, annexed to a conventional sugar mill (objective two), including a base case scenario that only produced electricity. This was followed by determining the techno-economic viability of the bio-energy self-sufficient biorefineries using developing countries’ economic parameters and a discounted cash flow rate of return methodology on real terms using a 9.7% hurdle rate that reflects South Africa’s and developing countries’ economic conditions (objective three). The internal rate of return (IRR), net present value (NPV) and minimum product selling price (MPSP) were indicators used to determine profitability. The most economically viable scenario coproduced levulinic acid, gamma valerolactone, furfural and electricity (LA-GVL-F-E) and attained a 23% IRR and US$253 million NPV at a 9.7$ 139 million. At present, most second generation bio-based chemicals cannot compete with first generation or fossil–based counterparts due to the large capital investment costs associated with processing lignocelluloses. A substantial premium is required on second-generation bio-based products if they are to compete with fossil-based or first generation products. In addition to economic viability, the overall sustainability of profitable biorefineries was assessed based on their environmental and social impacts (i.e. job creation) in objective four. For the environmental impact, a “cradle to factory gate” life cycle assessment in SimaPro® was used and the AWARE methodology applied for the water footprint. The most sustainable scenario produced glucaric acid via dilute acid pretreatment (Glucaric.DA) followed by LA-F-E. Objective five was a multi criteria decision assessment (MDCA) on profitable scenarios that ranked and scored the biorefineries based on equal and varied national sustainable (economic, environmental and social) representative weightings. When equal representative weightings of 33.33% were applied to the sustainability indicators, scenario LA-F-E attained the highest aggregate score followed by Glucaric.DA and Sorbitol.DA (chemicals produced via dilute acid pretreatment) and lastly, LA-GVL-F-E. The generated results can inform key sugar industry stakeholders of the most sustainable biorefineries for future feasibility studies. Therefore, potential exists at typical sugar mills for the sustainable valorisation of lignocelluloses for revenue generation and the advancement of a green economy. Future studies should investigate the sustainability of biorefineries utilising first and second generation feedstocks and also valorising part of the lignin to produce high-value chemicals.AFRIKAANSE OPSOMMING: Die suikerindustrie in Suid-Afrika en die streek word deur faktore geteister soos die lae internasionale suikerpryse, verlaagde rietopbrengs as gevolg van klimaatsverandering en kompetisie van nuwe markdeelnemers wat versoeters vervaardig. Daarom, om relevant en volhoubaar te bly, poog die industrie om ekstra inkomste te genereer deur bio-gebaseerde chemikalieë en bio-energie uit ’n gedeelte van die bagasse en bruin blare in bioraffinaderykompleks, saam met suikerprodukte, te produseer. Deur ’n vinnige siftingsbenadering, is bio-gebaseerde chemikalieë poliëtileen, sorbitol, suikersuur en levuliniensuur gekortlys vir moontlike produksie in sulke bioraffinaderye (doelwit 1). Konsepsuele bioraffinaderyprosesvloeidiagramme is ontwerp in Aspen Plus® v 8.6 wat die voorafgenoemde chemikalieë met elektrisiteitkogenerasie produseer in aanlegte wat hitte en krag kombineer, geannekseer aan ’n konvensionele suikermeul (doelwit 2), insluitend ’n basis scenario wat slegs elektrisiteit produseer. Dit is gevolg deur die bepaling van die tegno-ekonomiese uitvoerbaarheid van die bio-energie selfonderhoudende bioraffinaderye deur ontwikkelende lande se ekonomiese parameters te gebruik, en ’n korting op kontantvloeiopbrengsmetodologie op reële terme deur ’n 9.7% versperringskoers te gebruik wat Suid-Afrika en ontwikkelende lande se ekonomiese kondisies reflekteer (doelwit 3). Die interne opbrengskoers (IRR), netto huidige waarde (NPV) en minimum produkverkoopsprys (MPSP) was indikators wat gebruik is om winsgewendheid te bepaal. Die mees ekonomies uitvoerbare scenario het levuliniensuur, gamma valerolaktoon, furfuraal en elektrisiteit (LA-GVL-F-E) koproduseer en het ’n 23% IRR en US$253 miljoen NPV gehad by ’n 9.7$139 miljoen. Tans kan meeste tweede-generasie bio-gebaseerde chemikalieë nie met eerste generasie of fossiel-gebaseerde teenbeelde kompeteer nie as gevolg van die groot kapitaalbeleggingkostes geassosieer met prosessering van lignosellulose. ’n Aansienlike premie word vereis op tweede-generasie bio-gebaseerde produkte as hulle met fossiel-gebaseerde of eerste-generasie produkte wil kompeteer. Saam met ekonomiese uitvoerbaarheid, is die algehele volhoubaarheid van winsgewende bioraffinaderye geassesseer gebaseer op hul omgewings- en sosiale impak (i.e. werkskepping) in doelwit 4. Vir die omgewingsimpak is ’n lewenssiklusanalise van die “begin tot fabriekshek” in SimaPro® gebruik en die AWARE-metodologie toegepas vir die watervoetspoor. Die mees volhoubare scenario het suikersuur via verdunde suur voorbehandeling (Glucaric.DA) produseer, gevolg deur LA-F-E. Doelwit vyf was ’n multikriteriabesluitassessering (MDCA) op winsgewende scenario’s wat bioraffinaderye rangskik en punte gee gebaseer op gelyke en gevarieerde nasionale volhoubaarheid (ekonomies, omgewing, en sosiaal) verteenwoordigende gewigstoekennings. Toe gelyke verteenwoordigende gewigstoekennings van 33.33% toegepas is op die volhoubaarheidsindikators, het scenario LA-F-E die hoogste aggregaattelling behaal, gevolg deur Glucaric.DA en Sorbitol.DA (chemikalieë geproduseer via verdunde suur voorbehandeling), en laaste, LA-GVL-F-E. Die gegenereerde resultate kan sleutel suikerindustriebelanghebbers van die mees volhoubare bioraffinaderye inlig vir toekomstige uitvoerbaarheidstudies. Potensiaal bestaan daarom by tipiese suikermeule vir die volhoubare valorisasie van lignosellulose vir inkomstegenerasie en die bevordering van ’n groen ekonomie. Toekomstige studies moet die volhoubaarheid van bioraffinaderye wat eerste- en tweede-generasie toevoermateriale gebruik, ondersoek, en ook die valorisering van ʼn gedeelte van die lignien om hoë waarde chemikalieë te produseer.The financial assistance of the National Research Foundation (NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily attributed to the NRF

Rad51 and BRCA2 - New Molecular Targets for Sensitizing Glioma Cells to Alkylating Anticancer Drugs

First line chemotherapeutics for brain tumors (malignant gliomas) are alkylating agents such as temozolomide and nimustine. Despite growing knowledge of how these agents work, patients suffering from this malignancy still face a dismal prognosis. Alkylating agents target DNA, forming the killing lesion O6-alkylguanine, which is converted into DNA double-strand breaks (DSBs) that trigger apoptosis. Here we assessed whether inhibiting repair of DSBs by homologous recombination (HR) or non-homologous end joining (NHEJ) is a reasonable strategy for sensitizing glioma cells to alkylating agents. For down-regulation of HR in glioma cells, we used an interference RNA (iRNA) approach targeting Rad51 and BRCA2, and for NHEJ we employed the DNA-PK inhibitor NU7026. We also assessed whether inhibition of poly(ADP)ribosyltransferase (PARP) by olaparib would enhance the killing effect. The data show that knockdown of Rad51 or BRCA2 greatly sensitizes cells to DSBs and the induction of cell death following temozolomide and nimustine (ACNU). It did not sensitize to ionizing radiation (IR). The expression of O6-methylguanine-DNA methyltransferase (MGMT) abolished all these effects, indicating that O6-alkylguanine induced by these drugs is the primary lesion responsible for the formation of DSBs and increased sensitivity of glioma cells following knockdown of Rad51 and BRCA2. Inhibition of DNA-PK only slightly sensitized to temozolomide whereas a significant effect was observed with IR. A triple strategy including siRNA and the PARP inhibitor olaparib further improved the killing effect of temozolomide. The data provides evidence that down-regulation of Rad51 or BRCA2 is a reasonable strategy for sensitizing glioma cells to killing by O6-alkylating anti-cancer drugs. The data also provide proof of principle that a triple strategy involving down-regulation of HR, PARP inhibition and MGMT depletion may greatly enhance the therapeutic effect of temozolomide