A new approach to the authentication of goldwork

The study of goldwork encompasses several large fields of investigations. Scientific analyses can respond to questions concerning production techniques, provenance and preservation. However, what about authentication? This type of works of art generally has very high prices, leading to an increase in the number of forgeries. Today, fakes can imitate artworks produced by most civilisations and with different origins. Moreover, most of the objects we analyse cannot be submitted to destructive sampling. That is the reason why we employ external-beam PIXE for the analysis of such objects, a method able to offer reliable and non-intrusive scientific investigations. Our methodology consists of two steps, which, in their combination, provide information about the chronological compatibility of the objects with their presumed period. First, an optical and electronic microscope investigation allows us to identify tool marks, weathering features, to reveal traditional or fraudulent surface treatments, and to characterise superficial deposits. This first approach is able to identify bad quality fakes. However, these analyses are generally insufficient to establish the authentication of the objects. That is why we also perform external-beam PIXE analyses on goldwork. Thus, the qualitative and quantitative studies of trace elements are able to provide insights into metallurgical methods and the fineness of alloys. This paper describes our methodology and presents different examples of its application, including the discussion of specific problems encountered in the analysis of this type of objects.Les objets en or sont étudiés par des approches très diverses, et parmi celles-ci les analyses scientifiques répondent généralement à des problématiques concernant la recherche des techniques de fabrication ou l’étude de provenance et de conservation. Mais, qu’en est-il de l’authentification ? Ce type d’objets d’art étant en effet d’une valeur marchande élevée, ils sont de plus en plus souvent sujets à des contrefaçons, qui imitent aujourd’hui la plupart des styles et des civilisations. Les investigations scientifiques doivent être absolument non destructive et la technique PIXE en faisceau extrait est alors idéale pour ce type d’expertise. Nous avons ainsi développé une méthodologie qui nous fournira un faisceau d’indices qui sera compatible ou pas avec l’ancienneté présumée de l’objet. En premier lieu, l’examen par microscopie optique et électronique permet d’identifier les traces d’outils, les figures de corrosion, de révéler si l’objet a subi des traitements de surface anciens ou modernes et de caractériser la nature des dépôts superficiels. Ce premier niveau d’investigation permet d’écarter les faux flagrants ou de mauvaise qualité. Toutefois, cette étude est généralement insuffisante pour établir l’ancienneté d’un objet en or. C’est pourquoi, nous réalisons en complément une étude par PIXE en faisceau extrait qui détermine la composition en éléments traces, eux-mêmes révélateurs des méthodes métallurgiques et de la pureté des alliages. Ce texte décrit cette méthodologie et présente différents exemples d’application en précisant les problèmes auxquels nous avons été confrontés sur les différents types d’objets rencontrés

Propriétés optiques de nanoparticules de cuivre et d'argent dans des matrices silicatées (application aux archéomatériaux)

BORDEAUX3-BU Lettres-Pessac (335222103) / SudocBORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Emergence of vancomycin-intermediate Staphylococcus aureus in a Belgian hospital: microbiological and clinical features.

In 1999, all clinical Staphylococcus aureus isolates from patients admitted to a Belgian University hospital were tested for decreased vancomycin susceptibility. Three vancomycin-intermediate Staphylococcus aureus (VISA) and four hetero-VISA strains were detected among 2145 isolates tested. They emerged from strains that belonged to locally endemic methicillin-resistant S. aureus (MRSA) genotypes in three patients who had received repeated courses of vancomycin therapy. A cystic fibrosis patient with MRSA/VISA-associated broncho-pulmonary exacerbation was successfully treated by continuous vancomycin infusion plus fusidic acid followed by oral minocycline-fusidic acid. Two other patients had VISA recovered from specimens of undetermined clinical significance. Emergence of VISA variants of endemic MRSA strains in Belgium warrants active microbiological surveillance and careful monitoring of vancomycin therapy. Therapy with high-dose vancomycin administered by continuous infusion in combination with other antimicrobials may be a therapeutic option worth investigating for VISA infection.Case ReportsJournal Articleinfo:eu-repo/semantics/publishe

Multiscale Compact Modelling of UTC-Photodiodes Enabling Monolithic Terahertz Communication Systems Design

International audienceDue to the continuous increase in data traffic, it is becoming imperative to develop communication systems capable of meeting the throughput requirements. Monolithic Opto-Electronic Integrated Circuits (OEICs) are ideal candidates to meet these demands. With that in mind, we propose a compact and computationally efficient model for Uni-Traveling Carrier Photodiodes (UTC-PDs) which are a key component of OEICs because of their high bandwidth and RF output power. The developed compact model is compatible with existing SPICE design software, enabling the design of beyond 5G and terahertz (THz) communication circuits and systems. By introducing detailed physical equations describing, in particular, the dark current, the intrinsic series resistance, and the junction capacitance, the model accurately captures the physical characteristics of the UTC-PD. The model parameter extraction follows a scalable extraction methodology derived from that of the bipolar and CMOS technologies. A detailed description of the de-embedding process is presented. Excellent agreement between the compact model and measurements has been achieved, showing model versatility across various technologies and scalability over several geometries

Carfilzomib maintenance in newly diagnosed non-transplant eligible multiple myeloma

International audienc