Réalisation de structures optiques verticales en verres de chalcogénure pour des applications dans le proche et moyen infrarouge

National audienceDes structures verticales que sont des miroirs de Bragg et des microcavités ont été élaborées en verres de chalcogénure. Une étude préliminaire a permis d'étudier l'indice de réfraction des différentes couches de verres massifs de chalcogénure ainsi que la vitesse de formation de ces couches déposées par PLD. L'objectif de ce travail est de réaliser des microcavités actives en dopant la couche séparatrice par des ions Erbium émettant à 1,53 et à 4,65 µm

Manipulation and Optical Detection of Colloidal Functional Plasmonic Nanostructures in Microfluidic Systems

The very strong optical resonances of plasmonic nanostructures can be harnessed for sensitive detection of chemical and biomolecular analytes in small volumes. Here we describe an approach towards optical biosensing in microfluidic systems using plasmonic structures (functionalized gold nanoparticles) in colloidal suspension. The plasmonic nanoparticles provide the optical signal, in the form of resonant light scattering or absorption, and the microfluidic environment provides means for selectively manipulating the nanoparticles through fluid dynamics and electric fields. In the first part we discuss recent literature on functionalized colloidal particles and the methods for handling them in microfluidic systems. Then we experimentally address aspects of nanoparticle functionalization, detection through plasmonic resonant light scattering under dark-field illumination and the electrokinetic behavior of the particles under the action of an alternating electric field

Forensic Identification of Condom Lubricants by Advanced Statistical Analysis Processing of Direct Analysis in Real Time Mass Spectrometric Data – Towards Development of a Condom Residue Database for Forensic Science Practitioners

The ability to identify condom derived trace evidence is gaining importance because of the increasing frequency with which perpetrators of sexual assault use condoms in order to avoid leaving behind incriminating DNA evidence that might link them to the crime. Although DNA remains the gold standard for sexual assault evidence, other forms of trace evidence are needed in its absence. When condoms are used, the lubricants associated with them are the trace evidence. For the lubricant residue to be useful in a forensics context, a database of chemical signatures of lubricants against which acquired evidence can be screened is required, so that condom brands and types can be identified from the trace evidence. Towards the goal of developing such a database, this study used direct analysis in real time-high resolution mass spectrometry (DART-HRMS) to analyze 110 different types of condoms representing 16 brands. Over 700 spectra were acquired, each serving as a chemical fingerprint for the analyzed condom. The results showed that condoms of the same type within different brands exhibited the same chemical signatures, which differed from condoms of other brands, even when the condoms were advertised to have the same characteristics. For example, the mint flavored condoms of different brands had distinct diagnostic chemical signatures that allowed them to be distinguished from one another, even though they all contained the same chemical components that conferred the mint flavor. Both supervised and unsupervised multivariate statistical analyses were performed on the data. Hierarchical clustering analysis (unsupervised) showed that condoms could be differentiated by brand. Kernel discriminant analysis (supervised) showed that condoms within a given brand could be distinguished. The observed leave-one-out cross validation was 90-100% depending upon the brand. This indicates that a strong database has been developed with the capability of serving as a presumptive test that can be used not only to identify brands, but also the particular condom type within a brand. This database can be readily expanded as additional condom types emerge, and may be particularly useful for corroborating the accounts of victims, or exonerating the falsely accused in cases where DNA evidence is lacking. The positive brand identification of unknown condom residues implies that the database could serve as a tool to assist forensic science practitioners in prosecuting sexual assault cases

Tuberculosis Microepidemics among Dispersed Migrants, Birmingham, UK, 2004-2013

MIRU-VNTR typing was supported by the Public Health England National TB Strain Typing Project. M.M. is funded by the UK Clinical Research Collaboration Modernising Medical Microbiology Consortium. C.B. is funded by the Heart of Birmingham Primary Care Trust and Public Health England

Two new rapid SNP-typing methods for classifying Mycobacterium tuberculosis complex into the main phylogenetic lineages

There is increasing evidence that strain variation in Mycobacterium tuberculosis complex (MTBC) might influence the outcome of tuberculosis infection and disease. To assess genotype-phenotype associations, phylogenetically robust molecular markers and appropriate genotyping tools are required. Most current genotyping methods for MTBC are based on mobile or repetitive DNA elements. Because these elements are prone to convergent evolution, the corresponding genotyping techniques are suboptimal for phylogenetic studies and strain classification. By contrast, single nucleotide polymorphisms (SNP) are ideal markers for classifying MTBC into phylogenetic lineages, as they exhibit very low degrees of homoplasy. In this study, we developed two complementary SNP-based genotyping methods to classify strains into the six main human-associated lineages of MTBC, the 'Beijing' sublineage, and the clade comprising Mycobacterium bovis and Mycobacterium caprae. Phylogenetically informative SNPs were obtained from 22 MTBC whole-genome sequences. The first assay, referred to as MOL-PCR, is a ligation-dependent PCR with signal detection by fluorescent microspheres and a Luminex flow cytometer, which simultaneously interrogates eight SNPs. The second assay is based on six individual TaqMan real-time PCR assays for singleplex SNP-typing. We compared MOL-PCR and TaqMan results in two panels of clinical MTBC isolates. Both methods agreed fully when assigning 36 well-characterized strains into the main phylogenetic lineages. The sensitivity in allele-calling was 98.6% and 98.8% for MOL-PCR and TaqMan, respectively. Typing of an additional panel of 78 unknown clinical isolates revealed 99.2% and 100% sensitivity in allele-calling, respectively, and 100% agreement in lineage assignment between both methods. While MOL-PCR and TaqMan are both highly sensitive and specific, MOL-PCR is ideal for classification of isolates with no previous information, whereas TaqMan is faster for confirmation. Furthermore, both methods are rapid, flexible and comparably inexpensive

Diffraction techniques and vibrational spectroscopy opportunities to characterise bones

From a histological point of view, bones that allow body mobility and protection of internal organs consist not only of different organic and inorganic tissues but include vascular and nervous elements as well. Moreover, due to its ability to host different ions and cations, its mineral part represents an important reservoir, playing a key role in the metabolic activity of the organism. From a structural point of view, bones can be considered as a composite material displaying a hierarchical structure at different scales. At the nanometre scale, an organic part, i.e. collagen fibrils and an inorganic part, i.e. calcium phosphate nanocrystals are intimately mixed to assure particular mechanical properties

Global Origin of Mycobacterium tuberculosis in the Midlands, UK

DNA fingerprinting data for 4,207 Mycobacterium tuberculosis isolates were combined with data from a computer program (Origins). Largest population groups were from England (n = 1,031) and India (n = 912), and most prevalent strains were the Euro-American (45%) and East African–Indian (34%) lineages. Combining geographic and molecular data can enhance cluster investigation

A Virtual Testing Approach for Laminated Composites Based on Micromechanics

International audienceThe chapter deals with a crucial question for the design of composite structures: how can one predict the evolution of damage up to and including final fracture? Virtual testing, whose goal is to drastically reduce the huge number of industrial tests involved in current characterization procedures, constitutes one of today’s main industrial challenges. In this work, one revisits our multiscale modeling answer through its practical aspects. Some complements regarding identification, kinking, and crack initiation are also given. Finally, the current capabilities and limits of this approach are discussed, as well as the computational challenges that are inherent to “Virtual Structural Testing.