Articles of the day

New rapid diagnostic tests for neisseria meningitidis serogroups a, w135, c, and y.

S.Chanteau , S.Dartevelle , A.Elhadj , S.Djibo , P.Boisier , F.Nato


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BACKGROUND: Outbreaks of meningococcal meningitis are a major public health concern in the African "meningitis belt," which includes 21 countries from Senegal to Ethiopia. Of the several species that can cause meningitis, N. meningitidis is the most important cause of epidemics in this region. In choosing the appropriate vaccine, accurate N. meningitidis serogroup determination is key. To this end, we developed and evaluated two duplex rapid diagnostic tests for detecting N. meningitidis polysaccharide antigens of several important serogroups. METHODS AND FINDINGS: Mouse monoclonal IgG antibodies against N. meningitidis PS A, W135/Y, Y, and C were used to develop two immunochromatography duplex RDTs, RDT1 and RDT2. Standards for Reporting of Diagnostic Accuracy criteria were used to determine diagnostic accuracy of RDTs on reference strains and cerebrospinal fluid samples using culture and PCR, respectively, as reference tests. The cutoffs were 10 cfu/ml for reference strains and 1 ng/ml for PS. Sensitivities and specificities were 100% for reference strains, and 93. 8%-100% for CSF serogroups A, W135, and Y in CSF. For CSF serogroup A, the positive and negative likelihood ratios were 31. 867 and 0. 065 , respectively, and the diagnostic odds ratio was 492. 9. For CSF serogroups W135 and Y, the positive likelihood ratio was 159. 6 Both RDTs were equally reliable at 25 degrees C and 45 degrees C. CONCLUSIONS: These RDTs are important new bedside diagnostic tools for surveillance of meningococcus serogroups A and W135, the two serogroups that are responsible for major epidemics in Africa.

Scaling and dimensional analysis of acoustic streaming jets.

D.Henry , V.Botton , J.Garandet , B.Moudjed , H.Ben-Hadid


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The present paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of governing equations under the form of a non-linear hydrodynamics problem coupled with an acoustic propagation problem is revisited. To do so, a time scale discrimination approach is preferred to the usually invoked amplitude perturbations expansion. This is indeed more consistent with experimental observations of acoustic streaming flows featuring hydrodynamic non-linearities and turbulence. Experimental results are also presented together with a review of former experimental investigations concerning the power-to-velocity relationship for plane ultrasonic transducers in water. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications but a drawback for ultrasonic velocimetry.

Enhanced widely linear filtering to make quasi-rectilinear signals almost equivalent to rectilinear ones for saic/maic

P.Chevalier , R.Chauvat , J.Delmas


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Widely linear receivers have the capability to perform single antenna interference cancellation of one rectilinear or quasi-rectilinear co-channel interference , a function which is operational in global system for mobile communications handsets in particular. Moreover, SAIC technology for QR signals is still required for voice services over adaptive multi-user channels on one slot standard, a recent evolution of GSM/EDGE standard, to mitigate legacy GSM CCI in particular. It is also required for filter bank multi-carrier offset quadrature amplitude modulation networks, which are candidate for 5G mobile networks, to mitigate inter-carrier interference at reception for frequency selective propagation channels in particular. In this context, the purpose of this paper is twofold. The first one is to get more insights into the existing SAIC technology, and its extension to multiple antenna called MAIC, by showing analytically that, contrary to what is accepted as true in the literature, SAIC/MAIC implemented from standard WL filtering may be less efficient for QR signals than for R ones. From this result, the second purpose of the paper is to propose and to analyze, for QR signals and frequency selective fading channels, a SAIC/MAIC enhancement based on a three-input WL frequency shift receiver, making QR signals always almost equivalent to R ones for WL filtering in the presence of CCI. The results of the paper, completely new, may contribute to develop elsewhere new powerful WL receivers for QR signals and for both VAMOS and FBMC-OQAM networks in particular.

High-accuracy measurements on biperiodical circuits

A.D'Elia , M.Rosaria , V.Giorgio


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Coupled resonators in an assembled structure lose their individuality and in co-operation contribute to the generation of structure modes. The resonant frequencies of these modes are the only measurable quantities. In order to predict structural behaviour in a variety of cases, the problem that arises is the extraction of all the parameters characterizing the structure from the measurements mentioned here. If all the modes are confined in a bandwidth that is small with respect to the central frequency, the total coupled resonator system is well represented by a circuit of unknown lumped constants. The structure modes are the solutions of the equation obtained by equating to zero the determinant relevant to the lumped circuit representation. The equation is a polynomial of the squared frequency variable, the degree of which is equal to the number M of circuits. The analysis method described in this paper consists in varying, by an unknown amount, the frequency of a single resonator in the chain. This variation will produce a change in the frequencies of all structure modes. It is possible to find certain invariants linearly dependent on all the unchanged parameters of the circuit. These invariants have an algebraic representation that allows the extraction of the structure parameter values with extremely high accuracy. The proposed method is quite general and, in the present work, we give an example applying the method to the characterization of a side-coupled linac
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