Anti-aliasing Filter in Hybrid Filter Banks

International audienceHybrid Filter Banks allow wide-band, high frequency conversion. All existing design methods suppose that the input signal is band-limited and that each sub-band signal is sampled at 1/M times the effective Nyquist frequency of the input signal 1/T . To avoid aliasing in the sampling process, an analog anti-aliasing filter should be used in order to eliminate noise in frequency bands in which there is no signal (or a few signal) . In this paper, it is shown that this pre-filtering operation is critical and has to be done taking into account the respective power spectral densities of signal and noise due to the spectral aliasing with the sampling rate compressor. Results will be demonstrated for the design of a realistic 8 channel Hybrid Filter Bank

Digital estimation of analog imperfections using blind equalization

International audienceThe analog electronic circuits are always subject to some imperfections. Analog imperfections cause deviations from nominal values of electronic elements. In the case of Linear Time-Invariant (LTI) circuits, the coefficients of the transfer function include some deviations from related typical values leading to the differences between the typical (i.e. design) and the actual transfer functions. In this paper, the analog imperfections are digitally estimated using only the output samples, without any access to the input signal nor to the analog system (blind method). Super Exponential Algorithm (SEA) is used as the blind equalization technique, since it provides rapid convergence. The only assumption is that the input is a non-Gaussian independent and identically distributed (i.i.d.) signal. Using this algorithm, the effects of analog imperfections in the analog circuits can be digitally estimated and possibly compensated without any dependance on the types and the sources of the analog imperfections. It provides the possibility to have an online compensation of the imperfections (realization errors, drifts, etc.). The analog imperfections have been estimated with a precision of §0:2% and §1:3% for the exemplary RC and RLC circuits respectively

Hybrid Filter Bank A/D conversion systems applied to future telecommunication scenarios

Hybrid Filter Banks (HFB) A/D converters (ADC) are attractive to software-defined radio applications. Starting from a given sampling rate, they enlarge the conversion band-width. Also, it is possible to adapt the conversion characteristics (e.g. bandwidth and resolution) by software control. HFB have been studied in the context of the ANR VersaNum project. This work proposes optimal HFBs and a calibration technique to compensate the mismatch between the analog part and the digital part. Results are given for future telecommunication scenarios

Synthesis of Subband Hybrid Filter Banks ADCs with Finite Word-length Coefficients using Adaptive Equalization

International audienceSubband Hybrid Filter Banks (SHFB) ADCs are able to convert one or several narrow subbands among a given wideband signal. That provides an appropriate solution to "flexible spectrum" management for cognitive radio applications. In this paper, a SHFB ADC delivering a complex signal is considered. The optimal values of the digital coecients are obtained thanks to an adaptive equalization method. The impact of digital coecients quantization to the SHFB is studied. For a reconstruction quality target, the minimum quantization step is determined. This is validated in time and frequency domain with simulation results

Immunization enhances the natural antibody repertoire

The role of immunization in the production of antibodies directed against immunogens is widely appreciated in laboratory animals and in humans. However, the role of immunization in the development of “natural antibodies” has not been investigated. Natural antibodies are those antibodies present without known history of infection or immunization, and react to a wide range of targets, including “cryptic” self-antigens that are exposed upon cell death. In this study, the ability of immunization to elicit the production of natural antibodies in laboratory rats was evaluated. Laboratory rats were immunized with a series of injections using peanut extracts (a common allergen), a high molecular weight protein conjugated to hapten (FITC-KLH), and a carbohydrate conjugated to hapten (DNPFicall). Significantly greater binding of antibodies from immunized animals compared to controls was observed to numerous autologous organ extracts (brain, kidney, liver, lung, prostate, and spleen) for both IgM and IgG, although the effect was more pronounced for IgM. These studies suggest that immunization may have at least one unforeseen benefit, enhancing networks of natural antibodies that may be important in such processes as wound repair and tumor surveillance. Such enhancement of natural antibody function may be particularly important in Western society, where decreased exposure to the environment may be associated with a weakened natural antibody repertoire

Defining Components of the ßcatenin Destruction Complex and Exploring Its Regulation and Mechanisms of Action during Development

A subset of signaling pathways play exceptionally important roles in embryonic and post-embryonic development, and mis-regulation of these pathways occurs in most human cancers. One such pathway is the Wnt pathway. The primary mechanism keeping Wnt signaling off in the absence of ligand is regulated proteasomal destruction of the canonical Wnt effector ßcatenin (or its fly homolog Armadillo). A substantial body of evidence indicates that SCF(βTrCP) mediates βcat destruction, however, an essential role for Roc1 has not been demonstrated in this process, as would be predicted. In addition, other E3 ligases have also been proposed to destroy βcat, suggesting that βcat destruction may be regulated differently in different tissues.Here we used cultured Drosophila cells, human colon cancer cells, and Drosophila embryos and larvae to explore the machinery that targets Armadillo for destruction. Using RNAi in Drosophila S2 cells to examine which SCF components are essential for Armadillo destruction, we find that Roc1/Roc1a is essential for regulating Armadillo stability, and that in these cells the only F-box protein playing a detectable role is Slimb. Second, we find that while embryonic and larval Drosophila tissues use the same destruction complex proteins, the response of these tissues to destruction complex inactivation differs, with Armadillo levels more elevated in embryos. We provide evidence consistent with the possibility that this is due to differences in armadillo mRNA levels. Third, we find that there is no correlation between the ability of different APC2 mutant proteins to negatively regulate Armadillo levels, and their recently described function in positively-regulating Wnt signaling. Finally, we demonstrate that APC proteins lacking the N-terminal Armadillo-repeat domain cannot restore Armadillo destruction but retain residual function in negatively-regulating Wnt signaling.We use these data to refine our model for how Wnt signaling is regulated during normal development

Philosophy with children : facilitating children's voices on childhood

Increasingly there is a search for participatory research methods that work to ensure children’s authentic voices are heard. In this presentation we will propose that Philosophy with Children might be employed as a research method that facilitates children’s participation and voice in research. Further, it may also impact positively in children’s wider participation and engagement in recognising children’s agency and conceptual autonomy. We will discuss the advantages of using philosophical dialogue as a method for collecting data and will also consider challenges that arise from using Philosophy with Children as a research tool. In discussing the challenges and opportunities afforded by such a method, the presentation will draw on two studies to exemplify the approach. One study explored what kind of society children want to live in, and the second is an on-going international study that aims to explore children’s conceptions of child/childhood. We will also suggest that using Philosophy with Children might be considered as addressing the need for rights-based approaches to research as in affording children ownership of the dialogue it does not assume children as deficient in their capacities and it recognises children’s particular perspectives on the world. In addition, we will suggest that using a philosophical approach to gathering children’s views might offer a deeper insight into their thinking of and understanding about the world. Elements of the approaches used in the study will be discussed in order to gauge the strengths and limitations of using practical philosophy as a means of gathering data in subsequent analysis. In juxtaposition to the Philosophy with Children approach discussed, we will comment briefly on the use of an alternative research method, Nominal Group Technique, which was also used in the first project. In comparing the two approaches we aim to show where Philosophy with Children may provide richer and deeper evidence when seeking children’s views. While the presentation will not share the findings of either of the projects mentioned above, the approach taken in using Philosophy with Children as a research method, relates strongly to the findings of the initial project and the goals of the Children’s Voices on Childhood project. In using Philosophy with Children, it will be proposed that, while there may be some limitations in using the approach, it takes account of children’s voices in research; it affords opportunities to explore children’s conceptual thinking and the application to ‘real life’; it allows children to have ownership of the topic under consideration; and it potentially leads to addressing children’s status in wider society

CD1d-restricted NKT cells: an interstrain comparison

CD1d-restricted Va14-Ja281 invariant abTCR1 (NKT) cells are well defined in the C57BL/6 mouse strain, but they remain poorly characterized in non-NK1.1-expressing strains. Surrogate markers for NKT cells such as abTCR1CD42CD82 and DX51CD31 have been used in many studies, although their effectiveness in defining this lineage remains to be verified. Here, we compare NKT cells among C57BL/6, NK1.1-congenic BALB/c, and NK1.1-congenic nonobese diabetic mice. NKT cells were identified and compared using a range of approaches: NK1.1 expression, surrogate phenotypes used in previous studies, labeling with CD1d/a-galactosylceramide tetramers, and cytokine production. Our results demonstrate that NKT cells and their CD4/CD8-defined subsets are present in all three strains, and confirm that nonobese diabetic mice have a numerical and functional deficiency in these cells. We also highlight the hazards of using surrogate phenotypes, none of which accurately identify NKT cells,and one in particular (DX51CD31) actually excludes these cells. Finally, our results support the concept that NK1.1 expression may not be an ideal marker for CD1d-restricted NKT cells, many of which are NK1.1-negative, especially within the CD41 subset and particularly in NK1.1-congenic BALB/c mice

RNA helicase Belle/DDX3 regulates transgene expression in Drosophila

Belle (Bel), the Drosophila homolog of the yeast DEAD-box RNA helicase DED1 and human DDX3, has been shown to be required for oogenesis and female fertility. Here we report a novel role of Bel in regulating the expression of transgenes. Abrogation of Bel by mutations or RNAi induces silencing of a variety of P-element-derived transgenes. This silencing effect depends on downregulation of their RNA levels. Our genetic studies have revealed that the RNA helicase Spindle-E (Spn-E), a nuage RNA helicase that plays a crucial role in regulating RNA processing and PIWI-interacting RNA (piRNA) biogenesis in germline cells, is required for loss-of-bel-induced transgene silencing. Conversely, Bel abrogation alleviates the nuage-protein mislocalization phenotype in spn-E mutants, suggesting a competitive relationship between these two RNA helicases. Additionally, disruption of the chromatin remodeling factor Mod(mdg4) or the microRNA biogenesis enzyme Dcr-1 also rescued the transgene-silencing phenotypes in bel mutants, suggesting the involvement of chromatin remodeling and microRNA biogenesis in loss-of-bel-induced transgene silencing. Finally we showed that genetic inhibition of Bel function led to the de novo generation of piRNAs from the transgene region inserted in the genome, suggesting a potential piRNA-dependent mechanism that may mediate transgene silencing as Bel function is inhibited. Our findings have demonstrated a novel involvement of Bel in regulating transgene expression and its loss triggers a transgene silencing mechanism mediated by protein regulators implicated in RNA processing, piRNA biogenesis, chromatin remodeling and the microRNA pathway

Enduring mental health: Prevalence and prediction.

We review epidemiological evidence indicating that most people will develop a diagnosable mental disorder, suggesting that only a minority experience enduring mental health. This minority has received little empirical study, leaving the prevalence and predictors of enduring mental health unknown. We turn to the population-representative Dunedin cohort, followed from birth to midlife, to compare people never-diagnosed with mental disorder (N = 171; 17% prevalence) to those diagnosed at 1–2 study waves, the cohort mode (N = 409). Surprisingly, compared to this modal group, never-diagnosed Study members were not born into unusually well-to-do families, nor did their enduring mental health follow markedly sound physical health, or unusually high intelligence. Instead, they tended to have an advantageous temperament/personality style, and negligible family history of mental disorder. As adults, they report superior educational and occupational attainment, greater life satisfaction, and higher-quality relationships. Our findings draw attention to “enduring mental health” as a revealing psychological phenotype and suggest it deserves further study