High frequency electro-optic measurement of strained silicon racetrack resonators

The observation of the electro-optic effect in strained silicon waveguides has been considered as a direct manifestation of an induced $\chi^{(2)}$ non-linearity in the material. In this work, we perform high frequency measurements on strained silicon racetrack resonators. Strain is controlled by a mechanical deformation of the waveguide. It is shown that any optical modulation vanishes independently of the applied strain when the applied voltage varies much faster than the carrier effective lifetime, and that the DC modulation is also largely independent of the applied strain. This demonstrates that plasma carrier dispersion is responsible for the observed electro-optic effect. After normalizing out free carrier effects, our results set an upper limit of $8\,pm/V$ to the induced high-speed $\chi^{(2)}_{eff,zzz}$ tensor element at an applied stress of $-0.5\,GPa$. This upper limit is about one order of magnitude lower than the previously reported values for static electro-optic measurements

Fabrication tolerant high-speed SiP ring modulators and optical add-drop multiplexers for WDM applications

Silicon ring resonator modulators (RRMs) have great potential to reduce footprint and power consumption and to increase modulation speeds in wavelength division multiplexed (WDM) transmitters. However, the optical properties of RRMs are highly sensitive to fabrication variations, which makes them challenging to design for volume production or a large number of WDM-channels. In this work, we present an RRM design that was specifically designed and experimentally validated to have reduced sensitivity to fabrication variations. This includes a sensitivity analysis of resist over- and under-exposure (±30 nm lateral dimension deviation) and of etch depth variability (±10 nm depth variation) within the coupling section. For our design, the deviation from the targeted coupling strength is improved twofold. The proposed devices are fabricated on SOI wafers using a standard CMOS-compatible process. We demonstrate RRMs with an extinction ratio above 5 dB, an OMA better that -7 dB (at 2 Vpp) and a 29 GHz electro-optical bandwidth, showing open eye diagrams at 32 Gb/s limited only by our measurement setup. The measured coupling coefficients are in good agreement with the simulated values. Furthermore, we applied the same design modifications to realize low-doped RRMs as well as ring based adddrop-multiplexers (OADMs). The agreement between the simulated and the measured coupling coefficients (that we identified as the main source of device performance variability) further confirms the effectiveness of our design modifications. These results suggest that the proposed design can be exploited to enable reliable fabrication of resonantbased devices on a large scale, especially in WDM systems

Power-efficient lumped-element meandered silicon Mach-Zehnder modulators

Driving electro-optic modulators in lumped-element (LE) configuration allows for small footprint, reduced power consumption, and improved high-speed performance. The main shortcoming of conventional rectilinear LE modulators are the required high drive-voltages, resulting from their shortened phase-shifters. To address this, we introduce a Mach-Zehnder modulator with meandered phase shifters (M-MZM), which can be driven in LE configuration, while keeping the optical phase shifter length in the same order as traveling-wave modulators (TW-MZMs). A design limitation that needs to be taken into account consists in the optical transit time of the device, that limits the overall electro-optic bandwidth. First, we review the overall power consumption improvement as well as the bandwidth enhancement in LE modulators compared to TW-MZMs, also taking the driver output impedance and parasitics from wire- or bump-bonds into account. Then, we report on the design, implementation, and experimental characterization of carrier-depletion based M-MZMs fabricated on silicon-on-insulator (SOI) wafers using standard CMOS-compatible processes. The fabricated M-MZMs, provided with low (W1), moderately (W2) and highly (W3) doped junctions, require 9.2 Vpp, 5.5 Vpp, and 3.7 Vpp for full extinction, with optical insertion losses of 5 dB, 6.3 dB and 9.1 dB. For all three M-MZMs, open eye diagrams are recorded at 25 Gb/s using a 50Ω driver and termination. For unterminated M-MZMs, higher data rates could be achieved, provided that a low output impedance driver be wire- or bump-bonded to the modulators. Finally, we compare the power consumption of the M-MZMs with TW-MZMs and show that the M-MZMs feature a 4X reduced power consumption at 25 Gb/s

Design of a high-speed germanium-tin absorption modulator at mid-infrared wavelengths

We propose a high-speed electro-absorption modulator based on a direct bandgap Ge0.875Sn0.125 alloy operating at mid-infrared wavelengths. Enhancement of the Franz-Keldysh-effect by confinement of the applied electric field to GeSn in a reverse-biased junction results in 3.2dB insertion losses, a 35GHz bandwidth and a 6dB extinction ratio for a 2Vpp drive signal

Evolutionary distances in the twilight zone -- a rational kernel approach

Phylogenetic tree reconstruction is traditionally based on multiple sequence alignments (MSAs) and heavily depends on the validity of this information bottleneck. With increasing sequence divergence, the quality of MSAs decays quickly. Alignment-free methods, on the other hand, are based on abstract string comparisons and avoid potential alignment problems. However, in general they are not biologically motivated and ignore our knowledge about the evolution of sequences. Thus, it is still a major open question how to define an evolutionary distance metric between divergent sequences that makes use of indel information and known substitution models without the need for a multiple alignment. Here we propose a new evolutionary distance metric to close this gap. It uses finite-state transducers to create a biologically motivated similarity score which models substitutions and indels, and does not depend on a multiple sequence alignment. The sequence similarity score is defined in analogy to pairwise alignments and additionally has the positive semi-definite property. We describe its derivation and show in simulation studies and real-world examples that it is more accurate in reconstructing phylogenies than competing methods. The result is a new and accurate way of determining evolutionary distances in and beyond the twilight zone of sequence alignments that is suitable for large datasets.Comment: to appear in PLoS ON

Outcome of Occupational Latex Allergy—Work Ability and Quality of Life

OBJECTIVE: The quality of life (QOL) and work ability of health care workers allergic to natural rubber latex (NRL) were assessed after implementation of regulations on powder-free NRL gloves in Germany. METHODS: 196 HCW with reported NRL allergy answered a questionnaire (response rate 58%) containing the Work Ability Index (WAI), Mini Asthma Quality of Life Questionnaire (MiniAQLQ), and Dermatology Life Quality Index (DLQI). RESULTS: 63.2% still had NRL-related symptoms during the last 6 month. However on a scale from 0 to 10, the intensity of NRL-related symptoms decreased from 8.5 before to 2.3 after implementation of regulations on powder-free NRL gloves. A higher number of subjects were able to avoid NRL in the private than in the work environment (85% vs. 61%). NRL-related symptoms decreased and WAI increased with successful avoidance of NRL at workplace (b = 0.23, p = 0.003). QOL was only little affected by NRL allergy (mean: MiniAQLQ = 6.0; DLQI = 4.1). CONCLUSIONS: Although there was improvement after implementation of powder-free NRL gloves, there is still a considerable number of HCW with NRL-related symptoms. Further investigations on latex avoidance and the cause of persisiting allergic symptoms in HCW with NRL allergy are therefore needed

The Airway Microbiota in Cystic Fibrosis: A Complex Fungal and Bacterial Community—Implications for Therapeutic Management

International audienceBackground Given the polymicrobial nature of pulmonary infections in patients with cystic fibrosis (CF), it is essential to enhance our knowledge on the composition of the microbial community to improve patient management. In this study, we developed a pyrosequencing approach to extensively explore the diversity and dynamics of fungal and prokaryotic populations in CF lower airways. Methodology and Principal Findings Fungi and bacteria diversity in eight sputum samples collected from four adult CF patients was investigated using conventional microbiological culturing and high-throughput pyrosequencing approach targeting the ITS2 locus and the 16S rDNA gene. The unveiled microbial community structure was compared to the clinical profile of the CF patients. Pyrosequencing confirmed recently reported bacterial diversity and observed complex fungal communities, in which more than 60% of the species or genera were not detected by cultures. Strikingly, the diversity and species richness of fungal and bacterial communities was significantly lower in patients with decreased lung function and poor clinical status. Values of Chao1 richness estimator were statistically correlated with values of the Shwachman-Kulczycki score, body mass index, forced vital capacity, and forced expiratory volume in 1 s (p = 0.046, 0.047, 0.004, and 0.001, respectively for fungal Chao1 indices, and p = 0.010, 0.047, 0.002, and 0.0003, respectively for bacterial Chao1 values). Phylogenetic analysis showed high molecular diversities at the sub-species level for the main fungal and bacterial taxa identified in the present study. Anaerobes were isolated with Pseudomonas aeruginosa, which was more likely to be observed in association with Candida albicans than with Aspergillus fumigatus

Early incidence of occupational asthma among young bakers, pastry-makers and hairdressers: design of a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>Occupational exposures are thought to be responsible for 10-15% of new-onset asthma cases in adults, with disparities across sectors. Because most of the data are derived from registries and cross-sectional studies, little is known about incidence of occupational asthma (OA) during the first years after inception of exposure. This paper describes the design of a study that focuses on this early asthma onset period among young workers in the bakery, pastry making and hairdressing sectors in order to assess early incidence of OA in these "at risk" occupations according to exposure duration, and to identify risk factors of OA incidence.</p> <p>Methods/Design</p> <p>The study population is composed of subjects who graduated between 2001 and 2006 in these sectors where they experience exposure to organic or inorganic allergenic or irritant compounds (with an objective of 150 subjects by year) and 250 young workers with no specific occupational exposure. A phone interview focusing on respiratory and 'Ear-Nose-Throat' (ENT) work-related symptoms screen subjects considered as "possibly OA cases". Subjects are invited to participate in a medical visit to complete clinical and lung function investigations, including fractional exhaled nitric oxide (FE_NO) and carbon monoxide (CO) measurements, and to collect blood samples for IgE (Immunoglobulin E) measurements (total IgE and IgE for work-related and common allergens). Markers of oxidative stress and genetic polymorphisms exploration are also assessed. A random sample of 200 "non-cases" (controls) is also visited, following a nested case-control design.</p> <p>Discussion</p> <p>This study may allow to describ a latent period between inception of exposure and the rise of the prevalence of asthma symptoms, an information that would be useful for the prevention of OA. Such a time frame would be suited for conducting screening campaigns of this emergent asthma at a stage when occupational hygiene measures and adapted therapeutic interventions might be effective.</p> <p>Trial registration</p> <p>Clinical trial registration number is NCT01096537.</p

EAACI position paper on occupational rhinitis

The present document is the result of a consensus reached by a panel of experts from European and non-European countries on Occupational Rhinitis (OR), a disease of emerging relevance which has received little attention in comparison to occupational asthma. The document covers the main items of OR including epidemiology, diagnosis, management, socio-economic impact, preventive strategies and medicolegal issues. An operational definition and classification of OR tailored on that of occupational asthma, as well as a diagnostic algorithm based on steps allowing for different levels of diagnostic evidence are proposed. The needs for future research are pointed out. Key messages are issued for each item

Internal Transcribed Spacer 2 (nu ITS2 rRNA) Sequence-Structure Phylogenetics: Towards an Automated Reconstruction of the Green Algal Tree of Life

L). Some have advocated the use of the nuclear-encoded, internal transcribed spacer two (ITS2) as an alternative to the traditional chloroplast markers. However, the ITS2 is broadly perceived to be insufficiently conserved or to be confounded by introgression or biparental inheritance patterns, precluding its broad use in phylogenetic reconstruction or as a DNA barcode. A growing body of evidence has shown that simultaneous analysis of nucleotide data with secondary structure information can overcome at least some of the limitations of ITS2. The goal of this investigation was to assess the feasibility of an automated, sequence-structure approach for analysis of IT2 data from a large sampling of phylum Chlorophyta.Sequences and secondary structures from 591 chlorophycean, 741 trebouxiophycean and 938 ulvophycean algae, all obtained from the ITS2 Database, were aligned using a sequence structure-specific scoring matrix. Phylogenetic relationships were reconstructed by Profile Neighbor-Joining coupled with a sequence structure-specific, general time reversible substitution model. Results from analyses of the ITS2 data were robust at multiple nodes and showed considerable congruence with results from published phylogenetic analyses.Our observations on the power of automated, sequence-structure analyses of ITS2 to reconstruct phylum-level phylogenies of the green algae validate this approach to assessing diversity for large sets of chlorophytan taxa. Moreover, our results indicate that objections to the use of ITS2 for DNA barcoding should be weighed against the utility of an automated, data analysis approach with demonstrated power to reconstruct evolutionary patterns for highly divergent lineages