Sandwich patch with thermoviscous fluid core, for increasing damping of panels

International audienceThe introduction of a thermo-Viscous Fluid (TVF) between two skins, produces a sandwich with high dissipation. This was studied by Hussain and Guyader [An equivalent plate model for sandwich panels with thermoviscous fluid core, J. Vibration Acoustics, ASME trans., 031007 (2012)] leading to equivalent material properties depending on skins and fluid core properties. An important result is that contrary to standard sandwich panels with polymers cores, the damping loss factor of such TVF sandwich is constant with frequency. When applying damping treatment on structures, bonded patches are generally used. In this paper the use of TVF sandwich patches on a panel is described through a model of heterogeneous plate, the predicted vibration response of the structure shows an increase of damping due to the patch. Estimation of modal damping loss factors for the plate with TVF sandwich patches are given depending on the patch size and TVF thickness

A methodology for including the effect of a damping treatment in the mid-frequency domain using SmEdA method

International audienceAn additive damping treatment is an effective tool to control the dynamic response of built-up structures, and it is widely utilized through industrial applications. By applying a viscoelastic layer on a given structure, the vibratory energy is dissipated through shear and in-plane motions at the layer interface. Modeling the effect of such a treatment in a complex mechanical system for the mid frequency domain is of interest. Statistical modal Energy distribution Analysis (SmEdA) has been developed as an alternative approach to Statistical Energy Analysis (SEA) for describing subsystems with low modal overlap. This technique is developed from the knowledge of the uncoupled subsystem modes. In this paper, one proposes to extend SmEdA by including the effect of a damping treatment. A damped subsystem consisting of a composite layer is modeled with the equivalent modulus of a single layer, which gives the same transverse displacement as a multi-layered system. The modal loss factor of a partially damped structure is estimated by the Modal Strain Energy method (MSE), and the results are well agreed with the Complex Eigenvalue Method (CEM). Finally, energy transmission between the damped structure and a coupled cavity can be deduced from SmEdA modeling, knowing the modeshapes and modal loss factors of the equivalent single layer and of the cavity. This method is applied for modeling a rectangular plate partially damped with an unconstrained viscoleastic layer coupled to a small acoustic cavity

The antibacterial activity of peptide dendrimers and polymyxin B increases sharply above pH 7.4

pH-activity profiling reveals that antimicrobial peptide dendrimers (AMPDs) kill Klebsiella pneumoniae and Methicillin-resistant Staphylococcus aureus (MRSA) at pH = 8.0, against which they are inactive at pH = 7.4, due to stronger electrostatic binding to bacterial cells at higher pH. A similar effect occurs with polymyxin B and might be general for polycationic antimicrobials

Thiopurine withdrawal during sustained clinical remission in inflammatory bowel disease: relapse and recapture rates, with predictive factors in 237 patients

Background: Thiopurines (azathioprine and mercaptopurine) remain integral to most medical strategies for maintaining remission in Crohn's disease (CD) and ulcerative colitis (UC). Indefinite use of these drugs is tempered by long-term risks. While clinical relapse is noted frequently following drug withdrawal, there are few published data on predictive factors. Aim: To investigate the success of planned thiopurine withdrawal in patients in sustained clinical remission to identify rates and predictors of relapse. Methods: This was a multicentre retrospective cohort study from 11 centres across the UK. Patients included had a definitive diagnosis of IBD, continuous thiopurine use ≥3 years and withdrawal when in sustained clinical remission. All patients had a minimum of 12 months follow-up post drug withdrawal. Primary and secondary end points were relapse at 12 and 24 months respectively. Results: 237 patients were included in the study (129 CD; 108 UC). Median duration of thiopurine use prior to withdrawal was 6.0 years (interquartile range 4.4–8.4). At follow-up, moderate/severe relapse was observed in 23% CD and 12% UC patients at 12 months, 39% CD and 26% UC at 24 months. Relapse rate at 12 months was significantly higher in CD than UC (P = 0.035). Elevated CRP at withdrawal was associated with higher relapse rates at 12 months for CD (P = 0.005), while an elevated white cell count was predictive at 12 months for UC (P = 0.007). Conclusion: Thiopurine withdrawal in the context of sustained remission is associated with a 1-year moderate-to-severe relapse rate of 23% in Crohn's disease and 12% in ulcerative colitis

Effect of Surface and Bulk Properties of Mesoporous Carbons on the Electrochemical Behavior of GOx-Nanocomposites

Biofuel cell (BFC) electrodes are typically manufactured by combining enzymes that act as catalysts with conductive carbon nanomaterials in a form of enzyme-nanocomposite. However, a little attention has been paid to effects of the carbon nanomaterials' structural properties on the electrochemical performances of the enzyme-nanocomposites. This work aims at studying the effects of surface and bulk properties of carbon nanomaterials with different degrees of graphitization on the electrochemical performances of glucose oxidase (GOx)-nanocomposites produced by immobilizing GOx within a network of carbon nanopaticles. Two types of carbon nanomaterials were used: graphitized mesoporous carbon (GMC) and purified mesoporous carbon (PMC). Graphitization index, surface functional groups, hydrophobic properties, and rate of aggregation were measured for as-received and acid-treated GMC and PMC samples by using Raman spectrometry, X-ray photoelectron spectroscopy (XPS), contact angle measurement, and dynamic light scattering (DLS), respectively. In addition to these physical property characterizations, the enzyme loading and electrochemical performances of the GOx-nanocomposites were studied via elemental analysis and cyclic voltammetry tests, respectively. We also fabricated BFCs using our GOx-nanocomposite materials as the enzyme anodes, and tested their performances by obtaining current-voltage (IV) plots. Our findings suggest that the electrochemical performance of GOx-nanocomposite material is determined by the combined effects of graphitization index, electrical conductivity and surface chemistry of carbon nanomaterials

Pragmatic economic valuation of adaptation risk and responses across scales Case study in Vietnam

Vietnam is one of the countries particularly vulnerable to climate change. Increased temperatures, increased salinity intrusion due to sea-level rise and altering precipitation patterns significantly affect livelihood options of smallholder farmers, resulting in losses in agricultural production. These impacts are projected to become increasingly severe, hence, adaptation to climate change and sensitivity needs to be assessed and adaptation measures taken. This study provides a vulnerability assessment based on the results for exposure, sensitivity and adaptive capacity. This includes present and projected future climatic conditions and hazards, crop suitability analyses and socioeconomic assessments on a district scale. In addition, a case study is presented focusing on the two provinces of Tra Vinh and Ben Tre, identified as highly vulnerable in the Mekong Delta area. The case study shows opportunities, economic trade-offs and barriers of adoption of climate-smart agriculture (CSA) practices to adapt to progressive climate change

Population genomics of domestic and wild yeasts

The natural genetics of an organism is determined by the distribution of sequences of its genome. Here we present one- to four-fold, with some deeper, coverage of the genome sequences of over seventy isolates of the domesticated baker's yeast, _Saccharomyces cerevisiae_, and its closest relative, the wild _S. paradoxus_, which has never been associated with human activity. These were collected from numerous geographic locations and sources (including wild, clinical, baking, wine, laboratory and food spoilage). These sequences provide an unprecedented view of the population structure, natural (and artificial) selection and genome evolution in these species. Variation in gene content, SNPs, indels, copy numbers and transposable elements provide insights into the evolution of different lineages. Phenotypic variation broadly correlates with global genome-wide phylogenetic relationships however there is no correlation with source. _S. paradoxus_ populations are well delineated along geographic boundaries while the variation among worldwide _S. cerevisiae_ isolates show less differentiation and is comparable to a single _S. paradoxus_ population. Rather than one or two domestication events leading to the extant baker's yeasts, the population structure of _S. cerevisiae_ shows a few well defined geographically isolated lineages and many different mosaics of these lineages, supporting the notion that human influence provided the opportunity for outbreeding and production of new combinations of pre-existing variation

Student Development at the Boundaries: Makerspaces as Affordances for Engineering Students’ Development

University-based makerspaces are receiving increasing attention as promising innovations that may contribute to the development of future engineers. Using a theory of social boundary spaces, we investigated whether undergraduate student users at two university-based makerspaces in the United States viewed these spaces as affording their development as well-rounded professionals equipped with a variety of “soft” or “21st century” skills that go beyond engineering-specific content knowledge. Using interview data, we identified seven different types of boundary spaces that provided students with opportunities to engage with and learn from individuals and practices affiliated with various communities. Based on these findings, we recommend more university programs and faculty (both within and beyond engineering) consider intentionally integrating makerspaces into undergraduate curricula to support students in their development of skills, knowledge, and practices relevant for engineering as well as 21st century skills more broadly.Keywords: makerspaces; postsecondary education; engineering education; boundary spaces; 21st century skill

Using the Wigner-Ibach Surmise to Analyze Terrace-Width Distributions: History, User's Guide, and Advances

A history is given of the applications of the simple expression generalized from the surmise by Wigner and also by Ibach to extract the strength of the interaction between steps on a vicinal surface, via the terrace width distribution (TWD). A concise guide for use with experiments and a summary of some recent extensions are provided.Comment: 11 pages, 4 figures, reformatted (with revtex) version of refereed paper for special issue of Applied Physics A entitled "From Surface Science to Device Physics", in honor of the retirements of Prof. H. Ibach and Prof. H. L\"ut