Simple and low-cost fabrication of PDMS microfluidic round channels by surface-wetting parameters optimization

Convenient for both biologists and MEMS designers, Polydimethylsiloxane (PDMS) polymer is intensively investigated for its biocompatibility, transparency, high resistance under plasma treatment, flexibility and resistance to high temperature. However, for microfluidic applications, the fabrication of PDMS circular channels is difficult to achieve except by wire moulding. In this article, we present a simple, fast and low-cost fabrication method which can be applied out of clean-room environment. It is based on the deposition of alginic acid sodium salt aqueous solution, enabling the formation of a liquid cylinder on the most hydrophilic part of a hydrophilic/hydrophobic patterned surface. We experimentally studied the interaction between liquid rivulets and surfaces presenting a contrast of wettability and/or a stepwise texture. Subsequent moulding of the half-cylinder of liquid produces round PDMS microfluidic channels. The optimal parameters for hydrophilic/hydrophobic patterns have then been applied to produce the roundest possible channels. The realisation of both straight channels 300–500 μm wide, 1 cm long and 75° tangent chord angle at best, and Y-shaped channels with the same dimensions and 55° TCA is demonstrated.     

Strong accumulators from collision-resistant hashing

Accumulator schemes were introduced in order to represent a large set of values as one short value called the accumulator. These schemes allow one to generate membership proofs, that is, short witnesses that a certain value belongs to the set. In universal accumulator schemes, efficient proofs of non-membership can also be created. Li et?al. (Proceedings of applied cryptography and network security—ACNS ’07, LNCS, vol 4521, 2007), building on the work of Camenisch and Lysyanskaya (Advances in cryptology—proceedings of Crypto ’02, LNCS, vol 2442. Springer, Berlin, pp 61–76, 2002), proposed an efficient accumulator scheme, which relies on a trusted accumulator manager. Specifically, a manager that correctly performs accumulator updates. In this work, we introduce the notion of strong universal accumulator schemes, which are similar in functionality to universal accumulator schemes, but do not assume the accumulator manager is trusted. We also formalize the security requirements for such schemes. We then give a simple construction of a strong universal accumulator scheme, which is provably secure under the assumption that collision-resistant hash functions exist. The weaker requirement on the accumulator manager comes at a price; our scheme is less efficient than known universal accumulator schemes—the size of (non)membership witnesses is logarithmic in the size of the accumulated set in contrast to constant in the scheme of Camenisch and Lysyanskaya. Finally, we show how to use strong universal accumulators to solve a problem of practical relevance, the so-called e-Invoice Factoring Problem.     

The Esterase PfeE,the Achilles’ Heel in the Battle for Iron between Pseudomonas aeruginosa and Escherichia coli

Bacteria access iron, a key nutrient, by producing siderophores or using siderophores produced by other microorganisms. The pathogen Pseudomonas aeruginosa produces two siderophores but is also able to pirate enterobactin (ENT), the siderophore produced by Escherichia coli. ENT-Fe complexes are imported across the outer membrane of P. aeruginosa by the two outer membrane transporters PfeA and PirA. Iron is released from ENT in the P. aeruginosa periplasm by hydrolysis of ENT by the esterase PfeE. We show here that pfeE gene deletion renders P. aeruginosa unable to grow in the presence of ENT because it is unable to access iron via this siderophore. Two-species co-cultures under iron-restricted conditions show that P. aeruginosa strongly represses the growth of E. coli as long it is able to produce its own siderophores. Both strains are present in similar proportions in the culture as long as the siderophore-deficient P. aeruginosa strain is able to use ENT produced by E. coli to access iron. If pfeE is deleted, E. coli has the upper hand in the culture and P. aeruginosa growth is repressed. Overall, these data show that PfeE is the Achilles’ heel of P. aeruginosa in communities with bacteria producing ENT.     

Role of Scaffolds,Subchondral, Intra-Articular Injections of Fresh Autologous Bone Marrow Concentrate Regenerative Cells in Treating Human Knee Cartilage Lesions: Different Approaches and Different Results

The value of bone marrow aspirate concentrates for treatment of human knee cartilage lesions is unclear. Most of the studies were performed with intra-articular injections. However, subchondral bone plays an important role in the progression of osteoarthritis. We investigated by a literature review whether joint, subchondral bone, or/and scaffolds implantation of fresh autologous bone marrow aspirate concentrated (BMAC) containing mesenchymal stem cells (MSCs) would improve osteoarthritis (OA). There is in vivo evidence that suggests that all these different approaches (intra-articular injections, subchondral implantation, scaffolds loaded with BMAC) can improve the patient. This review analyzes the evidence for each different approach to treat OA. We found that the use of intra-articular injections resulted in a significant relief of pain symptoms in the short term and was maintained in 12 months. However, the clinical trials indicate that the application of autologous bone marrow concentrates in combination with scaffolds or in injection in the subchondral bone was superior to intra-articular injection for long-term results. The tendency of MSCs to differentiate into fibrocartilage affecting the outcome was a common issue faced by all the studies when biopsies were performed, except for scaffolds implantation in which some hyaline cartilage was found. The review suggests also that both implantation of subchondral BMAC and scaffolds loaded with BMAC could reduce the need for further surgery.     

Plasma Metabolomics Analysis of Polyvinyl Chloride Workers Identifies Altered Processes and Candidate Biomarkers for Hepatic Hemangiosarcoma and Its Development

Background: High-level occupational vinyl chloride (VC) exposures have been associated with hepatic hemangiosarcoma, which typically develops following a long latency period. Although VC is genotoxic, a more comprehensive mode of action has not been determined and diagnostic biomarkers have not been established. The purpose of this study is to address these knowledge gaps through plasma metabolomics. Methods: Plasma samples from polyvinyl chloride polymerization workers who developed hemangiosarcoma (cases, n = 15) and VC exposure-matched controls (n = 17) underwent metabolomic analysis. Random forest and bioinformatic analyses were performed. Results: Cases and controls had similar demographics and routine liver biochemistries. Mass spectroscopy identified 606 known metabolites. Random forest analysis had an 82% predictive accuracy for group classification. 60 metabolites were significantly increased and 44 were decreased vs. controls. Taurocholate, bradykinin and fibrin degradation product 2 were up-regulated by greater than 80-fold. The naturally occurring anti-angiogenic phenol, 4-hydroxybenzyl alcohol, was down-regulated 5-fold. Top affected ontologies involved: (i) metabolism of bile acids, taurine, cholesterol, fatty acids and amino acids; (ii) inflammation and oxidative stress; and (iii) nicotinic cholinergic signaling. Conclusions: The plasma metabolome was differentially regulated in polyvinyl chloride workers who developed hepatic hemangiosarcoma. Ontologies potentially involved in hemangiosarcoma pathogenesis and candidate biomarkers were identified.     

Polyethylene-layered silicate nanocomposites prepared by the polymerization-filling technique: synthesis and mechanical properties

Polyethylene-layered silicate nanocomposites were prepared by the in situ intercalative polymerization of ethylene by the so-called polymerization-filling technique and analyzed by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Non-modified montmorillonite and hectorite were first treated by trimethylaluminum-depleted methylaluminoxane before being contacted by a Ti-based constrained geometry catalyst. The nanocomposite was formed by addition and polymerization of ethylene. In the absence of a chain transfer agent, ultra high molecular weight polyethylene was produced. The tensile properties of these nanocomposites were poor and essentially independent of the nature and content of the silicate. Upon hydrogen addition, the molecular weight of the polyethylene was decreased with parallel improvement of the tensile and shear moduli, in relation to the filler content. The exfoliation of the layered silicates was confirmed by XRD analysis and TEM observation. The mechanical kneading of the molten nanocomposites resulted in the partial collapse of the exfoliated structure driven by the thermodynamic stability of the layered filler.     

Influence of compaction on the interfacial transition zone and the permeability of concrete

The interfacial transition zone (ITZ) is regarded as a key feature for the transport properties and the durability of concrete. In this study one self-compacting concrete (SCC) mixture and two conventionally vibrated concrete (CVC) mixtures are studied in order to determine the influence of compaction on the porosity of the ITZ. Additionally oxygen permeability and water conductivity were measured in vertical and horizontal direction. The quantitative analysis of images made with an optical microscope and an environmental scanning electron microscope shows a significantly increased porosity and width of the ITZ in CVC compared to SCC. At the same time oxygen permeability and water conductivity of CVC are increased in comparison to SCC. Moreover, considerable differences in the porosity of the lower, lateral and upper ITZ are observed in both types of concrete. The anisotropic distribution of pores in the ITZ does not necessarily cause anisotropy in oxygen permeability and water conductivity though.     

Dynamic thread mapping of shared memory applications by exploiting cache coherence protocols

In current computer architectures, the communication performance between threads varies depending on the memory hierarchy. This performance difference must be considered when mapping parallel applications to processor cores. In parallel applications based on the shared memory paradigm, the communication is difficult to detect because it is implicit. Furthermore, dynamic mapping introduces several challenges, since it needs to find a suitable mapping and migrate the threads with a low overhead during the execution of the application. We propose a mechanism to detect the communication pattern of shared memory applications by monitoring cache coherence protocols. We also propose heuristics that, combined with our communication detection mechanism, allow the mapping to be performed dynamically by the operating system. Experiments with the NAS Parallel Benchmarks showed a reduction of up to 13.9% of the execution time, 30.5% of the cache misses and 39.4% of the number of invalidation messages.     

Paramedics on the job: Dynamic trunk motion assessment at the workplace

Many paramedics' work accidents are related to physical aspects of the job, and the most affected body part is the low back. This study documents the trunk motion exposure of paramedics on the job. Nine paramedics were observed over 12 shifts (120 h). Trunk postures were recorded with the computer-assisted CUELA measurement system worn on the back like a knapsack. Average duration of an emergency call was 23.5 min. Sagittal trunk flexion of >40° and twisting rotation of >24° were observed in 21% and 17% of time-sampled postures. Medical care on the scene (44% of total time) involved prolonged flexed and twisted postures (∼10 s). The highest extreme sagittal trunk flexion (63°) and twisting rotation (40°) were observed during lifting activities, which lasted 2% of the total time. Paramedics adopted trunk motions that may significantly increase the risk of low back disorders during medical care and patient-handling activities.     

Ergonomic contribution of ABLE exoskeleton in automotive industry

In PSA Peugeot Citroen factories, high precision requirements of workstations make them being manual. One of the main goal of the car manufacturer is to minimize the pain of workers while maintaining high efficiency of production lines. Consequently, assisting operators with an exoskeleton is a potential solution for improving ergonomics of painful workstations while respecting industrial constraints. To determine ergonomic performances of an exoskeleton, human joint angles and torques, ground reaction forces, and duration of operations are analysed for eight subjects performing a representative screwing task. Experiments were performed using ABLE upper-limb exoskeleton, developed by the French Atomic Energy Commission (CEA), which has the functionality to compensate arm and tools loads. Results show a clear reduction of the sum of the joints torques, up to 38.9%, given by ABLE supply and invite to make concrete the use of exoskeletons in car assembly lines.