Quantifying Muscle Fatigue of the Low Back during Repetitive Load Lifting Using Lyapunov Analysis

Background: Occupational low back disorders are often associated with exposure to work-related physical risk factors such as muscle fatigue in the low back.Objective: The objective of this study was to investigate the possible relationship between the divergence of the kinematic trajectories of the low back system and the different stages of fatigue during the execution of a repetitive lifting task.Methods: The patterns of the low back system were recorded using markers on specific vertebras during the repetitive load lifting from the floor to a 0.75 m height table. The maximum Lyapunov exponent, λmax of the recorded patterns was calculated from the x and y coordinates of the lower back markers using the algorithm proposed by Wolf.Results: The results of the λmax values determined three different sections of muscle fatigue which were also in agreement with the Borg’s clinical scale of perceived fatigue results. The assessment of the λmax values between the three different sections showed a descriptive point where the muscle fatigue accumulation may have resulted in a change of the low back control.Conclusion: Lyapunov exponent methodology could be a reliable methodology for ergonomists to provide an index to design the work/rest ratio ergonomically

Insecticidal Effect of Diatomaceous Earth Against Three Species of Stored-Product Psocids on Maize, Rice, and Wheat

We evaluated the efficacy of three diatomaceous earth (DE) formulations, Dryacide, Protect-It, and Insecto, against three Psocoptera species, Liposcelis entomophila (Enderlein) (Liposcelididae), Lepinotus reticulatus Enderlein (Trogiidae), and Liposcelis decolor (Pearman), in the laboratory. Bioassays were conducted in three grain commodities, wheat, rice and maize, at 30°C and 75% RH, and the DEs were applied at the recommended dose rates of 1,000, 400, and 500 ppm for Dryacide, Protect-It, and Insecto, respectively. Differences in adult mortality were found among grains and DEs for L. entomophila and L. reticulatus, but these trends were not consistent for all combinations tested. Type of grain and DE did not affect L. decolor mortality significantly. Moreover, mortality increased with increasing exposure time for L. entomophila and L. reticulatus, but there was no effect of exposure time on L. decolor. After 7 d of exposure, mortalities of L. entomophila, L. reticulatus, and L. decolor were 56, 55, and 40%, respectively, and the respective mortality levels after 14 d were 63, 71, and 42%. Progeny production after 30 d was significantly suppressed for all species in the treated grains. However, progeny production was still high in the treated grains and reached 54, 42, and 76 individuals/10 g of grain for L. entomophila, L. reticulatus, and L. decolor, respectively. Progeny production did not vary with commodity. Our results suggest that DEs, when used alone, will not provide effective control of psocids

Smart photochromic gratings with switchable wettability realized by green-light interferometry

We demonstrate the enhancement of the wetting properties of smart photochromic surfaces by a specifically developed, gentle interferometric patterning employing green light. We realized photochromic gratings with 2.5–10.0μm period by a blend consisting of a green-curable matrix and spiropyran molecules. The structured surfaces exhibit photocontrolled and reversible wettability, and enhanced hydrophilicity with respect to the native substrates. The dynamics of liquid spreading onto the gratings was also investigated, and the wetting behavior analyzed according to Wenzel's [Ind. Eng. Chem. 28, 988 (1936)] model for rough surfaces. These results indicate switchable gratings as promising functional components for microfluidics and modulation, and green-light interferometry as a reliable lithographic method for patterning organics without degradation or photochemical reactions

Formation and magnetic manipulation of periodically aligned microchains in thin plastic membranes

We demonstrate the fabrication of polymeric membranes that incorporate a few layers of periodically aligned magnetic microchains formed upon the application of variable magnetic fields. A homogeneous solution containing an elastomeric polymer and a small amount of colloidal magnetic nanoparticles is spin coated on glass slides, thereby forming thin magnetic membranes of ca. 10 μm thickness. Subsequent application of a homogeneous magnetic field results in the orientation of the magnetic clusters and their further motion into the matrix along the field lines forming layers of aligned chains. The study of the kinetics of alignment demonstrates that the chains are formed in the first hour of exposure to the magnetic field. Above all, a detailed microscopy study reveals that the dimensions and the periodicity of the microchains are effectively controlled by the intensity of the magnetic field, in good agreement with the theoretical simulations. This ability to form and manipulate the size and the distribution of chains into the polymeric matrix gives the opportunity to develop multifunctional composite materials ready to be used in various applications such as electromagnetic shielding, or multifunctional magnetic membranes etc

Magnetically Driven Floating Foams for the Removal of Oil Contaminants from Water

In this study, we present a novel composite material based on commercially available polyurethane foams functionalized with colloidal superparamagnetic iron oxide nanoparticles and submicrometer polytetrafluoroethylene particles, which can efficiently separate oil from water. Untreated foam surfaces are inherently hydrophobic and oleophobic, but they can be rendered water-repellent and oil-absorbing by a solvent-free, electrostatic polytetrafluoroethylene particle deposition technique. It was found that combined functionalization of the polytetrafluoroethylene-treated foam surfaces with colloidal iron oxide nanoparticles significantly increases the speed of oil absorption. Detailed microscopic and wettability studies reveal that the combined effects of the surface morphology and of the chemistry of the functionalized foams greatly affect the oil-absorption dynamics. In particular, nanoparticle capping molecules are found to play a major role in this mechanism. In addition to the water-repellent and oil-absorbing capabilities, the functionalized foams exhibit also magnetic responsivity. Finally, due to their light weight, they float easily on water. Hence, by simply moving them around oil-polluted waters using a magnet, they can absorb the floating oil from the polluted regions, thereby purifying the water underneath. This low-cost process can easily be scaled up to clean large-area oil spills in wate

Magnetic Field Induced Formation of Magnetic Wires into Thin Elastic Membranes with Controlled Properties

We present the fabrication of magnetic elastomeric membranes consisting of aligned superparamagnetic microwires embedded in a polymeric matrix. The wires are formed by the magnetic assembly of colloidal iron oxide nanoparticles (NPs) dispersed in the prepolymer matrix, during the curing of the polymer and the solvent evaporation. The appropriate combination of the NPs quantity and of the viscosity of the matrix results in the formation of thin membranes of about 10mm, containing few layers of aligned wires which after the polymer curing are blocked in fixed position into the matrix. The orientation and the dimensions of the magnetic wires depend on the direction and intensity of the external MF respectively

Investigation of the electro-spinnability of alginate solutions containing gold precursor HAuCl4

Alginate nanofibers with an average diameter of 75 nm have been prepared by the electrospinning process. In addition, the spinnability of the solutions in the presence of the gold precursor HAuCl4 was investigated. At low concentrations of HAuCl4 well-formed nanofibers were produced, whereas as its concentration increases the nanofibrous mats present an increased number of bead-like defects. Herein, the in situ preparation of gold nanoparticles (Au NPs) is discussed since sodium alginate (SA) acts as the reducing agent and a mechanism is proposed in order to explain the bead-effect as well as the surface morphology of the alginate fibers decorated with Au NPs

Tailoring the morphology of poly(ethylene oxide)/silver triflate blends: from crystalline to self-assembled nanofibrillar structures.

Interaction of polyethylene oxide (PEO) with transition metal triflates is a newly emerging research area due to its numerous application fields, such as thin-film power conversion devices and sensors. In the present study, we demonstrate, for the first time, that PEO can solvate silver triflate organic salts in large quantities when formic acid is used as a common solvent for both. Nanocomposites with unique structural and electrical properties are fabricated by simply drop casting formic acid solutions of PEO and silver triflate salts. We present a detailed experimental study on the characterization of morphological and electrical properties of PEO–silver triflate nanocomposite films as a function of silver triflate concentration and discuss their potential applications as humidity sensors. In particular, by increasing the concentration of the salt in the initial solution the morphological features of the formed nanocomposites can be varied from well defined microcrystals to amorphous nanofibers. Of special interest are the nanocomposite films fabricated from a 1:1 (PEO-unit:Ag+) molar ratio, since they consist of self-assembled nanofibrillar structures, which exhibit good electrical conductivity as well as highly repeatable sensitivity towards humidity

A survey of parasitoids from Greece with new associations

We report 22 parasitoid species from Greece that have emerged from their hosts belonging to Blattodea, Coleoptera, Hymenoptera and Lepidoptera, including 12 Braconidae, one Eulophidae, one Evaniidae, seven Ichneumonidae, and one Tachinidae. Nine parasitoids are reported for the first time in Greece, i.e., three Ichneumonidae: Campoplex difformis (Gmelin, 1790), Gelis albipalpus (Thomson, 1884), and Lysibia tenax Townes, 1983; five Braconidae: Charmon cruentatus Haliday, 1833, Dendrosoter protuberans (Nees, 1834), Dolichogenidea longipalpis (Reinhard, 1880), Ecphylus silesiacus (Ratzeburg, 1848), and Spathius curvicaudis Ratzeburg, 1844; and one Eulophidae: Melittobia acasta (Walker, 1839). Nine of the 23 recorded parasitoid-host associations are new. These findings are discussed in relation to the overall related parasitoid-host associations in the target area, as well as the potential of parasitoid use in the biological control of pests