Prospective validation of a low-back disorder risk model and assessment of ergonomic interventions associated with manual materials handling tasks

The evaluation of low-back disorder risk associated with materials handling tasks can be performed using a variety of assessment tools. Most of these tools vary greatly in their underlying logic, yet few have been assessed for their predictive ability. It is important to document how well an assessment tool realistically reflects the job's injury risk, since only valid and accurate tools can reliably determine whether a given ergonomic intervention will result in a future reduction in back injuries. The goal of this study was to evaluate how well a previously reported low-back disorder (LBD) risk assessment model (Marras et al. 1993) could predict changes in LBD injury rates as the physical conditions to which employees are exposed were changed. Thirty-six repetitive materials handling jobs from 16 different companies were included in this prospective cohort study. Of these 36 jobs, 32 underwent an ergonomic intervention during the observation period, and four jobs in which no intervention occurred served as a comparison group. The trunk motions and workplace features of 142 employees performing these jobs were observed both before and after workplace interventions were incorporated. In addition, the jobs' LBD rates were documented for these pre- and post-intervention periods. The results indicated that a statistically significant correlation existed between changes in the jobs' estimated LBD risk values and changes in their actual low-back incidence rates over the observation period. Linear and Poisson regression models also were developed to predict a change in a job's incidence rate and the number of LBD on ajob respectively, as a function of the job's risk change using this assessment model. Finally, this prospective study showed which ergonomic interventions consistently reduced the jobs' mean low-back incidence rates. These results support use of the LBD risk model to assess accurately a job's potential to lead to low-back injuries among its employees.     

Thermodynamic investigation of KCl in the ternary KCl/LiCl/ H2 O mixed electrolyte system based on potentiometric method

The results of a thermodynamic investigation of KCl salt in the ternary KCl+LiCl+H₂O electrolyte system by potentiometric method are reported in this work. The experimental potentiometric data were obtained from a galvanic cell by combining a solvent polymeric (PVC) potassium-selective membrane electrode (K⁺ ISE), containing Valinomycin as ionophore, and an Ag/AgCl electrode. The measurements were performed, at similar constant ionic strengths, in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r$r$ (where r=_m1/_m2=0.1,0.2,1,5,10$r=m_1/m_2=0.1,0.2,1,5,10$, and _m1,_m2$m_1,m_2$ are the molalities of KCl and LiCl, respectively). The non-ideal behaviour of the system was described on the base of the Pitzer ion-interaction model for mixed salts, over the ionic strength ranging from 0.01 up to about 5 mol/kg, at 298.15 K. Based on the obtained Pitzer ion-interaction parameters, the osmotic coefficients, solvent activities, and excess Gibbs free energies were determined for these investigated ternary electrolyte systems.     

Regression models for predicting peak and continuous three-dimensional spinal loads during symmetric and asymmetric lifting tasks

Most biomechanical assessments of spinal loading during industrial work have focused on estimating peak spinal compressive forces under static and sagittally symmetric conditions. The main objective of this study was to explore the potential of feasibly predicting three-dimensional (3D) spinal loading in industry from various combinations of trunk kinematics, kinetics, and subject-load characteristics. The study used spinal loading, predicted by a validated electromyography-assisted model, from 11 male participants who performed a series of symmetric and asymmetric lifts. Three classes of models were developed: (a) models using workplace, subject, and trunk motion parameters as independent variables (kinematic models); (b) models using workplace, subject, and measured moments variables (kinetic models); and (c) models incorporating workplace, subject, trunk motion, and measured moments variables (combined models). The results showed that peak 3D spinal loading during symmetric and asymmetric lifting were predicted equally well using all three types of regression models. Continuous 3D loading was predicted best using the combined models. When the use of such models is infeasible, the kinematic models can provide adequate predictions. Finally, lateral shear forces (peak and continuous) were consistently underestimated using all three types of models. The study demonstrated the feasibility of predicting 3D loads on the spine under specific symmetric and asymmetric lifting tasks without the need for collecting EMG information. However, further validation and development of the models should be conducted to assess and extend their applicability to lifting conditions other than those presented in this study. Actual or potential applications of this research include exposure assessment in epidemiological studies, ergonomic intervention, and laboratory task assessment.     

Poly(tetramethylene oxide)-coated silica nanoparticles incorporated into poly(4,4′-oxydiphenylene-pyromellitimide) matrix

Telechelic poly(teramethylene oxide) with two isocyanate end groups (OCN-PTMO-NCO) was synthesized by the reaction of polytetrahydrofuran (M_n?=?1000?g?mol^?1) and hexamethylene diisocyanate in 1:2 molar ratio. The resulting macrochains were then covalently grafted to the surface of silica nanoparticles (SNPs). Thus, the inorganic nanoparticles could be thoroughly coated by a thick and soft organic shell. Thermogravimetric measurements showed that up to 85?wt.% of the organically modified SNPs (OSNPs) could be formed from the organic part. Different weight ratios of OSNPs were subsequently added to a solution of 4,4′-oxydiphenylamine/pyromellitic dianhydride poly(amic acid) (PAA) in dimethylformamide. Chemical cyclodehydration of the PAA in the presence of homogeneously dispersed OSNPs resulted in poly(4,4′-oxydiphenylene-pyromellitimide) (POPI) nanocomposites, labeled by POPI/OSNP 5, POPI/OSNP 7.5, and POPI/OSNP 10. The nanocomposites obtained were fully characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. According to the diffuse reflectance UV spectroscopy, in comparison with neat POPI, the POPI/OSNP series showed an appreciable redshift in the λ_max values up to 15–20?nm. Moreover, POPI/OSNP series showed significant stability toward heat at temperatures above 540°C. The endothermic phase transitions occurred by the first thermodegradation of the resulting nanocomposites could be obviously seen in the differential thermal analysis.     

A numerical study on the damping capacity of metal matrix nanocomposites

In the present study, the damping capacity of metal matrix nanocomposites (MMNCs) is predicted using a micro-mechanical modeling approach. The model is based on finite element analysis of a unit cell, which mimics a pure metallic lattice with stiff reinforcing nanoparticles. The dissipated energy of nanocomposite is predicted numerically by applying a harmonic load on the unit cell model. The influences of the grain size, boundary phase thickness and reinforcement size on the energy dissipation were calculated by the developed finite element model. Also, the damping capacities of three typical particulate reinforced nanocomposites have been simulated by the proposed model. The relationship between damping capacity and dislocations were also discussed with respect to the Granato–Lücke (G–L) theory. The results calculated from the developed model show good agreement with the G–L theory, which demonstrates the feasibility of damping calculation with the proposed method.     

Cracking energy density for rubber materials: Computation and implementation in multiaxial fatigue design

This article proposes a heuristic model to predict the fatigue life of rubber parts. The developed model is mainly based on the Cracking Energy Density (CED), originally developed by Mars, for the study of rubber parts fatigue. The main contribution consists in the integration of the theoretical framework of the critical plane analysis proposed by Mars with Saintier's experimental research carried out in tension and torsion modes. The CED parameter, derived from the Strain Energy Density (SED), can predict the occurrence of the first crack and its possible orientation depending on the type of loading path. In this context, an analytical analysis of this parameter is carried out for typical loading cases. Furthermore, the variation of CED by SED ratio (W_C/W), as a function of the probable crack angle θ and the principal stretch λ₁ is investigated. A finite element (FE) model is, then, developed to measure the performance and efficiency for some basic criteria used to investigate rubber fatigue life in literature. The pertinence of such criteria is evaluated in terms of a determination coefficient. The CED parameter can be considered as the most effective criterion for describing the multiaxial fatigue life of rubbers.     

TERNARY NaCl+LiCl+H2O MIXED ELECTROLYTE SYSTEM: DETERMINATION OF ACTIVITY COEFFICIENTS BASED ON POTENTIOMETRIC METHOD

The mean activity coefficients for NaCl in a ternary electrolyte system were determined by the potentiometric method, at 25°C, using a solvent polymeric (PVC) sodium-selective membrane electrode (Na⁺ ISE), containing N,N'-dibenzyl-N,N'-diphenyl-1,2-phenylenedioxydiacetamide as ionophore, and combined with an Ag/AgCl electrode. The potentiometric measurements were performed at the same ionic strengths in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m₁/m₂ = 1, 10, 50, 100). The nonideal behavior of the ternary NaCl(m₁) + LiCl(m₂) + H₂O electrolyte system was described based on the Pitzer ion-interaction model for mixed salts over the ionic strength ranging from 0.01 up to about 4 mol/kg. Two- and three-particle Pitzer interaction parameters for a mixed electrolyte system were determined based on potentiometric data, and the critical role of potentiometric selectivity coefficient (K₁₂) of ISE as limiting factor in the potentiometric measurements was analyzed.     

Photonics-based multi-band/multi-mode radar signal generation

Photonic Network Communications - Microwave/millimeter-wave photonics is playing a prominent role in overcoming the challenges of RF signal generation and processing. This evolving technology has...     

Mesoporous silica nanoparticles for efficient rivastigmine hydrogen tartrate delivery into SY5Y cells

Rivastigmine hydrogen tartrate (RT) is a molecule with both hydrophilic and hydrophobic properties used for the treatment of the Alzheimer’s disease. In this work, the larger pore size of mesoporous silica nanoparticles (P1-MSN) was synthesized and then, P1-MSN were functionalized by succinic anhydride (S-P1-MSN) and 3-aminopropyltriethoxysilane (APTES) (AP-CO-P1-MSN) using the grafting and co-condensation methods, respectively. A new method was used for the functionalization of P1-MSN by succinic anhydride at room temperature. Nanoparticles were characterized by special instrumental analysis and loaded by RT. Maximum entrapment efficiency and RT loading percentage into P1-MSN, AP-CO-P1-MSN and S-P1-MSN were respectively obtained as 21.26 and 25.5%, 41.5 and 49.8%, and 11.9 and 14.28% for 24?h. In the simulated gastric and body fluids, the release rate of RT-loaded AP-CO-P1-MSN (AP-CO-P1-MSN-RT) was lower than that of other RT-loaded nanoparticles. In oral pathway, the sustained release of RT was observed in AP-CO-P1-MSN-RT. Moreover, no cytotoxicity effect was observed for P1-MSN, but the cells treated by AP-CO-P1-MSN showed a reduction in SY5Y cell viability due to easy entrance of these nanoparticles and their accumulation in different parts of the cell as observed by TEM.