Mechanical Tolerance Research Articles

Central pain modulation after subthalamic nucleus stimulation

To investigate the acute effect of subthalamic nuclei deep brain stimulation (STN-DBS) and levodopa on pain and tolerance thresholds in patients with Parkinson disease. We hypothesized that a modification of pain threshold after STN-DBS would suggest a central modification of pain perception, whereas the absence of pain threshold change after STN-DBS would correspond to a peripheral mechanism via a decrease of painful stimuli. Nineteen patients with Parkinson disease were included in this double-blind, randomized, crossover study. Postoperatively, we evaluated pain thresholds (thermal and mechanical) and motor symptoms under 3 acute conditions: stimulation on/medication off; stimulation off/medication on; and stimulation off/medication off. We also conducted a retrospective analysis of the data prospectively recorded during the follow-up of the cohort pre- and postoperatively (Unified Parkinson's Disease Rating Scale [UPDRS] score, Hoehn and Yahr stage, equivalent levodopa daily dose, and tapping test score). We found a significant increase of pain and tolerance mechanical thresholds not only after acute STN-DBS but also after acute levodopa administration. We did not find any significant correlation between postoperative clinical pain improvement and UPDRS-III improvement after acute levodopa or STN-DBS, nor with motor complications improvement assessed with UPDRS-IV after chronic STN-DBS. No correlation was found between postoperative clinical pain improvement and mechanical pain threshold modification. Clinical pain alleviation after STN-DBS cannot be considered merely as a consequence of motor complications improvement and could be attributable to a direct central modulation of pain perception, via increased mechanical pain and tolerance thresholds.

Superconducting and Mechanical Properties of Impregnated REBCO Pancake Coils Under Large Hoop Stress

We performed hoop stress tests of REBCO multilayer pancake coils impregnated by epoxy resin. The mechanical deformation and electric field-current properties were measured under the large hoop stress. The maximum hoop stress of about 530 MPa per Hastelloy substrate, calculated from the BJR relation, was applied in the background magnetic field of 8 T. Because the hoop stress level is much smaller than the mechanical tolerance of the GdBCO tape, the coil performance was limited by the angular dependence of critical current in this test. Furthermore, the hoop stress test under the large electromagnetic stresses was also carried out for the other (Y, Gd)BCO coil. The (Y, Gd)BCO epoxy impregnated coil was operated without any degradation even in the huge hoop stress over 1300 MPa. The mechanical deformation of the coil is analysed on the basis of the measured strains. We confirmed the large strain about 0.3%-0.5% because of the hoop stress over 1300 MPa at Iop = 460 A and B = 13.5 T but no degradation of the coils. However, it is suggested that the coil deformation is very complicated under the large electromagnetic stress.

Cu-Sn Thin Film Production on Copper Substrate

We investigated the anode performance of Cu-Sn thin film for lithium ion batteries. The results show that the presence of copper improves the cycleability of the thin film since the mechanical tolerance of the thin film against the stress generated during the high volumetric changes in lithiation/delithiation processes is increased.However, some improvement in the microstructure of the thin film is still required tofacilitate lithium movements in thin film structure and increase the cycle life of the electrode.

Cu-Sn Thin Film as Anode for Thin Film Rechargeable Lithium-Ion Batteries

We investigated the anode performance of Cu-Sn flat thin film. The results show that the presence of copper improves the cycleability of the thin film since the mechanical tolerance of the thin film against the stress generated during the high volumetric changes in lithiation/delithiation processes is increased. However, some improvement in the microstructure of the thin film is still required to minimize the quantity or the sizes of Sn particles in thin film and facilitate lithium movements in thin film structure.

Diversity loss in the macrophyte vegetation of northwest German streams and rivers between the 1950s and 2010

This resampling study in 338 semi-per- manent plots analyses changes in river macrophyte diversity in 70 water courses (small streams to medium-sized rivers) from four regions of the north- west German lowlands during the last six decades. The total macrophyte species pool decreased between the 1950s and 2010/2011 by 28% (from 51 to 37 species), mean plot-level species richness by 19% (from 4.7 to 3.8 species per releve ´) and the number of red-listed species by 40% (from 30 to 18 species). Species loss was associated with marked change in species traits: species with presumably higher mechanical stress tolerance (indicated by low specific leaf area and short leaf longevity) are more abundant today. Nearly, half of the species present in the 1950s had either disappeared or been replaced by other species in the recent releves. The dramatic impoverishment is likely a consequence of continued nutrient input that drove oligo- and mesotraphent species to extinction, and of restructuring and maintenance works in the water courses that reduced stagnant and undisturbed river habitats, where stress-intolerant species can persist. Efficient measures to reduce the nutrient load and to re-naturalise stream and river beds are urgently needed to halt and reverse the loss of macrophyte diversity.

Mechanical Stimulation-Induced Chilling Tolerance in Tobacco Suspension Cultured Cells and Its Relation to Proline

Mechanical Stimulation-Induced Chilling Tolerance in Tobacco Suspension Cultured Cells and Its Relation to Proline

Mechanics and molecular filtration performance of graphyne nanoweb membranes for selective water purification

Two-dimensional carbon materials such as the 2D nanoweb-like graphyne membrane are promising as molecular sieves for energy and environmental applications. Based on the application of water purification - the removal of contaminants from wastewater and seawater - here we use molecular dynamics (MD) simulations to investigate the interplay between mechanical forces, filtration mechanisms, and overall performance for graphyne membranes with different pore sizes. We carry out biaxial tensile tests and verify the superior mechanical robustness and tolerance of graphyne membranes against possible deformations from the membrane installation process. A possible ultimate stress in excess of 15 GPa and an ultimate strain of 1.2-2.7% are determined. We also demonstrate their excellent filtration performance with barrier-free water permeation and perfect rejection of the representative contaminants considered here, including divalent heavy metal salts (copper sulfate), hydrophobic organic chemicals (benzene and carbon tetrachloride), and inorganic monovalent salts (sodium chloride). We find that graphtriyne, with an effective pore diameter of 3.8 Å, exhibits an optimal purification performance, because the contaminant rejection rate is more sensitive to pore size than water permeability. In addition, we find that the hydrophobic graphyne membranes exhibit higher rejection rates for hydrophilic contaminants compared to the hydrophobic ones. This size exclusion effect is a result of the larger hydrated radii of hydrophilic species due to stronger interactions between them and water molecules. Finally, we find that the maximum deformation of graphtriyne at the ultimate strain before material failure has only a minor impact on its filtration performance. One of the advantages of using graphyne for water purification is that no chemical functionalization or defects need to be introduced, which maintains the structural integrity of the membrane, and possibly, the long-term device performance.

Mechanical stimulation-induced chilling tolerance in tobacco suspension cultured cells and its relation to proline

Mechanical stimulation (MS), widely existing but usually ignored in nature, is one of the major environmental stress factors. MS by increasing the rotational speed of shaker incubator could alleviate a decrease in vitality of tobacco (Nicotiana tabacum L.) suspension cultured cells and reduce the accumulation of MDA under chilling stress at 1°C, which in turn improved survival percentage under chilling stress and regrowth ability of tobacco suspension cells after chilling stress. In addition, MS could increase the activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and induce the accumulation of endogenous proline in tobacco cells; exogenously applied proline also could enhance its endogenous level under normal culture conditions and survival percent-age of the cells under chilling stress. These results suggest that MS could improve chilling tolerance of tobacco suspension cells and the acquisition of this chilling tolerance was related to proline.

Epigenetic Regulation of Opioid-Induced Hyperalgesia, Dependence, and Tolerance in Mice

Repeated administration of opioids such as morphine induces persistent behavioral changes including opioid-induced hyperalgesia (OIH), tolerance, and physical dependence. In the current work we explored how the balance of histone acetyltransferase (HAT) versus histone deacetylase (HDAC) might regulate these morphine-induced changes. Nociceptive thresholds, analgesia, and physical dependence were assessed during and for a period of several weeks after morphine exposure. To probe the roles of histone acetylation, the HAT inhibitor curcumin or a selective HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) was administered daily to groups of animals. Histone acetylation in spinal cord was assessed by Western blot and immunohistochemistry. Concurrent administration of curcumin with morphine for 4 days significantly reduced development of opioid-induced mechanical allodynia, thermal hyperalgesia, tolerance, and physical dependence. Conversely, the HDAC inhibitor SAHA enhanced these responses. Interestingly, SAHA treatment after the termination of opioid administration sustained these behavioral changes for at least 4 weeks. Histone H3 acetylation in the dorsal horn of the spinal cord was increased after chronic morphine treatment, but H4 acetylation was unchanged. Moreover, we observed a decrease in HDAC activity in the spinal cords of morphine-treated mice while overall HAT activity was unchanged, suggesting a shift toward a state of enhanced histone acetylation. PerspectiveThe current study indicates that epigenetic mechanisms play a crucial role in opioid-induced long-lasting neuroplasticity. These results provide new sight into understanding the mechanisms of opioid-induced neuroplasticity and suggest new strategies to limit opioid abuse potential and increase the value of these drugs as analgesics.

Dexmedetomidine versus standard therapy with fentanyl for sedation in mechanically ventilated premature neonates.

To compare the efficacy and safety of dexmedetomidine and fentanyl for sedation in mechanically ventilated premature neonates. This was a retrospective, observational case-control study in a level III neonatal intensive care unit. Forty-eight premature neonates requiring mechanical ventilation were included. Patients received fentanyl (n=24) or dexmedetomidine (n=24) for pain or sedation. Each group also received fentanyl and lorazepam boluses as needed for agitation. The primary outcomes were efficacy and frequency of acute adverse events associated with each drug. Days on mechanical ventilation, stooling patterns, feeding tolerance, and neurologic outcomes were also evaluated. There were no significant differences in baseline demographics between the dexmedetomidine and fentanyl patients. Patients in the dexmedetomidine group required less adjunctive sedation and had more days free of additional sedation in comparison to fentanyl (54.1% vs. 16.5%, p<0.0001). There were no differences in hemodynamic parameters between the 2 groups. Duration of mechanical ventilation was shorter in the dexmedetomidine group (14.4 vs. 28.4 days, p<0.001). Meconium passage (7.5 vs. 22.4 days, p<0.0002) and time from initiation to achievement of full enteral feeds (26.8 vs. 50.8 days, p<0.0001) were shorter in the dexmedetomidine group. Incidence of culture-positive sepsis was lower in the dexmedetomidine group (48% vs. 88%). The incidence of either severe intraventricular hemorrhage or periventricular leukomalacia was not statistically significantly reduced (2% vs. 7%). Dexmedetomidine was safe and effective for sedation in the premature neonates included in this study. Prospective randomized-controlled trials are needed before routine use of dexmedetomidine can be recommended.

New Techniques to Compensate for Mistracking within Stereoscopic Acquisition Systems

When a lens is mounted to a camera, there is an inevitable mechanical tolerance associated with the lens optical center and another associated with the camera optical center. These separate tolerances can be additive or subtractive for a given lens-camera combination (both tolerances entail unpredictable additive and subtractive limits). This aberration poses the greatest challenge to the imaging alignment of stereoscopic rigs. Lens operational dynamics add another variable differential in terms of small mistracking between angle of view over the focal range of a zoom lens pair, mistracking between their optical focus, and mistracking between their aperture settings. Many workers in the field of three-dimensional (3D) technology are diligently seeking practical and cost-effective solutions to these disparities. This paper describes recent developments that entail automatic and dynamic corrections for these differential tolerances. New software in the digital servo systems that operate lens zoom, iris, and focus control allows entry of compensation data that corrects for mistracking errors in these three operational functions. Separately, a novel development by 3D rig designer Microfilms of France uses the technology of optical image stabilization built into a high-definition (HD) television lens to implement automatic realtime correction of both the fixed and the dynamic optical miscentering errors between two lenses. A different image stabilization technology—built into the lenses of integrated HD lens–camcorders (increasingly popular for small, handheld 3D rigs)—allows corrections for the fixed optical miscentering between any two such systems at specific focal length settings.

Development of low frequency, insulating thick diaphragms for power MEMS applications

Major challenges of micro thermal machines are the thermal insulation and mechanical tolerance in the case of sliding piston. Replacing piston by membrane in microengines can alleviate the latter and lead to planar architectures. However, the thermal isolation would call for very thick structures which are associated to too high resonant frequencies which are detrimental to the engine performances. A thermal and mechanical compromise is to be made. On the contrary, based on fluid structure interaction, using an incompressible fluid contained in a cavity sealed by deformable diaphragm it would be possible to design a thick, low frequency insulating diaphragm. The design involves a simple planar geometry that is easy to manufacture with standard microelectronics methods. An analytical fluid-structure model is proposed and theoretically validated. Experimental structures are realized and tested. The model is in agreement with the experimental results. A dimensionless model is proposed to design hybrid fluid structures for micromachines.

Heritability Analysis Suggests Comparable Genetic Component of Mechanical Pain Threshold and Tolerance: Table 1

Genetic basis of pain sensation became one of the hot topics in pain medicine over the past several years. Although numerous studies have suggested the existence of the genetic component of pain threshold, majority of these findings were based on a candidate-gene approach and remained un-replicated, and thus of limited importance (1). Commonly used approach to investigate genetic basis of any trait is to initially estimate heritability, which is defined as the proportion of the total variance of the measured trait attributable to genes. We performed a heritability analysis of the mechanical pain threshold and tolerance in a large-scale pedigree, based on the isolated population of the island of Vis in Croatia, within 10, 001 Dalmatians project (2). A total of 349 subjects were involved in the measurement of mechanical pain threshold and pain tolerance using Algometer Wagner ForceOne. After initial training measurement, subjects were exposed to the actual pain threshold measurement. Three consecutive pain threshold measurements on the dorsal side of the middle phalange of the index finger (on both hands) were performed by a single trained measurer. Additionally, we performed two consecutive measurements of pain tolerance on the same site of both hands. Mixed model analysis was performed using Sequential Oligogenic Linkage Analysis Routines – SOLAR (3), with age and gender as the predictor variables. The results indicated intermediate level of heritability of pain threshold (0.508 for right hand and 0.362 for left hand) and pain tolerance (0.542 for right hand and 0.307 for left hand, notably, the last heritability estimate was not significant ; Table 1). A strong gender and age effects were recorded in all models, with the exception of age in the pain threshold models (Table 1). These results suggest that gene mapping efforts are likely to have similar success both in pain threshold and pain tolerance, despite some previous suggestions that pain threshold is more a physiological function, while tolerance is influenced by stronger modifying effects of different environmental and psychological confounders (4). Furthermore, it should be noted that we detected difference in handedness - the heritability for pain tolerance in left hand was insignificant, with very large standard errors. This could arise from the overall small sample size or it could be pointing to differential mechanisms of pain tolerance in left vs. right, that is dominant, vs. non-dominant hand, which was implied before (5). Regardless of these results, high heritability does not warrant productive gene mapping. Heritability of height was commonly reported as one of the highest ones, generally in the range of 0.92-0.97. However, only creation of a mega-consortium of studies, which consisted of over 180, 000 measured subjects and used genome-wide approach, surpassed previous nearly futile efforts and yielded 180 loci involved in determination of the adult height, and showed a highly polygenic genetic architecture of height (6). If the same is applicable to pain, then we might be expecting a rather complex and lengthy search for genetic architecture of pain. However, the use of hypothesis-free approach, such as genome-wide association study, promises wider and deeper understanding of pain sensation, which is interesting not only for better understanding, but also for the development of new approaches to pain diagnosis and treatment.

Redox instability, mechanical deformation, and heterogeneous damage accumulation in solid oxide fuel cell anodes

Mechanical integrity and damage tolerance represent two key challenges in the design of solid oxide fuel cells (SOFCs). In particular, reduction and oxidation (redox) cycles, and the associated large transformation strains have a notable impact on the mechanical stability and failure mode of SOFC anodes. In this study, the deformation behavior under redox cycling is investigated computationally with an approach that provides a detailed, microstructurally based view of heterogeneous damage accumulation behavior within an experimentally obtained nickel/yttria stabilized zirconia SOFC anode microstructure. Simulation results underscore the critical role that the microstructure plays in the mechanical deformation behavior of and failure within such materials.

Planungsgenauigkeit bei Open Wedge HTO

The high tibial osteotomy (HTO) is regarded as an established method for varus deformity. To quantify the varus deformity, the anatomic and the mechanical leg axis can be determined. The success of HTO depends on the correct assessment of the preoperative axis deviation and the exact as planned correction. The aim of the retrospective study was to verify the accuracy (± 1.5° of mechanical tibiofemoral angle tolerance compared to the planning) with the preoperative planning compared to the postoperative result after correction using the TomoFix™ plate in open wedge HTO. A retrospective study of patients was carried out after open wedge HTO with the TomoFix™ plate. A full-weight bearing, long-standing anteroposterior radiograph of the whole lower extremity was performed before and after correction. The mechanical angles in the frontal plane were determined and compared with the plan as drawn. The preoperative mechanical tibiofemoral angle (mTFA) was -5.33 ± 3.29° (varus) and at follow-up -0.3 ± 3.0° (varus). The mean correction was 4.9 ± 2.9°. The planned mTFA was 2.2 ± 1.6°(valgus). The corrected lower extremity showed a mean difference of -2.5 ± 3.4° in angle correction of the varus deformity as preoperatively assumed to be the optimal correction compared to the planning. The planning goal was not achieved in 73 % of the cases. The results are comparable to those of other publications. However, taking into account the required accuracy of the drawn plan combined with the surgical precedure, it is not possible to achieve results within the desired tolerance.

Development of robust flexible OLED encapsulations using simulated estimations and experimental validations

This work analyses the overall stress/strain characteristic of flexible encapsulations with organic light-emitting diode (OLED) devices. A robust methodology composed of a mechanical model of multi-thin film under bending loads and related stress simulations based on nonlinear finite element analysis (FEA) is proposed, and validated to be more reliable compared with related experimental data. With various geometrical combinations of cover plate, stacked thin films and plastic substrate, the position of the neutral axis (NA) plate, which is regarded as a key design parameter to minimize stress impact for the concerned OLED devices, is acquired using the present methodology. The results point out that both the thickness and mechanical properties of the cover plate help in determining the NA location. In addition, several concave and convex radii are applied to examine the reliable mechanical tolerance and to provide an insight into the estimated reliability of foldable OLED encapsulations.

New method for controlling large fan of thermal power plant boiler using inverter in abnormal state

AbstractThis paper presents a new air flow controller for a thermal power plant. When an inverter power source is used for a forced draft fan (FDF) in order to save power, the conventional countermeasures do not cover all abnormal states. The proposed controller is evaluated by performing a simulation. The power source is shown to change from the inverter to a commercial power source within 0.5 second in the abnormal state. The changing time is determined to be 0.55 second based on the mechanical tolerance of the design. Testing was performed in an actual plant using the proposed control method, and the transient response was compared with the simulated and measured data. The errors were less than 3.4%. The FDF changed over smoothly and the plant conditions remained the same as the normal state in the actual plant testing. This paper deals with the safe operation of a thermal power plant that employs the proposed air flow controller. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 47–56, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21202

MONTMORILLONITE-REINFORCED NATURAL RUBBER NANOCOMPOSITES THROUGH EMULSION STABILIZATION–DESTABILIZATION METHOD

Abstract A nanoplatelet of montmorillonite (MMT) was incorporated in the natural rubber (NR) matrix at a high loading content using a newly developed stabilization–destabilization process in the colloid states. Examination of the surface charge of the colloid drops by zeta potential measurement led to the identification of the stable and unstable conditions of the colloid mixture as well as each colloid system as a function of pH. The stabilized mixture of the MMT and NR colloids was subsequently destabilized by changing the pH of the mixture to achieve a well-dispersed and intercalated NR/MMT precipitate. The resulting NR/MMT nanocomposites provided an exfoliated MMT morphology up to 25 phr, and the mechanical properties and aging tolerance of the resulting nanocomposite vulcanizates were substantially enhanced by the incorporated MMT nanofillers. The developed stabilization–destabilization methodology ensured a highly loaded MMT rubber composite system, which could be used to obtain high performance NR/MMT nanocomposite systems with ease without using high-shear processing techniques.

Uniform Dispersion of Liquid Crystal Droplets in the Polymer Matrix by Chemical Affinity Difference-Induced Phase Separation

We proposed a method to obtain uniformly dispersed liquid crystal (LC) droplets in the polymer matrix. Polymer spacers were formed on the bottom substrate and the LC–reactive monomer (RM) mixture was injected between the substrates in the isotropic phase. After cooling to the room temperature, the RM molecules which have higher chemical affinity to the polymer spacers were diffused to the polymer spacers. Simultaneously, the LC molecules were separated from the RM molecules and formed homogenously dispersed droplets with a uniform size. The phase retardation, mechanical tolerance, and response time of the cell suggested were examined.

Treatment-related changes in brain activation in patients with fibromyalgia syndrome

Little is known about the effects of successful treatment on brain function in chronic pain. This study examined changes in pain-evoked brain activation following behavioral extinction training in fibromyalgia patients. Using functional magnetic resonance imaging, brain activation to painful mechanical stimuli applied to the 2nd phalanx of the left 2nd digit (m. flexor digitorum) was assessed in 10 patients with fibromyalgia syndrome (FM) before and after behavioral extinction training. The behavioral treatment significantly reduced interference from pain in the FM patients. Mechanical pain threshold and pain tolerance increased significantly after treatment. Activation in the insula shifted bilaterally from a more anterior site before treatment to a more posterior location after treatment. The pre- to post-treatment reduction in both interference related to pain and pain severity were significantly associated with bilateral activation in pain-evoked activity in the posterior insula, the ipsilateral caudate nucleus/striatum, the contralateral lenticular nucleus, the left thalamus and the primary somatosensory cortex contralateral to the stimulated side. These data show a relation between successful behavioral treatment and higher activation bilaterally in the posterior insula and in the contralateral primary somatosensory cortex. Future studies should compare responders and non-responders for differential treatment effects and examine in more detail the mechanisms underlying these changes.