Repetitive Application Research Articles

Comparative Study of Taste Substance Sensing by Liquid Membrane Oscillator and Electrochemical Systems With All-Solid-State Electrodes

In food industry, different types of sensors are used for characterizing and quantifying taste substances. Therefore, it is important to establish the principal advantages and disadvantages of these sensors for optimal application. In this paper, two possible systems are compared for sensing the four fundamental tastes: sour (citric acid), salty (sodium chloride), sweet (sucrose), and bitter (caffeine or quinine hydrochloride). One system is a bulk liquid membrane oscillator containing benzyldimethyltetradecylammonium chloride surfactant present during its transport in nitrobenzene membrane phase. The other system is based on all-solid–state electrode (ASSE) containing the same surfactant dissolved in polymer support. It was shown that the liquid membrane oscillator is significantly more sensitive to the presence of taste substances than the ASSE III system. Unfortunately, the functioning characteristics of this oscillator prevent it from steady, repetitive application in food quality control. On the other hand, ASSE III system shows remarkable stability on the long run. It was also found that a system composed of several ASSEs III, each containing different lipid compound, can distinguish successfully substances belonging to different taste classes. The obtained results suggest that such ASSEs III system can be used for food analysis.

Dysfunction of the circadian transcriptional factor CLOCK in mice resists chemical carcinogen-induced tumorigenesis

The chronic disruption of circadian rhythms has been implicated in the risk of cancer development in humans and laboratory animals. The gene product CLOCK is a core molecular component of the circadian oscillator, so that mice with a mutated Clock gene (Clk/Clk) exhibit abnormal rhythms in various physiological processes. However, we demonstrated here that Clk/Clk mice resisted chemical carcinogen-induced tumorigenesis by suppressing epidermal growth factor (EGF) receptor-mediated proliferation signals. The repetitive application of 7,12-dimethylbenz[α]anthracene (DMBA) to skin on the back resulted in the significant development of tumors in wild-type mice, whereas chemically-induced tumorigenesis was alleviated in Clk/Clk mice. Although the degree of DMBA-induced DNA damage was not significantly different between wild-type and Clk/Clk mice, EGF receptor-mediated Ras activation was not detected in DMBA-treated Clk/Clk mice. Genetic and biochemical experiments revealed that the suppression of EGF receptor-mediated signal transduction in DMBA-treated Clk/Clk mice was associated with the expression of the cellular senescence factor p16INK4a. These results suggest an uncovered role for CLOCK in the development of chemical carcinogen-induced primary tumors and offers new preventive strategies.

Two Zero Forcing Beamfomers for the Full Duplex Two Way Relay Channel

We propose two closed form zero-forcing beamformers (ZFBF) for the full-duplex (FD) two way relay network, which efficiently suppress the self-interferences at the involved nodes so that the two way relaying can be implemented in a single time phase. We assume a large portion of the self-interferences are suppressed by analog circuit parts and the proposed digital domain beamforming remove the remaining interference. By repetitive applications of projection onto the orthogonal space combined with the geometric geodesic beamforming, the two schemes allow us to characterize the rate pair curves of the FD two way relay network by simply varying the angles forming the geodesic beamforming vectors. Two optimization approaches can be applied to find the angle parameters and the better ZFBF design.

Detecting the Glyphosate Contamination in Manihot esculenta (Variety Alu Peradeniya) Grown in Sri Lanka

Cassava is a popular local yam in Sri Lanka which is an important source of energy and a raw material for snack foods. A survey on cassava cultivation revealed that the most common cassava variety is “Alu Peradeniya” and there is a heavy usage of “Glyphosate” as a weedicide during the cultivation. This study was done to detect the contamination of glyphosate in outer peel, inner peel and starchy flesh of the M. esculenta variety as it directly relates with the human health. Tubers of variety “Alu peradeniya” were collected from local farmers from Colombo, Matara, Embilipitya, Galle, Anuradhapura and Ampara in Sri Lanka and control samples without glyphosate and with glyphosate were cultivated in my home in Mattegoda, which belongs to Colombo district. Glyphosate levels in samples were determined by a spectroscopic method using ninhydrin in the presence of sodium molybdate to give a Ruhemann’s purple product having visible absorption at 570 nm and further confirmation of results was done by using LC-MS at ITI. Due to the presence of free amino acids in inner peel and starchy flesh, ninhydrin test for glyphosate was limited to the outer peel of the tuber because ninhydrin gives a positive response with amino acids. Outer peel of the control sample with glyphosate showed a concentration of 10.1 mg/kg, which was the least concentration detected. The highest concentration of the glyphosate in outer peel was observed in one of the Colombo samples, which was 20.1±0.1 mg/kg. The amount was recorded twice than that of the recommended amount. Samples from Galle and Matara showed similar values as control sample with glyphosate, which has grown having the permitted amount. Outer peels of some of the samples did not show positive responses indicating that the usage of glyphosate is minimum or absence of glyphosate usage. Further confirmation using LC-MS for selected samples reveals that there is a possibility of penetration of glyphosate among the tuber because both inner peel and starchy flesh were positive for the detection of glyphosate. Due to the repetitive application of Glyphosate and its long half-life in the soil, the impact of the agrochemical on environment and on human life is becoming more pertinent. Keywords: Cassava, Glyphosate, Penetration

An analytical model which determines the apparent T1 for Modified Look-Locker Inversion Recovery – Analysis of the longitudinal relaxation under the influence of discontinuous balanced (classical MOLLI) and spoiled gradient echo readouts

Quantitative nuclear magnetic resonance imaging (MRI) shifts more and more into the focus of clinical research. Especially determination of relaxation times without/and with contrast agents becomes the foundation of tissue characterization, e.g. in cardiac MRI for myocardial fibrosis. Techniques which assess longitudinal relaxation times rely on repetitive application of readout modules, which are interrupted by free relaxation periods, e.g. the Modified Look-Locker Inversion Recovery = MOLLI sequence. These discontinuous sequences reveal an apparent relaxation time, and, by techniques extrapolated from continuous readout sequences, a putative real T1 is determined. What is missing is a rigorous analysis of the dependence of the apparent relaxation time on its real partner, readout sequence parameters and biological parameters as heart rate. This is provided in this paper for the discontinuous balanced steady state free precession (bSSFP) and spoiled gradient echo readouts. It turns out that the apparent longitudinal relaxation rate is the time average of the relaxation rates during the readout module, and free relaxation period. Knowing the heart rate our results vice versa allow to determine the real T1 from its measured apparent partner.

Repetitive Impulse Withstand Performance of Metal–Oxide Varistors

This study focuses on the relationship between test current waveforms and impulse withstand capability of metal–oxide varistors (MOVs) (withstand energy, current density, and the number of withstand shots) in repetitive impulse application and discusses the mechanical and electrical failure mechanisms. The performance and relationship of withstand energy and withstand shots for conventional 2-ms rectangular waveform, 4/10- $\mu $ s, and newly introduced 10/350- $\mu $ s impulses are investigated. Notably, the 10/350- $\mu $ s waveform has aspects of both steep rise impulse and long duration impulse. In addition, the varistor voltage change after repetitive impulse applications for 10/350- $\mu $ s and 4/10- $\mu $ s waveforms is investigated. There is no direct relationship between varistor voltage drop and repetitive withstand shots. However, ${V}_{1 {\rm mA}}$ and ${V}_{0.01 {\rm mA}}$ changes indicate the degree of MOV damage caused by the impulses and are important factors to monitor progressive damage. Based on these findings, optimal MOV design is discussed.

Decoding Nucleation and Growth of Zeolitic Imidazolate Framework Thin Films with Atomic Force Microscopy and Vibrational Spectroscopy.

The synthesis of metal‐organic framework (MOF) thin films has garnered significant attention during the past decade. By better understanding the parameters governing the nucleation and growth of such thin films, their properties can be rationally tuned, empowering their application as (reactive) membranes. Here, a combined AFM‐vibrational spectroscopy research strategy is employed to detail the chemistries governing the nucleation and growth of zeolitic imidazolate framework (ZIF) thin films, in particular isostructural Co‐ZIF‐67 and Zn‐ZIF‐8. First, a single step direct synthesis approach is used to investigate the influence of different synthesis parameters –metal/linker ratio, temperature, and metal type– on the thin film nucleation and growth behaviour. While the metal/linker ratio has a pronounced effect on the thin film nucleation rate, the temperature mainly influences the growth kinetics of nuclei forming the thin film. In addition, the nucleation and growth of ZIF thin films is shown to be highly dependent on the electronegativity of the metal type. Thin‐film thickness control can be achieved by using a multistep synthesis strategy, implying repetitive applications of single step deposition under identical synthesis conditions, for which a growth mechanism is proposed. This study provides insight into the influence of synthesis parameters on the ZIF thin film properties, using tools at hand to rationally tune MOF thin film properties.

Modulation of motor cortex excitability by paired peripheral and transcranial magnetic stimulation.

Repetitive application of peripheral electrical stimuli paired with transcranial magnetic stimulation (rTMS) of M1 cortex at low frequency, known as paired associative stimulation (PAS), is an effective method to induce motor cortex plasticity in humans. Here we investigated the effects of repetitive peripheral magnetic stimulation (rPMS) combined with low frequency rTMS ('magnetic-PAS') on intracortical and corticospinal excitability and whether those changes were widespread or circumscribed to the cortical area controlling the stimulated muscle. Eleven healthy subjects underwent three 10min stimulation sessions: 10HzrPMS alone, applied in trains of 5 stimuli every 10s (60 trains) on the extensor carpi radialis (ECR) muscle; rTMS alone at an intensity 120% of ECR threshold, applied over motor cortex of ECR and at a frequency of 0.1Hz (60 stimuli) and magnetic PAS, i.e., paired rPMS and rTMS. We recorded motor evoked potentials (MEPs) from ECR and first dorsal interosseous (FDI) muscles. We measured resting motor threshold, motor evoked potentials (MEP) amplitude at 120% of RMT, short intracortical inhibition (SICI) at interstimulus interval (ISI) of 2ms and intracortical facilitation (ICF) at an ISI of 15ms before and immediately after each intervention. Magnetic-PAS, but not rTMS or rPMS applied separately, increased MEP amplitude and reduced short intracortical inhibition in ECR but not in FDI muscle. Magnetic-PAS can increase corticospinal excitability and reduce intracortical inhibition. The effects may be specific for the area of cortical representation of the stimulated muscle. Application of magnetic-PAS might be relevant for motor rehabilitation.

Effects of two sliding motions on the superlubricity and wear of self-mated bearing steel lubricated by aqueous glycerol with and without nanodiamonds

Comparative experiments were performed to demonstrate how the lubricated sliding friction and wear behavior of a bearing steel can be affected by the type of relative motion. Data from rotary motion (ball-on-disk tests) were compared to that for reciprocating motion (high frequency ball-on-flat tests) using the same contact pressure, average velocity, temperature and humidity. Two lubricants were compared. The first was aqueous glycerol and the second was aqueous glycerol containing 0.1% w nanodiamonds. The aqueous glycerol solution showed superlubricity effects in rotary testing because its friction coefficient was lower than 0.01. This effect was attributed to a stable protective matrix comprised of free and bound water layers in aqueous glycerol and a thick film lubrication condition. Under reciprocating conditions, it is proposed that the protective matrix was damaged due to the repetitive application of compressive stress and boundary lubrication condition. As a result, there was no superlubricity behavior observed in reciprocating tests. In the rotary test method, the nanodiamond additives (dispersed in glycerol) and wear debris accumulate at the contact zone. That mixture grows into a large abrasive particle mix. However, during reciprocation there are fewer nanodiamonds and wear debris particles in the contact zone. They polish and smooth the surface, as indicated by the post wear surface images. The abrasive nature of nanodiamonds increases the micro polishing effect and thus decreases friction, significantly. It is shown that the lubricity behavior of a lubricant and additive can be influenced by the direction of motion used in the test method.

Changes in cortical excitability during paired associative stimulation in Parkinson's disease patients and healthy subjects

Paired associative stimulation (PAS) combines repetitive peripheral nerve stimulation with motor cortex (M1) transcranial magnetic stimulation (TMS), to induce plastic-like changes of cortical excitability. While much attention has been dedicated to post-PAS effects little is known about processes during PAS. We compared the time-course of changes in M1 excitability during standard facilitatory PAS intervention among patients with Parkinson’s disease (PD), known to have diminished post-PAS response, and healthy subjects. Compared to baseline pre-PAS MEPs, conditioned MEPs during PAS decreased significantly in both groups. The decrease was significantly larger in healthy subjects than in PD patients, regardless whether patients were drug-naïve or not. Although post-PAS excitability increase was also larger in healthy subjects than in PD patients, there was no significant correlation between the two phenomena, i.e. the extent of MEP decrease during PAS and the extent of the post-PAS excitability increase. The results highlight an apparent physiological paradox that repetitive application of an inhibitory stimulation pattern leads to subsequent prolonged facilitation, thus broadening the understanding of the phenomenology of PAS response. Results also suggest that in PD cortical circuits involved in conveying inhibition during PAS, are impaired at the clinical onset of the disease and are not influenced by subsequent PD treatment.

Adsorption and desorption of cationic malachite green dye on cellulose nanofibril aerogels

Ultra-light aerogels have been assembled from cellulose nanofibrils into hierarchically macroporous (several hundred μm) honeycomb cellular structure surrounded with mesoporous (8–60nm) thin walls. The high specific surface (193m2/g) and surface carboxyl content (1.29mmol/g) of these aerogels were demonstrated to be highly capable of removing cationic malachite green (MG) dye from aqueous media. The rapid MG adsorption was driven by electrostatic interactions and followed a pseudo-second-order adsorption kinetic and monolayer Langmuir adsorption isotherm. At a low 1:5mg/mL aerogel/MG ratio, both initial MG adsorption rate (2.3–59.8mgg−1min−1) and equilibrium adsorption capacity (53.0–203.7mgg−1) increased with increasing initial MG concentrations from 10 to 200mg/L, reaching a maximum adsorption of 212.7mgg−1. The excellent dye removal efficiency was demonstrated by complete MG removal through four repetitive adsorptions at a low 1:5mg/mL aerogel/MG ratio and 10mg/L dye concentration as well as 92% MG adsorption in a single batch at one order of magnitude higher10:5mg/mL aerogel/MG ratio and 100mg/L dye concentration. The adsorbed MG in aerogels could be desorbed in aqueous media by increasing ionic strength, demonstrating facile recovery of both dye and aerogel as well as the robust capability of this aerogel for repetitive applications.

4,5-Dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) modifies synaptic transmission in hippocampal CA3 neurons of rats

4,5-Dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) is an alternative to organotin antifoulants, such as tributyltin and triphenyltin. Since DCOIT is found in harbors, bays, and coastal areas worldwide, this chemical compound may have some impacts on ecosystems. To determine whether DCOIT possesses neurotoxic activity by modifying synaptic transmission, we examined the effects of DCOIT on synaptic transmission in a ‘synaptic bouton’ preparation of rat brain. DCOIT at concentrations of 0.03–1 μM increased the amplitudes of evoked synaptic currents mediated by GABA and glutamate, while it reduced the amplitudes of these currents at 3–10 μM. However, the currents elicited by exogenous applications of GABA and glutamate were not affected by DCOIT. DCOIT at 1–10 μM increased the frequency of spontaneous synaptic currents mediated by GABA. It also increased the frequency of glutamate-mediated spontaneous currents at0.3–10 μM. The frequencies of miniature synaptic currents mediated by GABA and glutamate, observed in the presence of tetrodotoxin under external Ca2+-free conditions, were increased by 10 μM DCOIT. With the repetitive applications of DCOIT, the frequency of miniature synaptic currents mediated by glutamate was not increased by the second and third applications of DCOIT. Voltage-dependent Ca2+ channels were not affected by DCOIT, but DCOIT slowed the inactivation of voltage-dependent Na+ channels. These results suggest that DCOIT increases Ca2+ release from intracellular Ca2+ stores, resulting in the facilitation of both action potential-dependent and spontaneous neurotransmission, possibly leading to neurotoxicity.

Fenton chemistry promoted by sub-microsecond pulsed corona plasmas for organic micropollutant degradation in water

Differences in the liquid chemistry due to different ground electrode materials (titanium, stainless steel) were compared for corona discharges in water. The plasma was generated by applying positive high voltage pulses that are characterized by short rise times of about 20 ns, a peak voltage of 80kV and pulse lengths of about 150–160ns (FWHM). Phenol was admixed to the water for quantification of the bulk reaction chemistry, such as phenol decomposition and H2O2-formation. Optical emission spectroscopy was conducted to relate chemistry to plasma processes. Possible electrode corrosion was determined by atomic absorption spectroscopy (AAS).The post-discharge chemistry strongly depends on ground electrode material. With stainless steel electrodes, decomposition efficiency of phenol increased by about three quarters (74.9 %) when compared with titanium electrodes. This result can be explained by dissolved metal ions corroded from the ground electrode, which catalytically decomposed the H2O2 that had been formed into hydroxyl radicals again. Ground electrodes were corroded due to electrochemical processes. Corrosion rates and overall reaction chemistries cannot readily be described similar to conventional DC electrochemical processes at low voltages. The repetitive application of sub-microsecond high voltage pulses has to be taken into account explicitly. Altogether, electrode materials, ground electrode corrosion and associated catalytic processes are more important for plasma processes in aqueous solutions than was recognized so far. Therefore, the effects need to be taken into account in the analysis of laboratory results as well as the development of respective novel water treatment technologies.

Influences on morphology and biomechanics in rabbit’s femur cortex of ovariectomy

Objective To investigate the influences on the femur cortex of the rabbit after ovariectomy and its mechanism. Methods Eighty 6 months-old female pure New Zealand rabbits were divided into two groups: 40 rabbits in ovariectomy group and 40 in sham-operation group. The weight averaged 2.2±0.28 kg. Four weeks and 8 weeks after operation, a series of tests were performed in both groups concerning the number, the volume, the rate and the maximal load of cortical bone porosity. The number, the length and the density of linear crack in rabbit femur cortex were documented after repetitive application of minor trauma. Results Micro-CT demonstrated that both on week 4 and 8 after operation, the number, the volume and the rate of cortical bone porosity were all significantly higher in ovariectomy group than that of the control group. Four weeks after operation, the biomechanical test showed the significantly lower average maximal load of rabbit femur in ovariectomy group (1 892.60±59.09) than that of in control group (1 949.25±53.12) (P=0.003). Eight weeks after operation, the average load of both groups decreased to some extent, which was 1 944.55±41.76 in control group and 1 692.40±85.08 in ovariectomy group respectively (P=0.000). However, the average maximal load of ovariectomy group decreased more significantly. Having application of repetitive minor trauma to the bone, the number, the length and the density of linear crack of cortical bone were 3.40±1.67, 216.80±17.60 μm and 0.40±0.08/mm2 in ovariectomy group, and 2.00±1.17, 160.45±16.89 μm and 0.29±0.13/mm2 in control group 4 weeks later. And after 8 weeks, they were 5.15±1.18, 334.60±13.94 μm and 0.35±0.10/mm2 in ovariectomy group, and 3.10±1.37, 182.10±9.80 μm and 0.24±0.09/mm2 in control group. The number, the length and the density of linear crack of cortical bone were all significantly higher in ovariectomy group than that of in control group both on week 4 and on week 8 after operation. Conclusion Ovariectomy increases the porosity of cortical bone of rabbit, destroys its biological property, accelerates the fatigued damage and delays the healing process. These changes may be attributed to fracture and delayed union after fracture. Key words: Rabbits; Ovariectomy; Femur; Biomechanics

External application of NF-κB inhibitor DHMEQ suppresses development of atopic dermatitis-like lesions induced with DNCB/OX in BALB/c mice

Context: Dehydroxymethylepoxyquinomicin (DHMEQ) which is originally developed as an analog of antibiotic epoxyquinomicin C is a specific and potent inhibitor of NF-κB and has been shown to possess promising potential as an anti-inflammatory and anti-tumor agent.Objective: This study examines DHMEQ’s effect on therapeutic potential for atopic dermatitis (AD)-like lesions.Materials and methods: AD lesions were chronically induced by the repetitive and alternative application of 2,4-dinitrochlorobenzene (DNCB) and oxazolone (OX) on ears in BALB/c mice. The mice were then externally treated with DHMEQ ointment. Macroscopic and microscopic changes of the skin lesions were observed and recorded.Results: DHMEQ inhibited ear swelling and relieved clinical symptoms of the AD-like lesions induced by DNCB/OX in BALB/c mice. Histopathology examination illustrated that it significantly decreased DNCB/OX-induced epidermal thickness, the infiltration of inflammatory cells, and the count of mast cell. The elevated level of immunoglobulin E (IgE) in serum and the mRNA levels of interferon γ (IFN-γ), interleukin 4 (IL-4) and IL-13 in the ear tissues, were also suppressed by DHMEQ.Discussion and conclusion: This study indicated that DHMEQ would be useful for the treatment of AD.

Surface‐confined electropolymerization of pyronin Y in the graphene composite paper structure for the amperometric determination of dopamine

ABSTRACTSurface‐confined electropolymerization allowed us to easily prepare homogeneous polymer composite paper structures. The fabrication of freestanding graphene (Gr)‐based composite electrodes is very important for many modular approaches in electrochemical applications, such as fuel cells, supercapacitors, and sensors. A Gr composite paper electrode doped with polymeric films of pyronin Y was fabricated by two repetitive simple applications: vacuum filtration and surface‐confined electropolymerization. The characterization of this composite paper was done with scanning tunneling microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, powder X‐ray diffraction spectroscopy, Raman spectroscopy, UV–visible absorption spectroscopy, four‐point probe conductivity measurement, cyclic voltammetry, and electrochemical impedance spectroscopy. The freestanding composite paper demonstrated good electrocatalytic activity for the electrooxidation of dopamine; this indicated that this composite paper could be used for the amperometric quantification of dopamine in real samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45139.

Design and simulation of the electromagnetic heating of a biological tissue

PurposeThe purpose of this paper is to present the design and the numerical calculation of the electromagnetic heating system for the ablation therapy. Hence, the heating of the tumor cells must be processed very carefully to achieve a localized coagulative necrosis and to avoid too high temperatures inside the tissue.Design/methodology/approachThe non-invasive method of the ablation therapy is implemented due to the inductive power transmission between the generator and implant. The ferromagnetic implant has a small size and can be placed intravenously into tumor cells. High-frequency driving currents are necessary to obtain high induced eddy currents within the ferromagnetic implant.FindingsFinite element analysis has been used for the design and numerical calculation of the electromagnetic heating system. The electromagnetic analysis is done in the time domain due to the nonlinearity of the ferromagnetic implant. Magnetic fields are computed based on a magnetic vector potential formulation. The thermal analysis is done in the time domain as well. The temperature computation in biological tissue is based on a heat balance equation.Research limitations/implicationsThis paper is focused on the design and simulation of the inductive system for the ablation therapy.Practical implicationsThe designed system can be practically implemented. It can be used for the clinical study of the immune response by the thermal ablation therapy.Originality/valueThe common method of thermal ablation is combined with an inductive power transmission. It enables a repetitive application of this method to study the immune response.

Removal of Cd(II) and Hg(II) from effluents by ionic solid impregnated chitosan

Ethylhexadecyldimethyl ammonium bromide impregnated chitosan (EHDAIC) was prepared to remove cadmium and mercury from synthetic effluent. The adsorbent was characterized by FTIR, XRD, SEM, EDX and TGA-DTA. Adsorption studies were carried out under different conditions of pH, adsorbent dose, temperature, and contact time. The results showed that the adsorption capacity of EHDAIC is a function of the solution pH and the optimum pH for these metal ions was found to be 3.0. The equilibrium data has been described using Langmuir and Freundlich isotherm models. The maximum adsorption capacity of 341.30mg/g was observed for Cd(II) and 43.43mg/g for Hg(II) in accordance with Langmuir adsorption isotherm in the form of their chloro complexes. The kinetic data fitted well with pseudo-second-order model, and equilibrium data was found to follow Freundlich isotherm model. The calculated thermodynamic parameters showed that the adsorption process was feasible, exothermic and spontaneous. Effect of common excipient ions was studied. Also the material was tested for large sample volumes using column extraction process. The adsorbent material could be regenerated for repetitive applications.

Skin Hardness and Epidermal Thickness Affect the Vibration Sensitivity of the Foot Sole

Objective: The cutaneous mechanoreceptors of the foot sole detect the changes in the application of mechanical loads on the plantar surface during gait and standing, and contribute to controlling the standing balance and postural reflexes in healthy subjects. A local thickening of the foot sole skin occurs in response to repetitive load application. We hypothesized that an elevated skin hardness of the foot sole could reduce its mechano sensitivity. Methods: In healthy subjects, we quantified the sensation produced by different amplitudes of vibratory stimulations at two frequencies (25 and 150 Hz). The vibration threshold was determined on the 1st or 2nd, and 5th metatarsal heads, and the heel at each vibration frequency. The Stevens power function (Ψ=k.Φn) allowed to obtain regression equations between the estimate (Ψ) of the vibratory stimuli and their physical magnitude (Φ). Any increase in the absolute k value (all were negative) indicated a reduced sensitivity to the lowest loads. The n coefficient measured the global perception. The highest skin hardness (Shore) was measured on the 5th metatarsal head and the heel. In some subjects, superficial skin abrasion of the 5th metatarsal head was performed and the vibration sensitivity was tested again. Results: The vibration threshold was significantly higher at the level of the 5th metatarsal head and the heel. The k value was significantly higher at the 25 and 150 Hz frequencies for the 5th metatarsal head, and only at 25 Hz for the heel. At both vibration frequencies, negative correlations were obtained between the k values and skin hardness. After skin abrasion, the n coefficient was significantly higher at both vibration frequencies. Conclusion: Skin hardness affects the foot sole mechano sensitivity and could alter the control of posture during standing and walking. This indicates that foot care by podiatrist are relevant to improve posture control.

Finite Element Simulation of Complex Thermomechanical Fatigue Evolution

Fatigue failures occur due to the application of fluctuating stresses that are much lower than the stress required to cause failure during a single application of stress. The process is dangerous because a single application of the load would not produce any ill effects, and a conventional stress analysis might lead to assumption of safety that does not exist. The fatigue process is thought to begin at an internal or surface flaw here the stresses are concentrated, and consists initially of shear flow along slip planes. The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallic and ceramics. Fatigue, as understood by materials technologists, is a process in which damage accumulates due to the repetitive application of leads that may be well below the yield point.