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Mechanical Pressure (mechanical + pressure)
Selected AbstractsExplicit solutions for the instantaneous undrained contraction of hollow cylinders and spheres in porous elastoplastic mediumINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2002A. Giraud Abstract In this article we present closed-form solutions for the undrained variations in stress, pore pressure, deformation and displacement inside hollow cylinders and hollow spheres subjected to uniform mechanical pressure instantaneously applied to their external and internal boundary surfaces. The material is assumed to be a saturated porous medium obeying a Mohr,Coulomb model failure criterion, exhibiting dilatant plastic deformation according to a non-associated flow rule which accounts for isotropically strain hardening or softening. The instantaneous response of a porous medium submitted to an instantaneous loading is undrained, i.e. without any fluid mass exchange. The short-term equilibrium problem to be solved is now formally identical to a problem of elastoplasticity where the constitutive equations involve the undrained elastic moduli and particular equivalent plastic parameters. The response of the model is presented (i) for extension and compression undrained triaxial tests, and (ii) for unloading problems of hollow cylinders and spheres through the use of appropriately developed closed-form solutions. Numerical results are presented for a plastic clay stone with strain hardening and an argilite with strain softening. The effects of plastic dilation, of the strain softening law and also of geometry of the cavity on the behaviour of the porous medium have been underlined. Analytical solutions provide valuable benchmarks enabling various numerical methods in undrained conditions with a finite boundary to be verified. Copyright © 2002 John Wiley & Sons, Ltd. [source] Are we aware of all complications following body piercing procedures?INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 4 2009Bogus, aw Antoszewski MD Background, The popularity of body piercing procedures is increasing around the world. Body piercing, depending on the age and social group, is believed to involve up to 51% of the general population. Complications following piercing procedures are variable. Objective, To present an unusual complication after lower lip piercing , embedding of a stud into the lip , and to determine why it occurred from the side of the mucous membrane and not from the side of the skin. Methods, A 21-year-old man presented to the plastic surgery outpatient clinic with embedding of piercing into the lower lip. Results, In lateral X-ray film, a metallic shadow was observed in the area of the oral soft tissues. The length of the stick was only 8 mm. In this patient, a stick that was too short in relation to the thickness of the lip was used. In this situation, the ends of the stud pressed too strongly on the surrounding tissues. Consequently, this may have caused necrosis of the mucous membrane and embedding of the stud into the lip. Conclusion, The observations described confirm a higher susceptibility to mechanical pressure of the mucous membrane than of the skin. An increasing rate of complications after body piercing reflects a lack of medical knowledge in individuals performing such procedures. [source] Persistent sensory dysfunction in pain-free herniotomyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2010E. K. AASVANG Background: Persistent post-herniotomy pain may be a neuropathic pain state based on the finding of a persistent sensory dysfunction. However, detailed information on the normal distribution of sensory function in pain-free post-herniotomy patients hinders identification of exact pathogenic mechanisms. Therefore, we aimed to establish normative data on sensory function in pain-free patients >1 year after a groin herniotomy. Methods: Sensory thresholds were assessed in 40 pain-free patients by a standardized quantitative sensory testing (QST). Secondary endpoints included comparison of sensory function between the operated and the naïve side, and correlation between sensory function modalities. Results: QST showed that on the operated side, thermal data were normally distributed, but mechanical pressure and pinch thresholds were normalized only after log-transformation, and cold pain and pressure tolerance could not be normalized. Comparison of QST results revealed significant (P<0.01) cutaneous hypoesthesia/hyperalgesia, but also significant pressure hyperalgesia (P<0.01) and decreased pressure tolerance (P=0.02) on the operated vs. the naïve side. Wind-up was seen in 6 (15%) but with a low pain intensity. Conclusion: Persistent sensory dysfunction is common in pain-free post-herniotomy patients. Future studies of sensory function in persistent post-herniotomy pain should compare the findings to the present data in order to characterize individual patients and potentially identify subgroups, which may aid in allocation of patients to pharmacological or surgical treatment. [source] ENZYMATIC HYDROLYSIS OF SOYBEAN FOR SOLVENT AND MECHANICAL OIL EXTRACTIONJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2000PRAVEEN C. BARGALE ABSTRACT Due to inefficient extractability of its low oil content, soybeans are often bypassed in village-scale processing. Soygrits, flakes, and expanded collets were hydrolyzed by proteases, cellulases, and pectinases before oil extraction by solvent and static mechanical pressure. Driselase with multi-enzyme activity and two proteases improved solvent extraction rates but only Driselase enhanced mechanical pressing. Up to 58% of seed oil was pressed from enzyme-hydrolyzed flakes but 88% was pressed from Driselase-treated collets. Either pretreatment is a feasible adjunct to mechanical pressing in small batch operations. [source] Accelerated DNA fragmentation of the denture-bearing mucosal epithelium in an animal model of diabetesJOURNAL OF ORAL REHABILITATION, Issue 4 2001Y. Maruo This study examined the effect of masticatory pressure transmitted directly to the hard palate mucosa on the final stage of terminal differentiation of keratinizing system of rats with and without streptozotocin-induced diabetes mellitus. In the nondiabetic rats with masticatory pressure, the number of terminal-deoxynucleotidyl-transferase-mediated deoxyuridine-triphospate-biotin nick end labelling (TUNEL) positive cells tended to increase about twice as much as in the nondiabetic rats without pressure with and without denture. A similar tendency of increase was observed in the diabetic rats without pressure. The synergy of the mechanical pressure and diabetic condition for 2 weeks greatly accelerated the DNA fragmentation, showing 8-fold increase in TUNEL positive cells over the normal control, and caused exfoliation of the stratum corneum. A 4-week exposure of diabetics to the masticatory pressure induced laminar splitting in the midst of the spinosum. Some cells in the stratum granulosum exhibited a sign of DNA fragmentation when laminar splitting took place in the vital cell layer. Premature DNA fragmentation may disturb the adhesion between spinosum cells and prevent the maturation of stratum corneum. Increase in Bax protein-like immunoreactivity in these epithelial cells as revealed by immunocytochemistry may underlie the premature DNA fragmentation in the oral masticatory epithelium under pressure in diabetic patients. [source] Simultaneous Spark Plasma Synthesis and Densification of TiC,TiB2 CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Antonio M. Locci The simultaneous synthesis and densification of dense TiC,TiB2 composite has been investigated starting from Ti, B4C, and C as reactants, and using the spark plasma sintering (SPS) technique. The optimal conditions for complete conversion of the reactants to the composite were determined for different applied DC current levels. A kinetic investigation performed allows us to conclude that solid-state diffusion is the mechanism governing the synthesis process. It is seen that TiC is the first phase formed, while TiB2 formation occurs afterward. Two intermediate boride phases, i.e. TiB and Ti3B4, are also formed but, as the SPS holding time was augmented, they were gradually and completely converted to TiB2. Moreover, it is found that in order to reach relatively high dense products, an electric current needs to be applied for time intervals longer than those required for obtaining complete conversion. A pure dense product (relative density ,98%) was obtained when an electric pulsed current of 1100 A and a mechanical pressure of 20 MPa were applied for about 4 min. [source] Attenuation of pain and inflammation in adjuvant-induced arthritis by the proteasome inhibitor MG132ARTHRITIS & RHEUMATISM, Issue 7 2010Aisha S. Ahmed Objective In rheumatoid arthritis (RA), pain and joint destruction are initiated and propagated by the production of proinflammatory mediators. Synthesis of these mediators is regulated by the transcription factor NF-,B, which is controlled by the ubiquitin proteasome system (UPS). The present study explored the effects of the proteasome inhibitor MG132 on inflammation, pain, joint destruction, and expression of sensory neuropeptides as markers of neuronal response in a rat model of arthritis. Methods Arthritis was induced in rats by injection of heat-killed Mycobacterium butyricum. Arthritis severity was scored, and nociception was evaluated by mechanical pressure applied to the hind paw. Joint destruction was assessed by radiologic and histologic analyses. NF-,B DNA-binding activity was analyzed by electromobility shift assay, and changes in the expression of the p50 NF-,B subunit and the proinflammatory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) were detected by immunohistochemistry. Results Arthritic rats treated with MG132 demonstrated a marked reduction in inflammation, pain, and joint destruction. The elevated DNA-binding activity of the NF-,B/p50 homodimer and p50, as well as the neuronal expression of SP and CGRP, observed in the ankle joints of arthritic rats were normalized after treatment with MG132. Conclusion In arthritic rats, inhibition of proteasome reduced the severity of arthritis and reversed the pain behavior associated with joint inflammation. These effects may be mediated through the inhibition of NF-,B activation and may possibly involve the peripheral nervous system. New generations of nontoxic proteasome inhibitors may represent a novel pharmacotherapy for RA. [source] Collagen dynamics in articular cartilage under osmotic pressureNMR IN BIOMEDICINE, Issue 8 2006Göran Zernia Abstract Cartilage is a complex biological tissue consisting of collagen, proteoglycans and water. The structure and molecular mobility of the collagen component of cartilage were studied by 13C solid-state NMR spectroscopy as a function of hydration. The hydration level of cartilage was adjusted between fully hydrated (,80 wt% H2O) and highly dehydrated (,30 wt% H2O) using the osmotic stress technique. Thus, the conditions of mechanical load could be simulated and the response of the tissue macromolecules to mechanical stress is reported. From the NMR measurements, the following results were obtained. (i) Measurements of motionally averaged dipolar 1H,13C couplings were carried out to study the segmental mobility in cartilage collagen at full hydration. Backbone segments undergo fast motions with amplitudes of ,35° whereas the collagen side-chains are somewhat more mobile with amplitudes between 40 and 50°. In spite of the high water content of cartilage, collagen remains essentially rigid. (ii) No chemical shift changes were observed in 13C cross-polarization magic angle spinning spectra of cartilage tissue at varying hydration indicating that the collagen structure was not altered by application of high osmotic stress. (iii) The 1H,13C dipolar coupling values detected for collagen signals respond to dehydration. The dipolar coupling values gradually increase upon cartilage dehydration, reaching rigid limit values at ,30 wt% H2O. This indicates that collagen is essentially dehydrated in cartilage tissue under very high mechanical load, which provides insights into the elastic properties of cartilage collagen, although the mechanical pressures applied here exceed the physiological limit. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||