Stresses in adhesively bonded joints: A closed form solution

The plane strain of adhesively bonded structures which consist of two different orthotropic adherents is considered. Assuming that the thicknesses of the adherends are constant and are small in relation to the lateral dimensions of the bonded region, the adherends are treated as plates. The transverse shear effects in the adherends and the in-plane normal strain in the adhesive are taken into account. The problem is reduced to a system of differential equations for the adhesive stresses which is solved in closed form. A single lap joint and a stiffened plate under various loading conditions are considered as examples. To verify the basic trend of the solutions obtained from the plate theory a sample problem is solved by using the finite element method and by treating the adherends and the adhesive as elastic continua. The plate theory not only predicts the correct trend for the adhesive stresses but also gives rather surprisingly accurate results

Effects of micelle nature and concentration on the acid dissociation constants of the metal extractor PADA

The pyridine-2-azo-p-dimethylaniline (PADA) ligand presents two acid dissociation constants, being pKa1 related to the pyridinium and pKa2 related to the anilinium residue. These have been measured by spectrophotometric titrations in aqueous solutions containing either the anionic (SDS), or the non–ionic (Triton X-100) or the cationic (DTAC) surfactants. The pKai shifts of the charged systems from that of the PADA/Triton X-100 reference (∆pKai0) are compared. For PADA/DTAC ∆pKa10 = 0.05 and ∆pKa20 = 0.6. For PADA/SDS ∆pKa10 = 2.1 and ∆pKa20 = 2.1 both yielding the value of -126 mV for the surface potential (ψ) of SDS. The ψ value, lying between the calculated Stern potential and the zeta potential, indicates that the dye is located on the SDS micelles between the fixed and the shear layer. In contrast, the behaviour of PADA/DTAC is explained assuming that the positively charged deprotonation sites of PADA are forced to protrude towards the bulk solvent by the positive charges of DTAC micelles. The shifts of the apparent pKai from the aqueous values (∆pKaiw) have also been analysed. Concerning PADA/Triton X-100, the shifts ∆pKa1w = -0.1 and ∆pKa2w = -0.9 are rationalized in terms of dielectric constant reduction at the reaction sites. Concerning PADA/DTAC, ∆pKa1w= -0.05 and ∆pKa2w= -0.3 whereas, for PADA/SDS, ∆pKa1w = 2.0 and ∆pKa2w = 1.2. The pKa2w values decrease on raising the surfactant concentrations for all the investigated systems. This behaviour is explained assuming that the increase of the overall micellar surface and, by consequence, of the reaction sites number, results in a site dilution effect which disfavours proton association. The addition of NaCl induces changes of pKa1 and pKa2 which are explained in terms of (large) reduction of ψ for PADA/SDS and of (small) reduction of the dielectric constant for the other systems

The role of arachidonic acid/cyclooxygenase cascade, phosphodiesterase IV and Rho-kinase in H2S-induced relaxation in the mouse corpus cavernosum

PubMedID: 28501682Background Penile corpus cavernosum is an extremely vascularized tissue and cavernosal smooth muscle tone is regulated by the balance between contractile and relaxant factor. We investigated the possible role of arachidonic acid/cyclooxygenase cascade, phosphodiesterase IV (PDEIV) and Rho-kinase in exogenous hydrogen sulfide (H2S)-induced relaxation in mouse corpus cavernosum. Methods The relaxant response to H2S (NaHS as exogenous H2S; 1–1000 µM) were obtained in isolated mouse corpus cavernosum tissues which pre-contracted by phenylephrine (5 µM). The effects of 4-(4-octadecylphenyl)-4-oxobutenoic acid (OBAA; 10 µM), a selective phospholipase A2 (PLA2) inhibitor, indomethacin (1 µM), a non-selective cyclooxygenase (COX) inhibitor, baicalein (10 µM), a lipoxygenase (LOX) inhibitor, and proadifen (10 µM), cytochrome P450 inhibitor, on the relaxant responses to H2S were investigated. Furthermore, the effects of theophylline (500 µM) and rolipram (1 µM), a non-selective and selective PDEIV inhibitor, and fasudil (3 µM), a specific Rho-kinase inhibitor, were studied on H2S-induced relaxation. Results H2S-induced relaxations were significantly reduced by OBAA, indomethacin and proadifen but not baicalein. Furthermore, theophylline, rolipram and fasudil reduced H2S-induced relaxations. Conclusion These results suggest that PLA2, COX, cytochrome P450, PDEIV and Rho-kinase pathway may involve in H2S-induced relaxation in mouse corpus cavernosum tissues. © 2017 Institute of Pharmacology, Polish Academy of Science

The relaxant mechanisms of hydrogen sulfide in corpus cavernosum

PubMedID: 31148111In several animal and human studies, the contribution of the endothelium, nitric oxide/soluble guanosine monophosphate (NO/cGMP) pathway, adenylyl cyclase, phosphodiesterase (PDE), potassium (K+) channels, L-type calcium channels, Na+-K+-ATPase, muscarinic acetylcholine receptors, RhoA/Rho-kinase pathway, and cyclooxygenase (COX)/arachidonic acid cascade on the relaxant mechanism of l-cysteine/H2S pathway in corpus cavernosum has been investigated. In this chapter the relaxant mechanisms of H2S in corpus cavernosum is discussed with data available in the current relevant literature. Also, in vitro experimental procedure for mice corpus cavernosum which used to investigate the relaxant effect of H2S is given in detail. © Springer Science+Business Media, LLC, part of Springer Nature 2019

The effects of thiol modulators on nitrergic nerve- and S-nitrosothiols-induced relaxation in duodenum

PubMedID: 23412870Background: The aim of this study was to investigate whether thiols are involved in the nitrergic neurotransmission in mouse duodenum. Methods: The effects of thiol-modulating agents, ethacrynic acid (100 µM), a non-specific sulfhydryl alkylator, and diamide (100 µM), an alkylating agent that oxidizes protein sulfhydryl groups and depletes intracellular glutathione, on relaxations to nitrergic stimulation (electrical field stimulation, EFS;10 Hz, 25 V, 1 ms, 15 s-train), S-nitrosoglutathione (GSNO; 5 µM), S-nitrosoacetylpenicillamine (SNAP; 5 µM), and S-nitrosocysteine (CysNO; 10 µM) were investigated. Moreover, the effects of buthionine sulfoximine (100 µM), an inhibitor of ?-glutamylcysteine synthetase, and sulfobromophthalein (100 µM), an inhibitor of glutathione-S-transferase, were studied on relaxant responses to EFS and S-nitrosothiols in mouse duodenum. Results: Exogenous free thiol, glutathione (GSH, 100 µM) did not influence relaxation to EFS, GSNO, SNAP, and CysNO. Ethacrynic acid and diamide significantly decreased relaxation of duodenum to EFS, GSNO, SNAP, and CysNO. This inhibition was prevented by addition of GSH. Buthionine sulfoximine and sulfobromophthalein significantly decreased relaxation to EFS and GSNO but did not influence relaxation to SNAP and CysNO. The inhibitory effect of buthionine sulfoximine and sulfobromophthalein on the relaxant response to EFS and GSNO was prevented by addition of GSH. Conclusions: These results suggest that relaxation to nitrergic stimulation is thiol-dependent, and nitrosothiols, possibly S-nitrosoglutathione may play a role, as an intermediate compound in nitrergic neurotransmission in mouse duodenum

The interaction of L-cysteine/H2S pathway and muscarinic acetylcholine receptors (mAChRs) in mouse corpus cavernosum

PubMedID: 28847570The aim of this study was to investigate the possible interaction of L-cysteine/H2S pathway and muscarinic acetylcholine receptors (mAChRs) in the mouse corpus cavernosum (CC). L-cysteine (endogenous H2S substrate; 10-6-10-3 M), sodium hydrogen sulfide (NaHS; exogenous H2S; 10-6–10-3 M) and acetylcholine (10-9-10-4 M) produced concentration-dependent relaxation in isolated mouse CC tissues. Relaxations to endogenous and exogenous H2S were reduced by non-selective mAChR antagonist atropine (5 × 10-5 M), selective M1 mAChR antagonist pirenzepine (5 × 10-5 M) and selective M3 mAChR antagonist 4-DAMP (10-7 M) but not by selective M2 mAChR antagonist AF-DX 116 (10-6 M). Also, acetylcholine-induced relaxations were reduced by atropine, pirenzepine, 4-DAMP and AF-DX 116, confirming the selective effects of mAChR antagonists. Furthermore, acetylcholine-induced relaxations were attenuated by cystathionine-gamma-lyase (CSE) inhibitor D,L-propargylglycine (PAG, 10-2 M) and cystathionine-ß-synthase inhibitor (CBS) aminooxyacetic acid (AOAA, 10-3 M). L-nitroarginine, nitric oxide synthase inhibitor, augmented the inhibitory effects of mAChR antagonists and H2S enzyme inhibitors on acetylcholine-induced relaxations. In addition, the existence and localization of CSE, CBS and 3-MST were demonstrated in mouse CC. Furthermore, tissue acetylcholine release was significantly increased by L-cysteine but not by exogenous H2S. The increase in acetylcholine level was completely inhibited by AOAA and PAG. These results suggest that M1 and M3 mAChRs contributes to relaxant effect mediated by endogenous H2S but at same time L-cysteine triggers acetylcholine release from cavernosal tissue. Also, the role of NO in the interaction of L-cysteine/H2S pathway and muscarinic acetylcholine receptors (mAChRs) could not be excluded. © 2017T-2015-3468This study was supported by the Cukurova University Research Foundation ( T-2015-3468 )

The interaction mechanism of gold(III) with the metal extractant PADA in DTAC micellar medium and applications to gold(III) extraction

The kinetics of binding of Au(III), initially present as AuCl4 -, to the azo-dye ligand pyridine-2-azo-p-dimethylaniline (PADA) in dodecyltrimethylammonium chloride (DTAC) micellar solution have been investigated as a preliminary study on gold micellar extraction and recovery. PADA (Figure 1) is endowed with excellent hydrophobic properties, which make it an ideal carrier for the transport of the metal ions from water to micelle, allowing the metal extraction process to be carried out. The kinetic study enables the mechanism of the binding reaction to be worked out under different investigated medium conditions, showing that in the presence of the DTAC micellar pseudo-phase the reaction is strongly accelerated (catalytic effect) compared to water. The results concur in suggesting that differently oxydrilated forms, originated from the starting AuCl4-, are reactive and, in DTAC at low pH, also the aquoform AuCl3(H2O) reacts with PADA, whereas the tetrachlorocomplex apparently does not react, except that in water at relatively low pH. The characteristics of the water/micelle system have been also exploited, for the purpose of extracting and recovering gold, by applying the micellar enhanced ultrafiltration (MEUF) procedure. Using MEUF the negative AuCl4- ion is extracted with yields near to 100% by DTAC, owing to direct adsorption on the micelle surface. The recovery step has been accomplished adding an electrolyte (NaCl) solution, which lowers the surface potential of the micelle, thus favoring the recovery process. Ammonia has been also added in order to convert the gold(III) chlorocomplexes into the ammonia complex, which is repelled from the positively charged DTAC surface and can be recovered. A recovery yield of 86% has been achieved, which provides a promising basis for the extraction of gold from water using the surfactant DTAC

The kinetics of gold(III) extraction by pyridine-2-azo-p-dimethylaniline in water and in micellar systems

The kinetics of reaction between AuCl4- and the azo-dye pyridine-2-azo-p-dimethylaniline (PADA) have been investigated in water and in the presence of DTAC micelles, using classical spectrophotometry and the stopped-flow technique. PADA reacts with different chloro/hydroxo gold(III) complexes, in turn formed as the pH and Cl- concentration were changed, according to a network of parallel paths. In aqueous solution, at low pH values, a fast step is observed which is ascribed to the ligand induced expulsion of a labile water molecule from the reacting species Au(H2O)Cl3 which forms at low pH values. At higher values of pH, the reaction is much slower because, in the key step, PADA has to replace the more inert Cl- ions in the gold coordination shell. In the presence of DTAC a remarkable catalytic effect is observed, owing to the absorption and attraction of the reactants on the micelle surface. Moreover, DTAC favors the formation of aquochloro aurates, thus inducing a change in the gold(III) speciation compared to that in water. The analysis of the data suggests that the aquo species Au(H2O)Cl3 and Au(H2O)2Cl2+ play a major role in the reaction mechanism. © 2015 Published by Elsevier B.V.“la Caixa” Foundation: OSLC-2012-007 Ministerio de Economía, Industria y Competitividad, Gobierno de España: MINECO CTQ2014-58812-C2-2-RThe financial support by Obra Social “la Caixa”, project OSLC-2012-007, and by the Ministerio de Economia y Competividad - Gobierno de España, project MINECO CTQ2014-58812-C2-2-R, are gratefully acknowledged. Appendix