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Purpose The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by ferro-fluid couple stress lubricant. Design/methodology/approach Based upon the Stokes couple stress theory, ferro-hydrodynamic model of Shliomis and Christensen rough surfaces model, squeeze-film characteristics between two rough parallel circular discs considering rotational inertia effects are obtained. Findings According to the results, it is found that the combined effects of couple stresses and ferro-fluid lubricants increases squeeze film performance with respect to the classical Newtonian lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it. Originality/value This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with ferro- fluid, rotational inertia, couple stresses and surface roughness effects.

Purpose The purpose of this paper is to investigate squeezing motion between conical plates lubricated by ferro-fluid couple stress lubricants considering convective fluid inertia effects. Design/methodology/approach Based upon the Stokes couple stress theory, Ferro-hydrodynamic model of Shliomis and averaged inertia principle, squeeze film characteristics between conical plates are obtained. Findings According to the results, it is found that couple stress ferro-fluid lubricants increase squeeze film characteristics. Moreover, with increasing convective fluid inertia parameter, the squeeze film characteristics are increased. In contrast, the dimensionless load-carrying capacity diminishes when half cone angle of conical plate increases. Originality/value This paper is relatively original and it describes the squeeze film characteristics between conical plates with ferro-fluid, convective inertia, couple stresses and half cone angle of conical plate effects.

Electromechanical nanothermometers are instruments that work on the basis of the van der Waals (vdW) potential energy and interaction force of their constituent carbon nanotubes (CNTs). The CNT-based nanothermometers have two di fferent con gurations: telescope and shuttle con gurations. In this article, based on the Lennard-Jones potential function together with the continuum approximation, fi rst, the vdW potential energy and interaction force for a telescope con guration with nite CNTs are derived, which have not been obtained in the previous research studies. Thereafter, by employing the interaction force, the equation of motion between constituent CNTs is solved. Subsequently, a new semi-analytical expression is obtained which enables one to precisely evaluate the oscillation frequency. By employing the given formulae, e ffects ofdi erent system parameters on the vdW interactions and oscillation frequency are shown.

The present study aims at investigating a couple stress ferrofluid lubricant effects on the performance of the squeezed film when a uniform external magnetic field is applied. For this purpose, Shliomis ferrohydrodynamic and couple stress fluid models are employed. The considered geometry is parallel triangular plates. The effects of couple stress, volume concentration, and Langevin parameters on squeeze film characteristics including time vs. height relationship and load-carrying capacity are investigated. According to the results, employing couple stress ferrofluid lubricant in the presence of the magnetic field leads to an increased performance of the squeeze film.

Purpose – The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by piezo – viscous couple stress lubricant with pressure-dependent viscosity variation. Design/methodology/approach – Based upon the Stokes couple stress theory, Barus viscosity-pressure dependency relation and Christensen rough surfaces model, squeeze film characteristics between two rough parallel circular discs are obtained. Findings – According to the results, it is found that, the combined effects of couple stresses and viscosity-pressure dependency increases squeeze film performance with respect to the classical Newtonian iso-viscous (constant viscosity) lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it. Originality/value – This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with viscosity-pressure dependency, rotational inertia, couple stresses and surface roughness effects.

Electromechanical carbon nanothermometers are devices that work based on the interactions and relative motions of double-walled carbon nanotubes (DWCNTs). In this paper, the mechanics of carbon nanotubes (CNTs) constituting two well-known configurations for nanothermometer, namely shuttle configuration and telescope configuration are fully investigated. Lennard-Jones (LJ) potential function along with the continuum approximation is employed to investigate van derWaals (vdW) interactions between the interacting entities. Accordingly, semi-analytical expressions in terms of single integrals are obtained for vdW interactions. Acceptance condition and suction energy are studied for the shuttle configuration. In addition, a universal potential energy is presented for the shuttle configuration consisting of two finite CNTs. Also, for the telescope configuration, extensive studies are performed on the distributions of potential energy and interaction force for various radii and lengths of CNTs. It is found that these geometrical parameters have a considerable effect on the potential energy.

The solution of a Volterra type screw dislocation problem in an orthotropic rectangular plane with finite length and width and various boundary conditions is obtained by means of a separation of variables technique. A distributed dislocation method is employed to obtain integral equations of the plane with cracks and cavities under an anti-plane traction. The ensuing equations are of the Cauchy singular type and have been solved numerically. Several examples are presented to demonstrate the applicability of the proposed solution.

The effectiveness of different cryodevices (open-pulled straw (OPS), electron microscopy grid (EMG), and Cryotop was evaluated for vitrification of immature bovine oocytes. Polar body, metaphase II stage (MII), survivability, and subsequent developmental rates were determined. Only oocytes with four or five layers of cumulus cells were used. Oocytes were equilibrated in two vitrification solutions - 1: 10% DMSO + 10% ethylene glycol (EG) for 30-45sec and 2: 20% DMSO + 20% EG +0.5M sucrose for 25sec -, mounted on one of the cryodevices and directly plunged into liquid nitrogen for 10 days. Immature vitrified oocytes using Cryotop showed the highest rates of polar body extrusion (PB) and nuclear maturity (MII); 41 and 58% respectively. Vitrified oocytes using OPS and EMG showed 26 and 32%; and 35 and 46% of PB and MII rates, respectively. The highest survivability resulted from Cryotop and EMG groups and no significant difference was found between them. Vitrified oocytes using Cryotop had the highest cleavage and blastocyst rates. All of the mean rates for vitrified immature oocytes were significantly lower than that of control group (P

Background Psoriasis is a chronic inflammatory skin disease characterized by pathological skin lesions because of various exogenous and endogenous factors and associated with a number of biochemical and immunological disturbances. Objective The aim of the present study was to determine the level of adenosine deaminase activity, serum trypsin inhibitory capacity and total antioxidant capacity of plasma in psoriatic patients. Subjects and methods The study was performed in controls (n = 46) and in psoriatic patients (n = 40). The patients were scored with PASI (psoriasis area and severity index). The serum ADA activity was determined using Aguisti and Galanti method and serum trypsin inhibitory capacity (sTIC) were measured by enzymatic assay. Besides, serum total antioxidant capacity was measured using ferric reducing ability of plasma. Results The serum ADA activity of the psoriatic patients was found to be significantly higher (P

Based on previous studies for vitrification of oocytes, it has been shown that short term exposure to DMSO during vitrification could improve the maturation rate and cause not spontaneous parthenogenesis (Isachenko et al., 2006). In addition, it was reported that DMSO in freezing media caused disassembly of microfilaments and chromosomal abnormalities in mouse oocytes (Vincent et al., 1990). On the other hand, DMSO is categorized as a potent glass former and its existence in vitrification solution seems necessary. The aim of this study was to determine the in vitro viability of immature bovine oocytes vitrified by short or long time exposure to DMSO. Materials and Methods: Cumulus oocytes complexes (COCs) with homogenous ooplasm were recovered from slaughterhouse ovaries and used in this study. The vitrification protocol was adapted from Kuwayama et al (2005) with minor modifications. Briefly, oocytes were washed twice in holding solution (HS, Hepes-buffered TCM medium supplemented with 20% fetal calf serum, FCS) and kept there for about 15 min. Group of four COCs were incubated in the first vitrification solution (VS1; 7.5% DMSO and 7.5% EG in HS) for 12 min. Equilibration in VS1 was performed in three steps of increasing concentration. First (F) and second (S) steps contained 1/3 and 2/3 of VS1 diluted in HS, and the third (T) step contained only pure VS1. Based on removal of DMSO from each step, five treatment groups were designed: (G1) control, (G2) VS1, (G3) F w/o DMSO, (G4) F+S w/o DMSO, and (G5) F+S+T w/o DMSO. For G3, G4 and G5, similar concentration of EG was added to replace DMSO in VS1. All treatment groups were equilibrated into the second vitrification solution (VS2; 15% DMSO, 15% EG and 0.5M sucrose in HS) for a further 60 sec. Two experiments were performed: (a) cytotoxicity after only exposure, and (b) in vitro viability after vitrification processes. In cytotoxicity test, immature oocytes were directly transferred to the warming solution (WS). In vitrification experiment, oocytes were instantly loaded on a Cryotop device and submerged into liquid nitrogen (LN2) for storage. The time of exposure from VS2 to LN2 was not longer than 90 s. Vitrified samples were maintained in LN2 for at least 10 days. Immediately after removing the Cryotop from LN2, thin strip of Cryotop was submerged in 3 ml HS plus 1M sucrose (WS; 39°C) and smoothly tried to detach oocytes from Cryotop device. Immature oocytes were left in WS for one minute and then transferred to HS plus 0.5M and 0.15M sucrose solution for 3 and 5 min, respectively. Finally, the immature oocytes were washed twice in HS for 5 min each and processed for in vitro maturation. Significant differences among treatments used in the experiment were revealed by one-way analysis of variance and followed by Duncan's multiple range test for mean comparisons (P < 0.05) using SAS software (ver. 9.1).