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PDF File, 132KB, PKD3 knockdown reduces MMP-9 activity in conditioned medium, but does not alter MMP-9 or MMP-14 transcripts.

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PDF file, 513KB, Transient knockdown of PKD2 and/or PKD3 reduces migration and invasion in PC3 cells.

PDF file, 170KB, Knockdown of PKD3 by multiple siRNAs and its effect on cell survival.

PDF file, 457KB, The effect of PKD3 on cell migration is mediated through secreted factors in PC3 cells.

PDF file, 59KB, Map of the cytokine antibody array.

We report here the impact of different alloying elements in steels on friction and wear behavior by performing ball-on-flat lubricated reciprocating tribotesting experiments on 52100 ball on steel flats with different compositions (52100, 1045, A2, D2, M2, and a specialty Cu-alloyed steel) heat-treated to give similar hardness and microstructure, with polyalphaolefin (PAO-4) as the lubricant. There are small variations of coefficient of friction among these alloys. The major observation is that steels containing high concentrations (≥ 10 wt.%) of Cr, Mo, and V gave rise to markedly reduced wear compared with 52100 or plain carbon steels. D2 steel, which contains 11.5 wt.% Cr as the major alloying element was the most wear-resistant. The wear resistance is strongly correlated with the efficiency of formation of carbon-containing oligomeric films at specimen surfaces as determined by Raman spectroscopy. This correlation holds for steels heat-treated to have higher hardness and with n-dodecane, a much less viscous lubricant compared with PAO-4. Given the strong affinity of chromium to oxygen, chromium should exist as Cr2O3 at the steel surfaces during testing. We have performed molecular dynamics simulation on Cr2O3 and demonstrated its ability to catalyze the formation of carbon-containing oligomeric films from hydrocarbon molecules, consistent with its known catalytic activity in other hydrocarbon reactions. We believe that chromium-containing alloys, such as D2, and coatings, such as CrN, derive their wear resistance in part from the efficient in-situ formation of wear-protective carbon tribofilms at contacting asperities.

The ring-liner interface of an internal combustion engine is a very important interface because its behavior directly affects fuel efficiency of an automobile and the engine life. The liner surface...

Many previous studies of tribofilms have interpreted D- and G-bands in Raman spectra as evidence that diamond-like carbon (DLC) was formed during sliding. DLC and other amorphous-carbon films are produced by high-energy processes or high-temperature pyrolysis. Since neither of these conditions commonly occurs in a sliding interface, it seems unlikely that such materials could be produced during simple frictional sliding. To understand this apparent contradiction, we systematically analyzed tribofilms produced from vapor and liquid lubrication experiments using Raman spectroscopy with varied laser power and wavelength. The results provide evidence that DLC-like features in Raman spectra of tribofilms formed from organic molecules originate, not by tribochemical synthesis in situ during the tribo-testing as suggested previously, but rather from post-synthesis photochemical degradation of carbonaceous organic matter during the Raman analysis.

This paper reports a numerical approach, based on a nonlinear particle spring model and a collision detection procedure, to simulate the shape of a draped cloth, or a flexible sheet, together with a simple but precise three-dimensional shape reconstruction method for real fabric applications. The latter is utilized to verify the accuracy of the proposed drape simulation model. The drapes of four types of fabric on a cylinder are simulated, and the results are compared with the reconstructed shapes of the same cloths; the results show an excellent agreement. The simulation model is further used to calculate the shapes of skirts of different materials and sizes, and the effects of fabric parameters, length, and waist size are numerically investigated. The results reveal that under the same conditions, the behaviors of different materials are affected by their properties in terms of stiffness coefficients of the springs. The silk skirt looks soft and fluttering; the outer contour curve of the skirt simulated for the polyester fabric appears relatively smoother, but the shape of the cotton skirt seems to be stiffer. The skirt made of fabric of 10% cotton and 90% polyester combines the characteristics of the polyester and cotton fabric.

Pour point, or the temperature below which a fluid ceases to flow, is an important lubricant property. A molecular-dynamics-based approach is developed to explore and identify the pour points of a ...

All-solid-state batteries (ASSBs) using an alkali metal anode and a solid-state electrolyte (SE) face several problems due to poor physical and electrical contact. Recent experiments have shown that applying a stack pressure can improve the interface contact and suppress void formation. The mechanical properties of Na metal are different from those of Li metal, leading to differences in the mechanisms of the pressure-dependent interface evolution. Herein, we report a three-dimensional time-dependent model for tracking the evolution of interfaces formed between Na metal and Na-β″-alumina SE. Our results show that Na metal contacts more conformally with the SE, providing a lower interfacial resistance, compared with Li metal, assuming equal resistance due to contamination. The differences due to contact elastoplasticity are larger than the differences in metal creep effects. In fact, we show that increased stack pressure can lead to lower creep because the contact is more conformal at high pressures. Our excellent agreement with recent experiments determines an effective hardness of Na in the Na-SE batteries to be 15 MPa. The results further reveal that the pressure dependence of void suppression is dominated by contact elastoplasticity.

The contact of nominally flat surfaces can be treated as a bilateral periodic contact problem considering the stochastic surface similarity to the asperity distribution in a representative region. This similarity treatment method can be extended to material inhomogeneities. A novel numerical model for simulating the elastoplastic contact between nominally flat surfaces of materials containing inhomogeneities or coatings is developed via extending the concept of the discrete convolution and FFT (DC–FFT) algorithm with double superpositions of influence coefficients, which is named the DCSS–FFT algorithm. Several cases are analyzed with this new algorithm to examine its convenience, efficiency, and accuracy in dealing with complicated nominally flat–flat contact problems. The effects of surface roughness and material inhomogeneity are explored, and the mechanisms of contact surface failure are discussed.

The present study is on the analytical solution for the elastic field due to a cuboidal inclusion of uniform eigenstrain within a transversely isotropic full-space material, and a numerical method to model inclusions of any arbitrary shapes and with any eigenstrain distributions as the integration of a set of such cuboidal inclusions. The fast Fourier transform (FFT) is applied for efficient computation. The developed method and results are implemented to analyze the elastic field in a transversely isotropic full-space material containing inclusions of different shapes, different eigenstrain distributions, and multiple cuboids of different densities. Furthermore, the effect of material anisotropy on the stress field subjected to a spherical inclusion with pure dilatant eigenstrains is explored by comparing the behavior of a transversely isotropic material with that of a corresponding isotropic one. The numerical results show that the induced stresses are drastically influenced by the Young’s moduli of transversely isotropic materials, and that material constant C 33 has a large influence on normal stress σ 33 .

Certain contact problems must be treated as three-dimensional (3D) axial periodic problems, such as the contact of cylinders with rough surfaces and/or inhomogeneities in the materials, whose structural features in contact are confined in a finite domain in one direction but extended infinitely in the other direction. A novel numerical model for simulating the contact of machined cylindrical components containing inhomogeneities is developed via extending the concept of the 3D line-contact fast Fourier transform (FFT) algorithms. Due to the stochastic similarity of asperity and inhomogeneity distributions in the length direction, the cylinder is divided into N segments in the length direction while taking the roughness and inhomogeneities in one of these segments as representatives. The periodic convolution and FFT is used in the length direction, together with superposing the influence coefficients (ICs) of the N segments, while the discrete (circular) convolution and fast Fourier transformation (DC–FFT) is used in the non-periodic direction; this is named the DCS–FFT algorithm. The accuracy of the DCS–FFT algorithm is examined by the comparison of the numerical results for a degenerated cylindrical contact with the corresponding analytical solution, and its efficiency is evaluated through the comparison of its execution speed with that of two other FFT-based algorithms. The developed method is implemented to study the influence of inhomogeneities on subsurface stress distributions with/without the periodic length direction extension and superposition of inhomogeneity ICs. A criterion is provided to decide whether the DCS procedure is needed for the contact analysis of inhomogeneity-containing cylinders.

This paper reports a unified analogy-based computation methodology, together with a concept of multifield, multifunctional sensing, from elasticity to electromagnetic-chemical-thermal fields, via utilizing the similarities of mechanical-electromagnetic-chemical-thermal (MEMCT) field variables, governing equations, and the material properties pertaining to each individual field. Two equivalences are systemized, which are the field-formulation equivalence and surface-value equivalence. Due to similarity, a number of thermal, electromagnetic, or chemical solutions can be obtained from the direct degeneration of existing mechanical solutions by making specified equivalences of 2G↔k0↔ϖ0↔μ0↔β0 with G for shear modulus, k0 for heat conductivity, ϖ0 for dielectric permittivity, μ0 for magnetic permeability, and β0 for chemical diffusivity, as well as by setting Poisson’s ratio ν → 0.5. These specified equivalences enable quick solutions to other fields directly from mechanics formulations, such as those in the forms of the Galerkin vectors and Papkovich-Neuber potentials, and field coupling, by means of analogy. Several examples are given, one is used to demonstrate that the field solutions of a layered half-space with imperfect thermal, electromagnetic, or chemical interfaces can be readily obtained from the elastic solutions involving interfacial imperfections via the obtained formulation equivalence. A set of simple equations are derived to relate surface behaviors of different fields via the obtained surface-value equivalence, on which a concept of multifield sensing is proposed.

Protein kinase D (PKD) belongs to a family of serine/threonine kinases in the calcium/calmodulin-dependent kinase superfamily. It modulates a number of signal transduction pathways involved in regulation of cell proliferation, survival, migration, angiogenesis, regulation of gene expression, and protein/membrane trafficking, mediated by variety of stimuli such as growth factors, hormones, and cellular stresses. Although its role in cancer progression remains elusive, current literature supports a potential tumor promoting function of the selective PKD isoforms in prostate cancer, making them promising therapeutic targets for cancer treatment.

Under severe conditions, solid contacts take place even when parts are lubricated. Precise mathematical conditions are needed to describe the interior interface between fluid lubrication and solid-contact zones. In order to distinguish the conditions for this interface from conventional lubrication boundary conditions, they are named lubrication–contact interface conditions (LCICs). In this work, mathematical LCICs are derived with local flow continuity from the continuum mechanics point of view and pressure inequality across the interface. Numerical implementations are developed and tested with problems having simple geometries and configurations, and they are integrated into a new mixed/boundary elastohydrodynamic lubrication solver that uses a new method to determine solid-contact pressures. This solver is capable of capturing film thickness and pressure behaviors involving solid contacts.

BackgroundDermal fibrosis occurs in many human diseases, particularly systemic sclerosis (SSc) where persistent inflammation leads to collagen deposition and fiber formation in skin and multiple organs. The family of protein kinase D (PKD) has been linked to inflammatory responses in various pathological conditions, however, its role in inflammation-induced dermal fibrosis has not been well defined. Here, using a murine fibrosis model that gives rise to dermal lesions similar to those in SSc, we investigated the role of PKD in dermal fibrosis in mice lacking PKD2 activity.MethodsHomozygous kinase-dead PKD2 knock-in mice (PKD2SSAA/SSAA-KI) were obtained through intercrossing mice heterozygous for PKD2S707A/S711A(PKD2SSAA). The wild-type and KI mice were subjected to repeated subcutaneous injection of bleomycin (BLM) to induce dermal inflammation and fibrosis. As controls, mice were injected with PBS. At the end of the experiment, mouse skin at the injection site was dissected, stained, and analyzed for morphological changes and expression of inflammatory and fibrotic markers. PKD-regulated signaling pathways were examined by real-time RT-qPCR and Western blotting. In a separate experiment, BLM-treated mice were administered with or without a PKD inhibitor, CRT0066101 (CRT). The effects of CRT on dermal fibrosis were analyzed similarly. The identity of the PKD expressing cells were probed using myeloid lineage markers CD45, CD68 in BLM-treated mouse tissues.ResultsDermal thickness and collagen fibers of kinase-dead PKD2-KI mice were significantly reduced in response to BLM treatment as compared to the wild-type mice. These mice also exhibited reduced α-smooth muscle actin (α-SMA) and collagen expression. At molecular levels, both transforming growth factor β1 (TGF-β1) and interleukin-6 (IL-6) mRNAs were decreased in the KI mice treated with BLM as compared to those in the wild-type mice. Similarly, CRT significantly blocked BLM-induced dermal fibrosis and inhibited the expression of α-SMA, collagen, and IL-6 expression. Further analysis indicated that PKD2 was mainly expressed in CD45+/CD68+myeloid cells that could be recruited to the lesional sites to promote the fibrotic process of the skin in response to BLM.ConclusionsKnock-in of the kinase-dead PKD2 or inhibition of PKD activity in mice protected against BLM-induced dermal fibrosis by reducing dermis thickness and expression of fibrotic biomarkers including α-SMA, collagen, and inflammatory/fibrotic mediators including TGF-β1 and IL-6. PKD2 does this potentially through modulating the recruitment and function of myeloid cells in skin of BLM-treated mice. Overall, our study demonstrated a potential critical role of PKD catalytic activity in inflammation-induced dermal fibrosis.

This paper reported a semi-analytical method (SAM)-fast Fourier transform (FFT) based model for three-dimensional (3D) steady-state elastodynamic frictional contact of an elastic ellipsoid sliding on an elastic half-space with a constant sliding velocity. The frequency response functions (FRFs) and their conversion into influence coefficients (ICs) for displacements and stresses in an elastic half-space are analytically derived pertaining to generalized normal and tangential forces. Fast numerical techniques used are based on the conjugate gradient method (CGM) for obtaining unknown pressure distribution in the contact interface, and the discrete convolution-fast Fourier transform (DC-FFT) algorithm for calculating displacements and stresses. The proposed SAM-FFT based model is employed to investigate the effects of friction, sliding velocity, and Young's modulus on contact pressure, surface deformation and sub-surface von Mises stress. A transition map, supported by appropriate limits of friction coefficient and sliding velocity, is constructed to determine whether the location of maximum von Mises stress to appear beneath the contact surface or in the contact surface. It deserves mentioning that the elastodynamic effect becomes more profound if the sliding velocity is higher than 0.4 times of shear wave speed, which corresponds to a sliding velocity of 1300 m/s for steel materials (shear wave speed ∼3250 m/s), or 60 m/s for a soil foundation (shear wave speed ∼150 m/s).

The lubricants for traction-continuously variable transmissions (t-CVT) could generate high traction under a high pressure, which requires the design of a special class of base stock molecules. This paper reports the development of a model, based on non-equilibrium molecular dynamics (NEMD) simulations, for estimating traction coefficients to facilitate the design of base stock molecules prior to their synthesis. The pressure-viscosity coefficients (α) of a number of base stocks in traction lubricants are calculated and the results are correlated with the corresponding traction coefficient τ. A linear α - τ correlation is obtained with a coefficient of determination of as high as 0.85.

A three dimensional model for solving steady state heat conduction in a semi-infinite domain containing an elementary cuboidal inhomogeneity is established in this paper. A set of analytical formulas for steady state heat conduction in a full space with an embedded cuboidal inclusion is derived. The temperature field of a half space distributed with arbitrarily shaped inhomogeneities is then obtained via the application of numerical discretization and the method of images. Benchmark comparisons involving a cuboidal/ellipsoidal inhomogeneity and double-inhomogeneity particle with the results produced by the finite element method (FEM) are conducted. Good agreements between the results of the two methods demonstrate the effectiveness and capability of the proposed model. Further, a case of heterogeneous material containing arrayed inhomogeneities is studied to explore the disturbance and interaction of the temperature field due to distributed inhomogeneities.

Mechanical power loss in hydraulic piston pumps comes from the friction between parts in relative motion, and wear is among the top pump failure mechanisms. Reducing friction and preventing wear require lubrication enhancement, which may be accomplished by proper surface texture design. Cylinder length is an important factor affecting the lubrication performance of the piston-cylinder system in a swash-plate pump. Our previous analyses revealed that under the same load, increasing the cylinder length could decrease the maximum pressure and increase the minimum film thickness, favorable for the pump operation with reduced wear; however, friction would become higher. The work reported in this paper intends to lower friction by textures in the piston surface while increasing, or at least maintaining, the load capacity of the piston system. Several textures are designed and their lubrication performances investigated, aiming at reducing the piston friction and improving the load-carrying ability of the system in a wide range of operation conditions. The effects of texture type, application location, and texture shape are studied, and their relationships with the friction and film thickness characteristics of the piston-cylinder interface are explored. Two optimal surface-texture designs are suggested, which are named the Step-Multiple-Grooves design and the Combine design.

Early transition metal catalysts produce high-density and linear low-density polyethylenes with spectacular efficiency. Nevertheless, these catalysts are ineffective in producing low-density polyethylene homopolymers with large –(CH2)xCH3 branch densities (x ≥ 5) or low-molecular-mass (Mn

This paper reports a semi-analytical model for studying general and critical heat-transfer characteristics at the interface between a coated sheet and a moving coated tool tip in incremental forming considering heat partition. Both of the tool tip and the sheet can be treated as a coating-substrate material system. The frequency response functions (FRFs) for temperature rise in each material system are analytically derived, in which the tool-tip velocity is incorporated by means of the Galilean transform. The FRFs are then converted into influence coefficients (ICs) in the frequency domain for solution efficiency and convenience. Fast numerical techniques are applied, such as the conjugate gradient method (CGM) for searching the distributed tool-tip/sheet heat partition and the fast Fourier transform (FFT) for obtaining temperature solutions. The proposed model is implemented to analyze the combined influences of Peclet number, coating thicknesses of the tool tip and the sheet, sheet thickness, and heat conductivity of each material on the temperature rise and the heat partition at the interface, and the sensitivity of the dependence of the peak temperature on these system parameters.

Author(s): Zhang, X; Wang, QJ; Harrison, KL; Jungjohann, K; Boyce, BL; Roberts, SA; Attia, PM; Harris, SJ | Abstract: We offer an explanation for how dendrite growth can be inhibited when Li metal pouch cells are subjected to external loads, even for cells using soft, thin separators. We develop a contact mechanics model for tracking Li surface and sub-surface stresses where electrodes have realistically (micron-scale) rough surfaces. Existing models examine a single, micron-scale Li metal protrusion under a fixed local current density that presses more or less conformally against a separator or stiff electrolyte. At the larger, sub-mm scales studied here, contact between the Li metal and the separator is heterogeneous and far from conformal for surfaces with realistic roughness: the load is carried at just the tallest asperities, where stresses reach tens of MPa, while most of the Li surface feels no force at all. Yet, dendrite growth is suppressed over the entire Li surface. To explain this dendrite suppression, our electrochemical/mechanics model suggests that Li avoids plating at the tips of growing Li dendrites if there is sufficient local stress; that local contact stresses there may be high enough to close separator pores so that incremental Li+ ions plate elsewhere; and that creep ensures that Li protrusions are gradually flattened. These mechanisms cannot be captured by single-dendrite-scale analyses.

Breast cancer stem cells (BCSCs) are essential for cancer growth, metastasis and recurrence. However, the regulatory mechanisms of self-renewal and interactions with the vascular niche within tumor microenvironment are currently under investigation. Here, we demonstrate that BCSCs are enriched within arteriolar niche within the tumor microenvironment of estrogen receptor positive (ER+) BC and bi-directionally interact with arteriolar endothelial cells (ECs). Mechanistically, this interaction is driven by the LPA/PKD-1 signaling pathway, which promotes arteriolar differentiation and self-renewal. Furthermore, this pathway directly promotes stemness features. These findings suggest that targeting LPA/PKD-1 signaling may disrupt the arteriolar niche within the tumor microenvironment and concomitantly eradicate BCSCs, thereby attenuating BC progression.

Computational contact mechanics seeks for numerical solutions to contact area, pressure, deformation, and stresses, as well as flash temperature, in response to the interaction of two bodies. The materials of the bodies may be homogeneous or inhomogeneous, isotropic or anisotropic, layered or functionally graded, elastic, elastoplastic, or viscoelastic, and the physical interactions may be subjected to a single field or multiple fields. The contact geometry can be cylindrical, point (circular or elliptical), or nominally flat-to-flat. With reasonable simplifications, the mathematical nature of the relationship between a surface excitation and a body response for an elastic contact problem is either in the form of a convolution or correlation, making it possible to formulate and solve the contact problem by means of an efficient Fourier-transform algorithm. Green's function inside such a convolution or correlation form is the fundamental solution to an elementary problem, and if explicitly available, it can be integrated over a region, or an element, to obtain influence coefficients (ICs). Either the problem itself or Green's functions/ICs can be transformed into a space-related frequency domain, via a Fourier transform algorithm, to formulate a frequency-domain solution for contact problems. This approach converts the original tedious integration operation into multiplication accompanied by Fourier and inverse Fourier transforms, and thus a great computational efficiency is achieved. The conversion between ICs and frequency-response functions facilitate the solutions to problems with no explicit space-domain Green's function. This paper summarizes different algorithms involving the fast Fourier transform (FFT), developed for different contact problems, error control, as well as solutions to the problems involving different contact geometries, different types of materials, and different physical issues. The related works suggest that (i) a proper FFT algorithm should be used for each of the cylindrical, point, and nominally flat-flat contact problems, and then (ii) the FFT-based algorithms are accurate and efficient. In most cases, the ICs from the 0-order shape function can be applied to achieve satisfactory accuracy and efficiency if (i) is guaranteed.

We recently reported the use of cyclopropanecarboxylic acid (CPCa) as a model additive that can readily react under the combined effect of flash heating and stress in steel tribocontacts to form tribopolymers, along with marked improvement in tribological performance. In this paper, we present results of how chemical structural modification of CPCa may impact on the formation of tribopolymers and hence friction and wear properties, both by experiments and molecular dynamics simulation. Four lubricant additives, viz., CPCa, cyclobutanecarboxylic acid (CBCa), cyclopropane-1,1-dicarboxylic acid (CPDCa), and cyclobutane-1,1-dicarboxylic acid (CBDCa) consisting of a metastable ring structure and one or two carboxyl groups dissolved in an ester base oil were studied. Friction and wear rate using these additives rank in the order of CPDCa

Stress distributions and plastic deformation zones are factors directly influencing the fatigue life of components under cyclic contact. An effective approach to improving the resistance of a steel to contact fatigue failure is surface hardening, which builds gradient yield strength from the surface of the steel to the bulk. When using the distortion energy theory as the criterion to identify failure initiation for a case-hardened steel, contact yield starts in the subsurface wherever the von Mises stress reaches the local material strength, rather than at the point of the maximum von Mises stress in the subsurface. If the yield strength changes from the surface to the bulk following a straight line, the location of yield initiation should occur at the tangency of the strength line and the von Mises stress curve. Analyses on circular, rectangular, and elliptical contacts are presented to reveal the locations of contact yield initiation for such case-hardened steels subjected to rolling contact stresses, for which the influence of friction can be ignored. A group of formulas relating contact yield initiation, in terms of the critical pressure, location of the first yield, and plasticity index (transition to plasticity) to case-hardening parameters, such as the case slope, the minimum case depth, and surface and bulk strengths, are derived to facilitate contact element designs using case-hardened materials. The results are applied to examine the rolling contact behaviors of several case-hardened steels, and the data correlation suggests that their rolling contact fatigue lives are related to a nondimensional case-hardening slope besides external loading.

A transient mixed lubrication model is used to study the performance of a journal bearing subjected to impulse loading, considering mass conservation and the effects of asperities on flow and contact, to explore a novel journal bearing surface design methodology. The bearing surface features include an outlet pocket and axial lip for topographical design consideration. A data-driven approach for a steadily loaded bearing was first presented to illustrate the behavior of an indented pocket design at low and high loads, and Pareto optimization and sensitivity analysis methods were employed to analyze the data and provide insight to the design. The results show that the pocket location was the most influential parameter for the optimal bearing surface design for energy-efficient lubrication performance. For transient operation, a comprehensive parametric study was conducted, and the results reveal that, when compared to the results of the unmodified bearing, the bearing designed with the optimal outlet pocket can run at 9% lower mean friction while maintaining the baseline film thickness. The bearing with the lip feature shows a 20% minimum film thickness increase and 3% mean friction reduction. The design with outlet pocket and lip features combined can lead to 20% film thickness increase and 10% mean friction reduction.