We investigate the adhesive and adhesiveless contact between a rigid regular wavy profile and an elastic substrate coated with an elastic layer. The contact stiffness is strongly influenced by the ...elasticity and thickness of the coating layer. Specifically, coatings more compliant than the substrate entail larger contact area, and vice versa. Under adhesive conditions, thin soft coatings may lead to complete contact, regardless of the applied load. Moreover, enhanced adhesive strength (toughness) can be achieved at the pull-off by adopting stiff (compliant) coatings. We compare our exact model with the Bec/Tonck model, which is one of the most adopted approximate model for biological tissues contact mechanics. The results show that predictions of the proposed model are in better qualitative agreement with experimental results taken from the literature.
This paper presents a numerical and experimental validation of ExoFing, a two-degrees-of-freedom finger mechanism exoskeleton. The main functionalities of this device are investigated by focusing on ...its kinematic model and by computing its main operation characteristics via numerical simulations. Experimental tests are designed and carried out for validating both the engineering feasibility and effectiveness of the ExoFing system aiming at achieving a human index finger motion assistance with cost-oriented and user-friendly features.
Epigenetic silencing of tumour suppressor genes is an important mechanism involved in cell transformation and tumour progression. The Set and RING-finger-associated domain-containing protein UHRF1 ...might be an important link between different epigenetic pathways. Here, we report that UHRF1 is frequently overexpressed in human prostate tumours and has an important role in prostate cancer pathogenesis and progression. Analysis of human prostate cancer samples by microarrays and immunohistochemistry showed increased expression of UHRF1 in about half of the cases. Moreover, UHRF1 expression was associated with reduced overall survival after prostatectomy in patients with organ-confined prostate tumours (P < 0.0001). UHRF1 expression was negatively correlated with several tumour suppressor genes and positively with the histone methyltransferase (HMT) EZH2 both in prostate tumours and cell lines. UHRF1 knockdown reduced proliferation, clonogenic capability and anchorage-independent growth of prostate cancer cells. Depletion of UHRF1 resulted in reactivation of several tumour suppressor genes. Gene reactivation upon UHRF1 depletion was associated with changes in histone H3K9 methylation, acetylation and DNA methylation, and impaired binding of the H3K9 HMT Suv39H1 to the promoter of silenced genes. Co-immunoprecipitation experiments showed direct interaction between UHRF1 and Suv39H1. Our data support the notion that UHRF1, along with Suv39H1 and DNA methyltransferases, contributes to epigenetic gene silencing in prostate tumours. This could represent a parallel and convergent pathway to the H3K27 methylation catalyzed by EZH2 to synergistically promote inactivation of tumour suppressor genes. Deregulated expression of UHRF1 is involved in the prostate cancer pathogenesis and might represent a useful marker to distinguish indolent cancer from those at high risk of lethal progression.
Hydrologic models provide a comprehensive tool to estimate streamflow response to environmental variables. Yet, an incomplete understanding of physical processes and challenges associated with ...scaling processes to a river basin, introduces model uncertainty. Here, we apply generalized additive models of location, scale and shape (GAMLSS) to characterize this uncertainty in an Atlantic coastal plain watershed system. Specifically, we describe distributions of residual errors in a two-step procedure that includes model calibration of the soil and water assessment tool (SWAT) using a sequential Bayesian uncertainty algorithm, followed by time-series modeling of residual errors of simulated daily streamflow. SWAT identified dominant hydrological processes, performed best during moderately wet years, and exhibited less skill during times of extreme flow. Application of GAMLSS to model residuals efficiently produced a description of the error distribution parameters (mean, variance, skewness, and kurtosis), differentiating between upstream and downstream outlets of the watershed. Residual error distribution is better described by a non-parametric polynomial loess curve with a smooth transition from a Box–Cox
t
distribution upstream to a skew
t
type 3 distribution downstream. Overall, the fitted models show that low flow events more strongly influence the residual probability distribution, and error variance increases with streamflow discharge, indicating correlation and heteroscedasticity of residual errors. These results provide useful insights into the complexity of error behavior and highlight the value of using GAMLSS models to conduct Bayesian inference in the context of a regression model with unknown skewness and/or kurtosis.
Background
Comprehensive datasets quantifying the coupled thermo-mechanical and electrical properties of shape memory alloys (SMAs) are lacking, as are standardized techniques for robust ...characterization. This hampers accurate modeling and design of SMA-based components. Objective: This work develops an automated experimental system to enable simultaneous measurement of stress-strain-temperature behavior and electrical resistivity evolution in NiTi SMA wires under controlled stress conditions. Methods: Customized test frames apply precise mechanical stresses while allowing for
in situ
electrical measurements and infrared imaging during complete thermal cycling protocols. Specialized instrumentation including a Keithley 2002 multimeter, Agilent E3631A programmable power supply, and FLIR A615 thermal camera are integrated with LabVIEW-based software routines for complete automation of the characterization process. Rigorous metrology principles are implemented throughout the measurement procedure to improve accuracy, repeatability, and consistency compared to prior manual techniques. Results: Extensive datasets are generated which reveal pronounced stress-dependencies in key SMA material parameters including transformation temperatures, recoverable strain, and electrical resistivity. A 3D regression model describes the comprehensive relationship between resistivity, temperature, and applied stress across the entire characterization domain. Conclusions: The automated measurement framework and methodology establishes a foundation for high-fidelity, reliable acquisition of coupled SMA property data. This will enable more accurate modeling and design of components and systems incorporating SMA actuation or sensing functions.
In this paper we present a generalized Cassie-Baxter equation to take into account the effect of drop pressure on the apparent contact angle θ(app). Also we determine the limiting pressure p(W) which ...causes the impalement transition to the Wenzel state and the pull-off pressure p(out) at which the drop detaches from the substrate. The calculations have been carried out for axial-symmetric pillars of three different shapes: conical, hemispherical-topped and flat-topped cylindrical pillars. Calculations show that, assuming the same pillar spacing, conical pillars may be more inclined to undergo an impalement transition to the Wenzel state, but, on the other hand, they are characterized by a vanishing pull-off pressure which causes the drop not to adhere to the substrate and therefore to detach very easily. We infer that this property should strongly reduce the contact angle hysteresis as experimentally observed in Martines et al (2005 Nano Lett. 5 2097-103). It is possible to combine large resistance to impalement transition (i.e. large value of p(W)) and small (or even vanishing) detaching pressure p(out) by employing cylindrical pillars with conical tips. We also show that, depending on the particular pillar geometry, the effect of drop pressure on the apparent contact angle θ(app) may be more or less significant. In particular we show that in the case of conical pillars increasing the drop pressure causes a significant decrease of θ(app) in agreement with some experimental investigations (Lafuma and Quéré 2003 Nat. Mater. 2 457), whereas θ(app) slightly increases for hemispherical or flat-topped cylindrical pillars.
The authors develop a numerical procedure to analyze the adhesive contact between a soft elastic layer and a rough rigid substrate. The solution of the problem, which belongs to the class of the free ...boundary problems, is obtained by calculating the Green's function which links the pressure distribution to the normal displacements at the interface. The problem is then formulated in the form of a Fredholm integral equation of the first kind with a logarithmic kernel, and the boundaries of the contact area are calculated by requiring that the energy of the system is stationary. The methodology is relatively simple and easy to implement in a numerical code. It has been utilized to analyze the adhesive properties of a confined layer in contact with a wavy rigid substrate as a function of thickness, applied stress or penetration. It is shown that reducing the thickness of the slab reduces the effective energy of adhesion, i.e. the work needed to separate the bodies, but nevertheless increases the adherence force between the slab and the substrate. However, thinning the slab also increases the confinement of the system and therefore increases the negative hydrostatic pressure in the layer. This, in turn, may produce cavitation. When this happens the rupture of the adhesive bond does not occur through interfacial crack propagation but, by the growth of new interfacial voids or cavities.
IntroductionThe relationship between mood disorders, particularly depression and cognitive impairment is complex. The symptoms of depression in the elderly include confusion, sleep alterations, low ...concentration, cognitive deficits, and somatic complaints that may are also present in dementia, with depression being often a prodrome.ObjectivesThe present study aimed at investigating the presence of cognitive disturbances in outpatients over 65 years of age consulting us for a mood episode, as well as to investigate the possible relationships between cognitive and depressive symptoms.MethodsThe study included 57 older patients attending the Psychiatric Clinic of Pisa, with a diagnosis of a major mood episode according to DSM-5 criteria. The psychometric scales included: Hamilton Depression Rating Scale (HAM-D), Beck Inventory Scale (BDI), Geriatric Depression Scale (GDS), to measure the severity of depression; Short Psychiatric Evaluation Schedule (SPES), to assess organic mental deficits; Cornell Scale for Depression in Dementia (CSDD), to assess depression in people with dementia; Adult Autism Subthreshold (AdAS) Spectrum, to evaluates the eventual presence of specific features of the autistic spectrum disorder(ASD). Moreover, patients were also assessed for cognitive screening with Montreal Cognitive Assessment (MoCA), Frontal Assessment Battery (FAB), Mini-Mental State Examination (MMSE).ResultsThe HAM-D total score was 10.18±6.33, that of BDI 12.79± 9.89, that of GDS 12.69±8.25 and that of CSDD 8.35±6.25. The showed a MoCA value was 21.30±4.86, that of FAB 14.12±3.92, and that of MMSE 25.06±4.20. The MoCA total score positively correlated with those of the FAB and of the MMSE, while the FAB score with the MMSE score. A positive correlation was found between SPES and the HAM-D, BDI, CSDD and GDS total scores. The AdAS score positively correlated with that of MMSE. By correlating scores of depressive dimensions with those of cognitive functions, a positive correlation was noted between FAB total score and those of the HAM-D, BDI, CSDD and SPESConclusionsThese findings suggest a possible link between the presence of ASD and depressive symptoms from the one side and cognitive performance and executive functions from the another side.Disclosure of InterestNone Declared
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