Influence of wettability on liquid water transport in gas diffusion layer of proton exchange membrane fuel cells (PEMFC)

Water management is a key factor that limits PEFC's performance. We show how insights into this problem can be gained from pore-scale simulations of water invasion in a model fibrous medium. We explore the influence of contact angle on the water invasion pattern and water saturation at breakthrough and show that a dramatic change in the invasion pattern, from fractal to compact, occurs as the system changes from hydrophobic to hydrophilic. Then, we explore the case of a system of mixed wettability, i.e. containing both hydrophilic and hydrophobic pores. The saturation at breakthrough is studied as a function of the fraction of hydrophilic pores. The results are discussed in relation with the water management problem, the optimal design of a GDL and the fuel cell performance degradation mechanisms. We outline how the study could be extended to 3D systems, notably from binarised images of GDLs obtained by X ray microtomography

On Verifying Causal Consistency

Causal consistency is one of the most adopted consistency criteria for distributed implementations of data structures. It ensures that operations are executed at all sites according to their causal precedence. We address the issue of verifying automatically whether the executions of an implementation of a data structure are causally consistent. We consider two problems: (1) checking whether one single execution is causally consistent, which is relevant for developing testing and bug finding algorithms, and (2) verifying whether all the executions of an implementation are causally consistent. We show that the first problem is NP-complete. This holds even for the read-write memory abstraction, which is a building block of many modern distributed systems. Indeed, such systems often store data in key-value stores, which are instances of the read-write memory abstraction. Moreover, we prove that, surprisingly, the second problem is undecidable, and again this holds even for the read-write memory abstraction. However, we show that for the read-write memory abstraction, these negative results can be circumvented if the implementations are data independent, i.e., their behaviors do not depend on the data values that are written or read at each moment, which is a realistic assumption.Comment: extended version of POPL 201

The Child and Youth Mental Health Assessment (ChYMH): An examination of the psychometric properties of an integrated assessment developed for clinically referred children and youth

Background: The Child and Youth Mental Health (ChYMH) assessment system was developed by interRAI (i.e., an international collective of researchers and clinicians from over thirty countries) in response to the unprecedented need for a coordinated approach to delivery of children\u27s mental health care. Many interRAI instruments are used across Canada and internationally, but the ChYMH represents the first assessment specifically for children and youth. In the present paper, a short overview of the development process of the ChYMH is provided, and then the psychometric properties of several embedded scales on the ChYMH are examined. Methods: Participants included 1297 children and youth and their families who completed the ChYMH after being referred to mental health agencies within Ontario, Canada. In addition, smaller subsets of participants (N = 48-53) completed additional criterion measures, including the Social Skills Improvement System (SSIS), the Child and Adolescent Functional Assessment Scale (CAFAS), the Child Behavior Checklist (CBCL), and the Brief Child and Family Phone Interview (BCFPI). Results: Results demonstrated that the ChYMH subscales had strong internal-consistency (Cronbach\u27s higher than.70), and correlated well with the criterion measures. Conclusions: Findings support the clinical utility of the ChYMH for use among clinically referred children and youth. Implications for children\u27s mental health assessment and practice are discussed

The Child and Youth Mental Health Assessment (ChYMH): An examination of the psychometric properties of an integrated assessment developed for clinically referred children and youth

Background: The Child and Youth Mental Health (ChYMH) assessment system was developed by interRAI (i.e., an international collective of researchers and clinicians from over thirty countries) in response to the unprecedented need for a coordinated approach to delivery of children\u27s mental health care. Many interRAI instruments are used across Canada and internationally, but the ChYMH represents the first assessment specifically for children and youth. In the present paper, a short overview of the development process of the ChYMH is provided, and then the psychometric properties of several embedded scales on the ChYMH are examined. Methods: Participants included 1297 children and youth and their families who completed the ChYMH after being referred to mental health agencies within Ontario, Canada. In addition, smaller subsets of participants (N = 48-53) completed additional criterion measures, including the Social Skills Improvement System (SSIS), the Child and Adolescent Functional Assessment Scale (CAFAS), the Child Behavior Checklist (CBCL), and the Brief Child and Family Phone Interview (BCFPI). Results: Results demonstrated that the ChYMH subscales had strong internal-consistency (Cronbach\u27s higher than.70), and correlated well with the criterion measures. Conclusions: Findings support the clinical utility of the ChYMH for use among clinically referred children and youth. Implications for children\u27s mental health assessment and practice are discussed

NRF2 regulates HER1 signaling pathway to modulate the sensitivity of ovarian cancer cells to lapatinib and erlotinib

NF-E2-related factor 2 (NRF2) regulates the transcription of a battery of metabolic and cytoprotective genes. NRF2 and epidermal growth factor receptors (EGFRs/HERs) are regulators of cellular proliferation and determinants of cancer initiation and progression. NRF2 and HERs confer cancers with resistance to several therapeutic agents. Nevertheless, there is limited understanding of the regulation of HER expression and activation and the link between NRF2 and HER signalling pathways. We show that NRF2 regulates both basal and inducible expression of HER1, as treatment of ovarian cancer cells (PEO1, OVCAR3, and SKOV3) with NRF2 activator tBHQ inducing HER1, while inhibition of NRF2 by siRNA knockdown or with retinoid represses HER1. Furthermore, treatment of cells with tBHQ increased total and phosphorylated NRF2, HER1, and AKT levels and compromised the cytotoxic effect of lapatinib or erlotinib. Treatment with siRNA or retinoid antagonised the effect of tBHQ on NRF2 and HER1 levels and enhanced the sensitivity of ovarian cancer cells to lapatinib or erlotinib. Pharmacological or genetic inhibition of NRF2 and/or treatment with lapatinib or erlotinib elevated cellular ROS and depleted glutathione. This extends the understanding of NRF2 and its regulation of HER family receptors and opens a strategic target for improving cancer therapy

Evolution of Superconductivity in Electron-Doped Cuprates: Magneto-Raman Spectroscopy

The electron-doped cuprates Pr_{2-x}Ce_xCuO_4 and Nd_{2-x}Ce_xCuO_4 have been studied by electronic Raman spectroscopy across the entire region of the superconducting (SC) phase diagram. The SC pairing strength is found to be consistent with a weak-coupling regime except in the under-doped region where we observe an in-gap collective mode at 4.5 k_{B}T_c while the maximum amplitude of the SC gap is ~8 k_{B}T_{c}. In the normal state, doped carriers divide into coherent quasi-particles (QPs) and carriers that remain incoherent. The coherent QPs mainly reside in the vicinity of (\pi/2, \pi/2) regions of the Brillouin zone (BZ). We find that only coherent QPs contribute to the superfluid density in the B_{2g} channel. The persistence of SC coherence peaks in the B_{2g} channel for all dopings implies that superconductivity is mainly governed by interactions between the hole-like coherent QPs in the vicinity of (\pi/2, \pi/2) regions of the BZ. We establish that superconductivity in the electron-doped cuprates occurs primarily due to pairing and condensation of hole-like carriers. We have also studied the excitations across the SC gap by Raman spectroscopy as a function of temperature (T) and magnetic field (H) for several different cerium dopings (x). Effective upper critical field lines H*_{c2}(T, x) at which the superfluid stiffness vanishes and H^{2\Delta}_{c2}(T, x) at which the SC gap amplitude is suppressed by field have been determined; H^{2\Delta}_{c2}(T, x) is larger than H*_{c2}(T, x) for all doping concentrations. The difference between the two quantities suggests the presence of phase fluctuations that increase for x< 0.15. It is found that the magnetic field suppresses the magnitude of the SC gap linearly at surprisingly small fields.Comment: 13 pages, 8 figures; submitted to Phys. Rev.

Diffusive propagation of wave packets in a fluctuating periodic potential

We consider the evolution of a tight binding wave packet propagating in a fluctuating periodic potential. If the fluctuations stem from a stationary Markov process satisfying certain technical criteria, we show that the square amplitude of the wave packet after diffusive rescaling converges to a superposition of solutions of a heat equation.Comment: 13 pages (v2: added a paragraph on the history of the problem, added some references, correct a few typos; v3 minor corrections, added keywords and subject classes