Machine learning (ML) is an increasingly popular statistical tool for analyzing either measured or calculated data sets. Here, we explore its application to a well-defined physics problem, investigating issues of how the underlying physics is handled by ML, and how self-consistent solutions can be found by limiting the domain in which ML is applied. The particular problem is how to find accurate approximate density functionals for the kinetic energy (KE) of noninteracting electrons. Kernel ridge regression is used to approximate the KE of noninteracting fermions in a one dimensional box as a functional of their density. The properties of different kernels and methods of cross-validation are explored, reproducing the physics faithfully in some cases, but not others. We also address how self-consistency can be achieved with information on only a limited electronic density domain. Accurate constrained optimal densities are found via a modified Euler-Lagrange constrained minimization of the machine-learned total energy, despite the poor quality of its functional derivative. A projected gradient descent algorithm is derived using local principal component analysis. Additionally, a sparse grid representation of the density can be used without degrading the performance of the methods. The implications for machinelearned density functional approximations are discussed.

It was demonstrated in this study that acidic environments coupled with rubbing are able to introduce noticeable morphological changes and corrosion on the surface of both titanium grades.

Implantable and extracorporeal cardiovascular devices are commonly made from titanium (Ti) (e.g. Ti-coated Nitinol stents and mechanical circulatory assist devices). Endothelializing the blood-contacting Ti surfaces of these devices would provide them with an antithrombogenic coating that mimics the native lining of blood vessels and the heart. We evaluated the viability and adherence of peripheral blood-derived porcine endothelial progenitor cells (EPCs), seeded onto thin Ti layers on glass slides under static conditions and after exposure to fluid shear stresses. EPCs attached and grew to confluence on Ti in serum-free medium, without preadsorption of proteins. After attachment to Ti for 15 min, less than 5 % of the cells detached at a shear stress of 100 dyne/cm2. Confluent monolayers of EPCs on smooth Ti surfaces (Rq of 10 nm), exposed to 15 or 100 dyne/cm2 for 48 hours, aligned and elongated in the direction of flow and produced nitric oxide dependent on the level of shear stress. EPC-coated Ti surfaces had dramatically reduced platelet adhesion when compared to uncoated Ti surfaces. These results indicate that peripheral blood-derived EPCs adhere and function normally on Ti surfaces. Therefore EPCs may be used to seed cardiovascular devices prior to implantation to ameliorate platelet activation and thrombus formation.

We demonstrate that electrocoagulation (EC) using iron electrodes can reduce arsenic below 10 µg/L in synthetic Bangladesh groundwater and in real groundwater from Bangladesh and Cambodia while investigating the effect of operating parameters that are often overlooked, such as charge dosage rate. We measure arsenic removal performance over a larger range of current density than in any other single previous EC study (5000 fold: 0.02 -100 mA/cm 2 ) and over a wide range of charge dosage rates (0.

Harvesting solar energy for photothermal conversion in an efficient manner for steam-electricity cogeneration is particularly opportune in the context of comprehensive solar utilization to address the challenge of a global shortage of fresh water. However, the fragile solar thermal devices and the single-energy utilization pattern greatly hinder extensive solar energy exploitation and practical application. Herein, a flexible carbon cloth nanocomposite with a biomimetic pelargonium hortorum-petal-like surface that embraces all desirable chemical and physical properties, that is, enhanced light acquisition, excellent photothermal property, and operational durability, for high-performance solar-driven interfacial water evaporation distillation is reported. Combined with the two-dimensional water channel, the solar evaporator shows a solar-to-steam conversion efficiency of 93% under the simulated solar illumination of 1 kW m–2. More strikingly, the solar steam generation-induced electricity based on the practical consideration toward more infusive solar thermal application is proposed. Such integrative steam-electricity generators presented here provide an attractive method to produce on-site electricity and fresh water in an individualized mode in various resource-constrained areas.