Silk Biomaterials with Vascularization Capacity

Functional vascularization is critical for the clinical regeneration of complex tissues such as kidney, liver, or bone. The immobilization or delivery of growth factors has been explored to improve vascularization capacity of tissue‐engineered constructs; however, the use of growth factors has inherent problems such as the loss of signaling capability and the risk of complications including immunological responses and cancer. Here, a new method of preparing water‐insoluble silk protein scaffolds with vascularization capacity using an all‐aqueous process is reported. Acid is added temporally to tune the self‐assembly of silk in the lyophilization process, resulting in water‐insoluble scaffold formation directly. These biomaterials are mainly noncrystalline, offering improved cell proliferation than previously reported silk materials. These systems also have an appropriate softer mechanical property that could provide physical cues to promote cell differentiation into endothelial cells, and enhance neovascularization and tissue ingrowth in vivo without the addition of growth factors. Therefore, silk‐based degradable scaffolds represent an exciting biomaterial option, with vascularization capacity for soft tissue engineering and regenerative medicine.     

Electrochemically Driven Hydroxyapatite Nanoparticles Coating of Medical Implants

Calcium phosphates are of great interest for biomedical applications such as bone tissue engineering, bone fillers, drug and gene delivery, and orthopedic and dental implant coating. Here, the first electrochemically driven coating of medical implants using hydroxyapatite (HAp) nanoparticles (NPs) as building blocks is reported. This uncommon combination offers a simple, straightforward, and economic process with well controllable, pure, single‐phase HAp. Crystalline, pure HAp NPs are formed by precipitation reaction. The HAp NPs are dispersed by either citrate or poly(acrylic acid) to form pH sensitive dispersion. Controllable and homogeneous coating of medical implants is accomplished by altering the pH on the surface upon applying either a constant potential or current. The process involves protonation of the carboxylic acid moieties, which causes the irreversible aggregation of the HAp NPs due to diminishing the repulsive forces between the particles. Deposition is further demonstrated on a commercial dental implant. Moreover, the adhesion of the coating satisfies FDA and international standard requirements. A porous interconnected network of bone‐like HAp layer is formed during soaking in a simulated body fluid for 30 d and is similar to bone generation, and it therefore holds promise for further in vivo testing.     

The exergy fields in transport processes: Their calculation and use

This paper is a brief review of the method for analyzing the space and time dependent exergy and irreversibility fields in processes. It presents the basic equations, the method for their use, major literature sources, and three examples from the authors' work: flow desiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Law analysis are used to attempt process improvement suggestions.     

Ultimate bistability: Hysteretic resonance of a slightly-relativistic electron

It was recently predicted by us that cyclotron resonance of free electrons in vacuum and conduction electrons in semiconductors may exhibit bistable and hysteretic behavior which is due to the relativistic mass-effect (or pseudo relativistic-in semiconductors). Consistent with this prediction, the hysteretic cyclotron resonance of a trapped single electron in vacuum has recently been experimentally observed by Gabrielse et al. A preliminary estimate shows that their experimental results are consistent with the relativistic nature of the observed hysteresis. In this paper we consider this phenomenon as ultimate bistability since it is based on the most fundamental mechanism of nonlinearity (the relativistic mass-effect), involves the interaction of an EM wave with the simplest single elementary particle, and exhibits the first known intrinsic bistability with no macroscopic optical feedback. We also show that a hysteretic resonance of a Single electron based on relativistic effects is feasible also in a parabolic potential (with no magnetic field required to attain a resonance).     

Multistable self-trapping of light and multistable soliton pulse propagation

It is demonstrated that a nonlinear Schrödinger equation with certain nonlinearities allows for an existence of multistate single solitons (i.e., single solitons with the same carried power but different propagation parameters). In nonlinear optics, these solitons may exist either in the form of short bistable pulses, or bistable self-trapping (both two- and three-dimensional).     

The Effects of Different Heat Treatment Regimes on the Wear Properties of Fe-Based Composite Materials

Powder Metallurgy and Metal Ceramics - In this study, different heat treatment regimes, such as sintering, sintering with low-pressure cementation, and only low-pressure cementation were applied to...