A Cooperative Copper Metal–Organic Framework‐Hydrogel System Improves Wound Healing in Diabetes

Chronic nonhealing wounds remain a major clinical challenge that would benefit from the development of advanced, regenerative dressings that promote wound closure within a clinically relevant time frame. The use of copper ions has shown promise in wound healing applications, possibly by promoting angiogenesis. However, reported treatments that use copper ions require multiple applications of copper salts or oxides to the wound bed, exposing the patient to potentially toxic levels of copper ions and resulting in variable outcomes. Herein the authors set out to assess whether copper metal organic framework nanoparticles (HKUST‐1 NPs) embedded within an antioxidant thermoresponsive citrate‐based hydrogel would decrease copper ion toxicity and accelerate wound healing in diabetic mice. HKUST‐1 and poly‐(polyethyleneglycol citrate‐co‐N‐isopropylacrylamide) (PPCN) are synthesized and characterized. HKUST‐1 NP stability in a protein solution with and without embedding them in PPCN hydrogel is determined. Copper ion release, cytotoxicity, apoptosis, and in vitro migration processes are measured. Wound closure rates and wound blood perfusion are assessed in vivo using the splinted excisional dermal wound diabetic mouse model. HKUST‐1 NPs disintegrated in protein solution while HKUST‐1 NPs embedded in PPCN (H‐HKUST‐1) are protected from degradation and copper ions are slowly released. Cytotoxicity and apoptosis due to copper ion release are significantly reduced while dermal cell migration in vitro and wound closure rates in vivo are significantly enhanced. In vivo, H‐HKUST‐1 induced angiogenesis, collagen deposition, and re‐epithelialization during wound healing in diabetic mice. These results suggest that a cooperatively stabilized, copper ion‐releasing H‐HKUST‐1 hydrogel is a promising innovative dressing for the treatment of chronic wounds.     

Autonomous and teleoperation control of a mobile robot

The present work proposes an autonomous tracking control system and a control structure to combine autonomous and teleoperation commands in a bicycle-type mobile robot. This compounded operation renders great flexibility to the control system of the mobile robot. For autonomous operation, a simple tracking controller that includes compensation of the robot dynamics is developed. This tracking control system is proved to be stable in the sense that it asymptotically reaches the tracking objective. Teleoperation with visual access to the robot’s workspace is integrated via a joystick with the autonomous operation of the robot. Simulations and experimental results on a prototype robot show the feasibility and performance of the proposed control system.     

Synergistic Computational‐Experimental Approach to Improve Ionene Polymer‐Based Functional Hydrogels

The manifold applications of ionene‐based materials such as hydrogels in daily life, biomedical sciences, and industrial processes are a consequence of their unique physical and chemical properties, which are governed by a judicious balance between multiple non‐covalent interactions. However, one of the most critical aspects identified for a broader use of different polyelectrolytes is the need of raising their gelation efficiency. This work focuses on surfactant‐free ionene polymers 1 ? 3 containing DABCO and N,N′‐(x‐phenylene)dibenzamide (x = ortho‐/meta‐/para‐) linkages as model systems to develop a combined computational‐experimental approach to improve the hydrogelation through a better understanding of the gelation mechanism. Molecular dynamics simulations of isomeric ionenes 1–3 with explicit water molecules point out remarkable differences in the assembly of the polymeric chains in each case. Interchain regions with high degree of hydration (i.e., polymer···water interactions) and zones dominated by polymer···polymer interactions are evident in the case of ortho‐ ( 1 ) and meta‐ ( 2 ) isomeric ionenes, whereas domains controlled by polymer···polymer interactions are practically inexistent in 3 . In excellent agreement, ortho‐ionene 1 provides experimentally the best hydrogels with unique features such as thixotropic behavior and dispersion ability for single‐walles carbon nanotubes.     

Determining the Dielectric Constants of Organic Photovoltaic Materials Using Impedance Spectroscopy

The photovoltaic and electrical properties of organic semiconductors are characterized by their low dielectric constant, which leads to the formation of polarons and Frenkel excitons. The low dielectric constant of organic semiconductors has been suggested to be significantly influential in geminate and bimolecular recombination losses in organic photovoltaics (OPVs). However, despite the critical attention that the dielectric constant has received in literature discussions, there has not yet been a thorough study of the dielectric constant in common organic semiconductors and how it changes when blended. In fact, there have been some inconsistent and contradictory reports on such dielectric constants, making it difficult to identify trends. Herein, at first a detailed explanation of a specific methodology to determine the dielectric constant in OPV materials with impedance spectroscopy is provided, including guidelines for possible experimental pitfalls. Using this methodology, the analysis for the dielectric constant of 17 common neat organic semiconductors is carried out. Furthermore, the relationship between the dielectric constant and blend morphology are studied and determined. It is found that the dielectric constant of a blend system can be very accurately predicted solely based on the dielectric constants of the neat materials, scaled by their respective weight ratios in the blend film.     

Theory,design, and evaluation of the rotating polarizer interferometer

We present the results of modeling the response of a Rotating Polarizer Interferometer (RPI), an actual design and the evaluation of it. The RPI was introduced almost 10 years ago by Erickson [1] and since then it has not received too much attention from the millimeter wave community despite its very attractive characteristics, this is perhaps due to a lack of proven designs to encourage potential users. Here we show that with proper design equations a predictable result can be achieved and that a working device with a low-loss dielectric filling (Teflon) is feasible     

Optimized reduction of spur tones in fractional frequency synthesizers

In this article the contribution of the digital \Upsigma\Updelta\Upsigma\Updelta modulator in fractional frequency synthesizers is explored. Due to the circuit’s non linear behavior, the spur tones generated by the digital \Upsigma\Updelta\Upsigma\Updelta modulation degrade the synthesizer’s phase noise even in regions where the charge pump noise is dominant. A new method to dither digital MASH \Upsigma\Updelta\Upsigma\Updelta modulators for fractional frequency synthesizers is proposed. The method barely increases the circuit complexity and has the same performance as more cumbersome architectures. Also, a new design consideration to linearize the voltage control oscillator is proposed. Experimental results are obtained in an on-chip fractional synthesizer manufactured in CMOS technology.     

Address Generation Optimization for Embedded High-Performance Processors: A Survey

Nowadays embedded systems are growing at an impressive rate and provide more and more sophisticated applications characterized by having a complex array index manipulation and a large number of data accesses. Those applications require high performance specific computation that general purpose processors can not deliver at a reasonable energy consumption. Very long instruction word architectures seem a good solution providing enough computational performance at low power with the required programmability to speed up the time to market. Those architectures rely on compiler effort to exploit the available instruction and data parallelism to keep the data path busy all the time. With the density of transistors doubling each 18 months, more and more sophisticated architectures with a high number of computational resources running in parallel are emerging. With this increasing parallel computation, the access to data is becoming the main bottleneck that limits the available parallelism. To alleviate this problem, in current embedded architectures, a special unit works in parallel with the main computing elements to ensure efficient feed and storage of the data: the address generator unit, which comes in many flavors. Future architectures will have to deal with enormous memory bandwidth in distributed memories and the development of address generators units will be crucial for effective next generation of embedded processors where global trade-offs between reaction-time, bandwidth, energy and area must be achieved. This paper provides a survey of methods and techniques that optimize the address generation process for embedded systems, explaining current research trends and needs for future.

Monomolecular and Bimolecular Recombination of Electron–Hole Pairs at the Interface of a Bilayer Organic Solar Cell

While it has been argued that field‐dependent geminate pair recombination (GR) is important, this process is often disregarded when analyzing the recombination kinetics in bulk heterojunction organic solar cells (OSCs). To differentiate between the contributions of GR and nongeminate recombination (NGR) the authors study bilayer OSCs using either a PCDTBT‐type polymer layer with a thickness from 14 to 66 nm or a 60 nm thick p‐DTS(FBTTh₂)₂ layer as donor material and C₆₀ as acceptor. The authors measure JV‐characteristics as a function of intensity and charge‐extraction‐by‐linearly‐increasing‐voltage‐type hole mobilities. The experiments have been complemented by Monte Carlo simulations. The authors find that fill factor (FF) decreases with increasing donor layer thickness (L_p) even at the lowest light intensities where geminate recombination dominates. The authors interpret this in terms of thickness dependent back diffusion of holes toward their siblings at the donor–acceptor interface that are already beyond the Langevin capture sphere rather than to charge accumulation at the donor–acceptor interface. This effect is absent in the p‐DTS(FBTTh₂)₂ diode in which the hole mobility is by two orders of magnitude higher. At higher light intensities, NGR occurs as evidenced by the evolution of s‐shape of the JV‐curves and the concomitant additional decrease of the FF with increasing layer thickness.