Direct‐Write Assembly of Microperiodic Silk Fibroin Scaffolds for Tissue Engineering Applications

Three–dimensional, microperiodic scaffolds of regenerated silk fibroin have been fabricated for tissue engineering by direct ink writing. The ink, which consisted of silk fibroin solution from the Bombyx mori silkworm, was deposited in a layer‐by‐layer fashion through a fine nozzle to produce a 3D array of silk fibers of diameter 5 µm. The extruded fibers crystallized when deposited into a methanol‐rich reservoir, retaining a pore structure necessary for media transport. The rheological properties of the silk fibroin solutions were investigated and the crystallized silk fibers were characterized for structure and mechanical properties by infrared spectroscopy and nanoindentation, respectively. The scaffolds supported human bone marrow‐derived mesenchymal stem cell (hMSC) adhesion, and growth. Cells cultured under chondrogenic conditions on these scaffolds supported enhanced chondrogenic differentiation based on increased glucosaminoglycan production compared to standard pellet culture. Our results suggest that 3D silk fibroin scaffolds may find potential application as tissue engineering constructs due to the precise control of their scaffold architecture and their biocompatibility.     

单一5V电源高速放大器针对高分辨率视频而优化

人们不断要求视频运算放大器用更少的资源做更多的事情,就像要求设计这些放大器的优良设计师一样.为了实现更高的视频分辨率,需要更高的模拟视频信号带宽,因而需要更快的运算放大器.同时,设计师们还在不停地寻找以更低的电压甚至是单电源轨来实现更高分辨率的方法.     

Photoinduced Electron Transfer Between Pyridine Coated Cadmium Selenide Quantum Dots and Single Sheet Graphene

Interest in graphene as a two‐dimensional quantum‐well material for energy applications and nanoelectronics has increased exponentially in the last few years. The recent advances in large‐area single‐sheet fabrication of pristine graphene have opened unexplored avenues for expanding from nano‐ to meso‐scale applications. The relatively low level of absorptivity and the short lifetimes of excitons of single‐sheet graphene suggest that it needs to be coupled with light sensitizers in order to explore its feasibility for photonic applications, such as solar‐energy conversion. Red‐emitting CdSe quantum dots are employed for photosensitizing single‐sheet graphene with areas of several square centimeters. Pyridine coating of the quantum dots not only enhances their adhesion to the graphene surface, but also provides good electronic coupling between the CdSe and the two‐dimensional carbon allotrope. Illumination of the quantum dots led to injection of n‐carrier in the graphene phase. Time‐resolved spectroscopy reveals three modes of photoinduced electron transfer between the quantum dots and the graphene occurring in the femtosecond and picosecond time‐domains. Transient absorption spectra provide evidence for photoinduced hole‐shift from the CdSe to the pyridine ligands, thereby polarizing the surface of the quantum dots. That is, photoinduced electrical polarization, which favors the simultaneous electron transfer from the CdSe to the graphene phase. These mechanistic insights into the photoinduced interfacial charge transfer have a promising potential to serve as guidelines for the design and development of composites of graphene and inorganic nanomaterials for solar‐energy conversion applications.     

Long‐Term Electrical and Mechanical Function Monitoring of a Human‐on‐a‐Chip System

The goal of human‐on‐a‐chip systems is to capture multiorgan complexity and predict the human response to compounds within physiologically relevant platforms. The generation and characterization of such systems is currently a focal point of research given the long‐standing inadequacies of conventional techniques for predicting human outcome. Functional systems can measure and quantify key cellular mechanisms that correlate with the physiological status of a tissue, and can be used to evaluate therapeutic challenges utilizing many of the same endpoints used in animal experiments or clinical trials. Culturing multiple organ compartments in a platform creates a more physiologic environment (organ–organ communication). Here is reported a human 4‐organ system composed of heart, liver, skeletal muscle, and nervous system modules that maintains cellular viability and function over 28 days in serum‐free conditions using a pumpless system. The integration of noninvasive electrical evaluation of neurons and cardiac cells and mechanical determination of cardiac and skeletal muscle contraction allows the monitoring of cellular function, especially for chronic toxicity studies in vitro. The 28‐day period is the minimum timeframe for animal studies to evaluate repeat dose toxicity. This technology can be a relevant alternative to animal testing by monitoring multiorgan function upon long‐term chemical exposure.     

An integrative and interactive framework for improving biomedical pattern discovery and visualization

Recent progress in medical sciences has led to an explosive growth of data. Due to its inherent complexity and diversity, mining such volumes of data to extract relevant knowledge represents an enormous challenge and opportunity. Interactive pattern discovery and visualization systems for biomedical data mining have received relatively little attention. Emphasis has been traditionally placed on automation and supervised classification problems. Based on self-adaptive neural networks and pattern-validation statistical tools, this paper presents a user-friendly platform to support biomedical pattern discovery and visualization. It has been tested on several types of biomedical data, such as dermatology and cardiology data sets. The results indicate that in comparison to traditional techniques, such as Kohonen Maps, this platform may significantly improve the effectiveness and efficiency of pattern discovery and classification tasks, including problems described by several classes. Furthermore, this study shows how the combination of graphical and statistical tools may make these patterns more meaningful.     

Printing Reconfigurable Bundles of Dielectric Elastomer Fibers

Active soft materials that change shape on demand are of interest for a myriad of applications, including soft robotics, biomedical devices, and adaptive systems. Despite recent advances, the ability to rapidly design and fabricate active matter in complex, reconfigurable layouts remains challenging. Here, the 3D printing of core-sheath-shell dielectric elastomer fibers (DEF) and fiber bundles with programmable actuation is reported. Complex shape morphing responses are achieved by printing individually addressable fibers within 3D architectures, including vertical coils and fiber bundles. These DEF devices exhibit resonance frequencies up to 700 Hz and lifetimes exceeding 2.6 million cycles. The multimaterial, multicore-shell 3D printing method opens new avenues for creating active soft matter with fast programable actuation.     

The Effect of Relationship Characteristics and Relational Communication on Experiences of Hurt From Romantic Partners

This study expands the relational turbulence model (RTM; Solomon & Knobloch,) by theorizing about how characteristics of relationships and relational judgments influence people's experiences of hurtful messages. Previous applications of RTM to hurt have uncovered associations among relational characteristics that influence people's hurtful experiences; however, the process by which these characteristics influence experiences of hurt remains unclear. We propose that relational communication (specifically, perceptions of dominance, and disaffiliation) is the mechanism linking relational qualities to hurt. A multigroup SEM was conducted to test for the possibility of sex differences. Results showed that people's experiences of hurt vary as a function of both relationship characteristics and relational inferences. Results also indicated a difference in path coefficients for males and females.     

Block Copolymer Surface Reconstuction: A Reversible Route to Nanoporous Films

Thin films of block copolymers have been used as templates and scaffolds for the fabrication of arrays of nanostructured materials. In general, a chemical modification of the film or the removal of one of the components by photodegradative methods is required to produce a nanoporous film that serves as a template or scaffold. Here, however, the preferential interaction of one of the components with a solvent is shown to produce a reconstruction of the block copolymer film that, upon drying, leads to the generation of a nanoporous template. The area density of the pores is identical to that of the original copolymer thin film. Since no chemical reactions occurr, the process is fully reversible. Upon heating the copolymer film above its glass‐transition temperature, mobility is imparted to the copolymer and the original copolymer film with oriented domains is recovered. The film reconstruction significantly simplifies the generation of nanoporous templates.     

Floating integrator technique for switched-capacitor circuits employing reset cycles

A simple `floating? integrator technique is presented that is applicable to both single-ended and differential switched-capacitor circuits which employ reset cycles. This method is useful in eliminating the effects of any input offset or interstage differential or common-mode offsets in DC-coupled circuits. A monolithic circuit is demonstrated which uses this technique to achieve accurate differential integration of low-level signals in the presence of substantial differential and common-mode input offsets.     

Slab waveguides characterized by moments of the index profile

The fundamental mode of a symmetric slab waveguide is described to a high degree of accuracy using only two moments of the refractive index profile rather than its exact form. The two moments can be used to define an equivalent step index slab waveguide, and the fundamental mode propagation constant of an arbitrary profile guide is given by the step index value multiplied by a simple correction factor. The limit to single-mode operation, the second-mode cutoff point, is also given by a simple formula requiring only profile moments. Numerical confirmation of the method is given.