We present a renormalizable theory of scalars in which the low-energy effective theory contains a pseudo-Goldstone boson with a compact field space of 2piF and an approximate discrete shift symmetry ...Z sub(Q) with Q >> 1, yet the number of fields in the theory goes as log Q. Such a model can serve as a UV completion to models of relaxions and is a new source of exponential scale separation in field theory. While the model is local in "theory space," it appears not to have a continuum generalization (i.e., it cannot be a deconstructed extra dimension). Our framework shows that super-Planckian field excursions can be mimicked while sticking to renormalizable four-dimensional quantum field theory. We show that a supersymmetric extension is straightforwardly obtained, and we illustrate possible UV completions based on a compact extra dimension, where all global symmetries arise accidentally as a consequence of gauge invariance and five-dimensional locality.
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Conspectus Soft bioelectronics that could be integrated with soft and curvilinear biological tissues/organs have attracted multidisciplinary research interest from material scientists, electronic ...engineers, and biomedical scientists. Because of their potential human health-related applications, soft bioelectronics require stringent demands for biocompatible components. Silk, as a kind of well-known ancient natural biopolymer, shows unique combined merits such as good biocompatibility, programmable biodegradability, processability into various material formats, and large-scale sustainable production. Such unique merits have made silk popular for intensive design and study in soft bioelectronics over the past decade. Due to the development of fabrication techniques in material processing and progress in research, silk has been engineered into a variety of advanced materials including silk fibers/textiles, nanofibers, films, hydrogels, and aerogels. Natural and regenerated silk materials can also be transformed into intrinsically nitrogen-doped and electrically conductive carbon materials, due to their unique molecular structure and high nitrogen content. The rich morphologies and varied processing options for silk materials can furnish transformed carbon materials with well-designed structures and properties. The favorable and unique material merits of silk materials and silk-derived carbon materials offer potential applications in soft electronics. Based on commercial silk fibers/textiles and the availability of re-engineered silk materials with versatile technological formats, functional soft electronics have been explored with silk as flexible biosupports/biomatrixes or active components. These soft systems include bioresorbable electronics, ultraconformal bioelectronics, transient electronics, epidermal electronics, textile electronics, conformal biosensors, flexible transistors, and resistive switching memory devices. Silk-derived carbon materials with rationally designed morphologies and structures have also been developed as active components for wearable sensors, electronic skins, and flexible energy devices, which provide novel concepts and opportunities for soft electronics. In this Account, we highlight the unique hierarchical and chemical structure of natural silk fibers, the fabrication strategies for processing silk into materials with versatile morphologies and into electrically conductive carbon materials, as well as recent progress in the development of silk-based advanced materials (silk materials and silk-derived carbon materials) for soft bioelectronics. The design and functionality of soft electronics developed with commercial silk fibers/textiles, re-engineered silk materials, and silk-derived carbon materials as biosubstrate/matrix and active components is introduced in detail. We further discuss future challenges and prospects for developing silk-based soft bioelectronics for wearable healthcare systems. By leveraging the unique advantages of silk-based advanced materials, the design and construction strategy for flexible electronics, as well as the potential of flexible electronics for conformable and intimate association with human tissues/organs, silk-based soft bioelectronics should have a significant impact on diverse healthcare fields.
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3.
Overview of Silk Fibroin Use in Wound Dressings Farokhi, Mehdi; Mottaghitalab, Fatemeh; Fatahi, Yousef ...
Trends in biotechnology (Regular ed.),
09/2018, Volume:
36, Issue:
9
Journal Article
Peer reviewed
Recently, biomimetic wound dressings were introduced as potential replacements for treating skin injuries. Although there are some clinically available skin replacements, the range of wound types and ...locations necessitates a broader range of options for the clinic. Natural polymeric-based dressings are of central interest in this area due to their outstanding biocompatibility, biodegradability, low toxicity, and non-allergenic nature. Among them, silk fibroin (SF) has exceptional characteristics as a wound dressing. SF-based dressings can also be used as carriers for delivering drugs, growth factors, and bioactive agents to the wound area, while providing appropriate support for complete healing. In this review, we describe recent advances in the development of SF-based wound dressings for skin regeneration.
The growing field of tissue engineering has introduced remarkable wound dressings based on natural polymers.
The unique properties of SF, such as its biocompatibility, biodegradability, high water and oxygen uptake, low immunogenicity, and robust mechanical properties, make it an exceptional choice for wound healing.
Scaffolds containing different growth factors and signaling molecules are preferable for wound regeneration because they can interact with cells and consequently enhance cell behavior during the healing process.
Despite the successful use of SF in wound dressings, it is not yet approved as an artificial skin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Advances in farming technology and intensification of animal agriculture increase the cost-efficiency and production volume of meat. Thus, in developed nations, meat is relatively inexpensive and ...accessible. While beneficial for consumer satisfaction, intensive meat production inflicts negative externalities on public health, the environment and animal welfare. In response, groups within academia and industry are working to improve the sensory characteristics of plant-based meat and pursuing nascent approaches through cellular agriculture methodology (i.e., cell-based meat). Here we detail the benefits and challenges of plant-based and cell-based meat alternatives with regard to production efficiency, product characteristics and impact categories.
I demonstrate how chiral fermions with an exact gauge symmetry can appear on the d-dimensional boundary of a finite volume (d+1)-dimensional manifold, without any light mirror partners. The condition ...for the d-dimensional boundary theory to be local is that gauge anomalies cancel and that the volume be large. This can likely be achieved on a lattice and provides a new paradigm for the lattice regularization of chiral gauge theories.
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The moment conditions or estimating equations for instrumental variables quantile regression involve the discontinuous indicator function. We instead use smoothed estimating equations (SEE), with ...bandwidth h. We show that the mean squared error (MSE) of the vector of the SEE is minimized for some h > 0, leading to smaller asymptotic MSE of the estimating equations and associated parameter estimators. The same MSE-optimal h also minimizes the higher-order type I error of a SEE-based χ
2 test and increases size-adjusted power in large samples. Computation of the SEE estimator also becomes simpler and more reliable, especially with (more) endogenous regressors. Monte Carlo simulations demonstrate all of these superior properties in finite samples, and we apply our estimator to JTPA data. Smoothing the estimating equations is not just a technical operation for establishing Edgeworth expansions and bootstrap refinements; it also brings the real benefits of having more precise estimators and more powerful tests.
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Silk fibroin (SF) was enzymatically crosslinked with tyramine-substituted silk fibroin (SF-TA) or gelatin (G-TA) to fabricate hybrid hydrogels with tunable gelation kinetics, mechanical properties ...and bioactivity. Horseradish peroxidase (HRP)/hydrogen peroxide (H2O2) mediated crosslinking of SF in physiological buffers results in slow gelation and limited mechanical properties. Moreover, SF lacks cell attachment sequences, leading to poor cell-material interactions. These shortcomings can limit the uses of enzymatically crosslinked silk hydrogels in injectable tissue fillings, 3D bioprinting or cell microencapsulation, where rapid gelation and high bioactivity are desired. Here SF/SF-TA and SF/G-TA composite hydrogels were characterized for hydrogel properties and the influence of conjugated cyclic arginine-glycine-aspartic acid (RGD) peptide or G-TA content on bioactivity was explored. Both SF-TA and G-TA significantly increased gelation kinetics, improved mechanical properties and delayed enzymatic degradation in a concentration-dependent manner. β-Sheet formation and hydrogel stiffening were accelerated by SF-TA content but delayed by G-TA. Both cyclic RGD and G-TA significantly improved morphology and metabolic activity of human mesenchymal stem cells (hMSCs) cultured on or encapsulated in composite hydrogels. The hydrogel formulations introduced in this study provide improved control of gel formation and properties, along with biocompatible systems that can be utilized in tissue engineering and cell delivery applications.
Statement of Significance: HRP-mediated covalent crosslinking of aqueous silk solutions allows for fabrication of highly elastic, mechanically tunable, degradable and biocompatible hydrogels. However, slow gelation and impaired mechanical properties of silk hydrogels enzymatically crosslinked in physiological media as well as the lack of cell-recognition sequences in silk fibroin limit potential cell encapsulation applications. In the present study, crosslinking of regenerated silk with tyramine-substituted silk or gelatin was performed to improve gelation kinetics and mechanical properties of silk hydrogels by increasing the number of phenol groups available for enzymatic crosslinking. Moreover, in situ conjugation of cyclic RGD peptides into silk hydrogels was employed to enhance cell-matrix interactions. Our findings indicate significant improvement of gelation kinetics and modulus, as well as modulation of silk secondary structure and enzymatic degradation of composite hydrogels in addition to enhanced bioactivity provided by cyclic RGD peptides or tyramine-substituted gelatin. Silk hydrogel formulations introduced here hold great promise as injectable cell-laden tissue fillers and as bioinks for cell encapsulation through 3D bioprinting or droplet-based microgel fabrication. Display omitted
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
As a biomaterial, silk presents unique features with a combination of excellent mechanical properties, biocompatibility, and biodegradability. The biodegradability aspects of silk biomaterials, ...especially with options to control the rate from short (days) to long (years) time frames in vivo, make this protein-based biopolymer a good candidate for developing biodegradable devices used for tissue repairs and tissue engineering, as well as medical device implants. Silk materials, including native silk fibers and a broad spectrum of regenerated silk materials, have been investigated in vitro and in vivo to demonstrate degradation by proteolytic enzymes. In this Review, we summarize the findings on these studies on the enzymatic degradation of Bombyx mori (B. mori) silk materials. We also present a discussion on the factors that dictate the degradation properties of silk materials. Finally, in future perspectives, we highlight some key challenges and potential directions toward the future study of the degradation of silk materials.
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A new class of solutions to the electroweak hierarchy problem is presented that does not require either weak-scale dynamics or anthropics. Dynamical evolution during the early Universe drives the ...Higgs boson mass to a value much smaller than the cutoff. The simplest model has the particle content of the standard model plus a QCD axion and an inflation sector. The highest cutoff achieved in any technically natural model is 10^{8} GeV.
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