With recent progress in graphics, it has become more tractable to train models on synthetic images, potentially avoiding the need for expensive annotations. However, learning from synthetic images may not achieve the desired performance due to a gap between synthetic and real image distributions. To reduce this gap, we propose Simulated+Unsupervised (S+U) learning, where the task is to learn a model to improve the realism of a simulator's output using unlabeled real data, while preserving the annotation information from the simulator. We develop a method for S+U learning that uses an adversarial network similar to Generative Adversarial Networks (GANs), but with synthetic images as inputs instead of random vectors. We make several key modifications to the standard GAN algorithm to preserve annotations, avoid artifacts, and stabilize training: (i) a 'self-regularization' term, (ii) a local adversarial loss, and (iii) updating the discriminator using a history of refined images. We show that this enables generation of highly realistic images, which we demonstrate both qualitatively and with a user study. We quantitatively evaluate the generated images by training models for gaze estimation and hand pose estimation. We show a significant improvement over using synthetic images, and achieve state-of-the-art results on the MPIIGaze dataset without any labeled real data.

No abstract

The orientation and spatial distribution of nanocrystals in the organic matrix are two distinctive structural characteristics associated with natural bone. Synthetic soft materials have been used to successfully control the orientation of mineral crystals. The spatial distribution of minerals in a synthetic scaffold, however, has yet to be reproduced in a biomimetic manner. Herein, we report using block copolymer-decorated polymer nanofibers to achieve biomineralized fibrils with precise control of both mineral crystal orientation and spatial distribution. Exquisite nanoscale structural control in biomimetic hybrid materials has been demonstrated.

A self-healing hydrogel ionic conductor has been developed by combining dynamic covalent chemistry with nanofiller reinforcement and micelle crosslinking, and used for sensing of diverse human activities.

Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery.

Injectable self-healing hydrogels, as implanted materials, have received great attention over the past decades. The tunable optical and mechanical properties as well as the ability to lower the risk of inflammatory responses are essential considerations for their applications in diverse bioengineering processes. In this work, we report a novel injectable selfhealing hydrogel with tunable optical, mechanical, and antimicrobial properties, fabricated by a multifunctional ABA triblock copolymer gelator, poly{(4 (methacryloyloxy)ethyl] trimethylammonium chloride]} and polyethylenimine. The self-healing capability of the hydrogel was demonstrated by rheology tests, and quantitative force measurements using a surface forces apparatus (SFA) provided molecular insights into the self-healing mechanism of Schiff base reaction. Additionally, the optical and mechanical properties of the hydrogel can be fine-tuned in a sensitive temperature-responsive manner because of the local nano-hydrophobic domains formed through the phase transition of the ABA triblock copolymer gelator. The hydrogel also demonstrated multiple sol−gel transitions subjected to pH change. Moreover, the hydrogel can also effectively inhibit the growth of both Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus aureus), while showing low cytotoxicity to both fibroblast and cancer cells (MRC-5 and HeLa). The novel multifunctional injectable self-healing hydrogel with tunable optical, mechanical, and excellent antimicrobial properties shows great potential in various bioengineering applications.

The use of click chemistry as a hydrogel cross-linking reaction is often limited by slow reaction rates and harsh conditions, such as exposure to UV light and/or use of nonspecific or toxic reagents. On the other hand, the process of boronic ester formation between arylboronic acids and diols suffers from its intrinsic reversibility and low binding affinity at low pH, which impede its potential in many biomedical applications where a fast and stable click reaction is needed. Herein, we report a new concept of click hydrogel fabrication that combines a traditional sugar-based boronic ester and a novel nopoldiol-based benzoxaborolate as a dual-crosslink network (DCN) system. The cooperation of dynamic and rigid networks and the unique sensitivity of benzoxaborolate cross-links toward stimulus provide an intelligent hydrogel with a set of interesting features: (i) catalyst/light-free nopoldiol–benzoxaborolate bioorthogonal click cross-linking, (ii) rapid in situ formation within 26 s, (iii) wide self-healing pH range from 8.5 to 1.5, (iv) exceptional stability under acidic condition and polyol solutions, (v) reactive oxygen species/pH-responsive degradation, (vi) pH-responsive drug release, and (vii) capability for viable cell encapsulation. The complementary click partners, a rigid diol monomer [1R)-(−)-nopol-methacrylamido-diol (nopoldiol)] and a benzoxaborole-based monomer [5-methacrylamido-1,2-benzoxaborole (MAAmBO)], can be easily incorporated into a variety of synthetic polymers through free-radical polymerization with poly­(ethylene glycol) methyl ether methacrylate (PEGMA) as the backbone component. The shortened gelation time, improved mechanical properties, and excellent self-healing properties of the resulting DCN hydrogel PBNG were evaluated through rheological measurements. The stability/degradation of PBNG under low pH buffer and H2O2 were monitored via hydrogel weight changes, and the potential of PBNG as a drug-releasing carrier was assessed by the pH-responsive release of doxorubicin. Finally, HeLa cells were successfully encapsulated and cultured in the 3D network to confirm the hydrogel’s biocompatibility as a cell culture scaffold. The nontoxic components and their fast click reaction under mild conditions make the nopoldiol–benzoxaborolate click hydrogels promising candidates for future biomedical applications such as gene delivery, cell therapy, and tissue engineering.

Photosystem II (PSII) is a multisubunit pigment-protein complex and catalyzes light-driven water oxidation, leading to the conversion of light energy into chemical energy and the release of molecular oxygen. Psb27 is a small thylakoid lumen-localized protein known to serve as an assembly factor for the biogenesis and repair of the PSII complex. The exact location and binding fashion of Psb27 in the intermediate PSII remain elusive. Here, we report the structure of a dimeric Psb27-PSII complex purified from a psbV deletion mutant (ΔPsbV) of the cyanobacterium Thermosynechococcus vulcanus, solved by cryo-electron microscopy. Our structure showed that Psb27 is associated with CP43 at the luminal side, with specific interactions formed between Helix 2 and Helix 3 of Psb27 and a loop region between Helix 3 and Helix 4 of CP43 (loop C) as well as the large, lumen-exposed and hydrophilic E-loop of CP43. The binding of Psb27 imposes some conflicts with the N-terminal region of PsbO and also induces some conformational changes in CP43, CP47, and D2. This makes PsbO unable to bind in the Psb27-PSII. Conformational changes also occurred in D1, PsbE, PsbF, and PsbZ; this, together with the conformational changes occurred in CP43, CP47, and D2, may prevent the binding of PsbU and induce dissociation of PsbJ. This structural information provides important insights into the regulation mechanism of Psb27 in the biogenesis and repair of PSII.