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Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using a cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp interfaces between Bi₂Sr₂CaCu₂O_8+xcrystals, with quality approaching the limit set by intrinsic JJs. Near 45° twist angle, we observe fractional Shapiro steps and Fraunhofer patterns, consistent with the existence of two degenerate Josephson ground states related by time-reversal symmetry (TRS). By programming the JJ current bias sequence, we controllably break TRS to place the JJ into either of the two ground states, realizing reversible Josephson diodes without external magnetic fields. Our results open a path to engineering topological devices at higher temperatures.

 

Collagen serves as an essential structural material in the human body. Despite the complex mechanical conditions surrounding the collagen hydrogels, previous studies mostly focus on analyzing the mechanical behavior under dynamically varying compressive or shear loads, but the tensile properties at the quasistatic time scale are relatively less studied. This work aims to investigate the quasistatic tensile behavior of reconstituted collagen hydrogels under uniaxial tensile stresses. The evolution of the collagen fiber network structures with straining is visually observed using the confocal microscope equipped with the tensile strain actuator. While the unfolding of the initially undulated fibers accommodates the early‐stage strains, the deformation mechanism continuously changes to the stretching of fibers through the network alignment to the tensile direction. This transition commences with the buckling of a fiber lying transverse to the loading direction, which otherwise locks the rotation of adjacent fibers.

 

Quasicrystals have been discovered in a variety of materials ranging from metals to polymers. Yet, why and how they form is incompletely understood. In situ transmission electron microscopy of alloy quasicrystal formation in metals suggests an error-and-repair mechanism, whereby quasiperiodic crystals grow imperfectly with phason strain present, and only perfect themselves later into a high-quality quasicrystal with negligible phason strain. The growth mechanism has not been investigated for other types of quasicrystals, such as dendrimeric, polymeric, or colloidal quasicrystals. Soft-matter quasicrystals typically result from entropic, rather than energetic, interactions, and are not usually grown (either in laboratories or in silico ) into large-volume quasicrystals. Consequently, it is unknown whether soft-matter quasicrystals form with the high degree of structural quality found in metal alloy quasicrystals. Here, we investigate the entropically driven growth of colloidal dodecagonal quasicrystals (DQCs) via computer simulation of systems of hard tetrahedra, which are simple models for anisotropic colloidal particles that form a quasicrystal. Using a pattern recognition algorithm applied to particle trajectories during DQC growth, we analyze phason strain to follow the evolution of quasiperiodic order. As in alloys, we observe high structural quality; DQCs with low phason strain crystallize directly from the melt and only require minimal further reduction of phason strain. We also observe transformation from a denser approximant to the DQC via continuous phason strain relaxation. Our results demonstrate that soft-matter quasicrystals dominated by entropy can be thermodynamically stable and grown with high structural quality––just like their alloy quasicrystal counterparts. 

A bstract While the study of bordered (pseudo-)holomorphic curves with boundary on Lagrangian submanifolds has a long history, a similar problem that involves (special) Lagrangian submanifolds with boundary on complex surfaces appears to be largely overlooked in both physics and math literature. We relate this problem to geometry of coassociative submanifolds in G 2 holonomy spaces and to Spin(7) metrics on 8-manifolds with T 2 fibrations. As an application to physics, we propose a large class of brane models in type IIA string theory that generalize brane brick models on the one hand and 2d theories T [ M 4 ] on the other. 

Complex crystallization pathways are common in protein crystallization, tetrahedrally coordinated systems, and biomineralization, where single or multiple precursors temporarily appear before the formation of the crystal. The emergence of precursors is often explained by a unique property of the system, such as short-range attraction, directional bonding, or ion association. But, structural characteristics of the prenucleation phases found in multistep crystallization remain unclear, and models are needed for testing and expanding the understanding of fluid-to-solid ordering pathways. Here, we report 3 instances of 2-step crystallization of hard-particle fluids. Crystallization in these systems proceeds via a high-density precursor fluid phase with prenucleation motifs in the form of clusters, fibers and layers, and networks, respectively. The density and diffusivity change across the fluid–fluid phase transition increases with motif dimension. We observe crystal nucleation to be catalyzed by the interface between the 2 fluid phases. The crystals that form are complex, including, notably, a crystal with 432 particles in the cubic unit cell. Our results establish the existence of complex crystallization pathways in entropic systems and reveal prenucleation motifs of various dimensions. 

Motor rehabilitation is a long term, labor intensive and patient-specific process that requires one-on-one care from skilled clinicians and physiotherapists. Virtual rehabilitation is an alternative rehabilitation technology that can provide intensive motor training with minimal supervision from physiotherapists. However, virtual rehabilitation exercises lack of realism and less connected with Activities of Daily Livings. In this paper, we present six Virtual Reality games that we developed for 5DT data glove, 1-DOF IntelliStretch robot and Xbox Kinect to improve the accessibility of motor rehabilitation. 

Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins. While there are numerous computer studies, there are few experimental realizations due to a lack of means to produce such colloids with a well-controlled variable Janus balance. Here, we report a simple scalable method to precisely vary the Janus balance over a wide range and selectively functionalize one patch with DNA. We observe, via experiment and simulation, the dynamic formation of diverse superstructures: colloidal micelles, chains, or bilayers, depending on the Janus balance. Flexible dimer chains form through cooperative polymerization while trimer chains form by a two-stage process, first by cooperative polymerization into disordered aggregates followed by condensation into more ordered stiff trimer chains. Introducing substrate binding through depletion catalyzes dimer chains to form nonequilibrium rings that otherwise do not form.

 

The oligosaccharyltransferase (OT) complex catalyzesN‐glycosylation of nascent secretory polypeptides in the lumen of the endoplasmic reticulum. Despite their importance, little is known about the structure and function of plantOTcomplexes, mainly due to lack of efficient recombinant protein production systems suitable for studies on large plant protein complexes. Here, we purified ArabidopsisOTcomplexes using the tandem affinity‐taggedOTsubunitSTAUROSPORINE AND TEMPERATURE SENSITIVE3a (STT3a) expressed by an Arabidopsis protein super‐expression platform. Mass‐spectrometry analysis of the purified complexes identified three essentialOTsubunits,OLIGOSACCHARYLTRANSFERASE1 (OST1),HAPLESS6 (HAP6),DEFECTIVE GLYCOSYLATION1 (DGL1), and a number of ribosomal subunits. Transmission‐electron microscopy showed thatSTT3a becomes incorporated intoOT–ribosome super‐complexes formedin vivo, demonstrating that this expression/purification platform is suitable for analysis of large protein complexes. Pairwisein plantainteraction analyses of individualOTsubunits demonstrated that all subunits identified in animalOTcomplexes are conserved in Arabidopsis and physically interact withSTT3a. Genetic analysis of newly establishedOTsubunit mutants forOST1andDEFENDER AGAINST APOTOTIC DEATH(DAD) family genes revealed thatOST1 andDAD1/2 subunits are essential for the plant life cycle. However, mutations in these individual isoforms produced much milder growth/underglycosylation phenotypes than previously reported for mutations inDGL1,OST3/6andSTT3a.