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Mechanoresponsive Alignment of Molecular Self-Assembled Negatively Charged Nanofibrils
Get PDFInspired by the mechanoresponsive orientation of actin filaments in cell, we introduce a design paradigm of synthetic molecular self-assembling fibrils that respond to external mechanical force by transforming from a macroscopically disorder state to a highly ordered uniaxial aligned state. The incorporation of aromatic-containing amino acids and negatively charged amino acids lead to self-assembly motifs that transform into uniform nanofibrils in acidic solution. Adjusting the pH level of aqueous solution introduces optimal negative charge to the surface of self-assembling nanofibrils inducing long-range electrostatic repulsion forming a nematic phase. Upon external mechanical force, nanofibrils align in the force direction. Via evaporation casting in capillary confinement, the solvated synthetic self-assembling nanofibrils transform into scalable lamellar domains. Adjusting capillary geometry and drying procedure offers further parameters for tuning the mesoscale alignment of nanofibrils generating a variety of interference colors. The design paradigm of mechanoresponsive alignment of self-assembled nanofibrils as an addition of nanofabrication techniques is potentially employable for realizing biomimetic optical structures.journal articl
Self-organization of action hierarchy and compositionality by reinforcement learning with recurrent neural networks
Get PDFRecurrent neural networks (RNNs) for reinforcement learning (RL) have shown distinct advantages, e.g., solving memory-dependent tasks and meta-learning. However, little effort has been spent on improving RNN architectures and on understanding the underlying neural mechanisms for performance gain. In this paper, we propose a novel, multiple-timescale, stochastic RNN for RL. Empirical results show that the network can autonomously learn to abstract sub-goals and can self-develop an action hierarchy using internal dynamics in a challenging continuous control task. Furthermore, we show that the self-developed compositionality of the network enhances faster re-learning when adapting to a new task that is a re-composition of previously learned sub-goals, than when starting from scratch. We also found that improved performance can be achieved when neural activities are subject to stochastic rather than deterministic dynamics.journal articl
A noninequality for the fractional gradient
No full textIn this paper we give a streamlined proof of an inequality recently obtained by the author: For every α∈(0,1) there exists a constant C=C(α,d)>0 such that
[Formula: see text]
for all u∈Lq(Rd) for some 1≤q<d/(1−α) such that Dαu:=∇I1−αu∈L1(Rd;Rd). We also give a counterexample which shows that in contrast to the case α=1, the fractional gradient does not admit an L1 trace inequality, i.e. [Formula: see text] cannot control the integral of u with respect to the Hausdorff content [Formula: see text]. The main substance of this counterexample is a result of interest in its own right, that even a weak-type estimate for the Riesz transforms fails on the space [Formula: see text], β∈[1,d). It is an open question whether this failure of a weak-type estimate for the Riesz transforms extends to β∈(0,1).journal articl
Spontaneous emission and energy shifts of a Rydberg rubidium atom close to an optical nanofiber
Get PDFIn this paper, we report on numerical calculations of the spontaneous emission rates and Lamb shifts of a 87Rb atom in a Rydberg-excited state (n≤30) located close to a silica optical nanofiber. We investigate how these quantities depend on the fiber's radius, the distance of the atom to the fiber, the direction of the atomic angular momentum polarization, as well as the different atomic quantum numbers. We also study the contribution of quadrupolar transitions, which may be substantial for highly polarizable Rydberg states. Our calculations are performed in the macroscopic quantum electrodynamics formalism, based on the dyadic Green's function method. This allows us to take dispersive and absorptive characteristics of silica into account; this is of major importance since Rydberg atoms emit along many different transitions whose frequencies cover a wide range of the electromagnetic spectrum. Our work is an important initial step toward building a Rydberg atom-nanofiber interface for quantum optics and quantum information purposes.journal articl
Catalytic Sulfone Upgrading Reaction with Alcohols via Ru(II)
Get PDFSulfones and sulfonamides with an α-CH bond can be easily alkylated by aliphatic alcohols to add the carbon skeleton of the alcohol via a one-step, Ru(II)-catalyzed redox neutral reaction. The reaction requires a substoichiometric amount of base and produces only water as a byproduct. Several pharmaceutically relevant functional groups such as piperidine, morpholine, etc. are well-tolerated under the reaction conditions to give higher value-added products in one step from widely available substrates. The reaction proceeds through a sulfone carbanion addition to an in-situ-generated aldehyde formed via catalytic dehydrogenation and subsequent catalyst-mediated replacement of the secondary alcohol by hydrogen.journal articl
Trail-Following Pheromones in the Termite Subfamily Syntermitinae (Blattodea, Termitoidae, Termitidae)
Get PDFTrail-following behavior is a key to ecological success of termites, allowing them to orient themselves between the nesting and foraging sites. This behavior is controlled by specific trail-following pheromones produced by the abdominal sternal gland occurring in all termite species and developmental stages. Trail-following communication has been studied in a broad spectrum of species, but the "higher" termites (i.e. Termitidae) from the subfamily Syntermitinae remain surprisingly neglected. To fill this gap, we studied the trail-following pheromone in six genera and nine species of Syntermitinae. Our chemical and behavioral experiments showed that (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol is the single component of the pheromone of all the termite species studied, except for Silvestritermes euamignathus. This species produces both (3Z,6Z)-dodeca-3,6-dien-1-ol and neocembrene, but only (3Z,6Z)-dodeca-3,6-dien-1-ol elicits trail-following behavior. Our results indicate the importance of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol, the most widespread communication compound in termites, but also the repeated switches to other common pheromones as exemplified by S. euamignathus.journal articl
Thyroid hormone receptor beta mutations alter photoreceptor development and function in Danio rerio (zebrafish)
Get PDFWe investigate mutations in trbeta2, a splice variant of thrb, identifying changes in function, structure, and behavior in larval and adult zebrafish retinas. Two N-terminus CRISPR mutants were identified. The first is a 6BP+1 insertion deletion frameshift resulting in a truncated protein. The second is a 3BP in frame deletion with intact binding domains. ERG recordings of isolated cone signals showed that the 6BP+1 mutants did not respond to red wavelengths of light while the 3BP mutants did respond. 6BP+1 mutants lacked optomotor and optokinetic responses to red/black and green/black contrasts. Both larval and adult 6BP+1 mutants exhibit a loss of red-cone contribution to the ERG and an increase in UV-cone contribution. Transgenic reporters show loss of cone trbeta2 activation in the 6BP+1 mutant but increase in the density of cones with active blue, green, and UV opsin genes. Antibody reactivity for red-cone LWS1 and LWS2 opsin was absent in the 6BP+1 mutant, as was reactivity for arrestin3a. Our results confirm a critical role for trbeta2 in long-wavelength cone development.journal articl
Goal-Directed Planning for Habituated Agents by Active Inference Using a Variational Recurrent Neural Network
Get PDFIt is crucial to ask how agents can achieve goals by generating action plans using only partial models of the world acquired through habituated sensory-motor experiences. Although many existing robotics studies use a forward model framework, there are generalization issues with high degrees of freedom. The current study shows that the predictive coding (PC) and active inference (AIF) frameworks, which employ a generative model, can develop better generalization by learning a prior distribution in a low dimensional latent state space representing probabilistic structures extracted from well habituated sensory-motor trajectories. In our proposed model, learning is carried out by inferring optimal latent variables as well as synaptic weights for maximizing the evidence lower bound, while goal-directed planning is accomplished by inferring latent variables for maximizing the estimated lower bound. Our proposed model was evaluated with both simple and complex robotic tasks in simulation, which demonstrated sufficient generalization in learning with limited training data by setting an intermediate value for a regularization coefficient. Furthermore, comparative simulation results show that the proposed model outperforms a conventional forward model in goal-directed planning, due to the learned prior confining the search of motor plans within the range of habituated trajectories.journal articl
Functional shell matrix proteins tentatively identified by asymmetric snail shell morphology
Get PDFMolluscan shell matrix proteins (SMPs) are essential in biomineralization. Here, we identify potentially important SMPs by exploiting the asymmetric shell growth in snail, Lymnaea stagnalis. Asymmetric shells require bilaterally asymmetric expression of SMP genes. We examined expression levels of 35,951 transcripts expressed in the left and right sides of mantle tissue of the pond snail, Lymnaea stagnalis. This transcriptome dataset was used to identify 207 SMPs by LC-MS/MS. 32 of the 207 SMP genes show asymmetric expression patterns, which were further verified for 4 of the 32 SMPs using quantitative PCR analysis. Among asymmetrically expressed SMPs in dextral snails, those that are more highly expressed on the left side than the right side are 3 times more abundant than those that are more highly expressed on the right than the left, suggesting potentially inhibitory roles of SMPs in shell formation. The 32 SMPs thus identified have distinctive features, such as conserved domains and low complexity regions, which may be essential in biomineralization.journal articl
Molecular approaches underlying the oogenic cycle of the scleractinian coral, Acropora tenuis
Get PDFThis study aimed to elucidate the physiological processes of oogenesis in Acropora tenuis. Genes/proteins related to oogenesis were investigated: Vasa, a germ cell marker, vitellogenin (VG), a major yolk protein precursor, and its receptor (LDLR). Coral branches were collected monthly from coral reefs around Sesoko Island (Okinawa, Japan) for histological observation by in situ hybridisation (ISH) of the Vasa (AtVasa) and Low Density Lipoprotein Receptor (AtLDLR) genes and immunohistochemistry (IHC) of AtVasa and AtVG. AtVasa immunoreactivity was detected in germline cells and ooplasm, whereas AtVG immunoreactivity was detected in ooplasm and putative ovarian tissues. AtVasa was localised in germline cells located in the retractor muscles of the mesentery, whereas AtLDLR was localised in the putative ovarian and mesentery tissues. AtLDLR was detected in coral tissues during the vitellogenic phase, whereas AtVG immunoreactivity was found in primary oocytes. Germline cells expressing AtVasa are present throughout the year. In conclusion, Vasa has physiological and molecular roles throughout the oogenic cycle, as it determines gonadal germline cells and ensures normal oocyte development, whereas the roles of VG and LDLR are limited to the vitellogenic stages because they act in coordination with lipoprotein transport, vitellogenin synthesis, and yolk incorporation into oocytes.journal articl