Plant Age Effect on Mechanical Properties of Moso Bamboo (Phyllostachys Heterocycla Var. Pubescens) Single Fibers

Bamboo fiber has greater mechanical strength than certain other natural fibers and could therefore be a candidate for production of fiber-reinforced composites. Single fibers were isolated from Moso bamboo samples taken from plants between 0.5 and 8.5 yr old. Mechanical properties of single fibers (tensile strength, modulus of elasticity (MOE), and other mechanical related properties such as the microfibril angle and fiber cross-sectional area) were studied. There was no significant variation with age in average MOE and fracture strain of the bamboo fibers. Results indicate that the thickening growth of cell walls in bamboo fibers near the outer surface of bamboo is almost complete by 0.5 yr. Therefore, fibers from 0.5 to 8.5 yr old plants may be used for making fiber-reinforced composites

Dual closed-loop chemical recycling of synthetic polymers by intrinsically reconfigurable poly(disulfides)

The excessive use of plastics has led to severe global problems involving environmental, energy, and health issues and demands for sustainable and recyclable alternatives. Toward circular plastics, the development of efficient chemical recycling methods without loss of properties or allowing reprocessing into new materials offer tremendous opportunities. Here, we report an intrinsically recyclable and reconfigurable poly(disulfide) polymer using a natural small molecule, thioctic acid (TA), as the feedstock. Taking advantage of its dynamic covalent ring-opening polymerization, this material enables a dual closed-loop chemical recycling network among TA monomers and two kinds of polymer products, including self-healing elastomers and mechanically robust ionic films. Mild and complete depolymerization into monomers in diluted alkaline aqueous solution is achieved with yields of recovered monomers up to 86%. The polymer materials can be repeatedly recycled and reused with reconfigurable polymer composition and tunable mechanical properties offering prospects for sustainable functional plastics

Conformationally Strained trans- Cyclooctene (sTCO) Enables the Rapid Construction of 18 F-PET Probes via Tetrazine Ligation

The bioorthogonal reaction between tetrazines and trans-cyclooctenes is a method for the rapid construction of F-18 probes for PET imaging. Described here is a second generation 18F-labeling system based on a conformationally strained trans-cyclooctene (sTCO)—a dienophile that is approximately 2 orders of magnitude more reactive than conventional TCO dienophiles. Starting from a readily prepared tosylate precursor, an 18F labeled sTCO derivative (18F-sTCO) could be synthesized in 29.3 +/- 5.1% isolated yield and with high specific activity. Tetrazine ligation was carried out with a cyclic RGD-conjugate of a diphenyl-s-tetrazine analogue (RGD-Tz) chosen from a diene class with an excellent combination of fast reactivity and stability both for the diene as well as the Diels-Alder adduct. For both the tetrazine and the sTCO, mini-PEG spacers were included to enhance solubility and improve the in vivo distribution profile of the resulting probe. Extremely fast reactivity (up to 2.86 x 105 M-1s-1 at 25 °C in water) has been observed in kinetic studies in the reaction of sTCO with diphenyl-s-tetrazine derivatives. A kinetic study on sTCO diastereomers in 55:45 MeOH:water showed that the syn-diastereomer displayed slightly faster reactivity than the anti-diastereomer. An 18F-sTCO conjugate with RGD-Tz demonstrated prominent and persistent tumor uptake in vivo with good tumor-to-background contrast. Unlike most radiolabeled RGD peptides, the tumor uptake of this PET agent increased from 5.3 +/- 0.2% ID/g at 1 h post injection (p.i.), to 8.9 +/- 0.5% ID/g at 4 h p.i., providing evidence for prolonged blood circulation. These findings suggest that tetrazine ligations employing 18F-sTCO should serve as a powerful and general platform for the rapid construction of peptide or protein derived PET agents

Assembling a Natural Small Molecule into a Supramolecular Network with High Structural Order and Dynamic Functions

Programming the hierarchical self-assembly of small molecules has been a fundamental topic of great significance in biological systems and artificial supramolecular systems. Precise and highly programmed self-assembly can produce supramolecular architectures with distinct structural features. However, it still remains a challenge how to precisely control the self-assembly pathway in a desirable way by introducing abundant structural information into a limited molecular backbone. Here we disclose a strategy that directs the hierarchical self-assembly of sodium thioctate, a small molecule of biological origin, into a highly ordered supramolecular layered network. By combining the unique dynamic covalent ring-opening-polymerization of sodium thioctate and an evaporation-induced interfacial confinement effect, we precisely direct the dynamic supramolecular self-assembly of this simple small molecule in a scheduled hierarchical pathway, resulting in a layered structure with long-range order at both macroscopic and molecular scales, which is revealed by small-angle and wide-angle X-ray scattering technologies. The resulting supramolecular layers are found to be able to bind water molecules as structural water, which works as an interlayer lubricant to modulate the material properties, such as mechanical performance, self-healing capability, and actuating function. Analogous to many reversibly self-assembled biological systems, the highly dynamic polymeric network can be degraded into monomers and reformed by a water-mediated route, exhibiting full recyclability in a facile, mild, and environmentally friendly way. This approach for assembling commercial small molecules into structurally complex materials paves the way for low-cost functional supramolecular materials based on synthetically simple procedures

Be Stars in the Open Cluster NGC 6830

We report the discovery of 2 new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven H-alpha emitters were discovered using the H-alpha imaging photometry of the Palomar Transient Factory Survey. Stellar membership of the candidates was verified with photometric and kinematic information using 2MASS data and proper motions. The spectroscopic confirmation was carried out by using the Shane 3-m telescope at Lick observatory. Based on their spectral types, three H-alpha emitters were confirmed as Be stars with H-alpha equivalent widths > -10 Angstrom. Two objects were also observed by the new spectrograph SED-Machine on the Palomar 60 inch Telescope. The SED-Machine results show strong H-alpha emission lines, which are consistent with the results of the Lick observations. The high efficiency of the SED-Machine can provide rapid observations for Be stars in a comprehensive survey in the future.Comment: 11 pages, 8 figures, AJ in pres

Exploring a naturally tailored small molecule for stretchable, self-healing, and adhesive supramolecular polymers

Polymeric materials with integrated functionalities are required to match their ever-expanding practical applications, but there is always a trade-off between complex material performances and synthetic simplification. A simple and effective synthesis route is reported to transform a small molecule of biological origin, thioctic acid, into a high-performance supramolecular polymeric material, which combines processability, ultrahigh stretchability, rapid self-healing ability, and reusable adhesivity to surfaces. The proposed one-step preparation process of this material involves the mixing of three commercially available feedstocks at mild temperature without any external solvent and a subsequent cooling process that resulted in a dynamic, high-density, and dry supramolecular polymeric network cross-linked by three different types of dynamic chemical bonds, whose cooperative effects in the network enable high performance of this supramolecular polymeric material

Visible-Light-Driven Rotation of Molecular Motors in Discrete Supramolecular Metallacycles

The organization of molecular motors in supramolecular assemblies to allow the amplification and transmission of motion and collective action is an important step toward future responsive systems. Metal-coordination-driven directional self-assembly into supramolecular metallacycles provides a powerful strategy to position several motor units in larger structures with well-defined geometries. Herein, we present a pyridyl-modified molecular motor ligand (MPY) which upon coordination with geometrically distinct di-Pt(II) acceptors assembles into discrete metallacycles of different sizes and shapes. This coordination leads to a red-shift of the absorption bands of molecular motors, making these motorized metallacycles responsive to visible light. Photochemical and thermal isomerization experiments demonstrated that the light-driven rotation of the motors in the metallacycles is similar to that in free MPY in solution. CD studies show that the helicity inversions associated with each isomerization step in the rotary cycle are preserved. To explore collective motion, the trimeric motor-containing metallacycle was aggregated with heparin through multiple electrostatic interactions, to construct a multi-component hierarchical system. SEM, TEM, and DLS measurements revealed that the photo- and thermal-responsive molecular motor units enabled selective manipulation of the secondary supramolecular aggregation process without dissociating the primary metallacycle structures. These visible-light-responsive metallacycles, with intrinsic multiple rotary motors, offer prospects for cooperative operations, dynamic hierarchical self-assembled systems, and adaptive materials

Transcutaneous Vagus Nerve Stimulation for the Treatment of Depression: A Study Protocol for a Double Blinded Randomized Clinical Trial

Background: Depressive disorders are the most common form of mental disorders in community and health care settings. Unfortunately, the treatment of Major Depressive Disorder (MDD) is far from satisfactory. Vagus nerve stimulation (VNS) is a relatively new and promising physical treatment for depressive disorders. One particularly appealing element of VNS is the long-term benefit in mood regulation. However, because this intervention involves surgery, perioperative risks, and potentially significant side effects, this treatment has been limited to those patients with treatment-resistant depression who have failed medication trials and exhausted established somatic treatments for major depression, due to intolerance or lack of response. This double-blinded randomized clinical trial aims to overcome these limitations by introducing a novel method of stimulating superficial branches of the vagus nerve on the ear to treat MDD. The rationale is that direct stimulation of the afferent nerve fibers on the ear area with afferent vagus nerve distribution should produce a similar effect as classic VNS in reducing depressive symptoms without the burden of surgical intervention. Design: One hundred twenty cases (60 males) of volunteer patients with mild and moderate depression will be randomly divided into transcutaneous vagus nerve stimulation group (tVNS) and sham tVNS group. The treatment period lasts 4 months and all clinical and physiological measurements are acquired at the beginning and the end of the treatment period. Discussion: This study has the potential to significantly extend the application of VNS treatment for MDD and other disorders (including epilepsy, bipolar disorder, and morbid obesity), resulting in direct benefit to the patients suffering from these highly prevalent disorders. In addition, the results of this double-blinded clinical trial will shed new light on our understanding of acupuncture point specificity, and development of methodologies in clinical trials of acupuncture treatment

Δ\Delta-scaling and Information Entropy in Ultra-Relativistic Nucleus-Nucleus Collisions

The $\Delta$-scaling method has been applied to ultra-relativistic p+p, C+C and Pb+Pb collision data simulated using a high energy Monte Carlo package, LUCIAE 3.0. The $\Delta$-scaling is found to be valid for some physical variables, such as charged particle multiplicity, strange particle multiplicity and number of binary nucleon-nucleon collisions from these simulated nucleus-nucleus collisions over an extended energy ranging from $E_{lab}$ = 20 to 200 A GeV. In addition we derived information entropy from the multiplicity distribution as a function of beam energy for these collisions.Comment: 4 pages, 4 figures, 1 table; to appear in the July Issue of Chin. Phys. Lett.. Web Page: http://www.iop.org/EJ/journal/CP

Transcutaneous Auricular Vagus Nerve Stimulation Protects Endotoxemic Rat from Lipopolysaccharide-Induced Inflammation

Background. Transcutaneous auricular vagus nerve stimulation (ta-VNS) could evoke parasympathetic activities via activating the brainstem autonomic nuclei, similar to the effects that are produced after vagus nerve stimulation (VNS). VNS modulates immune function through activating the cholinergic anti-inflammatory pathway. Methods. VNS, ta-VNS, or transcutaneous electrical acupoint stimulation (TEAS) on ST36 was performed to modulate the inflammatory response. The concentration of serum proinflammatory cytokines and tissue NF-kappa B p65 (NF-κB p65) were detected in endotoxaemia affected anesthetized rats. Results. Similar to the effect of VNS, ta-VNS suppressed the serum proinflammatory cytokines levels, such as tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) as well as NF-kappa B p65 expressions of lung tissues. ST36 stimulation also decreases LPS-induced high TNF-α level and NF-κB signal, but it did not restrain proinflammatory cytokine IL-1β and IL-6. Neither ta-VNS nor ST36 stimulation could suppress LPS-induced TNF-α and NF-κB after vagotomy or with α7nAChR antagonist injection. Conclusions. The present paper demonstrated that ta-VNS could be utilized to suppress LPS-induced inflammatory responses via α7nAChR-mediated cholinergic anti-inflammatory pathway