Video_1_A brain-inspired robot pain model based on a spiking neural network.MP4

IntroductionPain is a crucial function for organisms. Building a “Robot Pain” model inspired by organisms' pain could help the robot learn self-preservation and extend longevity. Most previous studies about robots and pain focus on robots interacting with people by recognizing their pain expressions or scenes, or avoiding obstacles by recognizing dangerous objects. Robots do not have human-like pain capacity and cannot adaptively respond to danger. Inspired by the evolutionary mechanisms of pain emergence and the Free Energy Principle (FEP) in the brain, we summarize the neural mechanisms of pain and construct a Brain-inspired Robot Pain Spiking Neural Network (BRP-SNN) with spike-time-dependent-plasticity (STDP) learning rule and population coding method.MethodsThe proposed model can quantify machine injury by detecting the coupling relationship between multi-modality sensory information and generating “robot pain” as an internal state.ResultsWe provide a comparative analysis with the results of neuroscience experiments, showing that our model has biological interpretability. We also successfully tested our model on two tasks with real robots—the alerting actual injury task and the preventing potential injury task.DiscussionOur work has two major contributions: (1) It has positive implications for the integration of pain concepts into robotics in the intelligent robotics field. (2) Our summary of pain's neural mechanisms and the implemented computational simulations provide a new perspective to explore the nature of pain, which has significant value for future pain research in the cognitive neuroscience field.</p

Microsolvated Model for the Kinetics and Thermodynamics of Glycosidic Bond Dissociative Cleavage of Nucleoside D4G

Using the microsolvated model that involves explicit water molecules and implicit solvent in the optimization, two proposed dissociative hydrolysis mechanisms of 2′,3′-didehydro-2′,3′-dideoxyguanosine (d4G) have been first investigated by means of M06-2X­(CPCM, water)/6-31++G­(d,p) method. The glycosidic bond dissociation for the generation of the oxacarbenium ion intermediate is the rate-determining step (RDS). The subsequent nucleophilic water attack from different side of the oxacarbenium ion intermediate gives either the α-product [(2<i>S</i>,5<i>S</i>)-5-(hydroxymethyl)-2,5-dihydrofuran-2-ol] or β-product [(2<i>R</i>,5<i>S</i>)-5-(hydroxymethyl)-2,5-dihydrofuran-2-ol] and is thus referred to as α-path (inversion) and β-path (retention). Two to five explicit water molecules (<i>n</i> = 2–5) are considered in the microsolvated model, and <i>n</i> = 3 or 4 is the smallest model capable of minimizing the activation energy for α-path and β-path, respectively. Our theoretical results suggest that α-path (<i>n</i> = 3) is more kinetically favorable with lower free energy barrier (RDS) of 27.7 kcal mol^–1, in contrast to that of 30.7 kcal mol^–1 for the β-path (<i>n</i> = 4). The kinetic preference of the α-path is rationalized by NBO analysis. Whereas thte β-path is more thermodynamically favorable over the α-path, where the formation of β-product and α-product are exergonic and endergonic, respectively, providing theoretical support for the experimental observation that the β-cleavage product was the major one after sufficient reaction time. Comparisons of d4G with analogous cyclo-d4G and dG from kinetic free energy barriers and thermodynamic heterolytic dissociation energies were also carried out. Our kinetic and thermodynamic results manifest that the order of glycosidic bond stability should be d4G < cyclo-d4G < dG, which agrees well with the reported experimental stability order of d4G compounds and analogues and gives further understanding on the influence of 6-cyclopropylamino and unsaturated ribose to the glycosidic bond instability of d4G

Tuning Effects for Some Cyclic Aromatic Carbenes Bearing Remote Amino Groups

Yamamoto and co-workers synthesized two cyclic aromatic carbenes with remote amino groups. Here we theoretically studied related compounds to explore tuning effects on the singlet–triplet splitting by variations of functional groups. For the Yamamoto compound, the lowest singlet state lies 15.7 kcal/mol below the lowest triplet. The singlet–triplet separation is reduced by ∼7 kcal/mol when the dimethylamino groups are replaced by H. In one set of carbenes, when X = O, we substitute S, Se, Te, SO, SeO, and TeO for X; the resulting Δ<i>E</i>(S–T) predictions are 9.9, 7.3, 3.9, 4.3, 2.3, and −0.1 kcal/mol, respectively. A different set of X fragments yields triplet electronic ground states with Δ<i>E</i>(S–T) values of −8.6 (X = BH), −6.8 (X = AlH), −7.2 (X = GaH), −7.5 (X = InH), and −7.0 kcal/mol (X = TlH). We also predicted Δ<i>E</i>(S–T) with N­(CH₃)₂ replaced by PH₂, AsH₂, SbH₂, BiH₂, BH₂, CH₃, OH, and F. Of all the molecules considered, that with N­(CH₃)₂ replaced with BH₂ and X = BH most favors the triplet state, lying 13.7 kcal/mol below the singlet. Finally, we have relocated the N­(CH₃)₂ and NH₂ groups from the (3, 6) positions to the (4, 5), (2, 7), and (1, 8) terminal ring positions, with very interesting results

Table_1_Grafting enhances plants drought resistance: Current understanding, mechanisms, and future perspectives.docx

Drought, one of the most severe and complex abiotic stresses, is increasingly occurring due to global climate change and adversely affects plant growth and yield. Grafting is a proven and effective tool to enhance plant drought resistance ability by regulating their physiological and molecular processes. In this review, we have summarized the current understanding, mechanisms, and perspectives of the drought stress resistance of grafted plants. Plants resist drought through adaptive changes in their root, stem, and leaf morphology and structure, stomatal closure modulation to reduce transpiration, activating osmoregulation, enhancing antioxidant systems, and regulating phytohormones and gene expression changes. Additionally, the mRNAs, miRNAs and peptides crossing the grafted healing sites also confer drought resistance. However, the interaction between phytohormones, establishment of the scion-rootstock communication through genetic materials to enhance drought resistance is becoming a hot research topic. Therefore, our review provides not only physiological evidences for selecting drought-resistant rootstocks or scions, but also a clear understanding of the potential molecular effects to enhance drought resistance using grafted plants.</p

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

The relative energies of singlet and triplet metallocene, metallabenzene, and metallacyclopentadiene C₁₀H₁₀M isomers (M = Ni, Pd, Pt) have been examined using density functional theory. For the C₁₀H₁₀Ni system, the experimentally known triplet nickelocene (η⁵-Cp)₂Ni is the lowest energy isomer by ∼17 kcal/mol with respect to singlet nickelocene. For the C₁₀H₁₀Pd system, the triplet and singlet palladocene structures have similar energies within ∼2 kcal/mol. However, the singlet palladocene has a “slipped ring” (η³-Cp)₂Pd structure with two trihapto Cp rings. The C₁₀H₁₀Pt system is different since the platinabenzene CpPtC₅H₅ isomer is the lowest energy structure. This is in accord with the synthesis of stable substituted CpPtC₅H₃R₂ platinabenzenes by Haley and co-workers [Haley, M. M.; et al. Organometallics 2004, 23, 1174]. However, the slipped ring singlet platinocene (η³-Cp)₂Pt to the isomeric platinocene lies only ∼2 kcal/mol above the platinabenzene global minimum, so the energy barrier for conversion of the platinabenzene must be substantial. The following general observations can be made regarding the relative stabilities of isomeric C₁₀H₁₀M (M = Ni, Pd, Pt) structures: (1) Triplet structures become less favorable energetically than isomeric singlet structures in the sequence Ni < Pd < Pt. (2) Slipped metallocene structures with trihapto η³-Cp rather than pentahapto η⁵-Cp rings leading ultimately to 16- rather than 18-electron metal configurations become increasingly favorable energetically in the sequence Ni < Pd < Pt. (3) Metallabenzene (η⁵-Cp)­MC₅H₅ structures with pentahapto Cp rings are always more favorable energetically than isomeric metallacyclopentadiene (η⁶-C₆H₆)­MC₄H₄ structures with hexahapto benzene rings

Dinickelametallocenes: Sandwich Compounds of the First-Row Transition Metals (M = Fe, Co, Ni) with Two Pentahapto Planar Nickelacycle Ligands

Buchalski and co-workers showed in 2008 that reactions of the nickelafluorenyl anion CpNiC₁₂H₈^– with MX₂ (M = Co, Ni) give the dinickelametallocene sandwich compounds (CpNiC₁₂H₈)₂M. We now report theoretical studies on the related bis­(nickelacyclopentadienyl)­metal derivatives (CpNiC₄H₄)₂M and bis­(nickelaindenyl)­metal derivatives (CpNiC₈H₆)₂M as well as the bis­(nickelafluorenyl)metal derivatives. The structures of the lowest energy bis­(nickelacyclopentadienyl) sandwich compounds (CpNiC₄H₄)₂M may be derived from those of the corresponding metallocenes Cp₂M by replacing a CH group in each Cp ring with an isolobal CpNi unit. The Ni–M distances of ∼2.5 Å indicate formal single bonds and thus a pentahapto η⁵-CpNiC₄H₄ ligand. The spin states of the lowest energy (CpNiC₄H₄)₂M derivatives are similar to those of the corresponding metallocenes Cp₂M, namely, singlet, doublet, and triplet for M = Fe, Co, and Ni, respectively. Fusion of benzene rings to the nickelacyclopentadienyl rings to give first the bis­(nickelaindene) sandwich compounds (CpNiC₈H₆)₂M and then the experimentally known bis­(nickelafluorene) sandwich compounds (CpNiC₁₂H₈)₂M lowers the energy of the higher spin state. As a result, the lowest energy (CpNiC₁₂H₈)₂Co structure is not the doublet spin state of Cp₂Co and (CpNiC₄H₄)₂Co but instead a quartet spin state. This is in accord with experimental work showing (CpNiC₁₂H₈)₂Co to have a magnetic moment of ∼3.7 μ_B, indicating three unpaired electrons and thus the predicted quartet spin state

Tetrathiafulvalene Terminal-Decorated PAMAM Dendrimers for Triggered Release Synergistically Stimulated by Redox and CB[7]

A series of polyamidoamine (PAMAM) dendrimers with tetrathiafulvalene (TTF) at the periphery (G<i>n</i>-PAMAM-TTF), generation 0–2, were synthesized. These functionalized dendrimers exist as nanospheres with diameters around 80–100 nm in aqueous phase, which can encapsulate hydrophobic molecules. The terminal TTF groups can go through a reversible redox process upon addition of the oxidizing and reducing agents. Each terminal TTF^+• group of the oxidized G<i>n</i>-PAMAM-TTF assembled with cucurbit[7]­uril (CB[7]) forming a 1:1 inclusion complex with association constants of (3.14 ± 0.36) × 10⁵, (1.29 ± 0.12) × 10⁶, and (1.79 ± 0.24) × 10⁶ M^–1 for generation 0–2, respectively, even at the aggregate state. The formation of the inclusion complex loosened the structure of the nanospheres and initiated the release of cargo, and the release mechanism was validated by dynamic light scattering (DLS), cryo-transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) experiments. This study provides a potential strategy for the development of drug delivery systems synergistically triggered by redox and supramolecular assembly

Reactivity Switch Enabled by Counterion: Highly Chemoselective Dimerization and Hydration of Terminal Alkynes

A counterion-controlled reactivity tuning in Pd-catalyzed highly chemoselective and regioselective dimerization and hydration of terminal alkynes is reported. The use of acetate as counterion favors the formation of an alkenyl alkynyl palladium intermediate which forms hitherto less reported 1,3-diaryl-substituted conjugated enynes after reductive elimination. Using chloride, which is a better leaving group, leads to anion exchange on the alkenylpalladium intermediate with hydroxide which after reductive elimination and tautomerization delivered the hydration products

Approximately linear relationship of arc equivalent resistance vs. arc gap.

<p>Approximately linear relationship of arc equivalent resistance vs. arc gap.</p