Uncharged States Research Articles

Aqueous electrolytes at the charged graphene Surface: Electrode-Electrolyte coupling

Electrochemical energy sources support the growth in performance and portability of consumer electronics. Further sustainable development assumes an atomistically precise understanding of how the electrolyte binds to the electrode in the charged and uncharged states of the supercapacitors and Li-ion batteries. The present work investigates electrode–electrolyte interactions at the cathode using ab initio molecular dynamics simulations and representative energy-minimized ion-molecular configurations. Graphene is chosen as a material for the cathode, whereas the aqueous solutions of LiCl, NaCl, and KCl are model electrolytes. The study reveals a few fundamentally new physical insights regarding the performance of a supercapacitor. First, the graphene-ions coordination regularities are qualitatively different at charged and uncharged cathode. It is, therefore, essential to account for the effect of charging when studying the physical chemistry of supercapacitors. Second, the energy capacity offered by the aqueous Na-ion electrolyte is worse than those of the aqueous Li-ion and K-ion electrolytes. This observation is a result of an interplay between the dehydration energies and adsorption energies at the cathode energies. Third, the role of cation-solvent binding represents a cornerstone contribution to the capacity of an energy storage device in addition to the well-recognized cation-cathode binding thermodynamics. The reported results are fundamentally important to thoughtfully designing electrolyte compositions and electrode materials for supercapacitors and alkali-ion batteries.

Stable three-dimensional (un)charged AdS gravastars in gravity’s rainbow

In this work, we study the three-dimensional AdS gravitational vacuum stars (gravastars) in the context of gravity’s rainbow theory. Then we extend it by adding the Maxwell electromagnetic field. We compute the physical features of gravastars, such as proper length, energy, entropy, and junction conditions. Our results show that the physical parameters for charged and uncharged states depend significantly on rainbow functions. Besides from charged state, they also depend on the electric field. Finally, we explore the stability of thin shell of three-dimensional (un)charged AdS gravastars in gravity’s rainbow. We show that the structure of thin shell of these gravastars may be stable and is independent of the type of matter.

Predicting reaction rate constants of ozone with ionic/non-ionic compounds in water

Ozonation is a significant technology for the mitigation of pollutants in water. The second-order reaction rate constant (kO3) of ozone (O3) with compounds is essential for measuring their reactivity toward O3 and understanding their fate during ozonation. However, there is a huge gap between the number of existing chemicals and the available experimental kO3 values. Moreover, the reactivity of ionizable compounds with different ionization forms toward O3 may differ greatly. In this study, two quantitative structure activity relationship (QSAR) models for non-ionic and ionic species, are respectively established with partial least squares (PLS) and support vector machine (SVM) methods based on the large datasets (324 non-ionic states and 188 ionic states). These models exhibit good fitting ability (non-ionic model: R2tr > 0.760; ionic model: R2tr > 0.780), robustness (Q2CUM > 0.700), predictive performance (non-ionic model: R2ext > 0.760; ionic model: R2ext > 0.810) and wide applicability domain. The molecular parameters in two models are revealed to be significantly different, which may be attributed to the significant difference in molecular structures in two datasets and different reactivities of uncharged and charged states toward O3. Additionally, the overall kO3 for compounds at certain pH can be estimated by combining the two single QSAR models. These models and methods can become the effective tools for predicting the conversion rate of pollutants by O3 in the urban sewage and drinking water treatment.

Release of Per- and Polyfluoroalkyl Substances from Aqueous Film-Forming Foam Impacted Soils.

Per- and polyfluoroalkyl substances (PFASs) are highly mobile in the saturated subsurface, yet aqueous film-forming foam (AFFF)-impacted source zones appear to be long lasting PFAS reservoirs. This study examined the release of over one hundred anionic and zwitterionic PFASs from two AFFF-impacted surface soils under saturated conditions with packed soil columns. Perfluoroalkyl acids (PFAAs) were released more rapidly than their polyfluorinated precursors, while anionic PFASs that were present in partially uncharged states were released more slowly than PFASs that were present entirely as anions, as were zwitterionic PFASs with terminal cationic functional groups when compared with analogous zwitterions with only anionic terminal groups. Nonideal transport was observed in both per- and polyfluorinated classes, as soil column effluent concentrations of slowly released PFASs increased by up to 107-fold with sustained artificial groundwater flow. A flow-interruption experiment suggested the influence of rate-limited desorption on diverse PFAS classes, including PFAAs with as few as four perfluorinated carbons. These results suggest that during infiltration the slow, rate-limited desorption of anionic and zwitterionic PFAA precursors may result in these compounds comprising an increasingly large fraction of the remaining PFASs in AFFF-impacted surface soils.

Charged complexity and the thermofield double state

We establish a systematic framework for studying quantum computational complexity of Gaussian states of charged systems based on Nielsen’s geometric approach. We use this framework to examine the effect of a chemical potential on the dynamics of complexity. As an example, we consider the complexity of a charged thermofield double state constructed from two free massive complex scalar fields in the presence of a chemical potential. We show that this state factorizes between positively and negatively charged modes and demonstrate that this fact can be used to relate it, for each momentum mode separately, to two uncharged thermofield double states with shifted temperatures and times. We evaluate the complexity of formation for the charged thermofield double state, both numerically and in certain analytic expansions. We further present numerical results for the time dependence of complexity. We compare various aspects of these results to those obtained in holography for charged black holes.

Synthesis of Holey Graphene Nanoparticle Compounds.

Bulk-scale syntheses of sp2 nanocarbon have typically been generated by extensive chemical oxidation to yield graphite oxide from graphite, followed by a reductive step. Materials generated via harsh random processes lose desirable physical characteristics. Loss of sp2 conjugation inhibits long-range electronic transport and the potential for electronic band manipulation. Here, we present a nanopatterned holey graphene material electronically hybridized with metal-containing nanoparticles. Oxidative plasma etching of highly ordered pyrolytic graphite via previously developed covalent organic framework (COF)-5-templated patterning yields bulk-scale materials for electrocatalytic applications and fundamental investigations into band structure engineering of nanocomposites. We establish a broad ability (Ag, Au, Cu, and Ni) to grow metal-containing nanoparticles in patterned holes in a metal precursor-dependent manner without a reducing agent. Graphene nanoparticle compounds (GNCs) show metal-contingent changes in the valence band structure. Density functional theory investigations reveal preferences for uncharged metal states, metal contributions to the valence band, and embedding of nanoparticles over surface incorporation. Ni-GNCs show activity for oxygen evolution reaction in alkaline media (1 M KOH). Electrocatalytic activity exceeds 10,000 mA/mg of Ni, shows stability for 2 h of continuous operation, and is kinetically consistent via a Tafel slope with Ni(OH)2-based catalysis.

Silicene/boron nitride heterostructure for the design of highly efficient anode materials in lithium-ion battery

The performance of silicene/boron nitride heterostructure as anode material in lithium-ion batteries (LIBs) has been investigated by first-principles calculations. From the interfacial synergy effect, an enhanced adsorption of Li ions on BN is found in the resulted heterostructure compared with pristine BN system. Also, lowered diffusion barriers are found in the BN/Li/silicene and BN/silicene/Li systems compared with pristine silicene system. In addition, silicene/BN system can achieve high Li storage capacity with a maximum value reaching 1015 mA h g−1. The junction shows a volume change of only 1.3% between the charged and uncharged states. It means the highly enhanced thermodynamic stability compared with the pristine silicene sheet, which is promising as a good potential anode material in LIBs.

UC2 search: using unique connectivity of uncharged compounds for metabolite annotation by database searching in mass spectrometry-based metabolomics.

SummaryFor metabolite annotation in metabolomics, variations in the registered states of compounds (charged molecules and multiple components, such as salts) and their redundancy among compound databases could be the cause of misannotations and hamper immediate recognition of the uniqueness of metabolites while searching by mass values measured using mass spectrometry. We developed a search system named UC2 (Unique Connectivity of Uncharged Compounds), where compounds are tentatively neutralized into uncharged states and stored on the basis of their unique connectivity of atoms after removing their stereochemical information using the first block in the hash of the IUPAC International Chemical Identifier, by which false-positive hits are remarkably reduced, both charged and uncharged compounds are properly searched in a single query and records having a unique connectivity are compiled in a single search result.Availability and implementationThe UC2 search tool is available free of charge as a REST web service (http://webs2.kazusa.or.jp/mfsearcher) and a Java-based GUI tool.Supplementary information Supplementary data are available at Bioinformatics online.

Effects of external radiation on an Alcubierre warp bubble

This paper contends that the spacetime distortions resulting from the experimentally obtainable electric field of a parallel plate capacitor configuration cannot be detected by the White-Juday Warp Field Interferometer [1]. Any post-processing results indicating a vanishing, non-zero difference between the charged and uncharged states of the capacitor are due to local effects rather than spacetime perturbations.

The Compressibility of pH‐Sensitive Microgels at the Oil–Water Interface: Higher Charge Leads to Less Repulsion

AbstractpH‐responsive microgels are unique stabilizers for stimuli‐sensitive emulsions that can be broken on demand by changing the pH value. However, recent experiments have indicated that electrostatic interactions play a different role to that in conventional Pickering emulsions. The influence of charges on the interactions between microgels at the oil–water interface is now described. Compression isotherms of microgels with different charge density and architecture were determined in a Langmuir trough, and counter‐intuitive results were obtained: Charged microgels can be compressed more easily than uncharged microgels. The compressibility of microgels is thus not determined by direct Coulomb repulsion. Instead, the different swelling of the microgels in the charged and the uncharged states is proposed to be the key parameter.

The Compressibility of pH‐Sensitive Microgels at the Oil–Water Interface: Higher Charge Leads to Less Repulsion

pH-responsive microgels are unique stabilizers for stimuli-sensitive emulsions that can be broken on demand by changing the pH value. However, recent experiments have indicated that electrostatic interactions play a different role to that in conventional Pickering emulsions. The influence of charges on the interactions between microgels at the oil-water interface is now described. Compression isotherms of microgels with different charge density and architecture were determined in a Langmuir trough, and counter-intuitive results were obtained: Charged microgels can be compressed more easily than uncharged microgels. The compressibility of microgels is thus not determined by direct Coulomb repulsion. Instead, the different swelling of the microgels in the charged and the uncharged states is proposed to be the key parameter.

Tunable Ionic Transport Control inside a Bio‐Inspired Constructive Bi‐Channel Nanofluidic Device

Inspired by the cooperative functions of the asymmetrical ion channels in living cells, a constructive bi-channel nanofluidic device that demonstrates the enhanced capability of multiple regulations over both the ion flux amount and the ionic rectification property is prepared. In this bi-channel system, the construction routes of the two asymmetric conical nanochannels provide a way to efficiently transform the nanodevice into four different functional working modes. In addition, the variation of external pH conditions leads the nanodevice to the uncharged, semi-charged and charged states, where the multistory ionic regulating function property is enhanced by the charged degree. This intelligent integration of the single functional nanochannels demonstrates a promising future for building more functional multi-channel integrated nanodevices as well as expands the functionalities of the bio-inspired smart nanochannels.

Direct Observation of the Electroadsorptive Effect on Ultrathin Films for Microsensor and Catalytic‐Surface Control

Microchemical sensors and catalytic reactors make use of gases during adsorption in specific ways on selected materials. Fine-tuning is normally achieved by morphological control and material doping. The latter relates surface properties to the electronic structure of the bulk, and this suggests the possibility of electronic control. Although unusual for catalytic surfaces, such phenomena are sometimes reported for microsensors, but with little understanding of the underlying mechanisms. Herein, direct observation of the electroadsorptive effect by a combination of X-ray photoelectron spectroscopy and conductivity analysis on nanometre-thick semiconductor films on buried control electrodes is reported. For the SnO2/NO2 model system, NO3 surface species, which normally decay at the latest within minutes, can be kept stable for 1.5 h with a high coverage of 15% under appropriate electric fields. This includes uncharged states, too, and implies that nanoelectronic structures provide control over the predominant adsorbate conformation on exterior surfaces and thus opens the field for chemically reactive interfaces with in situ tunability.

The Effect of Hydrophilic Substitutions and Anionic Lipids upon the Transverse Positioning of the Transmembrane Helix of the ErbB2 (neu) Protein Incorporated into Model Membrane Vesicles

The sequence of the transmembrane (TM) helix of ErbB2, a member of the epidermal growth factor receptor (ErbB) family, can influence its activity. In this report, the sequence and lipid dependence of the transverse position of a model-membrane-inserted peptides containing the ErbB2 TM helix and some of the juxtamembrane (JM) residues were studied. For the ErbB2 TM helix inserted into phosphatidylcholine vesicles, the activating V664E mutation was found to induce a transverse shift involving the movement of the E residue toward the membrane surface. This shortened the effective length of the TM-spanning portion of the sequence. The transverse shift was observed with the E664 residue in both the uncharged and charged states, but the extent of the shift was larger when the E residue was charged. When a series of hydrophilic residues was substituted for V664, the resulting transverse shifts at pH 7.0 decreased in the order D,H>E>Q>K>G>V. Except for His, this order is strongly correlated to that reported for the degree to which these substitutions induce cellular transformation when introduced into full-length ErbB2. To examine the effect of lipid on transverse shift, we studied the uncharged V664Q mutation. The presence of 20% of the anionic lipid DOPS (dioleoylphosphatidylserine) in the model membrane vesicles, which introduces a physiologically relevant level of anionic lipid, did not affect the degree of transverse shift. However, in the case of a peptide containing a V674Q substitution, in which the Q is closer to the C-terminus of the ErbB2 TM helix than the N-terminus, transverse shift was suppressed in vesicles containing 20% DOPS. This suggests that the interaction of the cationic JM residues flanking the C-terminus of the ErbB2 TM helix interact with anionic lipids to anchor the C-terminal end of the TM helix. This anchoring site may act as a pivot that amplifies transverse movements of the ErbB2 TM segment to induce a large swinging-type motion in the extracellular domain of the protein, affecting ErbB2 activity. Interactions interrupting C-terminal JM residue association with anionic lipid might partly impact ErbB2 activity by disrupting this pivoting.

Fundamental strings and black holes

We propose a black hole thermodynamic description of highly excited charged and uncharged perturbative string states in 3+1 dimensional type II and 4+1 dimensional heterotic string theory. We also discuss the generalization to extremal and non-extremal black holes carrying magnetic charges.

Silicon photonic read-only memory

In this paper, a CMOS-compatible in-plane micrometer-size optically readable nonvolatile-memory device is proposed and analyzed. It consists of an electrically erasable programmable read-only memory (EEPROM) integrated on a high-index-contrast silicon-on-insulator (SOI) rib waveguide. Our calculations indicate that variations on the order of 10/sup -4/ of the waveguide effective refractive index can be achieved for the typical values of stored charge (on the order of 10/sup 12/ q/sub e//cm/sup 2/) on a floating gate. A microring resonator, based on such waveguide, efficiently converts the calculated index variations into strong intensity variations. This photonic structure can be used to create nonvolatile optically readable memory states in a photonic device [photonic EEPROM (PEEPROM)] with an ultrafast read time. A microring-resonator intensity-modulator PEEPROM is predicted to exhibit a modulation depth of 91% (10.4 dB) between the uncharged and charged (3.75/spl times/10/sup 12/ q/sub e//cm/sup 2/) states. The read time of the device is only 9 ps, which is at least two orders of magnitude shorter than that of a standard two-transistor electrically readable EEPROM.

Molecular dynamics of a biophysical model for β 2-adrenergic and G protein-coupled receptor activation

This study analyzes 16 molecular dynamic simulations of a biophysical model for β 2-adrenergic (B2AR) and G protein-coupled receptor (GPCR) activation. In this model, a highly conserved cysteine residue, C106 (C3.25 or CysIII:01), provides a free sulfhydryl or thiol group in an acid–base equilibrium between uncharged (RSH) and charged (RS −) states that functions as an electrostatic molecular switch for receptor activation. The transition of C106 in the B2AR between acid and base states significantly changes the helical/transmembrane (TM) domain interactions and the electrostatic interaction energy differences (ΔΔ E EL). The ΔΔ E EL changes correlate well with the experimentally observed ligand efficacies. The TM interaction energies display patterns compatible with those previously recognized as responsible for GPCR activation. Key differences between the agonist, epinephrine, and the antagonist, pindolol, are seen for the TM3 × 6, TM3 × 4, TM6 × 7 and TM1 × 7 interaction energies. Pindolol also produces a weaker ΔΔ E EL interaction and less TM interaction energy changes, which are important differences between the agonist and antagonist ligands. The D115E mutant with pindolol displays a greater ΔΔ E EL and TM interactions than for the wild-type B2AR with pindolol. This explains the higher activity of pindolol in the D115E mutant. The constitutively active D130A mutant displays TM interaction patterns similar to those for the activating ligands implying a common pattern for receptor activation. These findings support the broad concept of protean agonism and demonstrate the potential for allosteric modulation. They also demonstrate that this two-state model agrees with many previous experimental and theoretical observations of GPCRs.

Discrimination of native loop conformations in membrane proteins: decoy library design and evaluation of effective energy scoring functions.

The recent determination of crystal structures for several important membrane proteins opens the way for comparative modeling of their membrane-spanning regions. However, the ability to predict correctly the structures of loop regions, which may be critical, for example, in ligand binding, remains a considerable challenge. To meet this challenge, accurate scoring methods have to discriminate between candidate conformations of an unknown loop structure. Some success in loop prediction has been reported for globular proteins; however, the proximity of membrane protein loops to the lipid bilayer casts doubt on the applicability of the same scoring methods to this problem. In this work, we develop "decoy libraries" of non-native folds generated, using the structures of two membrane proteins, with molecular dynamics and Monte Carlo techniques over a range of temperatures. We introduce a new approach for decoy library generation by constructing a flat distribution of conformations covering a wide range of Calpha-root-mean-square deviation (RMSD) from the native structure; this removes possible bias in subsequent scoring stages. We then score these decoy conformations with effective energy functions, using increasingly more cpu-intensive implicit solvent models, including (1) simple Coulombic electrostatics with constant or distance-dependent dielectrics; (2) atomic solvation parameters; (3) the effective energy function (EEF1) of Lazaridis and Karplus; (4) generalized Born/Analytical Continuum Solvent; and (5) finite-difference Poisson-Boltzmann energy functions. We show that distinction of native-like membrane protein loops may be achieved using effective energies with the assumption of a homogenous environment; thus, the absence of the adjacent lipid bilayer does not affect the scoring ability. In particular, the Analytical Continuum Solvent and finite-difference Poisson-Boltzmann energy functions are seen to be the most powerful scoring functions. Interestingly, the use of the uncharged states of ionizable sidechains is shown to aid prediction, particularly for the simplest energy functions.

A semiempirical simulation methodology: atomistic and ionic dissociation of silica

Modeling defects, surfaces and interfaces of silica is complicated by the presence of charged and uncharged states of the atoms, and the existence of local nonstoichiometric structure. The changes in the local molecular environments associated with defects and surfaces are a consequence of changes in the electronic structure away from the bulk values. The ability to capture the electronic structure changes in simulations is highly desirable to study defects and surfaces. Moreover, the properties and problems of interest also require the use of large scale simulations. Hence, a semiempirical methodology is introduced that contains these desirable properties. The model approach is described and results using the model in the absence of long range interactions are presented. The motivation to ignore Coulombic interactions is driven by the desire to understand the model's ability to describe the bonding interactions and to what degree it captures any of the medium and long range order.

The embedding structure of unitary N = 2 minimal models

We derive the embedding structure of unitary N = 2 minimal models and show as a result that these representations have a degeneration of uncharged singular states. This corrects some earlier mistakes made in the literature. We discuss the connection to the N = 2 character formulae and finally give a proof for the embedding diagrams.