Charge Variation Research Articles

Proton Migration on Top of Charged Membranes.

Proton relay between interfacial water molecules allows rapid two-dimensional diffusion. An energy barrier, ΔGr‡, opposes proton-surface-to-bulk release. The ΔGr‡-regulating mechanism thus far has remained unknown. Here, we explored the effect interfacial charges have on ΔGr‡'s enthalpic and entropic constituents, ΔGH‡ and ΔGS‡, respectively. A light flash illuminating a micrometer-sized membrane patch of a free-standing planar lipid bilayer released protons from an adsorbed hydrophobic caged compound. A lipid-anchored pH-sensitive dye reported protons' arrival at a distant membrane patch. Introducing net-negative charges to the bilayer doubled ΔGH‡, while positive net charges decreased ΔGH‡. The accompanying variations in ΔGS‡ compensated for the ΔGH‡ modifications so that ΔGr‡ was nearly constant. The increase in the entropic component of the barrier is most likely due to the lower number and strength of hydrogen bonds known to be formed by positively charged residues as compared to negatively charged moieties. The resulting high ΔGr‡ ensured interfacial proton diffusion for all measured membranes. The observation indicates that the variation in membrane surface charge alone is a poor regulator of proton traffic along the membrane surface.

Synchrotron-based operando X-ray diffraction and X-ray absorption spectroscopy study of LiCo0.5Fe0.5PO4 mixed d-metal olivine cathode

Lithium-ion batteries based on high-voltage cathode materials, such as LiCoPO4, despite being promising in terms of specific power, still suffer from poor cycle life due to the lower stability of common non-aqueous electrolytes at higher voltages. One way to overcome this issue might be decreasing the working potential of the battery by doping LiCoPO4 by Fe, thus reducing electrolyte degradation upon cycling. However, such modification requires a deep understanding of the structural behavior of cathode material upon lithiation/delithiation. Here we used a combination of operando synchrotron-based XRD and XAS to investigate the dynamics of d-metal local atomic structure and charge state upon cycling of LiCo0.5Fe0.5PO4 mixed d-metal olivine cathode material. Principal components analysis (PCA) of XAS data allowed the extraction of spectra of individual phases in the material and their concentrations. For both Co and Fe two components were extracted, they correspond to fully lithiated and delithiated phases of LixMPO4 (where M = Fe, Co). Thus, we were able to track the phase transitions in the material upon charge and discharge and quantitatively analyze the M2+/M3+ electrochemical conversion rate for both Fe and Co. Rietveld's refinement of XRD data allowed us to analyze the changes in the lattice of cathode material and their reversibility upon (de)lithiation during cycling. The calculation of DFT and Bader charge analysis expects the oxygen redox procedure combined with d-metals redox, which supplements iron charge variations and dominates at high voltages when x < 0.75 in LixCoFePO4.

Meniscus Work and Implant Selection Are Major Cost Drivers of Anterior Cruciate Ligament Reconstruction.

Background The current study examines the financial charges associated with primary anteriorcruciate ligament reconstruction (ACLR), specifically the contribution of graft choice, graft type, and concomitant meniscus surgery, in the outpatient hospital setting. Methods A retrospective financial billing review was performed on patients who underwent ACLR at a singleacademic medical center from January to December 2019. Age, BMI, insurance, length of operation, regional block, implants, meniscus surgery, graft type, and graft choice were extracted from hospital electronic patient records. Charges attributed with graft, anesthesia services, supplies, implants, surgeon fees, radiology charges, and total charges were collected. Total amount that insurance and patient paid were also obtained. Descriptive and quantitative statistics were performed. Results A total of 28 patients were studied (18 males, 10 females). The average age was 23.8 years. There were 20 concomitant meniscus surgeries. Six allografts and 22 autografts were used [eight bone-patellar tendon-bone (BPTB), eight hamstrings, six quadriceps]. The average and median total charge was $61,004 and $60,390, respectively (range: $31,403 to $97,914). The average insurance paid was $26,045 while out-of-pocket costs were $402. The average paid by privateinsurance was higher compared to government insurance($31,111 vs. $11,066, p<0.001). Graft choicesuch as allograft vs. autograft (p=0.035) and meniscus surgery (p=0.048) were significant factors to the overall cost. Conclusions Graft choice, specifically the quadrupled hamstring autograft, and concomitant meniscal surgery are major contributors to variations in ACLR charges. Decreasing implant and graft costs and limiting surgical time can decrease charges associated with ACLR.We hope these findings can help guide surgeon financial decisions, by demonstrating the need to take into account the increased total charges and amount paid associated with specific grafts, meniscus surgery, and prolonged OR time.

Comparative Assessment of Supervisory Control Algorithms for a Plug-In Hybrid Electric Vehicle

The study examines alternative on-board energy management system (EMS) supervisory control algorithms for plug-in hybrid electric vehicles. The optimum fuel consumption was sought between an equivalent consumption minimization strategy (ECMS) algorithm and a back-engineered commercial rule-based (RB) one, under different operating conditions. The RB algorithm was first validated with experimental data. A method to assess different algorithms under identical states of charge variations, vehicle distance travelled, and wheel power demand criteria is first demonstrated. Implementing this method to evaluate the two algorithms leads to fuel consumption corrections of up to 8%, compared to applying no correction. We argue that such a correction should always be used in relevant studies. Overall, results show that the ECMS algorithm leads to lower fuel consumption than the RB one in most driving conditions. The difference maximizes at low average speeds (&lt;40 km/h), where the RB leads to more frequent low load engine operation. The two algorithms lead to fuel consumption differences of 3.4% over the WLTC, while the maximum difference of 24.2% was observed for a driving cycle with low average speed (18.4 km/h). Further to fuel consumption performance optimization, the ECMS algorithm also appears superior in terms of adaptability to different driving cycles.

Modelling of PFAS-surface interactions: Effect of surface charge and solution ions

Per-and poly-fluoroalkyl substances (PFAS) are a class of substances of increasing concern as environmental contaminants. The interactions between PFAS and surfaces play an important role in PFAS transport and remediation. Previous studies have found PFAS adsorption to be dependent upon properties including pH, organic matter and particle size, along with PFAS functional group and carbon chain length. It is hypothesised that a theoretical examination of PFAS-surface interactions, via Monte Carlo molecular simulation, would show differences resulting from changes in surface charge, H+, OH−, Ca2+ concentrations and PFAS carbon chain length. Monte Carlo molecular simulations of perfluorooctane and perfluorobutane sulfonic acids interacting with a graphite surface in an aqueous medium were performed. Variations in surface charge, H+, OH− and Ca2+ concentrations were made. The distance-dependent density of molecules from the surface was analysed as a proxy for PFAS adsorption to the surface. Simulation results showed differences in surface behaviour that depended on surface charge, H+, OH− and Ca2+ concentrations, along with carbon chain length, with surface charge playing the most prominent role in controlling PFAS adsorption. For negatively charged surfaces, adsorption due to divalent cation bridging was observed in Ca2+ solutions. Modelling, such as in this study, of the thermodynamic equilibrium behaviour of low concentrations of molecules, in scenarios where both adsorption and mobility of PFAS occur, can aid in the design and testing of sorptive surfaces for amendment-based PFAS remediation.

A complementary high linearity bootstrap switch based on negative voltage bootstrap capacitor

The sample-and-hold (S/H) circuit is an important part of the analog-to-digital converter (ADC). A bootstrap switch with capacitive load can form a basic S/H circuit. A complementary high linearity gate voltage bootstrap switch based on bootstrap capacitor is proposed in this paper. By reducing the size of the key node transistors, the parasitic capacitance is reduced. The sampling metal-oxide-semiconductor field-effect transistor (MOSFET) in this structure is composed of complementary NMOS and PMOS, which reduces the channel charge injection effect and variations in on-resistance (Ron). The simulation results show that the effective number of bits (ENOB), signal-to-noise and distortion ratio (SNDR) and spurious-free dynamic range (SFDR) of the structure are 16.5 bits, 101.11 dB and 101.83 dB respectively at the sampling frequency of 50 MHz and full swing voltage input of 1.8 V based on SMIC 0.18 μm process. Compared with the conventional NMOS switch, ENOB, SDNR, and SFDR are increased by 2.45 bits, 14.73 dB, and 13.38 dB, respectively. In addition, Monte Carlo (MC) and corner simulations of the proposed circuit are performed, and the results show that the proposed circuit has good performance.

Variability of Prostate MRI Charges Among U.S. Hospital-Based Facilities.

The Premier Healthcare Database was used to assess charge variation for prostate MRI examinations in U.S. hospitals from January 2010 to March 2020. In 552 facilities performing 37,073 examinations, the median charge per examination was $4419 with 26-fold variation between the lowest ($593) and highest ($15,150) median facility charges. In multilevel linear regression analysis, interfacility variation explained 63.9% of charge variation. Patients may be charged vastly different prices for prostate MRI depending on the facility.

Efficient automatic construction of atom-economical QM regions with point-charge variation analysis.

The setup of QM/MM calculations is not trivial since many decisions have to be made by the simulation scientist to achieve reasonable and consistent results. The main challenge to be tackled is the construction of the QM region to make sure to take into account all important parts of the adjacent environment and exclude less important ones. In our previous work [F. Brandt and Ch. R. Jacob, Systematic QM Region Construction in QM/MM Calculations Based on Uncertainty Quantification, J. Chem. Theory Comput., 2022, 18, 2584-2596.], we introduced the point charge variation analysis (PCVA) as a simple and reliable tool to systematically construct QM regions based on the sensitivity of the reaction energy with respect to variations of the MM point charges. Here, we assess several simplified variants of this PCVA approach for the example of catechol O-methyltransferase and apply PCVA for another system, the triosephosphate isomerase. Furthermore, we extend its scope by applying it to a DNA system. Our results indicate that PCVA offers an efficient and versatile approach of the automatic construction of atom-economical QM regions, but also identify possible pitfalls and limitations.

Impacts of external fields on aromaticity and acidity of benzoic acid: a density functional theory, conceptual density functional theory and information-theoretic approach study.

The impact of external fields on the molecular structure and reactivity properties has been of considerable interest in the recent literature. Benzoic acid as one of the most widely used compounds in medicinal and materials sciences is known for its dual propensity in aromaticity and acidity. In this work, we systematically investigate the impact of a uniform external electric field on these properties. We apply density functional theory, conceptual density functional theory, and an information-theoretic approach to appreciate the change pattern of aromaticity and acidity properties in external fields with different strengths. Our results show that they possess different change patterns under external fields, which can be satisfactorily rationalized by variations in reactivity descriptors and partial charges. The surprising yet novel results from this study should enrich the body of our knowledge about the impact of external fields for different kinds of electronic properties and provide guidance and foundation for future studies of this phenomenon in other molecular systems.

Supramolecular Photonic Hydrogel for High-Sensitivity Alkaline Phosphatase Detection via Synergistic Driving Force.

Structurally-colored photonic hydrogels which are fabricated by introducing hydrogels into thin films or photonic crystal structures are promising candidates for biosensing. Generally, the design of photonic hydrogel biosensors is based on the sensor-analyte interactions induced charge variation within the hydrogel matrix, or chemically grafting binding sites onto the polymer chains, to achieve significant volume change and color variation of the photonic hydrogel. However, relatively low anti-interference capability or complicated synthesis hinder the facile and low-cost fabrication of high-performance photonic hydrogel biosensors. Here, a facilely prepared supramolecular photonic hydrogel biosensor is developed for high-sensitivity detection of alkaline phosphatase (ALP), which is an extensively considered clinical biomarker for a variety of diseases. Responding to ALP results in the broken supramolecular crosslinking and thus increased lattice distancing of the photonic hydrogel driven by synergistic repulsive force between nanoparticles embedded in photonic crystal structure and osmotic swelling pressure. The biosensor shows sensitivity of 7.3nm spectral shift per mUmL-1 ALP, with detection limit of 0.52 mUmL-1 . High-accuracy colorimetric detection can be realized via a smartphone, promoting point-of-care sensing and timely diagnosis of related pathological conditions.

COMPUTATIONAL STUDY OF NICOTINAMIDE WITH PARENT URACIL AND ANTICANCER URACIL DERIVATIVES

The density functional theory calculations have been applied to investigate hydrogen-bonded complexes of nicotinamide with parent uracil and its anticancer derivatives namely 5 fluorouracil and 2 thiouracil. The optimized complexes are analyzed in terms of structural, electronic, and energetic changes, binding free energy and enthalpy changes, dipole moments, atomic charge variation, electron delocalizations, topological parameters, chemical reactivity descriptors, etc. The study suggests that the most stable complexes are formed by nicotinamide with fluorouracil and the least stable with thiouracil. The uracil and its derivatives act as far better hydrogen bond donors than nicotinamide in the optimized complexes. Significant charge transfer between nicotinamide and parent uracil and its derivatives is suggested by Frontier Molecular Orbital (FMO) analysis and E(2) from Natural Bond Orbital analysis. The present computational study shows that uracil drugs form stable intercalation sites with nicotinamide. The results may prove useful in the molecular designing of new anticancer agents.

Protein network centralities as descriptor for QM region construction in QM/MM simulations of enzymes.

The construction of a suitable QM region is the most crucial step in setting up hybrid quantum mechanics/molecular mechanics (QM/MM) simulations for enzymatic reactions. The QM region should ideally include all important amino acids residues, while being as small as possible to save computational effort. Most available methods for systematic QM region construction are based either on the distance of single amino acids to the active site or on their electrostatic effect. Such approaches might miss non-electrostatic and long-range allosteric interactions. Here, we present a proof of concept study for the application of protein network analysis to tackle this problem. Specifically, we explore the use of the protein network centralities as descriptor for QM region construction. We find that protein network centralities, in particular the betweenness centrality, can be a useful descriptor for systematic QM region construction. We show that in combination with our previously developed point charge variation analysis, they can be used to identify important residues that are missed in purely electrostatic approaches.

The effect of electrically pre-stressing of high DC electric field on performance of SDBD thruster in near space

The space charge on the surface of solid dielectric has great influence on the surface dielectric barrier discharge (SDBD). In this paper, the surface space charge of SDBD is effectively regulated by the effect of electrically pre-stressing of high DC electric field to improve the dynamic performance of ion wind thruster. The conduction current, surface charges, thrust and thrust-to-power ratio are measured respectively for the ion wind thruster with and without the effect of electrically pre-stressing. The experimental results show that compared with the ion wind thruster without the effect of electrically pre-stressing, the instantaneous polarization current of the SDBD ion wind thruster with the effect of electrically pre-stressing is reduced by 42.7%, and the attenuation constant of the relaxation polarization current is reduced by about 28.8%, which effectively reduces the relaxation polarization loss of the thruster under the alternating electric field. In addition, the discharge time of anode and cathode increases respectively by about 20.0% and 43.3%, and the variation of surface space charge increases by about 50.6% in one voltage cycle. The saturation thrust of the thruster is increased from 1070 μN/m to 1660 μN/m by about 55.1%. The maximum thrust-to-power ratio of the thruster is increased from 993 μN/kW to 2125 μN/kW by about 114.0%.

Evolution of the Fe-Co magnetism and magnetic proximity effects in alternate Fe/Co monolayers on nonmagnetic Cu3Au(001)

Magnetic heterostructures with ferromagnetic/nonmagmetic interfaces are very interesting materials due to the possibility to switch the magnetization, to control the induced magnetic moment, and also due to interfacial effects. The tuning of the spin-orbit coupling in magnetic materials allows engineering new spintronic devices. Using density functional theory, the induced local magnetic moments in copper and gold surface atoms of ${\mathrm{Cu}}_{3}\mathrm{Au}(001)$ due to the deposited alternate magnetic Fe and Co monolayers were studied. To observe the tuning mechanism, the spin density of the $\mathrm{FeCo}/{\mathrm{Cu}}_{3}\mathrm{Au}(001)$ as a function of the number of deposited magnetic monolayers was extensively investigated. The Fe/Co deposition induces a hybridization between electronic states of the magnetic and nonmagnetic interface atoms, generating a broadening in $d$ bands of the deposited material, engineering the magnetic moments of the interface atoms. This observed hybridization elucidates the charge variation in the interface atoms for stacking sequences starting with Fe or with Co as the first magnetic layer in direct contact with the ${\mathrm{Cu}}_{3}\mathrm{Au}(001)$ substrate. By performing the spin-charge density calculations, we demonstrated that this magnetic induction occurs only for the nonmagnetic Cu-Au atoms at the ${\mathrm{Cu}}_{3}\mathrm{Au}(001)$ surface.

Mechanical tuning of virus-like particles

HypothesisVirus-like particles (VLPs) are promising scaffolds for developing mucosal vaccines. For their optimal performance, in addition to design parameters from an immunological perspective, biophysical properties may need to be considered. ExperimentsWe investigated the mechanical properties of VLPs scaffolded on the coat protein of Acinetobacter phage AP205 using atomic force microscopy and small angle X-ray scattering. FindingsInvestigations showed that AP205 VLP is a tough nanoshell of stiffness 93 ± 23 pN/nm and elastic modulus 0.11 GPa. However, its mechanical properties are modulated by attaching muco-inert polyethylene glycol to 46 ± 10 pN/nm and 0.05 GPa. Addition of antigenic peptides derived from SARS-CoV2 spike protein by genetic fusion increased the stiffness to 146 ± 54 pN/nm although the elastic modulus remained unchanged. These results, which are interpreted in terms of shell thickness and coat protein net charge variations, demonstrate that surface conjugation can induce appreciable changes in the biophysical properties of VLP-scaffolded vaccines.

Quantum dot photoluminescence as charge probe for plasma exposed surfaces

Quantum dots (QDs) are used as nanometer-sized in situ charge probes for surfaces exposed to plasma. Excess charges residing on an electrically floating surface immersed in a low-pressure argon plasma are detected and investigated by analysis of variations in the photoluminescence spectrum of laser-excited QDs that were deposited on that surface. The experimentally demonstrated redshift of the PL spectrum peak is linked to electric fields associated with charges near the QDs’ surfaces, a phenomenon entitled the quantum-confined Stark effect. Variations in the surface charge as a function of plasma input power result in different values of the redshift of the peak position of the PL spectrum. The values of redshift are detected as 0.022 nm and 0.073 for 10 and 90 W plasma input powers, respectively; therefore indicating an increasing trend. From that, a higher microscopic electric field, V m−1 for 90 W compared to V m−1 for 10 W input power, which is coupled to an increased electric field in the plasma sheath, is sensed by the QDs when plasma input power is increased.

Critical parameters controlling wettability in hydrogen underground storage - An analytical study

The large-scale implementation of hydrogen economy requires immense storage spaces to facilitate the periodic storage/production cycles. Extensive modelling of hydrogen transport in porous media is required to comprehend the hydrogen-induced complexities prior to storage to avoid energy loss. Wettability of hydrogen-brine-rock systems influence flow properties (e.g. capillary pressure and relative permeability curves) and the residual saturations, which are all essential for subsurface hydrogen systems. This study aims to understand which parameters critically control the contact angle for hydrogen-brine-rock systems using the surface force analysis following the DLVO theory and sensitivity analysis. Furthermore, the effect of roughness is studied using the Cassie-Baxter model. Our results reveal no considerable difference between H 2 and other gases such as N 2 . Besides, the inclusion of roughness highly affects the observed apparent contact angles, and even lead to water-repelling features. It was observed that contact angle does not vary significantly with variations of surface charge and density at high salinity, which is representative for reservoir conditions. Based on the analysis, it is speculated that the influence of roughness on contact angle becomes significant at low water saturation (i.e. high capillary pressure).

Unraveling photo-induced proton transfer mechanism and proposing solvent regulation manner for the two intramolecular proton-transfer-site BH-BA fluorophore

To expound specific excited state processes of the novel excitation wavelength dependent emission BH-BA fluorophore for better subsequent applications, this wok mainly focus on exploring photo-induced hydrogen bonding geometrical changes, excited state intramolecular proton transfer (ESIPT) mechanism and related regulated behavior via solvent polarity. The differences of structural parameters, infrared (IR) vibrational spectra, core-valence bifurcation (CVB) index as well as electronic densities ρ(r) between S0 and S1 states related to dual hydrogen bonds (O1-H2···N3 and O4-H5···N6) reveal S1-state hydrogen bonding strength facilitate ESIPT behaviors for BH-BA system. Of particular note, O4-H5···N6 plays a more dominant role. Photo-induced intramolecular charge transfer (ICT) and variations of Hirshfled and NPA charges over atoms related to hydrogen bonding moieties promote the ESIPT tendency for BH-BA. Combined potential energy surfaces (PESs), transition state (TS) and intrinsic reaction coordinate (IRC) paths, we illustrate the excited state intramolecular single proton transfer (ESISPT) mechanism of BH-BA should occur along with O4-H5···N6 hydrogen bonding wire, which could be adjusted by surrounding solvent polarity.

Real-Space Charge Density Profiling of Electrode-Electrolyte Interfaces with Angstrom Depth Resolution.

The accumulation and depletion of charges at electrode-electrolyte interfaces is crucial for all types of electrochemical processes. However, the spatial profile of such interfacial charges remains largely elusive. Here we develop charge profiling three-dimensional (3D) atomic force microscopy (CP-3D-AFM) to experimentally quantify the real-space charge distribution of the electrode surface and electric double layers (EDLs) with angstrom depth resolution. We first measure the 3D force maps at different electrode potentials using our recently developed electrochemical 3D-AFM. Through statistical analysis, peak deconvolution, and electrostatic calculations, we derive the depth profile of the local charge density. We perform such charge profiling for two types of emergent electrolytes, ionic liquids, and highly concentrated aqueous solutions, observe pronounced sub-nanometer charge variations, and find the integrated charge densities to agree with those derived from macroscopic electrochemical measurements.

Air shower radio signal electric field orientation as measured with the Astroneu Cosmic Ray telescope.

The Astroneu cosmic ray telescope is a small scale hybrid array consisting of both scintillator counters and electromagnetic radiation detectors in the radio-wave frequency (RF) band (antennas). Astroneu was installed and operated in the area of the Hellenic Open University (HOU) campus near the city of Patras in Greece. In the present development phase, the Astroneu telescope includes two stations consisting of 3 scintillation detectors modules (SDM) and one RF antenna while a third station includes 3 particle detectors and 4 RF antennas (3SDM-4RF). In this context we present the resent results from both the 3SDM-4RF autonomous station and simulations related to the estimation of the direction of the electric field emitted during the air shower development. The electric field measured in the ground level is the superposition of the two dominant emission mechanism, the time depended transverse current induced by the geomagnetic field and the net negative charge variation at the shower front. Since the electric field emitted by the two contributions is polarized in different directions the measured electric field in the ground encloses information about the charge-excess to geomagnetic ratio (CGR). Furthermore the orientation of the electric field emitted by charge-excess mechanism is strongly depends from the distance to the shower core (the intersection of the shower axis with the ground level). In this study we use the core information as reconstructed using the radio data and simulations. The estimated charge-excess to geomagnetic ratio is in agreement with previous studies which reveals that the shower core reconstruction method is efficient. Finally we report on that CGR measurements can be used for an efficient noise rejection in a future self trigger mode