Positive Total Energy Research Articles

Mechanistic evaluation of contrasting modulation in conformation and catalytic performance of urease by surface interaction of graphene oxide and amine- functionalized graphene oxide nanosheets

The increasing use of graphene-based nanomaterials raises concerns about their potential environmental impact as ecotoxicants. This article examines the interaction and effects of graphene oxide (GO) and its amine-derived (GONH2) 2-D nanosheets on urease dynamics, a crucial enzyme in soil nutrient cycling, through spectroscopic, microscopic, and computational analyses. The findings reveal the distinct interaction mechanisms: GO formed ground - and excited-state complexes with urease; thus, fluorescence quenching was static and dynamic via hydrophobic interaction. In contrast, GONH2 nanosheets formed a ground-state complex by static quenching involving Van der Waals and hydrogen bonding. These interactions were energetically favored and altered tryptophan (Trp) residues’ microenvironment more than tyrosine (Tyr). The average exciton lifetime of urease in the presence of GO have decreased from 4.34 ns to 3.647 ns at the mere concentration of 7.11 µM, while for GONH2, no discernable change (4.16 ns) was observed even at the concentration of 16.75 µM. Primarily, the strong interaction of GO leads to the rearrangement of polypeptide structure, reduced α-helices to 12 %, and increased β-sheets by six times. In contrast, with GONH2, α-helices were reduced to 79 %, and β-sheets were increased by 1.8 times at the similar concentration. Molecular docking revealed that neither GO nor GONH2 interacted with the active site of urease, and binding was primarily via hydrophobic, Van der Waals, and hydrogen bonding, concurrent with in-vitro incubation results. Positive total energy (3.85 kJ mol−1) during molecular docking analysis of urease-GO interaction and inhibition in enzyme activity to 62 %, altered Vmax value (0.04606 ± 0.001 mM/s), without affecting the Km (4.78045 ± 0.12 mM) suggested that inhibition was noncompetitive and steric clashes due to disruptive binding might drove the inhibition. Meanwhile, negative total internal energy (-3.97 kJ mol−1) during urease + GONH2 binding and enhanced enzymatic activity by 32 % in-vitro without altering Vmax (0.063091 ± 0.003 mM/s) and Km (4.953943 ± 0.2 mM) values suggested that urease's binding site was well-complemented by GONH2 nanosheets, serving as a redox-mediator and radical-quencher.

Breitenlohner-Freedman Bound on Hyperbolic Tilings.

We establish how the Breitenlohner-Freedman (BF) bound is realized on tilings of two-dimensional Euclidean Anti-de Sitter space. For the continuum, the BF bound states that on Anti-de Sitter spaces, fluctuation modes remain stable for small negative mass squared m^{2}. This follows from a real and positive total energy of the gravitational system. For finite cutoff ϵ, we solve the Klein-Gordon equation numerically on regular hyperbolic tilings. When ϵ→0, we find that the continuum BF bound is approached in a manner independent of the tiling. We confirm these results via simulations of a hyperbolic electric circuit. Moreover, we propose a novel circuit including active elements that allows us to further scan values of m^{2} above the BF bound.

Effect of MgFe2O4 catalyst preparation method on its surface characteristics and Fenton-like oxidation of tartrazine: Statistical comparison and DFT-assisted predation of mechanism

In this study, MgFe2O4 nanoparticles fabricated by co-precipitation (MgF-Cop) and sol-gel auto-ignition (MgF-SG) methods were applied in a Fenton-like process for the degradation of Tartrazine (TA) dye. XRD, FTIR, SEM, and EDX techniques were used to characterize the nanoparticles. Our aim is to compare the relative characteristics of catalysts synthesized by two different methods and to investigate which combinations resulted in better catalytic activity. The interactions between three operating parameters, including catalyst dosage, hydrogen peroxide concentration, and initial TA concentration, were evaluated by employing the Box–Behnken design. The optimal TA removal efficiency D (%) conditions were as follows: catalyst dosage of 0.1 g/L, initial H2O2 dosage of 229 mg/L, and initial TA concentration of 30 mg/L. D (%) achieved on this condition were 79.9% and 98.0% within 60 min for MgF-Cop and MgF-SG, respectively. The co-precipitation method yields a slightly less active catalyst with a lower crystallinity than the sol-gel auto-ignition method. Molecular dynamic (MD) simulations and density functional theory were applied to study the adsorption mechanism and the possible degradation mechanism of TA dye, respectively. The positive total energy calculated indicates that TA has almost no adsorption on the MgFe2O4 nanoparticles. The quantum parameters show that the dye is more reactive and has many sites for HO• radical attack. The Theoretical results correlated with the experimental findings.

Facile pyrrole oxidative polymerization with ionic liquid to modify ceramic membrane for sustainable fouling control

Ceramic membrane bioreactor (CMBR) is an attractive alternative for wastewater treatment, although still subjects to fouling problem. This study facilely modified CM by oxidative polymerization of pyrrole with ionic liquid, to greatly enhance its conductivity and hydrophilic, and to sustainably mitigate fouling in an electric CMBR. Highly conductive ceramic membrane, BVIMBF4-CM, was facile obtained involving an ionic liquid 1-vinyl-3-butylimidazolium tetrafluoroborate (BVIMBF4) on the base CM (Base-CM). After simple modification, the electrical resistance of CM was reduced significantly from 1017 Ω/sq to 349 Ω/sq, while its water contact angle decreased from 44.0° to 30.5°. With the assistant of minute electric field, BVIMBF4-CM exhibited a high rejection efficiency of over 85% Cu2+, 65% Ni2+ and 93% bovine serum albumin (BSA). The interaction energy analysis verified BVIMBF4-CM itself prevent BSA from the membrane surface by the positive total interfacial energy. Meanwhile, the electrophoretic force provided by electric field enhanced the removal efficiency and antifouling capability of the BVIMBF4-CM. By using this modified CM to form an E-CMBR, a comparable removal efficiency as the CMBR could be stably obtained, which especially demonstrated significantly anti-fouling performance, as fouling rate decreased by 31.4–43.5%, and the total membrane resistance was only 60.8% of the Base-CM, under a minute electric field of 0.8 V/m. Enhanced hydrophilicity and conductivity of the BVIMBF4-CM take major responsible for this stable fouling alleviation in the E-CMBR. The new and facile method for CM modification proposed herein can serve as a reliable effort towards the application of antifouling E-CMBR system in wastewater treatment.

Impacts of Greenland Block Location on Clouds and Surface Energy Fluxes Over the Greenland Ice Sheet

AbstractClouds and blocking activity have been implicated as causes of increased Greenland Ice Sheet (GrIS) melt in the 21st century. Although Greenland blocks (i.e., long‐lasting, mostly stationary anticyclones) generally reduce cloud cover and move warm air over Greenland, the elevated GrIS perturbs air and moisture transport in complex ways, implying a need to better understand how blocks affect cloud and surface energy flux anomaly patterns. In this study, we use a combination of daily MODIS cloud data and meteorological and energy flux data from MERRA‐2 reanalysis to better understand how Greenland block location, separated into four equal‐area quadrants, affects regional cloud and surface energy flux spatial patterns in the summer months of 2002–2018. Overall, cloud fraction and cloud water path reductions are approximately four times greater during northern block days than southern block days. Net cloud radiative forcing anomalies are negative for all Greenland block locations because negative longwave cloud radiative forcing anomalies exceed positive shortwave cloud radiative forcing changes. However, greater cloud cover reductions during northern block days produce more negative net cloud radiative forcing anomalies than southern block days. Greenland‐average (i.e., latitude‐weighted average of all GrIS grids) net surface energy flux anomalies range from +7 to +12W/m2 for all block quadrants. While net shortwave energy anomalies dominate the total surface energy response during western Greenland block days, sensible heating is responsible for approximately half of positive total surface energy change during eastern Greenland block days.

Hydrogen vs. Halogen Bonds in 1-Halo-Closo-Carboranes.

A theoretical study of the hydrogen bond (HB) and halogen bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique intermolecular bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.

Soliton-Like Spherical Symmetric Solutions of the Nonlinear Spinor Field Equations Depending on the Invariant Function <i>I<sub>P</sub></i>=<i>P</i><sup>2</sup> in the General Relativity Theory

The present research work is considered as part II of the previous work entitled [Plane Symmetric Solutions to the Nonlinear Spinor Field Equations in General Relativity Theory, jmp, 2019, 10, 1222-1234]. Here, we opt for the static spherical symmetric metric. In this metric, we have obtained spherical symmetric soliton-like solutions to the spinor field equations with nonlinear terms, which are arbitrary functions of , taking into account the proper gravitational field of elementary particles. Equations with power and polynomial nonlinearities are investigated in detail. It is shown that the initial set of the Einstein and spinor field equations with a power-law nonlinearity possess regular solutions with a localized energy density of the spinor field only if we consider massless particle without losing the generality (m = 0). In this case, a soliton-like configuration has negative energy. In order to define the role of the nonlinearity and the own gravitational field of the elementary particles in this model, we have obtained exact static symmetric solutions to the above spinor field equations in the linear case by considering Dirac’s equations and in flat space-time. It is proved that soliton-like solutions are absent in the linear case. But in flat space-time soliton-like configurations exist and have positive total energy.

Short note on conditional collapse of self-gravitating system with positive total energy

In this study, we first show a finite time collapse of a three-dimensional Smoluchowski–Poisson system in the micro-canonical ensemble (i.e., μSP system) with positive total energy. Using a precise estimation of the bound of the gravitational contribution to total energy, we provide blow-up conditions on the initial state of the μSP system. The conditions indicate that highly clustered self-gravitating particles in the μSP system induce a finite time collapse, even for positive total energy.

Atmospheric response to anomalous autumn surface forcing in the Arctic Basin

AbstractData from four reanalyses are analyzed to evaluate the downstream atmospheric response both spatially and temporally to anomalous autumn surface forcing in the Arctic Basin. Running weekly mean skin temperature anomalies were classified using the self‐organizing map algorithm. The resulting classes were used to both composite the initial atmospheric state and determine how the atmosphere evolves from this state. The strongest response was to anomalous forcing—positive skin temperature and total surface energy flux anomalies and reduced sea ice concentration—in the Barents and Kara Seas. Analysis of the evolution of the atmospheric state for 12 weeks after the initial forcing showed a persistence in the anomalies in this area which led to a buildup of heat in the atmosphere. This resulted in positive 1000–500 hPa thickness and high‐pressure circulation anomalies in this area which were associated with cold air advection and temperatures over much of central and northern Asia. Evaluation of days with the opposite forcing (i.e., negative skin temperature anomalies and increased sea ice concentration in the Barents and Kara Seas) showed a mirrored, opposite downstream atmospheric response. Other patterns with positive skin temperature anomalies in the Arctic Basin did not show the same response most likely because the anomalies were not as strong nor did they persist for as many weeks following the initial forcing.

Natural organic matter fouling behaviors on superwetting nanofiltration membranes

Nanofiltration has been widely recognized as a promising technology for the removal of micro-molecular organic components from natural water. Natural organic matter (NOM), a very important precursor of disinfection by-products, is currently considered as the major cause of membrane fouling. It is necessary to develop a membrane with both high NOM rejection and anti-NOM fouling properties. In this study, both superhydrophilic and superhydrophobic nanofiltration membranes for NOM removal have been fabricated. The fouling behavior of NOM on superwetting nanofiltration membranes has been extensively investigated by using humic acid (HA) as the model foulant. The extended Derjaguin−Landau−Verwey−Overbeek approach and nanoindentor scratch tests suggested that the superhydrophilic membrane had the strongest repulsion force to HA due to the highest positive total interaction energy (ΔGTOT) value and the lowest critical load. Excitation emission matrix analyses of natural water also indicated that the superhydrophilic membrane showed resistance to fouling by hydrophobic substances and therefore high removal thereof. Conversely, the superhydrophobic membrane showed resistance to fouling by hydrophilic substances and therefore high removal capacity. Long-term operation suggested that the superhydrophilic membrane had high stability due to its anti-NOM fouling capacity. Based on the different anti-fouling properties of the studied superwetting membranes, a combination of superhydrophilic and superhydrophobic membranes was examined to further improve the removal of both hydrophobic and hydrophilic pollutants. With a combination of superhydrophilic and superhydrophobic membranes, the NOM rejection (RUV254) and DOC removal rates (RDOC) could be increased to 83.6% and 73.3%, respectively.

Investigation into the metallophilic interaction in coinage-metal halides: an ab initio study of CMX (CM = Cu and Ag, X = F - I).

Investigation of the metallophilic interactions of the title coinage-metal halide series, CMX (CM = Ag and Cu, X = F - I), and their cationic and anionic systems, were performed at CCSD(T) theoretical level with extended basis sets. Natural bond orbital analysis shows that the interactions come mainly from the overlap of the sp hybrid on the halogen and the spd hybrid on the coinage-metal atom. Electron density deformation analysis demonstrates a pronounced electron accumulation in the interaction region between the heavier X and the coinage-metal atoms, and suggests a covalent character of the interaction. Positive Laplacian values and negative total energy densities at bond critical points (BCPs) show the "intermediate" character of the interactions. Reduced density gradient analysis visualizes the interaction; a linear relationship between energy densities and eigenvalues can be found at BCPs.

Thin-shell wormholes supported by total normal matter

The Zipoy–Voorhees–Weyl (ZVW) spacetime characterized by mass (\(M\)) and oblateness (\(\delta \)) is proposed in the construction of viable thin-shell wormholes (TSWs). A departure from spherical/cylindrical symmetry yields a positive total energy in spite of the fact that the local energy density may take negative values. We show that oblateness of the bumpy sources/black holes can be incorporated as a new degree of freedom that may play a role in the resolution of the exotic matter problem in TSWs. A small velocity perturbation reveals, however, that the resulting TSW is unstable.

TIME ELEMENTS FOR ENHANCED PERFORMANCE OF THE DROMO ORBIT PROPAGATOR

We propose two time elements for the orbit propagator named Dromo. One is linear and the other constant with respect to the independent variable, which coincides with the osculating true anomaly in the Keplerian motion. They are defined from a generalized Kepler's equation written for negative values of the total energy and, unlike the few existing time elements of this kind, are free of singularities. To our knowledge it is the first time that a constant time element is associated with a second-order Sundman time transformation. Numerical tests to assess the performance of the Dromo method equipped with a time element show the remarkable improvement in accuracy for the perturbed bounded motion around the Earth compared to the case in which the physical time is a state variable. Moreover, the method is competitive with and even better than other efficient sets of elements. Finally, we also derive a time element for a null and positive total energy.

Global well-posedness and stability of semilinear Mindlin–Timoshenko system

We study long-term behavior of Reissner–Mindlin–Timoshenko (RMT) plate systems, focusing on the interplay between nonlinear viscous damping and source terms. The sources may represent restoring forces, but may also be focusing thus potentially amplifying the total energy which is the primary scenario of interest. This work complements [28] which established local well-posedness of this problem, global well-posedness when damping dominates the sources (in an appropriate sense) and a blow-up in the complementary scenario assuming negative “total” initial energy. The current paper develops the potential well theory for the RMT system: it proves global existence for potential well solutions without restricting the source exponents, derives explicit energy decay rates dependent on the order of the damping exponents, and verifies a blow-up result for positive total initial energy.

The zero-mass spinless Salpeter equation with a regularized inverse square potential

Abstract We present a detailed study for the classical and the quantum motion of a relativistic massless particle in an inverse square potential. The classical treatment shows that it is possible to find trajectories for which the system has a positive total energy and yet the particle remains bound to the potential center. The quantum approach to the problem is based on the exact solution of the corresponding semirelativistic spinless Salpeter equation for bound states. The connection between the classical and the quantum descriptions is made via the comparison of the associated probability densities for momentum.

Analytical solutions for J 2-perturbed unbounded equatorial orbits

While solutions for bounded orbits about oblate spheroidal planets have been presented before, similar solutions for unbounded motion are scarce. This paper develops solutions for unbounded motion in the equatorial plane of an oblate spheroidal planet, while taking into account only the J2 harmonic in the gravitational potential. Two cases are distinguished: A pseudo-parabolic motion, obtained for zero total specific energy, and a pseudo-hyperbolic motion, characterized by positive total specific energy. The solutions to the equations of motion are expressed using elliptic integrals. The pseudo-parabolic motion unveils a new orbit, termed herein the fish orbit, which has not been observed thus far in the perturbed two-body problem. The pseudo-hyperbolic solutions show that significant differences exist between the Keplerian flyby and the flyby performed under the the J2 zonal harmonic. Numerical simulations are used to quantify these differences.

Cumulation of de broglie waves of electrons, endoions and endoelectrons of fullerenes, and resonances in the properties of nanocomposite materials with spatial charge layers

The cumulation of de Broglie waves of electrons in hollow molecules (for example, C60) has been investigated. The existence of negatively charged endoions of fullerenes with trapped electrons in the inner cavity (endoelectrons) is proved. The Schrodinger (Helmholtz) stationary equation for hollow polarized molecules is solved analytically. An endoelectron has a positive total energy, but, because of the polarization forces, it is localized (constantly cumulating) in the center of the hollow spherically symmetric molecule (C60). The analytically calculated Eigen ϕ-function and eigen energy determine the probability of finding an electron in the cavity of a hollow molecule. The Eigen energy of a quantum cavity (C60) is compared with experimental studies of cross sections of electrons attachment to C60 dependencies on the electron energy. The importance of the polarization hollow molecules in the stabilization of the fullerene endoions with endoelectrons (with energies from 0.2 to 12 eV) is proved. The effect of the cumulation of electrons in the hollow of the molecule (the trap for electrons) can be used to control the concentration of the charge carriers, the thermal and electrical properties of semiconductors, and the hardening of materials with free electrons. The quantum properties of polarized cavities could cause the variation of the parameters of nanocomposites with a concentration of quantum modifiers (C60).

On the dynamics of exotic matter: Towards creation of Perpetuum Mobile of third kind

The one-dimensional dynamics of a classical ideal ‘exotic’ fluid with equation of state p=p(ϵ)<0 violating the weak energy condition is discussed. Under certain assumptions it is shown that the well-known Hwa–Bjorken exact solution of one-dimensional relativistic hydrodynamics is confined within the future/past light cone. It is also demonstrated that the total energy of such a solution is equal to zero and that there are regions within the light cone with negative (−) and positive (+) total energies. For certain equations of state there is a continuous energy transfer from the (−)-regions to the (+)-regions resulting in indefinite growth of energy in the (+)-regions with time, which may be interpreted as action of a specific ‘Perpetuum Mobile’ (Perpetuum Motion). It is speculated that if it is possible to construct a three-dimensional non-stationary flow of an exotic fluid having a finite negative value of energy such a situation would also occur. Such a flow may continuously transfer positive energy to gravitational waves, resulting in a runaway. It is conjectured that theories plagued by such solutions should be discarded as inherently unstable.

Electron state density and electron diffusion coefficient in energy space in nonideal nonequilibrium plasmas

We suggest a model for a hydrogenic low-temperature nonequilibrium nonideal plasma that allows the kinetic parameters of the plasma to be calculated by the method of molecular dynamics by taking into account the interparticle interaction. The charges interact according to Coulomb’s law; for unlike charges, the interaction is assumed to be equal to a constant at a distance smaller than several Bohr radii. For a system of particles, we solve the classical equations of motion under periodic boundary conditions. The initial conditions are specified in such a way that the electrons have a positive total energy. We consider the temperatures 1-50 K and densities n = 109−1010 cm−3 produced in an experiment through laser cooling and resonant excitation. We calculate the electron state density as a function of the plasma coupling parameter and the electron diffusion coefficient in energy space for highly excited (Rydberg) electron states close to the boundary of the discrete and continuum spectra.

Full ionization in binary-binary encounters of equal masses with a small positive total energy

Interactions between pairs of binary stars play an important role in the dynamics of dense stellar systems. One possible outcome of a binary-binary encounter is full ionization: the destruction of both interacting binaries resulting in four separating single stars. This process is only possible for positive total energy, and the cross-section for full ionization falls to zero at zero total energy. In the context of a stellar system, full ionization is most likely to involve the interaction of two soft binaries with low binding energies. We consider the case where the four stars have a similar mass and derive an asymptotic power law relating the cross-section for full ionization with the total energy when this latter quantity is small. Our new theory makes use of the fact that the most dramatic changes in scale and energies of a few-body system occur when its components pass near to a central configuration. Numerical simulations are used to verify the result.