Electric Fields Of Different Strengths Research Articles

Rapidly determining the 3D structure of proteins by surface-enhanced Raman spectroscopy.

Despite great advances in protein structure analysis, label-free and ultrasensitive methods to obtain the natural and dynamic three-dimensional (3D) structures are still urgently needed. Surface-enhanced Raman spectroscopy (SERS) can be a good candidate, whereas the complexity originated from the interactions between the protein and the gradient surface electric field makes it extremely challenging to determine the protein structure. Here, we propose a deciphering strategy for accurate determination of 3D protein structure from experimental SERS spectra in seconds by simply summing SERS spectra of isolated amino acids in electric fields of different strength with their orientations in protein. The 3D protein structure can be reconstructed by comparing the experimental spectra obtained in a well-defined gap-mode SERS configuration with the simulated spectra. The gradient electric field endows SERS with a unique advantage to section biomolecules with atomic precision, which makes SERS a competent tool for monitoring biomolecular events under physiological conditions.

Electric field effects on hydrogen/methane oxidation: A reactive force field based molecular dynamics study

In the study, molecular dynamics simulations associated with reactive force fields are performed to examine the effect of an imposed electric field at different strengths upon the reactive systems of hydrogen/methane mixture oxidation. Temporal evolution results regarding the initial species evidence the distinct alteration of external electric effects to the consumption rates and the reaction-starting time of the reactants in hydrogen/methane oxidation systems. Significantly, hydrogen molecules play contrasting roles under electric and electric-free reactions. The discoveries about the various categories of intermediate radicals and the differences in the temporal progress reveal that the introduction of an electric field to the reactive system modifies the diversities and generation trends of intermediate radicals and alters the reaction rates by affecting the reaction pathways. Different unique species are formed under electric fields of different strength. The current findings prove and support that molecular dynamics simulation associated with reactive force field is a feasible and promising technique for detailed investigation into combustion/oxidation reaction kinetics, involving high temperature and pressure.

Buckybowls as gas adsorbents: binding of gaseous pollutants and their electric-field induced release.

The adsorption of nitric oxide and nitrogen dioxide (NOx) to the Buckybowls sumanene and corannulene was investigated. Binding energies were up to 1.8× larger than for coronene as the planar analogue, demonstrating the advantages of Buckybowls for gas adsorption. In agreement with previous reports on carbon dioxide and methane adsorption, the favorable binding energies for NOx were shown to be associated with the curvature of the Buckybowls. It is shown that applying an electric field along the bowl symmetry axis modifies the bowl curvatures and impacts adsorbate binding energies, including the potential to desorb adsorbates. As a proof of concept, it is shown that applying electric fields of different strengths and orientations selectively controls sumanene's preference to bind nitric oxide, nitrogen dioxide, and carbon dioxide, suggesting potential applications for dynamically tunable gas adsorption. Moreover, it is demonstrated that adsorbates can be desorbed by applying suitable electric field strengths, allowing cleaning of the Buckybowls for renewed usage.

Molecular Dynamics Simulation on the Electrowetting Behaviors of the Ionic Liquid [BMIM][BF4] on a Solid Substrate.

Compared with traditional aqueous solutions, ionic liquids have important application prospects in the field of wetting and electrowetting due to the advantages of high electric conductivity, long liquid range, and low volatility. In this paper, molecular dynamics method was employed to investigate the wetting and electrowetting behaviors of the nanodroplet of ionic liquid on a solid substrate, as well as the distribution of ionic groups. The ionic liquid is 1-butyl-3-methyl tetra-fluoroborate and coarse grained to simplify the molecular simulation model. The results show that the anion and cation groups are distributed in layers above the wall, and the peaks are different corresponding to different ionic groups. Due to the attraction of the solid substrate and the electrostatic force between anions and cations, the contact angle tends to increase slightly with the increase of ionic liquid pairs. To investigate the electrowetting behaviors of ionic liquid droplet, several electric fields of different strengths and directions have been applied to the system, respectively. The results show that the static contact angles decrease obviously with the increase of electric field, and the ionic liquid droplet wets the solid surface asymmetrically under electric fields in positive and negative directions due to different diffusion abilities of cationic and anionic coarse particles. However, for a hydrophilic surface (ε = 2.0 kcal/mol), the ionic liquid droplet wets symmetrically under the electric field E = ±0.18 V/Å because of the strong interaction from the solid surface. Thus, the wetting and electrowetting behaviors are determined by the combine effect of electric field, interaction among cationic/anionic coarse particles, and solid substrates.

Туннельная эмиссия электронов из наноструктурированных кремниевых катодных матриц с фтор-углеродным покрытием

AbstractVariations of the morphology and field-emission properties of surface-structured n - and p -type silicon wafers have been studied. The silicon surface has been structured by etching in a fluorine–carbon plasma and depositing subnanodimensional island carbon masks. It has been shown that surface structuring in a fluorine–carbon plasma makes it possible to reach desired field-emission currents in electric fields of different strengths. Physicochemical models of field emission mechanisms and models of destruction of surface-modified multipoint silicon array cathodes have been considered.

Electromagnetic-field effects on structure and dynamics of amyloidogenic peptides.

Electromagnetic fields (EMFs) are ever-present, and so is the need to better understand their influence on human health and biological matter in general. The interaction between a molecular system and external EMF can alter the structure, and dynamical behaviour, and, hence, biological function of proteins with uncertain health consequences. This urges a detailed investigation of EMF-induced effects on basic protein biophysics. Here, we used all-atom non-equilibrium molecular dynamics simulations to understand and quantify the response mechanisms of the amyloidogenic apoC-II(60-70) peptides to non-ionising radiation by modelling their behaviour under external electromagnetic and electric fields of different strengths. Our simulations show high strength fields (>0.04 V/nm) cause structural changes in apoC-II(60-70) due to the peptide dipole alignment along the applied field direction, which disrupts the inherent β-hairpin conformation known to be the intermediate state for fibril formation. The intermediate field-strength range (0.04-0.004 V/nm) causes a significant acceleration in peptide dynamics, which leads to the increased population of structures with fibril-inhibiting characteristics, such as the separated N- and C-termini and colocation of the aromatic residues at the same peptide face. In contrast, lower field strengths (<0.004 V/nm) promote the formation of the amyloid-prone hairpin structures relative to the ambient conditions. These findings suggest that intermediate-strength electromagnetic fields could be considered for designing alternative treatments of amyloid diseases, while the very high and low field strengths could be employed for engineering well-ordered fibrillar aggregates for non-medicinal applications.

Simulations of the secondary cosmic ray propagation in the thunderstorm atmospheres resulting in the Thunderstorm ground enhancements (TGEs)

GEANT4 simulations of the propagation of electrons in the thunderstorm atmospheres were performed to explain the Thunderstorm Ground Enhancements (TGEs), detected by the particle detectors of the Aragats Space Environmental Center (ASEC) operating at altitude 3200 m on slopes of Mt. Aragats in Armenia. The charged particle propagation and multiplication processes were simulated in the uniform electric fields of different strengths and elongation. The Gamma ray, electron and neutron energy spectra were obtained on the exit of the electrical field and beneath. Simulation results prove existence of 2 mechanisms of particle enhancements, first connected with electron – gamma ray avalanche process; and the second – with modification of energy spectra of particles in the strong electrical fields of the thunderclouds. The avalanche process can multiply number of electrons and gamma rays by several orders of magnitude well above the cosmic ray background in the energy range up to 40MeV; the energy spectra modifications lead to a few percent enhancements in the energy range up to 100MeV, as well as to depletion of the high-energy muon flux. Consequently the energy spectra at low energy are better fitted by exponential law; at high energies – by the power law.

Nanospray FAIMS Fractionation Provides Significant Increases in Proteome Coverage of Unfractionated Complex Protein Digests

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an atmospheric pressure ion mobility technique that can be used to reduce sample complexity and increase dynamic range in tandem mass spectrometry experiments. FAIMS fractionates ions in the gas-phase according to characteristic differences in mobilities in electric fields of different strengths. Undesired ion species such as solvated clusters and singly charged chemical background ions can be prevented from reaching the mass analyzer, thus decreasing chemical noise. To date, there has been limited success using the commercially available Thermo Fisher FAIMS device with both standard ESI and nanoLC-MS. We have modified a Thermo Fisher electrospray source to accommodate a fused silica pulled tip capillary column for nanospray ionization, which will enable standard laboratories access to FAIMS technology. Our modified source allows easily obtainable stable spray at flow rates of 300 nL/min when coupled with FAIMS. The modified electrospray source allows the use of sheath gas, which provides a fivefold increase in signal obtained when nanoLC is coupled to FAIMS. In this work, nanoLC-FAIMS-MS and nanoLC-MS were compared by analyzing a tryptic digest of a 1:1 mixture of SILAC-labeled haploid and diploid yeast to demonstrate the performance of nanoLC-FAIMS-MS, at different compensation voltages, for post-column fractionation of complex protein digests. The effective dynamic range more than doubled when FAIMS was used. In total, 10,377 unique stripped peptides and 1649 unique proteins with SILAC ratios were identified from the combined nanoLC-FAIMS-MS experiments, compared with 6908 unique stripped peptides and 1003 unique proteins with SILAC ratios identified from the combined nanoLC-MS experiments. This work demonstrates how a commercially available FAIMS device can be combined with nanoLC to improve proteome coverage in shotgun and targeted type proteomics experiments.

Electrorheology of suspensions of mesostructured and mesoporous silica in poly(dimethylsiloxane)

The effect of electric fields on the viscosity and shear stress of dispersions of mesostructured silicon dioxide powders and the products of their thermal treatment, that is, mesoporous silicas, in silicone oil is investigated. Mesostructured silicon dioxide powders are prepared using different structuring reagents, namely, octylamine, dodecylamine, and polyethylenimine. It is shown that the shear stresses developing in systems containing mesostructured powders as dispersed phases under the action of electric fields are several times higher than those in dispersions of mesoporous materials. The shear stresses developing in the systems containing powders of mesostructured materials as dispersed phases under the effect of electric fields depend on the nature of organic substrates present in pores and the conductivity of the systems. Electrorheological effect in dispersions of mesoporous silicas slightly depends on the structure of the materials. The observed synergism may be related to the interactions between the components of a mesostructured material, which manifest themselves as a rise in interfacial polarization. The stress-strain curves were measured upon tensile and compression in electric fields of different strengths.

Computed effects of electric fields upon the CNO2 and NNO2 bonds of nitromethane and dimethylnitramine

AbstractWe report the results of a computational (B3PW91/6‐31G**) investigation of the effects of electric fields of different strengths and directions upon some properties related to the CNO2 and NNO2 bonds in nitromethane, H3CNO2, and dimethylnitramine, (H3C)2NNO2. We look at the interaction energies of the fields with the molecules, the dipole moments of the latter, the lengths of the CNO2 and NNO2 bonds, and we particularly focus upon their stretching vibration frequencies. The field‐induced frequency shifts are determined by means of a formula linking them to the dipole moment derivatives and the field strengths. This formula was derived originally for hydrogen‐bonded systems, but we show that it is applicable as well to these CNO2 and NNO2 bonds; their predicted relative frequency shifts correlate extremely well with directly computed Δω(ϵ) (R2 = 0.9992). It was found that the fields that reinforce the intrinsic H3CNO2 and (H3C)2NNO2 polarities also interact favorably energetically with the molecules and, particularly important, increase the CNO2 and NNO2 stretching frequencies. This presumably indicates the strengthening of these bonds. Fields in the opposite direction do the reverse. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Influence of a Weak DC Electric Field on Root Meristem Architecture

Electric fields are an important environmental factor that can influence the development of plants organs. Such a field can either inhibit or stimulate root growth, and may also affect the direction of growth. Many developmental processes directly or indirectly depend upon the activity of the root apical meristem (RAM). The aim of this work was to examine the effects of a weak electric field on the organization of the RAM. Roots of Zea mays seedlings, grown in liquid medium, were exposed to DC electric fields of different strengths from 0.5 to 1.5 V cm(-1), with a frequency of 50 Hz, for 3 h. The roots were sampled for anatomical observation immediately after the treatment, and after 24 and 48 h of further undisturbed growth. DC fields of 1 and 1.5 V cm(-1) resulted in noticeable changes in the cellular pattern of the RAM. The electric field activated the quiescent centre (QC): the cells of the QC penetrated the root cap junction, disturbing the organization of the closed meristem and changing it temporarily into the open type. Even a weak electric field disturbs the pattern of cell divisions in plant root meristem. This in turn changes the global organization of the RAM. A field of slightly higher strength also damages root cap initials, terminating their division.

Accelerated Diffusion Test on the Intact Rock Mass

Abstract Contaminant transport through intact rock mass is predominantly diffusive and its modeling using the conventional laboratory tests is extremely time consuming. In addition, maintaining constant ambient conditions over a long duration is difficult and practically impossible. This necessitates modification of the conventional laboratory diffusion experiments so that the diffusion of ions through the intact rock mass is accelerated. To achieve this, researchers have employed an electric field across the samples of concrete and clays. However, the influence of the applied electric field on diffusion characteristics of the intact rock mass has not been studied in detail. With this in view, diffusion tests were conducted on the samples of chalk and sandstone by applying electric fields of different strength. Details of the testing methodology are presented in this paper. Efforts were also made to study the influence of the applied electric field on diffusion characteristics of these rocks.

Hysteresis of dielectric properties of Li-Ti-Ferrite ceramics

Field dependences of Li-Ti ferrite ceramics polarization are obtained. When related to temperature, these dependences exhibit either non-linear behavior or non-linearity and hysteresis. Electric Barkhausen’s pulses are revealed. Temperature dependences of the electric pulse heights are obtained after re-polarization of the specimens in the electric fields of different strengths. The results provide evidence on the presence of ferroelectric properties in Li-Ti ferrite ceramics.

Electrically induced dynamic processes in nematic liquid crystals: H1 nuclear magnetic resonance investigations

The director reorientation of some nematic liquid crystals in the presence of both magnetic and electric field is described by a modified from of the Leslie equation. Proton nuclear magnetic resonance experiments observing static director orientations in different angles between the director and the magnetic field are described together with reorientation experiments driven by various electric fields. A new technique to measure Δχ/Δε is presented which gives direct access to the anisotropies without any influence of elastic properties. Using electric fields of different strength and in different angles with respect to the magnetic field the dynamic processes in liquid crystals can be investigated in a very flexible way. A number of experiments investigating the homogeneous director reorientation in the electric field is presented. As one result the rotational viscosity was determined. As a surprising result we found a homogeneous reorientation in the electric field and an inhomogeneous reorientation back in the magnetic field even though the initial angles between the director and the external field were the same.

Haptic Device Working with an Electrorheological Fluid

A haptic device based on an electrorheological fluid has been designed and tested. The device is similar to ajoystick which controls the motion of a cursor on a computer screen. In electric fields of different strength the shear stress of the electrorheological fluid is increased accordingly, which is perceived by the user by different resistance forces against the motion of the joystick. Controlled by the software the user can feel if the cursor enters a selected field on the screen. Such haptic devices can be useful in various possible applications like supporting tools for the operation of machines, assisting interfaces for blind persons working with a computer, virtual reality or computer games. The design of the haptic device, its components and the electrorheological fluid used are described.

Electric field effects on bioluminescent cells of Lampito mauritii: Electrofusion and enhancement of bioluminescence intensity

The bioluminescence of coelomic cells of Lampito mauritii has been monitored in oxygenated phosphate buffer saline (pH 7.4) after subjecting the coelomic cells to d.c. electric fields of different strengths; these cells have also been examined by electrochemical and optical techniques. The results suggest that the electric field produces poration of the bioluminescent cells, resulting in higher consumption of dissolved oxygen in the medium. Enhancement of bioluminescence intensity has also been observed. At field strengths of greater than 125 V cm −1, optical microscopic examination reveals that agglomeration and fusion of the cells has occurred.

Investigations of the structure of a cholesteric phase with a temperature induced helix inversion and of the succeeding Sc∗ phase in thin liquid crystal cells

Abstract Investigations of 4-[(S, S)-2, 3 epoxyhexyloxy]-phenyl-4-(decyloxy)-benzoate by polarizing microscopy, the Cano-Grandjean method, optical rotation dispersion and UV-VIS spectroscopy reveal a cholesteric phase with temperature induced reversal of the helical twist. Switching time experiments in the Sc* phase show that the intrinsic helix can be unwound reversibly and irreveribly by application of electric fields of different strengths.

Statistics and Transport Behaviour of Electrons in SiO2

AbstractAn analytical expression for the statistical distribution function of conduction electrons in SiO2 is derived by taking into account static electric fields of different strengths and various types of electron‐phonon interaction (i.e. scattering of electrons due to longitudinal‐optical, transversaloptical, and acoustic modes). Electronic energy balances and critical electric field strengths as well as the threshold and runaway behaviour of conduction electrons are derived from their distribution function, the time and field dependence of which is analysed quantitatively.