Nitrile IR intensities characterize electric fields and hydrogen bonding in protic, aprotic, and protein environments

Nitriles are widely used as vibrational probes; however, the interpretation of their IR frequencies is complicated by hydrogen bonding (H-bonding) in protic environments. We report a new vibrational Stark effect (VSE) that correlates the electric field projected on the nitrile bond to the transition dipole moment and, by extension, the nitrile peak area or integrated intensity. This linear VSE applies to both H-bonding and non-H-bonding interactions. It can therefore be generally applied to determine electric fields in all environments. Additionally, it allows for semi-empirical extraction of the H-bonding contribution to the blueshift of the nitrile frequency. Nitriles were incorporated at H-bonding and non-H-bonding protein sites using amber suppression, and each nitrile variant was structurally characterized at high resolution. We exploited the combined information now available from variations in frequency and integrated intensity and demonstrate that nitriles are a generally useful probe for electric fields.

Physics Students’ Conceptual Understanding of Electricity and Magnetism in Nine Years Basic Education in Rwanda

We investigate students’ misconceptions in electrostatics, direct current (DC) and magnetism which are important in electricity and magnetism. We developed and administered a multiple-choice questionnaire test to reveal students’ misconceptions related to charged bodies, lightning, electric fields, electric potential, forces, DC resistive electric circuits and magnets. This test aimed at obtaining quantitative information about misconceptions and was administered to 380 senior two students from Nine Year Basic Education (9YBE) Schools. The selected students have some experience with the new Rwandan secondary physics Competence Based Curriculum (CBC) that is currently under implementation. We find that senior two students have several common misconceptions related to these concepts. The data indicate that although students have some backgrounds on the subject matter, they still seem to believe that if the two charges are separated by a distance, a large-charged object exerts a greater force of attraction or repulsion on the small one. Considerable number of participated students held the misconception of considering current consumption in the resistor/bulb or the electrical devices in the circuits. They also believed that the battery was a continuous current source. The findings also revealed that students held a misconception that a bar magnet when broken into pieces, it is demagnetized. Moreover, a considerable number of participants hold the misconception that all metals are attracted by a magnet. Our study also revealed some of the statistically significant differences in terms of either gender or location of schools for some items.

Investigations of Optical Coulomb Blockade Oscillations in Plasmonic Nanoparticle Dimers

The exploration of Coulomb blockade oscillations in plasmonic nanoparticle dimers is the subject of this study. When two metal nanoparticles are brought together at the end of their journey, tunnelling current prevents an infinite connection dipolar plasmon and an infinite amplification in the electric fields throughout the hot spot in between nanoparticles from occurring. One way to think about single-electron tunnelling through some kind of quantum dot is to think about Coulomb blockage oscillations in conductance. The electron transport between the dot and source is considered. The model of study is the linear conductance skilled at describing the basic physics of electronic states in the quantum dot. The linear conductance through the dot is defined as G = lim ⟶ 0 I / V in the limit of infinity of small bias voltage. We discuss the classical and quantum metallic Coulomb blockade oscillations. Numerically, the linear conductance was plotted as a function gate voltage. The Coulomb blockade oscillation occurs as gate voltage varies. In the valleys, the conductance falls exponentially as a function gate voltage. As a result of our study, the conductance is constant at high temperature and does not show oscillation in both positive and negative gate voltages. At low temperature, conductance shows oscillation in both positive and negative gate voltages.

Strength-frequency curve for micromagnetic neurostimulation through excitatory postsynaptic potentials (EPSPs) on rat hippocampal neurons and numerical modeling of magnetic microcoil (μcoil)

Objective: The objective of this study was to measure the effect of micromagnetic stimulation (μMS) on hippocampal neurons, by using single microcoil (μcoil) prototype, Magnetic Pen (MagPen). MagPen will be used to stimulate the CA3 magnetically and excitatory post synaptic potential (EPSP) measurements will be made from the CA1. The threshold for μMS as a function of stimulation frequency of the current driving the µcoil will be demonstrated. Finally, the optimal stimulation frequency of the current driving the μcoil to minimize power will be estimated. Approach: A biocompatible prototype, MagPen was built, and customized such that it is easy to adjust the orientation of the μcoil over the hippocampal tissue in an in vitro setting. Finite element modeling (FEM) of the μcoil was performed to estimate the spatial profiles of the magnetic flux density (in T) and the induced electric fields (in V/m). The induced electric field profiles generated at different values of current applied to the µcoil whether can elicit a neuron response was validated by numerical modeling. The modeling settings were replicated in experiments on rat hippocampal neurons. Main results: The preferred orientation of MagPen over the Schaffer Collateral fibers was demonstrated such that they elicit a neuron response. The recorded EPSPs from CA1 due to μMS at CA3 were validated by applying tetrodotoxin (TTX). Finally, it was interpreted through numerical analysis that increasing frequency of the current driving the μcoil, led to a decrease in the current amplitude threshold for μMS. Significance: This work reports that μMS can be used to evoke population EPSPs in the CA1 of hippocampus. It demonstrates the strength-frequency curve for µMS and its unique features related to orientation dependence of the µcoils, spatial selectivity and distance dependence. Finally, the challenges related to µMS experiments were studied including ways to overcome them.

Inquisition of Electro-Magnetic Riga Plate for Laminar Flow

The probation is made to study the stagnation point flow of non-Newtonian fluid for Riga plate. Electric potential and magnetic flux density with time dependent flow is examined. Mesh for electric potential, magnetic flux, laminar flow with physics controlled fine, finer and extra finer option is also represented in details. Inquisition is solved in COMSOL Multi-physics 5.4 to obtain the results of surface magnitude, counter, table surface, magnetic flux, electric potential and coarse mesh for velocity, pressure, magnetic and electric fields. Coarse mesh of electric insulation and magnetic flux of the geometry is created with 6067, 18688 domain elements and 901, 1448 boundary elements. Tables for velocity surface, mesh domain, quadrilateral and triangular elements are also presented. Obtained results are discussed with graphs and tables in details.

Quantification of pulsed electric field for the rupture of giant vesicles with various surface charges, cholesterols and osmotic pressures

Electropermeabilization is a promising phenomenon that occurs when pulsed electric field with high frequency is applied to cells/vesicles. We quantify the required values of pulsed electric fields for the rupture of cell-sized giant unilamellar vesicles (GUVs) which are prepared under various surface charges, cholesterol contents and osmotic pressures. The probability of rupture and the average time of rupture are evaluated under these conditions. The electric field changes from 500 to 410 Vcm-1 by varying the anionic lipid mole fraction from 0 to 0.60 for getting the maximum probability of rupture (i.e., 1.0). In contrast, the same probability of rupture is obtained for changing the electric field from 410 to 630 Vcm-1 by varying the cholesterol mole fraction in the membranes from 0 to 0.40. These results suggest that the required electric field for the rupture decreases with the increase of surface charge density but increases with the increase of cholesterol. We also quantify the electric field for the rupture of GUVs containing anionic mole fraction of 0.40 under various osmotic pressures. In the absence of osmotic pressure, the electric field for the rupture is obtained 430 Vcm-1, whereas the field is 300 Vcm-1 in the presence of 17 mOsmL-1, indicating the instability of GUVs at higher osmotic pressures. These investigations open an avenue of possibilities for finding the electric field dependent rupture of cell-like vesicles along with the insight of biophysical and biochemical processes.