Electrical Inhomogeneity Research Articles

Electrical Inhomogeneity in Left Ventricular Hypertrophy

Recent studies designed to assess the relationship between aortic compliance and heterogeneity of heart electrical activity has shown that hypertrophy aggravates repolarization disturbances in the myocardium. Numerous mechanisms of electrical instability and inhomogeneity associated with left ventricular hypertrophy are now under investigation. Most of the studies have been found to be focused on ventricular Gradient, QT dispersion, amplitudes of isointegral maps during ventricular repolarization, abnormally low-QRST areas, dispersion of the QT interval, and spatial QRS-T(angle). These studies point to marked repolarization abnormalities in left ventricular hypertrophy and the dispersion of the QT interval as a valuable index for inhomogeneity of repolarization and the subsequent heart rate variability. The heart rate-corrected QT dispersion and QT apex dispersion seem to be significantly longer in the patients with left ventricular hypertrophy than in normal individuals. The review study has also identified QRST isointegral map as a valuable technique in assessment of the electro-cardiac events in LVH.

P‐Wave Abnormality Predicts Recurrence of Atrial Fibrillation after Electrical Cardioversion: A Prospective Study

Maintenance of atrial fibrillation (AF) is related to atrial electrical inhomogeneity and resultant chaotic reentry. Our aim was to test the hypothesis that abnormalities of P morphology on the surface electrocardiogram (ECG) predict recurrent AF following electrical cardioversion (ECV). A 12-lead ECG was recorded after ECV for persistent AF in 77 patients (51 men, 65 ± 10 years) and repeated 1 month later. P-wave duration was obtained in each lead using blinded on-screen measurement. Maximum P-wave duration (P-max) was defined as the longest measurable P-wave duration in any lead. P-wave dispersion (PWd) was calculated as the maximum-minimum P-wave duration. One month after ECV, 29 (38%) patients maintained sinus rhythm. Compared with the sinus rhythm group, those with recurrent AF had significantly greater PWd (66 ± 19 vs 57 ± 16 ms, P = 0.024) and included more patients with P-max ≥142 ms (65% vs 38%, P = 0.023). Using a cutoff of ≥62 ms for PWd and ≥142 ms for P-max, both indices had similar predictive value (sensitivity 66.7 and 64.6%, specificity 58.6 and 62.1%, respectively). In multiple regression analysis, including established clinical predictors, P-max ≥142 ms was the only independent predictor of AF recurrence (P = 0.025). A prolonged P-wave duration measured by 12-lead ECG predicts recurrent AF within 1 month after ECV.

Exploring electrical conductivity within mesoscopic phases of semiconducting poly(3,4-ethylenedioxythiophene):poly(4-styrene-sulfonate) films by broadband dielectric spectroscopy

Poly(3,4-ethylenedioxythiophene): poly(4-styrene sulfonate) (PEDOT:PSS), an optically transparent organic semi-conductor, constitutes a suspension of conducting PEDOT:PSS grains, shelled by an insulating layer of PSS. While a percolation network enhances dc conductivity, structural and electrical inhomogeneity hinters electric charge flow giving rise to capacitance effects. In the present work, two distinct relaxation mechanisms are detected by Broadband Dielectric Spectroscopy. Double polarization mechanisms are predicted by bi-phase suspension dielectric theory. Within the frame of interfacial polarization, we propose a methodology to have an insight into the local conductivity of the interior of mesoscopic conducting phase.

Local electrical characterization of cadmium telluride solar cells using low-energy electron beam

We investigate local electronic properties of cadmium telluride solar cells using electron beam induced current (EBIC) measurements with patterned contacts. EBIC measurements are performed with a spatial resolution as high as ≈20nm both on the top surface and throughout the cross-section of the device, revealing a remarkable degree of electrical inhomogeneity near the p–n junction and enhanced carrier collection in the vicinity of grain boundaries (GB). Simulation results of low energy EBIC suggest that the band bending near a GB is downward, with a magnitude of at least 0.2eV for the most effective current-collecting GBs. Furthermore, we demonstrate a new approach to investigate local open-circuit voltage by applying an external bias across electrical contact with a point electron-beam injection. The length scale of the nanocontacts is on the length scale of a single or a few grains, confining current path with highly localized photo-generated carriers.

Pulmonary veins isolation vs linear radiofrequency ablation assessment in paroxysmal atrial fibrillation patients using either mathematical scanning or clinical approach

Aim: 1) To compare clinical results of linear ablation vs. PVI approach in patients with paroxysmal AF, and 2) to estimate theoretical probability of 4-waves re-entry to eliminate as a results of simulation the both ablative techniques in 2D mathematical modeling of left atrium (LA). Material and methods: Study was conducted on 20 pts (6 women, 51.4±13.6 years of age) with paroxysmal AF underwent index RFA. All pts were divided into two age-sex-arrhythmia history duration as well as antiarrhythmic drugs (AAD)-matched groups. The first group consisted of 10 pts (3 women, 51.1±11.9 years of age, history of arrhythmia – 3.2±1.2 years) in whom ablation strategy consisted of PVI using LASSO technique. The second group concluded of 10 pts (3 women, 51.1±12.9 years of age, history of arrhythmia – 3.1±1.1 years) in whom ablation strategy consisted of circumferential ablation combined with roof line and mitral isthmus modification (3D approach). As the first step numeric reconstruction of the autowave process in excitable tissues of the LA and the simulation of AF was performed. Fitzhugh-Nagumo equation was used for simulation of electrical inhomogeneity of the atria (PV ostia). A special scanning method was used for calculating characteristics of autowave processes in a 2D mathematical model of the LA. As the second step simulation of circular (corresponding to LASSO approach) and linear ablation (corresponding to 3D approach) was performed. Results: 7 pts of the first group vs 4 pts of the second group had early recurrences of arrhythmia. AAD free effectiveness in the first/second groups was 80%/20% at 12 months respectively (p=0,003). There was no elimination of 4-waves re-entry turning around the PVs and vortex waves caused by them in a distributed 2D atrial medium after the time period equaling to re-entry period while circular LASSO-like ablation pattern was used. In contrast, linear ablation patterns suppress arrhythmias caused by 4-waves re-entry in 2D mathematical modeling of the LA. Conclusion: Mathematical scanning approach using linear ablation to simulate clinical impact suppressed 4-waves re-entry more effectively comparing to PVI-only modeling. Our clinical results are consistent with ablation formatting data obtained by means of 4-waves re-entry simulation in 2D mathematical modeling of the LA.

Fusion of biventricular incomplete bundle branch block, in healthy young adults and in patients with moderate pulmonary hypertension. Fragmented depolarization – a new real ECG entity

Introduction: Within the QRS complex, the vector components either compete with each other or can appear at the same time. The two best examples of rewriting the original ECG curves are preexcitation and complete left bundle branch block. In contrast, the rS complex of left anterior hemiblock (LAH) and the Q wave of postero-inferior myocardial infarction (PI MI) can be observed simultaneously forming a W complex in the inferior leads. Methods: First, variants of incomplete right bundle branch blocks (IRBBB) were studied in healthy young adults and in patients with moderate pulmonary hypertension. According to the QRS morphology in the frontal plane (59 patients), three IRBBB patterns were formed: 1. SI-SII-SIII (n = 20); 2. SI-QIII (n = 18); 3. Both 1 and 2 patterns (n = 8). Presence or absence of IRBBB signs in lead V1 was meanwhile registered. Secondly, two further patterns were formed relating to comparison of biventricular incomplete blocks with arborization block. Both are characterized by depolarization inhomogeneity. 4. IRBBB + LAH (n = 11); 5. IRBBB + LAH + PI MI (n = 2). Results: In pattern 3, initial and terminal vectors (QIII-SIII) occurred simultaneously in the ECG lead III. Frequently, waves occurring in the same period of the depolarization in certain leads remained separable (two-component S-wave). In pattern 4, after the initial “r” wave, a two component S wave (rW complex) appeared in the inferior leads. Such separation of the depolarization vector components does not mean high electrical inhomogeneity if the width of QRS remains under 110 ms. In pattern 5, the ventricular depolarization is fragmented, and appears as three negative waves in the inferior leads (VW complex). In these cases, the duration of ventricular depolarization is also not wider than 110 ms. In contrast, the arborization block is characterized by fragmented depolarization, but the duration of QRS is wider than 140 ms, resulting in extreme inhomogeneity. Conclusion: By wave form analysis of biventricular incomplete blocks, we could describe a new ECG entity, of less dangerous “arborization block-like” form.

Electrical and optical inhomogeneity in N-face GaN grown by hydride vapor phase epitaxy

A detailed study on electrical and optical inhomogeneity in N-face GaN grown by hydride vapor phase epitaxy is presented. There are two distinctive regions with non-homogeneous electrical and optical properties in N-face of GaN revealed by wet etching, Raman and cathodoluminescence. One region exclusively exhibited stronger donor–acceptor pair emission and higher carrier concentration due to impurity incorporation. A strong red-shift of near band edge emission of ∼24meV was also observed owing to additional carrier concentration. Furthermore, the activation energy difference of the etching process between the two regions is ∼0.12eV. The distinctive etching topography was probably due to the difference of surface potentials related to the level of carrier concentration in GaN.

Geophysical Evidence through a CSAMT Survey of the Deep Geological Structure at a Potential Radioactive Waste Site at Beishan, Gansu, China

This paper describes a controlled-source audio-frequency magnetotellurics (CSAMT) survey conducted in August 2009 over a potential high-level radioactive waste (HLRW) disposal site in northwestern China. The site is primarily covered with well-developed metamorphic rocks. The purpose of the CSAMT survey was to map the outcropped faults to depth and identify any hidden faults or weakened zone in the subsurface. The site is located in the arid Beishan area, Gansu Province. Substantial challenges were encountered in acquiring quality electrical field data because of the highly resistive ground. Satisfactory electrode contact conditions were generally maintained by applying salt-saturated water to both the transmitting electrodes and the receiving electrodes. The excitation frequency ranges from 9,600 Hz to 1 Hz with a target depth of investigation of 1,000 m. The CSAMT data were processed in several steps. Low-pass filtering was applied to remove the static effect caused by the local electrical inhomogeneities near the ground surface. An optimum filter length was found through experiment to yield the maximum static effect reduction. The pre-processed data are inverted for geoelectrical cross sections using a 2-D inversion method. Inversion artifacts were suppressed by imposing a model smoothness constraint. The inversion reveals several important results. First, the inversion cross sections correctly recognized the fractures and deformation bands mapped at the surface. The cross sections also identified four new faults that were not observed in the geological survey. The inversion profiles suggested that the narrow factures and deformation bands observed along survey line 1 extend to a great depth. The profile helped identify a possible weak mineralization zone along survey line 2. Considering the regional tectonic stress direction, the lower resistivity zone suggests that the faults parallel to survey line 2 are subject to an extensional or transtensional force that produces a broad and broken alteration zone. Although subject to further drilling confirmation, these interpretation results greatly enhance the understanding of the deep geological hazards at the Beishan site.

Dynamics of spiral waves in a cardiac electromechanical model with a local electrical inhomogeneity

Joint effect of electrical heterogeneity (e.g. induced by ischemia) and mechanical deformation is investigated for an anisotropic, quasi–incompressible model of cardiac electromechanical coupling (EMC) using the active strain approach and periodic boundary conditions. Three local inhomogeneities with different geometry are simulated. Under a specific stimulation protocol, the heterogeneities are able to induce spirals. The interplay between the dimension of the electrical inhomogeneity, the EMC and the mechano-electrical feedback provided by the stretch activated current (SAC) determines the dynamics of the spiral waves of excitation, which could extinguish (in the case of low SAC), or be stable (with the tip rotating inside the inhomogeneity), or drift and be annihilated (in the case of high SAC).

Amorphous InGaZnO4 films: Gas sensor response and stability

Abstract The response characteristics of amorphous-InGaZnO 4 (a-IGZO 4 ) thin films toward reducing/oxidizing gases (H 2 /NO 2 ), at sensor operating temperatures, are reported for the first time. The lack of grain boundaries eliminates a major source of electrical, microstructural and chemical inhomogeneities associated with polycrystalline semiconducting metal oxides (SMOs), rendering a-IGZO 4 a highly promising model sensor system. Gas sensor tests were carried out in the temperature range of 200–400 °C by monitoring changes in DC resistance during cyclic exposure to trace concentrations (between 1.25 and 50 ppm) of H 2 or NO 2 in dry air. The response ( S ) to H 2 was found to go through a temperature maximum (e.g. S ∼ 0.7 at 350 °C for pH 2 = 12.5 ppm) that value being a function of pH 2 . The response to NO 2 , on the other hand, decreased with increasing temperatures with the highest recorded values at 200 °C (e.g. S ∼ 33 at 200 °C for pNO 2 = 5 ppm). The response followed an approximate power law dependence on gas partial pressure ( p ), S = Ap β , with β taking on values of ∼0.5–1.0 as temperature increased from 200 to 400 °C. Response times were found to range from 10 s to greater than 1000 s as temperature decreased. The hysteretic behavior exhibited by a-IGZO films between 150 and 400 °C, under temperature sweep conditions, is attributed to kinetically limited adsorption/desorption and reaction rates.

Field-dependent permittivity in nanostructured BaTiO3ceramics: Modeling and experimental verification

The grain size (GS) effect on the electric field dependence of the dielectric constant in ferroelectric nanoceramics was studied using a detailed model and the predicted behavior compared to experimental data obtained for BaTiO${}_{3}$. In the finest ceramics the permittivity reduces below 1000 and a tendency to linearization of the permittivity vs field dependence is observed. The composite structure of ferroelectric ceramics corresponding to ferroelectric grain cores separated by nonferroelectric grain boundaries determines a progressive increase of the electrical inhomogeneity of the system with decreasing GS. The local electric field was computed at various applied voltages for different GSs by a finite element approach, and then the effective permittivity-field response ${\ensuremath{\varepsilon}}_{\mathrm{eff}}$($E$) was determined by taking into consideration the local field distribution. A remarkable agreement between the model and experimental data was obtained for BaTiO${}_{3}$ ceramics. The local field distribution explains with considerable accuracy the reduction of permittivity and tunability observed with decreasing GS as well as the tendency towards linearization of ${\ensuremath{\varepsilon}}_{\mathrm{eff}}$($E$) in nanoceramics.

Effect of the ion-exchange-membrane/solution interfacial characteristics on the mass transfer at severe current regimes

In the electrodialysis of dilute solutions, performed at intense current regimes, the membrane electrical conductance and diffusion permeability are no more crucial. Of more importance become the membrane properties that control increase in the overlimiting mass transfer of salt ions, as well as H+ and OH− ions in membrane systems. In this work different methods of the improving of mass-exchange characteristics of commercial ion-exchange membranes intended for operation at intense current regimes are discussed. They are based on modern concepts of mechanisms of the electroconvection (which proceeds as electroosmosis of 2nd kind), as well as mechanisms of H+ and OH− ions generation at the membrane/solution interface. Influence on the membrane electrochemical and mass-exchange characteristics is possible via (a) control of chemical nature of fixed groups at membrane surfaces, in order to weaken their catalytic activity with respect to water dissociation reaction, (b) increase in the surface hydrophobicity, and (c) design of electrical inhomogeneity of the membrane/solution interface; the purpose is the facilitating of intense development of electrical convection.

Electrical Inhomogeneities of Guinea Pig Atrial Tissue in High Resolution Optical Potential Mapping

Inhomogeneities in the tissue are a determining factor for cardiac function and can be either structural or functional. Using the voltage sensitive fluorescent dye di-4-ANEPPS on incubation stained guinea pig preparations allows to map the tissue's response to externally applied electric shocks. Previous work on ventricular muscle preparations revealed a membrane potential morphology that could be relevant during defibrillation [1]. Using a two pulse stimulus protocol we are able to map the excitation response to a short triggering field pulse and to consequently map the membrane potential morphology resulting from a second field pulse, which is applied in the depolarized state and is attributed to the interaction of the electric field with the tissue. This approach is now carried over to atrial preparations. A custom developed object-positioning and image-stitching method allows for wide view analysis of the atrial tissue structure. Objective-magnifications of 10x, 20x, 40x and 63x enable a multi-scale based analysis with resolutions up to 15 micrometers. This is augmented with information from transmitted light microscopy so that it is possible to correlate the membrane potential patterns with the visible structure of the atrial tissue, providing further insight into atrial excitation and conduction.[1] Windisch,H. et al. (2007) Quantification of shock-induced microscopic virtual electrodes assessed by subcellular resolution optical potential mapping in guinea pig papillary muscle. J Cardiovasc Electrophysiol; 18(10):1086-1094

Left atrial speckle tracking analysis in patients with mitral insufficiency and history of paroxysmal atrial fibrillation

The occurrence of atrial fibrillation (AF), especially in patients with mitral regurgitation (MR), is related to the degree of left atrial (LA) myopathy, remodeling and fibrosis, that are responsible of LA electrical inhomogeneity and abnormal conduction velocities. Speckle tracking echocardiography (STE) has recently enabled the quantification of longitudinal myocardial LA deformation dynamics. Our aim was to investigate by STE the effects of the occurrence of paroxysmal AF on LA myocardial deformation, in a population of patients with asymptomatic chronic MR. We compared two groups of a total of 197 patients with MR: 54 with history of paroxysmal AF and 143 with MR alone. Subgroups were created according to MR degree. Peak atrial longitudinal strain (PALS) was measured in all subjects. Values were obtained by averaging all segments (global PALS), measured in the 4-chamber and 2-chamber views. Compared to the mild MR group (46.1 ± 4.9%), global PALS was lower in moderate MR group (22.1 ± 5.8%) and further reduced in the severe MR group (13.9 ± 4.2%; overall P < 0.0001 by ANOVA, P < 0.05 for all pair-wise comparisons). Besides, in each MR group, patients with history of paroxysmal AF presented a global PALS significantly reduced (overall P < 0.0001 by ANOVA). After multivariate analysis, global PALS was significantly and independently associated with paroxysmal AF. STE enables noninvasive quantification of LA dysfunction due to MR and paroxysmal AF. MR have a major negative impact on LA function. In patients with MR, the history of paroxysmal AF is associated to a further impair of LA myocardial reservoir function.

A-waves in Guillain–Barré syndrome: Correlation with electrophysiological subtypes and antiganglioside antibodies

ObjectiveTo investigate the relationship of A-waves with conventional electrophysiological subtypes of Guillain–Barré syndrome (GBS), as well as with anti-ganglioside antibodies. MethodsThe subjects consisted of 30GBS patients who were classified into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy, and unclassified based on the results of nerve conduction studies. “Abundant A-waves” were defined for the upper-limb nerves (median and ulnar nerves) using receiver–operator characteristic curves. The presence or absence of IgG anti-ganglioside antibodies was also noted. ResultsAbundant A-waves at weeks 3–6 from onset were observed in 64% of the 14 AIDP patients and 0% of 16 non-AIDP patients, and in 60% of 15 antibody-negative patients and 0% of 15 antibody-positive patients. In the earlier period, this relationship was less clear. The correlation between the conventional electrophysiological subtypes and antibodies was present, but was much weaker. ConclusionsAbundant A-waves in GBS after the acute phase were strongly associated with demyelination that was not mediated by antiganglioside antibodies, possibly through the mechanism of proximal re-excitation induced by electrical inhomogeneities due to segmental demyelination. SignificanceAbundant A-waves are promising as a novel reliable marker of demyelination.

Conducting and topographic AFM analysis of Hf-doped and Al-doped Ta 2O 5 films

A conductive atomic force microscopy (C-AFM) has been used to study conductivity and electrical degradation of ultrathin (4 nm) Hf- and Al-doped Ta 2O 5 at the nanometer scale. The hardness testing has been also performed using the force measuring ability of the AFM. Since the size of the analyzed area is very small, features which are not visible by macroscopic tests are observed: extremely low leakage current (~ pA) up to significantly higher than the fields during standard current–voltage measurements; charge trapping/detrapping processes manifesting as current peaks at pre-breakdown voltages. Hf and Al addition improves the local conductivity of Ta 2O 5, provokes modification of the leakage current mechanism, and is effective in extending the potential of pure Ta 2O 5 as a high- k material at the nanoscale. The results point to a decisive role of the type of the dopant on the electrical and mechanical properties of the films and their local response to short term microwave irradiation. Hf-doped Ta 2O 5 exhibits excellent electrical stability and high hardness. Al doping provides more plastic films with large electrical inhomogeneities; the microwave treatment at room temperature is a way to improve these parameters to a level comparable to those of Hf-doped films.

Analysis and Control of the DC Drift in LiNbO3Based Mach–Zehnder Modulators

The drift issue induces slow drifting of the optimum operating point for high efficiency or large nonlinearities in analog optical links, and requires complex control of the offset bias voltage for achieving high extinction ratio in digital optical links. We discuss and analyze the different sources of the drift in commercially LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Mach-Zehnder modulators. The different extrinsic and intrinsic origins are compared in terms of phase shift and the different corresponding orders of magnitude are given, pointing out the predominant role of the intrinsic (dc) drift. We show the large role played by the electrical inhomogeneities at the surface of the LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate by highlighting the link between the time dependence of the dc drift and the electrical conductivity measured at the surface and in the volume of the LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. This allows to propose a solution to the drift issue which consists in the engineering of the electrical conductivity of the lithium niobate substrate.

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Organic solar cells (OSCs) based on polymers and small molecules have seen a tremendous increase in interest during the past few years. Signifi cant progress in this fi eld seeded the prospect for a cost-effective and easy-to-fabricate photovoltaic technology—typical advantages claimed for organic (opto-)electronic devices. Very recently, certifi ed cell effi ciencies in excess of 7% have been reported for polymer based cells. [ 1 ] For large-scale and high-throughput production of OSCs, liquid processing of the functional layers is desirable. Aside from the active organic layers, inter-layers are typically required to facilitate the extraction of the photo-generated charges. Specifi cally, on the anode side, polyethylene dioxythiophene:polystyrenesulfonate (PEDOT:PSS) is regularly used. [ 2 ] However, PEDOT:PSS is burdened with structural and electrical inhomogeneity [ 3,4 ] and has been demonstrated to be an origin of limited device lifetime. [ 5 ] Particularly, the aqueous PEDOT:PSS dispersion and the acidic nature can cause substantial degradation. [6,7 ] Very recently, transition metal-oxides (TMOs) such as molybdenum-, vanadium-, or tungsten-oxide (MoO 3 , V 2 O 5 , and WO 3 ) with high work functions (WFs) of up to 6.9 eV have been shown to be promising alternatives to PEDOT:PSS. [ 8‐11 ] TMOs have also been used as constituents of the connecting architecture in stacked organic light-emitting diodes and organic tandem solar cells. [ 12‐15 ] The unique energetics of these TMOs has so far been predominantly

Current density and state of charge inhomogeneities in Li-ion battery cells with LiFePO4 as cathode material due to temperature gradients

Current density distributions and local state of charge (SoC) differences that are caused by temperature gradients inside actively cooled Li-ion battery cells are discussed and quantified. As an example, a cylindrical Li-ion cell with LiFePO4 as cathode material (LiFePO4-cell) is analyzed in detail both experimentally and by means of spatial electro-thermal co-simulations. The reason for current density inhomogeneities is found to be the local electrochemical impedance varying with temperature in different regions of the jelly roll. For the investigated cell, high power cycling and the resulting temperature gradient additionally cause SoC-gradients inside the jelly roll. The local SoCs inside one cell diverge firstly because of asymmetric current density distributions during charge and discharge inside the cell and secondly because of the temperature dependence of the local open circuit potential. Even after long relaxation periods, the SoC distribution in cycled LiFePO4-cells remains inhomogeneous across the jelly roll as a result of hysteresis in the open circuit voltage. The occurring thermal electrical inhomogeneities are expected to influence local aging differences and thus, global cell aging. Additionally the occurrence of inhomogeneous current flow and SoC-development inside non-uniformly cooled battery packs of parallel connected LiFePO4-cells is measured and discussed.

Electrical stress and strain in lunar regolith simulants

Experiments to entrain dust with electrostatic and fluid-dynamic forces result in particulate clouds of aggregates rather than individual dust grains. This is explained within the framework of Griffith-flaw theory regarding the comminution/breakage of weak solids. Physical and electrical inhomogeneities in powders are equivalent to microcracks in solids insofar as they facilitate failure at stress risers. Electrical charging of powders induces bulk sample stresses similar to mechanical stresses experienced by strong solids, depending on the nature of the charging. A powder mass therefore “breaks” into clumps rather than separating into individual dust particles. This contrasts with the expectation that electrical forces on the Moon will eject a submicron population of dust from the regolith into the exosphere. A lunar regolith will contain physical and electrostatic inhomogeneities similar to those in most charged powders.