Publications by authors named "Mark Kroll"

91 Publications

Computational models for contact current dosimetry at frequencies below 1 MHz.

Med Biol Eng Comput 2021 Jan 2;59(1):107-119. Epub 2020 Dec 2.

Research Center for Bioelectromagnetic Interaction (femu), Institute for Occupational, Social and Environmental Medicine, Uniklinik RWTH Aachen University, Aachen, Germany.

Electric contact currents (CC) can cause muscle contractions, burns, or ventricular fibrillation which may result in life-threatening situations. In vivo studies with CC are rare due to potentially hazardous effects for participants. Cadaver studies are limited to the range of tissue's electrical properties and the utilized probes' size, relative position, and sensitivity. Thus, the general safety standards for protection against CC depend on a limited scientific basis. The aim of this study was therefore to develop an extendable and adaptable validated numerical body model for computational CC dosimetry for frequencies between DC and 1 MHz. Applying the developed model for calculations of the IEC heart current factors (HCF) revealed that in the case of transversal CCs, HCFs are frequency dependent, while for longitudinal CCs, the HCFs seem to be unaffected by frequency. HCFs for current paths from chest or back to hand appear to be underestimated by the International Electrotechnical Commission (IEC 60479-1). Unlike the HCFs provided in IEC 60479-1 for longitudinal current paths, our work predicts the HCFs equal 1.0, possibly due to a previously unappreciated current flow through the blood vessels. However, our results must be investigated by further research in order to make a definitive statement. Contact currents of frequencies from DC up to 100 kHz were conducted through the numerical body model Duke by seven contact electrodes on longitudinal and transversal paths. The resulting induced electric field and current enable the evaluation of the body impedance and the heart current factors for each frequency and current path.
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http://dx.doi.org/10.1007/s11517-020-02284-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7811986PMC
January 2021

Safety of a High-Efficiency Electrical Fence Energizer.

Annu Int Conf IEEE Eng Med Biol Soc 2020 07;2020:5016-5020

Introduction: Our primary goal was to evaluate the performance of a new high-efficiency electric fence energizer unit using resistive load changes. Our secondary goal was to test for compliance with the classical energy limits and the newer charge-based limits for output.

Methods: We tested 4 units of the Nemtek Druid energizer with 2 channels each. We used a wide load-resistance range to cover the worst-case scenario of a barefoot child making a chest contact (400 Ω) up to an adult merely touching the fence (2 kΩ).

Results: The energy output was quite consistent between the 8 sources. Even at the lowest resistance, 400 Ω, the outputs were well below the IEC 60335-2-76 limit of 5 J/pulse. The charge delivered was also quite consistent. Even at the lowest resistance, 400 Ω, the outputs (679 ± 23 μC) were well below the proposed limits of 4 mC for short pulses.

Conclusions: The high-efficiency electric fence energizers satisfied all relevant safety limits. Charge, energy, voltage, and current outputs were consistent between channels and units.
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http://dx.doi.org/10.1109/EMBC44109.2020.9176351DOI Listing
July 2020

Electrical weapons and rhabdomyolysis.

Forensic Sci Med Pathol 2021 Mar 18;17(1):58-63. Epub 2020 Sep 18.

Biomedical Engineering, Texas A&M University, College Station, TX, USA.

It has been suggested that an application of a conducted electrical weapon (CEW) might cause muscle injury such as rhabdomyolysis and an acute inflammatory response. We explored this hypothesis by testing the effects of electrical weapons on circulating markers of inflammation and muscle damage. In a prospective study, 29 volunteers received a full-trunk 5-s TASER® X26(E) CEW exposure. Venous blood samples were taken before, 5 min after, and at 24 h following the discharge. We tested for changes in serum levels of C-reactive protein (CRP), alkaline phosphatase (ALP), myoglobin, albumin, globulin, albumin/globulin ratio, aspartate and alanine aminotransferase, creatine kinase, total protein, bilirubin, and lactic acid dehydrogenase. Uncorrected CRP and myoglobin levels were lower in the immediate post exposure period (CRP levels 1.44 ± 1.39 v 1.43 ± 1.32 mg/L; p = 0.046 and myoglobin 36.8 ± 11.9 v 36.1 ± 13.9 μg/L; p = 0.0019) but these changes were not significant after correction for multiple comparisons. There were no changes in other biomarkers. At 24 h, CRP levels had decreased by 30% to 1.01 ± 0.80 mg/L (p = 0.001 from baseline). ALP was unchanged immediately after the CEW application but was reduced by 5% from baseline (66.2 ± 16.1 to 62.7 ± 16.1 IU/L; p = 0.0003) at 24 h. No other biomarkers were different from baseline at 24 h. A full-trunk electrical weapon exposure did not lead to clinically significant changes in the acute phase protein levels or changes in measures of muscle cellular injury. We found no biomarker evidence of rhabdomyolysis.
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http://dx.doi.org/10.1007/s12024-020-00311-7DOI Listing
March 2021

Electrical weapons, hematocytes, and ischemic cardiovascular accidents.

J Forensic Leg Med 2020 Jul 29;73:101990. Epub 2020 May 29.

Biomedical Engineering, Texas A&M University, USA.

Background: There have been case reports following the use of a conducted electrical weapon (CEW) suggesting that these devices might affect coagulation or thrombosis in at-risk individuals. The aim of this manuscript therefore is firstly to explore this hypothesis by reviewing each of these cases and secondly to report the results of a prospective study exploring a priori the effects of electrical weapons on hematocytes in a group of human volunteers.

Methods: First, we systematically reviewed all cases of adverse outcomes following CEW discharge that could be due to an effect on coagulation or thrombosis, with particular focus on the clinical scenario and its relationship with the weapon discharge. Second, we assessed hematocyte levels in venous blood from 29 volunteers before, 5 min after, and 24 h after receiving a full-trunk 5-s TASER® X26(E) CEW exposure.

Results: Following extensive review of the literature, we found 3 relevant case reports of possible vascular thromboembolic clinical events after CEW exposure, specifically a case of ischemic stroke, and 2 cases of ST-segment elevation myocardial infarctions. Review of these published cases failed to establish a plausible linkage to the CEW beyond a temporal association with significant emotional and physiological stress from a violent struggle. Our prospective study of biomarker change following CEW discharge revealed acutely increased values for WBC (white blood cells), specifically lymphocytes and monocytes, and a raised platelet count. Neutrophil levels decreased as a percentage of WBC. While these changes were statistically significant at 5 min, all results remained within established reference ranges. At 24 h, all values had returned to baseline except total WBC which decreased to slightly below baseline but was still within the normal reference range.

Conclusions: A review of clinical cases, of ischemic or thrombotic events revealed no direct association with the CEW discharge. A full-trunk electrical weapon exposure did not lead to hematocyte changes beyond normal clinically expected variations in similar acute response scenarios. The case report and biomarker data do not support the hypothesis that a CEW discharge is associated with changes likely to promote coagulation or thrombus formation.
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http://dx.doi.org/10.1016/j.jflm.2020.101990DOI Listing
July 2020

Impedance in the Diagnosis of Lead Malfunction.

Circ Arrhythm Electrophysiol 2020 02 27;13(2):e008092. Epub 2020 Jan 27.

Division of Cardiology, VCU School of Medicine, Richmond, VA (J.N.K., K.A.E.).

Impedance is the ratio of voltage to current in an electrical circuit. Cardiovascular implantable electronic devices measure impedance to assess the structural integrity electrical performance of leads, typically using subthreshold pulses. We review determinants of impedance, how it is measured, variation in clinically measured pacing and high-voltage impedance and impedance trends as a diagnostic for lead failure and lead-device connection problems. We consider the differential diagnosis of abnormal impedance and the approach to the challenging problem of a single, abnormal impedance measurement. Present impedance provides a specific but insensitive diagnostic. For pacing circuits, we review the complementary roles of impedance and more sensitive oversensing diagnostics. Shock circuits lack a sensitive diagnostic. This deficiency is particularly important for insulation breaches, which may go undetected and present with short circuits during therapeutic shocks. We consider new methods for measuring impedance that may increase sensitivity for insulation breaches.
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http://dx.doi.org/10.1161/CIRCEP.119.008092DOI Listing
February 2020

Dosimetry for Ventricular Fibrillation Risk with Short Electrical Pulses: History and Future.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:1788-1794

Electrical safety limits for unidirectional pulses with short durations are increasingly important due to the proliferation of electric-car and factory energy storage systems with potentially dangerous voltages. Electrocution by a short-duration direct-current pulse is not understood as well as that by alternating current and the data are limited. The primary international guidance comes from IEC 60479-2 section 11.

Methods: We have analyzed the dosimetry for short pulse safety limits based on a fuller understanding of the scientific principles involved and human data. Implantable defibrillators have been tested by externally delivering short-duration pulses giving us human data which we analyze for this paper.

Results: The present IEC current limit (60479-2:11) for short pulse durations is based on an exponent of -0.68 in the equation I = d, (d being pulse width), while the correct exponent should be -1.0 given the constant charge for the VF threshold of short pulses. We also propose a baseline charge value based on the human data.

Conclusions: Charge-based VF thresholds give the correct dosimetry for short-duration pulses. Results from this paper should be considered in support of revising the IEC 60479-2 standard section 11.
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http://dx.doi.org/10.1109/EMBC.2019.8857787DOI Listing
July 2019

High Impedance Electrical Accidents: Importance of Source and Subject Impedance.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:1769-1775

In most cases, the diagnosis of an electrical injury or electrocution is straightforward. However, there is a necessity for much closer analysis in many cases. There exist sophisticated electrical safety standards that predict outcomes for shocks of various currents applied to different parts of the body. Unfortunately, the actual current is almost never known in an accident investigation. A common source of errors is the assumption that the source (including the return) has zero impedance. Another surprisingly common problem is the erroneous assumption that the body current is equal to the source current capability.

Methods: We used the following methodology for analyzing such cases: (1) Determine body pathway, (2) Estimate body pathway impedance, (3) Determine source voltage, (4) Determine source impedance, (5) Calculate delivered current using total pathway impedance, and (6) Ignore available current as it is largely confounding in most cases.

Results: We analyzed 6 difficult cases using the above methodology. This includes 2 subtle situations involving pairs of matched case-control subjects where a subject was electrocuted while his work partner was not.

Conclusions: Careful calculations of the amplitude and duration of the shock is required for understanding the limits and potential causation of such electrical injury. This requires the determination of both the source and body pathway impedance. Available current is usually irrelevant and overemphasized.
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http://dx.doi.org/10.1109/EMBC.2019.8857037DOI Listing
July 2019

Ascending Defibrillation Waveform Significantly Reduces Myocardial Morphological Damage and Injury Current.

JACC Clin Electrophysiol 2019 07 29;5(7):854-862. Epub 2019 May 29.

Department of Biomedical Engineering, University of Minnesota Crystal Bay, Minnesota; Department of Biomedical Engineering, California Polytechnical University, San Luis Obispo, California. Electronic address:

Objectives: This study tested the hypothesis that a biphasic defibrillation waveform with an ascending first phase (ASC) causes less myocardial damage by pathology and injury current than a standard biphasic truncated exponential (BTE) waveform in a swine model.

Background: Although lifesaving, defibrillation shocks have significant iatrogenic effects that reduce their benefit for patient survival.

Methods: An ASC waveform with an 8-ms linear ramp followed by an additional positive 0.5-ms decaying portion with amplitudes of 20 J (ASC 20J) and 25 J (ASC 25J) was used. The control was a 25-J BTE conventional waveform (BTE 25J) RESULTS: The ASC 20J and ASC 25J shocks were both successful in 6 of 6 pigs, but the BTE 25J was successful in only 6 of 14 pigs (p < 0.05). Post-shock ST-segment elevation (injury current) in the right ventricular electrode was significantly greater with BTE 25J than with ASC 20J and ASC 25J. With a blinded pathology reading, hemorrhage, inflammation, thrombi, and necrosis 24 h post-shock were significantly greater with BTE 25J than with ASC 20J and ASC 25J. Troponin levels were also markedly lower at 3, 4, 5, and 6 h post-shock.

Conclusions: Defibrillation shocks cause electrophysiological, histological, and biochemical signs of myocardial damage and necrosis. These signs of damage are markedly less for an ASC waveform than for a conventional BTE waveform.
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http://dx.doi.org/10.1016/j.jacep.2019.04.006DOI Listing
July 2019

Why low-voltage shock impedance measurements fail to reliably detect insulation breaches in transvenous defibrillation leads.

Heart Rhythm 2019 11 21;16(11):1729-1737. Epub 2019 May 21.

University of Minnesota, Minneapolis, Minnesota.

Background: Implantable cardioverter-defibrillators (ICDs) use low-voltage measures of shock impedance (LVSZ) to monitor integrity of leads.

Objective: To determine the separation distance between conductors required for LVSZ to detect insulation breaches that produce short circuits during shocks, causing failed defibrillation.

Methods: We simulated in-pocket insulation breaches between the ICD generator (CAN) and cables to the distal coil of 10 leads from 2 manufacturers. The ICD and lead were placed in an electrolyte bath. Polystyrene sheets were used to control the breach-CAN separation. We determined both the maximum lead-CAN separation for shorts during 800 V shocks and the shock strength at which shorts occurred for a fixed separation. We also calculated breach impedance and measured it using a low-voltage instrument.

Results: The maximum breach-CAN separation for shorting was 350-500 μm for all leads. The minimum shock strength to short varied from 650 to 771 V (24-32 J). LVSZ never triggered a warning, even with no separation between the cable's inner insulation and the CAN. Using low-voltage pulses, breach impedance was measured at approximately 500-1000 Ω.

Conclusion: LVSZ is insensitive to insulation breaches that cause life-threatening, shorted shocks. The explanation likely relates to impedance differences between ionic conduction during LVSZ measurements and free-electron conduction in plasma discharges.
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http://dx.doi.org/10.1016/j.hrthm.2019.05.021DOI Listing
November 2019

Perceived Electrical Injury: Misleading Symptomology Due to Multisensory Stimuli.

J Emerg Med 2019 05 28;56(5):e71-e79. Epub 2019 Feb 28.

University of Queensland, St. Lucia, Queensland, Australia.

Background: An electrical accident victim's recollection is often distorted by Bayesian inference in multisensory integration. For example, hearing the sound and seeing the bright flash of an electrical arc can create the false impression that someone had experienced an electrical shock. These subjects will often present to an emergency department seeking either treatment or reassurance.

Case Reports: We present seven cases in which the subjects were startled by an electrical shock (real or perceived) and injury was reported. Calculations of the current and path were used to allocate causality between the shock and a history of chronic disease or previous trauma. In all seven cases, our analysis suggests that no current was passed through the body. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Symptomology seen as corroborating may actually be confounding. Witness and survivor descriptions of electrical shocks are fraught with subjectivity and misunderstanding. Available current is usually irrelevant and overemphasized, such as stress on a 100-ampere welding source, which is orders of magnitude beyond lethal limits. History can also be biased for a number of reasons. Bayesian inference in multisensory perception can lead to a subject sincerely believing they had experienced an electrical shock. Determination of the current pathway and calculations of the amplitude and duration of the shock can be critical for understanding the limits and potential causation of electrical injury.
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http://dx.doi.org/10.1016/j.jemermed.2019.01.013DOI Listing
May 2019

Applied Force During Prone Restraint: Is Officer Weight a Factor?

Am J Forensic Med Pathol 2019 Mar;40(1):1-7

Valdosta State University, Valdosta, GA.

Introduction: It has been suggested that law enforcement officer (LEO) weight on the backs of prone subjects may cause asphyxia.

Methods: Law enforcement officers used their agency-trained "local" single- and double-knee techniques, the "Wisconsin" 3-Point Ground Stabilization, and the Human Factor Research Group Inc single-knee tactical handcuffing techniques, and the weight force was measured.

Results: Forty-one LEOs (36 men, 5 women) participated, aged 38.4 ± 8.3 years, and weighing 96.2 ± 19.4 kg. The double-knee technique transmitted more weight than single knee (P < 0.0001). Wisconsin technique force was lower than other single-knee techniques (P < 0.0001). Double-knee weight was 23.3 kg plus 24% of LEO's body weight. Mean values for local and Human Factor Research Group Inc single-knee were 30.9 and 32.9 kg, respectively. The Wisconsin single knee weight force was given by 15.4 kg plus 9.5 kg for a male.

Conclusions: A double-knee technique applies more weight force than single-knee techniques. The Wisconsin single-knee technique provides the least weight force of single-knee techniques. Law enforcement officer body weight is irrelevant to prone-force weight with single-knee techniques. With double-knee restraint, it has a modest influence. Our data do not support the hypothesis of restraint asphyxia.
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http://dx.doi.org/10.1097/PAF.0000000000000457DOI Listing
March 2019

Electrical Weapon Charge Delivery With Arcing.

Annu Int Conf IEEE Eng Med Biol Soc 2018 Jul;2018:2234-2239

Introduction: Human electronic control with the Conducted Electrical Weapon (CEW) has gained widespread acceptance as the preferred law enforcement force option technology due to its dramatic injury and fatal shooting reduction. However, with bulky or baggy clothing, a CEW probe may fail to make direct skin contact and thus arcing is critical to complete the circuit. The goal of the study was to evaluate the ability of modern CEWs to deliver their pulse charges across typical required arcing distances.

Methods: Popular TASER CEW models X26E (openloop output), and the X2 and X26P (with closed-loop outputs) were activated using a cartridge connected to a custom polymer air-gap fixture. For each model 5 units were tested. The raw and normalized charge delivery were evaluated according to ANSI-CPLSO-17.

Results: All 5 units of each model satisfied ANSICPLSO-17 even at maximum arcing length. The X26P CEW had the greatest arcing gap capability.

Conclusions: The stabilized closed-loop charge output feedback of modern electrical weapons (X2 and X26P CEWs) provides a significantly improved output consistency under arcing conditions. With arc lengths of 10-20 mm per probe, the X2 CEW normalized output charge exceeds that of some units of the older higher output X26E CEW model.
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http://dx.doi.org/10.1109/EMBC.2018.8512753DOI Listing
July 2018

Perceived electrical shock and Bayesian inference with multisensory stimuli.

Am J Emerg Med 2019 03 21;37(3):547-548. Epub 2018 Jul 21.

University of Queensland, Australia.

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http://dx.doi.org/10.1016/j.ajem.2018.07.042DOI Listing
March 2019

Electrical weapons and excited delirium: shocks, stress, and serum serotonin.

Forensic Sci Med Pathol 2018 12 11;14(4):478-483. Epub 2018 Aug 11.

Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA.

It has been suggested that a CEW (conducted electrical weapon) exposure could elicit a stress response that could cause ExDS (excited delirium syndrome). There are some parallels between the signs of ExDS and serotonin syndrome (SS). Electroconvulsive therapy raises serotonin levels and therefore provides a plausible link between CEW applications and elevated serotonin levels. This study was designed to determine whether a CEW exposure elevates serum serotonin. A total of 31 police academy cadets were exposed to a very broad-spread 5-s CEW stimulus from a TASER brand X26 CEW. Blood was drawn before and after the exposure and at 24 h post exposure to measure serum serotonin levels. Lactic acid and cortisol levels were also compared. Median serum serotonin levels were 30 IQR (21,46), 36 IQR (22,50), and 32 IQR (21,45) ng/mL before exposure, after exposure, and 24 h after exposure (NS by pooled comparisons). The increase from baseline to post-test serotonin (∆ median = +6, ∆ mean = +2.7) ng/mL was not significant by a paired T-test (p = .29) but was significant by the Wilcoxon signed-rank test (p = .037). The increase to post-test log serotonin was not significant by a paired T-test (p = .13) but was significant by the Wilcoxon test (p = .049). All serotonin levels remained within the normal reference range of 0-200 ng/mL. Post-hoc analysis demonstrated that the study was powered to detect a ½ SD change, in log serotonin, with a 90% likelihood. With a very-broad electrode spread, CEW exposure did not significantly raise serum serotonin levels.
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http://dx.doi.org/10.1007/s12024-018-0005-8DOI Listing
December 2018

Cardiac and skeletal muscle effects of electrical weapons : A review of human and animal studies.

Forensic Sci Med Pathol 2018 09 28;14(3):358-366. Epub 2018 Jun 28.

Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.

Conducted Electrical Weapons (CEWs) are being used as the preferred non-lethal force option for police and special forces worldwide. This new technology challenges an exposed opponent similarly to the way they would be challenged by physical exercise combined with emotional stress. While adrenergic and metabolic effects have been meta-analyzed and reviewed, there has been no systematic review of the effects of CEWs on skeletal and cardiac muscle. A systematic and careful search of the MedLine database was performed to find publications describing pathophysiological cardiac and skeletal muscle effects of CEWs. For skeletal muscle effects, we analyzed all publications providing changes in creatine kinase, myoglobin and potassium. For cardiac effects, we analyzed reported troponin changes and arrhythmias related to short dart-to-heart-distances. Conducted electrical weapons satisfy all relevant electrical safety standards and there are, to date, no proven electrocution incidents caused by CEWs. A potential cardiovascular risk has been recognized by some of the experimental animal data. The effects on the heart appear to be limited to instances when there is a short dart-to-heart-distance. The effect on the skeletal muscle system appears to be negligible. A responsible use of a CEW on a healthy adult, within the guidelines proposed by the manufacturer, does not imply a significant health risk for that healthy adult.
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http://dx.doi.org/10.1007/s12024-018-9997-3DOI Listing
September 2018

Eye injury from electrical weapon probes: Mechanisms and treatment.

Am J Emerg Med 2019 03 2;37(3):427-432. Epub 2018 Jun 2.

School of Criminal Justice, Texas State University, San Marcos, TX, United States.

Purpose: While generally reducing morbidity and mortality, TASER® electrical weapons have risks associated with their usage, including burn injuries and head and cervical trauma associated with uncontrolled falls. The primary non-fatal complications appear to be significant eye injury but no analysis of the mechanisms or suggested treatments has been published.

Methods: We used a biomechanical model to predict the risk of eye injury as a function of distance from the weapon muzzle to the eye. We compared our model results to recently published epidemiological findings. We also describe the typical presentation and suggest treatment options.

Results: The globe rupture model predicted that a globe rupture can be expected (50% risk) when the eye is within 6 m of the muzzle and decreases rapidly beyond that. This critical distance is 9 m for lens and retinal damage which is approximately the range of the most common probe cartridges. Beyond 9 m, hyphema is expected along with a perforation by the dart portion of the probe. Our prediction of globe rupture out to 6 m (out of a typical range of 9 m) is consistent with the published risk of enucleation or unilateral blindness being 69 ± 18%, with an eye penetration.

Conclusions: Significant eye injury is expected from a penetration by an electrical weapon probe at close range. The risk decreases rapidly at extended distances from the muzzle. Not all penetrating globe injuries from electrical weapon probes will result in blindness.
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http://dx.doi.org/10.1016/j.ajem.2018.06.004DOI Listing
March 2019

Authorship identification of documents with high content similarity.

Scientometrics 2018;115(1):223-237. Epub 2018 Feb 2.

Know-Center GmbH, Inffeldgasse 13, Graz, Austria.

The goal of our work is inspired by the task of associating segments of text to their real authors. In this work, we focus on analyzing the way humans judge different writing styles. This analysis can help to better understand this process and to thus simulate/ mimic such behavior accordingly. Unlike the majority of the work done in this field (i.e. authorship attribution, plagiarism detection, etc.) which uses content features, we focus only on the stylometric, i.e. content-agnostic, characteristics of authors. Therefore, we conducted two pilot studies to determine, if humans can identify authorship among documents with high content similarity. The first was a quantitative experiment involving crowd-sourcing, while the second was a qualitative one executed by the authors of this paper. Both studies confirmed that this task is quite challenging. To gain a better understanding of how humans tackle such a problem, we conducted an exploratory data analysis on the results of the studies. In the first experiment, we compared the decisions against content features and stylometric features. While in the second, the evaluators described the process and the features on which their judgment was based. The findings of our detailed analysis could (1) help to improve algorithms such as automatic authorship attribution as well as plagiarism detection, (2) assist forensic experts or linguists to create profiles of writers, (3) support intelligence applications to analyze aggressive and threatening messages and (4) help editor conformity by adhering to, for instance, journal specific writing style.
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http://dx.doi.org/10.1007/s11192-018-2661-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5838116PMC
February 2018

Eye injuries from electrical weapon probes: Incidents, prevalence, and legal implications.

J Forensic Leg Med 2018 Apr 14;55:52-57. Epub 2018 Feb 14.

School of Criminal Justice, Texas State University, San Marcos, TX, United States.

Purpose: While generally reducing morbidity and mortality, electrical weapons have risks associated with their usage, including burn injuries and trauma associated with uncontrolled fall impacts. However, the prevalence of significant eye injury has not been investigated.

Methods: We searched for incidents of penetrating eye injury from TASER conducted electrical weapon (CEW) probes via open source media, litigation filings, and a survey of CEW law-enforcement master instructors.

Results: We report 20 previously-unpublished cases of penetrating eye injury from electrical weapon probes in law-enforcement field uses. Together with the 8 previously published cases, there are a total of 28 cases out of 3.44 million field uses, giving a demonstrated CEW field-use risk of penetrating eye injury of approximately 1:123 000. Confidence limits [85 000, 178 000] by Wilson score interval. There have been 18 cases of total unilateral blindness or enucleation. We also present legal decisions on this topic.

Conclusions: The use of electrical weapons presents a rare but real risk of total or partial unilateral blindness from electrical weapon probes. Catastrophic eye injuries appear to be the dominant non-fatal complication of electronic control.
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http://dx.doi.org/10.1016/j.jflm.2018.02.013DOI Listing
April 2018

New conducted electrical weapons: Thoracic cage shielding effects.

Annu Int Conf IEEE Eng Med Biol Soc 2017 Jul;2017:2191-2196

Introduction: The TASER conducted electrical weapon (CEW) delivers electrical pulses that can temporarily incapacitate subjects. For existing CEW models, we have previously presented the distribution of currents in tissues posterior to the sternum and their likelihood of triggering cardiac arrhythmias. New models, the eXperimental Rotating-Field (XRF) waveform CEW (in development) and the X2 CEW (released) have not been investigated. Both the XRF and X2 CEWs target a precise amount of delivered charge per pulse, 64 μC and 62 μC, respectively. The goal of this study was to numerically model the thoracic cage attenuation of currents and electric fields delivered by the new CEWs and to find whether the heart is shielded from the induction of any dangerous arrhythmias.

Methods And Results: Finite element modeling (FEM) was used to approximate the current density and electric field strength in tissues around the thoracic cage. FEM boundary conditions were set to correspond to output waveforms of the new CEWs, the XRF and the X2. We analyzed a CEW dart deployment scenario that had both darts located over the anterior aspect of the sternum. We found that the sternum and thoracic cage provided significant attenuation of currents and electrical fields.

Conclusion: The sternum and the thoracic cage significantly attenuated currents and electric fields delivered by XRF and X2 CEWs. These tissues `shielded' the heart against potentially dangerous cardiac arrhythmias. The shorter durations and reduced amount of charged delivered by the XRF and the X2 CEWs resulted in increased cardiac safety margins.
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http://dx.doi.org/10.1109/EMBC.2017.8037289DOI Listing
July 2017

New conducted electrical weapons: Electrical safety relative to relevant standards.

Annu Int Conf IEEE Eng Med Biol Soc 2017 Jul;2017:2185-2190

Introduction: We have previously published about TASER conducted electrical weapons (CEW) compliance with international standards. CEWs deliver electrical pulses that can inhibit a person's neuromuscular control or temporarily incapacitate. An eXperimental Rotating-Field (XRF) waveform CEW and the X2 CEW are new 2-shot electrical weapon models designed to target a precise amount of delivered charge per pulse. They both can deploy 1 or 2 dart pairs, delivered by 2 separate cartridges. Additionally, the XRF controls delivery of incapacitating pulses over 4 field vectors, in a rotating sequence. As in our previous study, we were motivated by the need to understand the cardiac safety profile of these new CEWs. The goal of this paper is to analyze the nominal electrical outputs of TASER XRF and X2 CEWs in reference to provisions of all relevant international standards that specify safety requirements for electrical medical devices and electrical fences. Although these standards do not specifically mention CEWs, they are the closest electrical safety standards and hence give very relevant guidance.

Methods: The outputs of several TASER XRF and X2 CEWs were measured under normal operating conditions. The measurements were compared against manufacturer specifications. CEWs electrical output parameters were reviewed against relevant safety requirements of UL 69, IEC 60335-2-76 Ed 2.1, IEC 60479-1, IEC 60479-2, AS/NZS 60479.1, AS/NZS 60479.2, IEC 60601-1 and BS EN 60601-1.

Results And Conclusion: Our study confirmed that the nominal electrical outputs of TASER XRF and X2 CEWs lie within safety bounds specified by relevant standards.
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http://dx.doi.org/10.1109/EMBC.2017.8037288DOI Listing
July 2017

New conducted electrical weapons: Finite element modeling of safety margins.

Annu Int Conf IEEE Eng Med Biol Soc 2017 Jul;2017:2170-2176

Introduction-We have previously published on the ventricular fibrillation (VF) risk with TASER X26 conducted electrical weapon (CEW). Our risk model accounted for realistic body mass index distributions, modeled the effects of partial or oblique dart penetration, and used epidemiological CEW statistics. As new CEWs have become available to law enforcement, their cardiac safety profile was not quantified. Therefore, we applied our VF probability model to evaluate their cardiac risk. Methods and Results-An eXperimental Rotating-Field (XRF) waveform CEW and the X2 CEW are new 2-shot electrical weapon models designed to target a precise amount of delivered charge per pulse, 64 μC and 62 μC, respectively. They can deploy 1 or 2 probe pairs, delivered by 2 separate cartridges. New Smart Probes (SP), which carry 11.5 mm long CEW darts, can be used with XRF and X2 CEWs. Finite element modeling (FEM) was used to approximate the current and charge densities produced by XRF and X2 CEWs in tissues located in the vicinity of darts, including accounting for the effects of fat, anisotropic skeletal muscles, sternum, ribs, and lungs. Using our previous cardiac risk probabilistic model, the new XRF and X2 CEWs operated with 11.5 mm SPs, had an estimated overall theoretical VF risk of less than 1 in 1 300 000 and 1 in 1 490 000 cases, respectively. We also found that the XRF and X2 CEWs had increased cardiac safety margins with respect to those previously reported for the X26 CEWs when all three CEW models were operated with 9 mm CEW darts. Lastly, the cardiac risk of these new CEWs (<; 0.76 ppm) was found to be much lower than reported levels of CEW non-cardiac fatal injuries (e.g. falls and burns, > 7.2 ppm). Conclusions-While not risk-free, the new TASER XRF and X2 CEWs offer increased cardiac safety margins and extremely low cardiac risk profiles.
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http://dx.doi.org/10.1109/EMBC.2017.8037285DOI Listing
July 2017

Fatal and non-fatal burn injuries with electrical weapons and explosive fumes.

J Forensic Leg Med 2017 Aug 20;50:6-11. Epub 2017 Jun 20.

School of Criminal Justice, Texas State University, San Marcos, TX, USA.

Introduction: While generally reducing morbidity and mortality, electrical weapons have risks associated with their usage, including eye injuries and falls. With the presence of explosive fumes or fuels there also exists the possibility of burn injury.

Methods: We searched for cases of fatal and non-fatal major burns with TASER electrical weapon usage where there was a possibility that the weapon ignited the explosion.

Results: We confirmed 6 cases of fatal burn injury and 4 cases of major non-fatal burns out of 3.17 million field uses. The mean age was 35.5 ± 9.7 years which is consistent with the typical arrest-related death. Moderate, minor, and noninjurious fires - typically due to a cigarette lighters in a pocket, petrol, recreational inhalants, or body spray were also noted.

Conclusions: The use of electrical weapons presents a small but real risk of death from fatal burn injury. It also presents a small risk of major non-fatal burn injury. The ignition of petrol fumes dominates these cases of major fatal and nonfatal burns.
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http://dx.doi.org/10.1016/j.jflm.2017.06.001DOI Listing
August 2017

Acute forces required for fatal compression asphyxia: A biomechanical model and historical comparisons.

Med Sci Law 2017 Apr 3;57(2):61-68. Epub 2017 Apr 3.

5 California Polytechnic University, San Luis Obispo, USA.

Background Fatalities from acute compression have been reported with soft-drink vending machine tipping, motor vehicle accidents, and trench cave-ins. A major mechanism of such deaths is flail chest but the amount of force required is unclear. Between the range of a safe static chest compression force of 1000 N (102 kg with earth gravity) and a lethal dynamic force of 10-20 kN (falling 450 kg vending machines), there are limited quantitative human data on the force required to cause flail chest, which is a major correlate of acute fatal compression asphyxia. Methods We modeled flail chest as bilateral fractures of six adjacent ribs. The static and dynamic forces required to cause such a ribcage failure were estimated using a biomechanical model of the thorax. The results were then compared with published historical records of judicial "pressing," vending machine fatalities, and automobile safety cadaver testing. Results and conclusion The modeling results suggest that an adult male requires 2550 ± 250 N of chest-applied distributed static force (260 ± 26 kg with earth gravity) or 4050 ± 320 N of dynamic force to cause flail chest from short-term chest compression.
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http://dx.doi.org/10.1177/0025802417695711DOI Listing
April 2017

Current distribution in tissues with conducted electrical weapons operated in drive-stun mode.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:5241-5245

Introduction: The TASER® conducted electrical weapon (CEW) is best known for delivering electrical pulses that can temporarily incapacitate subjects by overriding normal motor control. The alternative drive-stun mode is less understood and the goal of this paper is to analyze the distribution of currents in tissues when the CEW is operated in this mode.

Methods And Results: Finite element modeling (FEM) was used to approximate current density in tissues with boundary electrical sources placed 40 mm apart. This separation was equivalent to the distance between drive-stun mode TASER X26™, X26P, X2 CEW electrodes located on the device itself and between those located on the expended CEW cartridge. The FEMs estimated the amount of current flowing through various body tissues located underneath the electrodes. The FEM simulated the attenuating effects of both a thin and of a normal layer of fat. The resulting current density distributions were used to compute the residual amount of current flowing through deeper layers of tissue. Numerical modeling estimated that the skin, fat and skeletal muscle layers passed at least 86% or 91% of total CEW current, assuming a thin or normal fat layer thickness, respectively. The current density and electric field strength only exceeded thresholds which have increased probability for ventricular fibrillation (VFTJ), or for cardiac capture (CCTE), in the skin and the subdermal fat layers.

Conclusion: The fat layer provided significant attenuation of drive-stun CEW currents. Beyond the skeletal muscle layer, only fractional amounts of the total CEW current were estimated to flow. The regions presenting risk for VF induction or for cardiac capture were well away from the typical heart depth.
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http://dx.doi.org/10.1109/EMBC.2016.7591909DOI Listing
August 2016

Validity of the small swine model for human electrical safety risks.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:2343-2348

Small swine are the most common model now used for electrical safety studies. Because of the significant anatomical and electrophysiological differences and the effect of animal size on the ventricular fibrillation (VF) threshold, there are concerns that these differences may exaggerate the risks of electrical devices to humans. We chose, as an illustrative and relevant example, swine studies of the TASER® conducted electrical weapon (CEW) as it has numerous published VF studies. We reviewed the published electrical swine safety studies for CEWs and compared them to finite element modeling studies, electrical safety standards, and epidemiological experience from field usage. We also compared the body weights of the swine to those of law enforcement arrest-related deaths. Studies of small swine exaggerate the risks of CEWs to humans. This conclusion may be extrapolated to suggest that the use of small swine for electrical safety studies should be questioned in general.
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http://dx.doi.org/10.1109/EMBC.2016.7591200DOI Listing
August 2016

Defibrillation thresholds with right pectoral implantable cardioverter defibrillators and impact of waveform tuning (the Tilt and Tune trial).

Europace 2017 Nov;19(11):1810-1817

St. Jude Medical, Sylmar, CA, USA.

Aims: Assess defibrillation thresholds (DFTs) with right active pectoral implantable cardioverter defibrillator (RICDs). Defibrillation thresholds in patients receiving RICDs are regarded as 'high' and potentially improved by waveform optimization (tuning). However, this has not been systematically tested.

Methods And Results: Patients receiving RICDs [Single chamber (VVI) = 16, DDD = 32, cardiac resynchronization therapy (CRT) = 43] were randomized to either 50/50% fixed tilt (FT) or tuned waveform (3.5 ms time constant based). Defibrillation threshold was tested with a binary search protocol in single coil anodal configuration. Then RICDs were compared with left-sided placements. Baseline patient characteristics in FT (n = 54) and tuned (n = 37) were similar (65 ± 14 years, 71% male, Left ventricular ejection fraction 31 ± 13%; and proportions VVI/DDD/Cardiac resynchronization therapy defibrillator). Tuning reduced Phase 1 by 15% and Phase 2 by 45%. For FT vs. tuned: high voltage impedance was 61.9 ± 13.2 vs. 64.5 ± 12.7 Ω (P = 0.33) and mean DFT 14.2 ± 8.8 vs. 14.9 ± 9.2 J (P = 0.8). When high voltage impedance was >62 Ω (mean 73.6 ± 8.6 Ω), DFT was identical [FT 13.0 ± 7.9 J vs. tuned 12.0 ± 5.9 J (P= 0.7)]. Defibrillation thresholds exceeded 20 J (600 V) in >20% of patients [FT 11/54 (20.4%) vs. tuned 12/37 (32%) patients]. Defibrillation threshold with RICD was greater and exhibited wider dispersion compared with left ICDs (n = 54) under similar conditions.

Conclusion: This first randomized trial investigating DFTs with right ICDs confirms relatively higher DFTs with RICDs than reported for left pectoral ICDs. However, DFTs were generally unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% tilt waveform. Implant testing may be preferred with RICDs.

Clinical Trial Number: NCT00873691.
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http://dx.doi.org/10.1093/europace/euw306DOI Listing
November 2017

Infection Risk From Conducted Electrical Weapon Probes: What Do We Know?

J Forensic Sci 2016 Nov 18;61(6):1556-1562. Epub 2016 Jul 18.

Advanced Cardiac Therapeutics, Inc., San Jose, CA.

Concern has been raised over the infection risk of the TASER electrical weapon since the probes penetrate the skin. The manufacturing process produces unsterilized probes with a 5% rate of Staphylococcus aureus contamination. Voluntary recipients (n = 208) of probe exposures were surveyed and there were no self-observations of infection. With over 3.3 million probe landings, there have been 10 case reports of penetrations of sensitive tissue with no reported infections. The electrical field was modeled and found that the electrical pulses generate a field of over 1200 V/mm on the dart portion. This is sufficient to sterilize the dart via electroporation. Electrical weapon probes appear to have a very low (possibly zero) rate of infection. The factors leading to this low infection rate appear to be a manufacturing process producing a low rate of bacterial contamination and the pulses sterilizing the dart via electroporation.
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http://dx.doi.org/10.1111/1556-4029.13148DOI Listing
November 2016

Fatal traumatic brain injury with electrical weapon falls.

J Forensic Leg Med 2016 Oct 5;43:12-19. Epub 2016 Jul 5.

School of Criminal Justice, Texas State University, San Marcos, TX, USA. Electronic address:

Introduction: While generally reducing morbidity and mortality, electrical weapons have risks associated with their usage, including eye injuries and falls. With sufficient probe spread, an uncontrolled fall to the ground typically occurs along with the possibility of a fatal brain injury.

Methods: We analyzed possible risk factors including running and elevated surfaces with established head-injury criteria to estimate the risk of brain injury. We searched for cases of arrest-related or in-custody death, with TASER(®) electrical weapon usage where fall-induced injuries might have contributed to the death. We found 24 cases meeting our initial inclusion criteria of a fatal fall involving electronic control. We then excluded 5 cases as intentional jumps, leaving 19 cases of forced falls. Autopsy reports and other records were analyzed to determine which of these deaths were from brain injury caused by the fall.

Results: We found 16 probable cases of fatal brain injuries induced by electronic control from electrical weapons. Out of 3 million field uses, this gives a risk of 5.3 ± 2.6 PPM which is higher than the theoretical risk of electrocution. The mean age was 46 ± 14 years which is significantly greater that the age of the typical ARD (36 ± 10). Probe shots to the subject's back may present a higher risk of a fatal fall.

Conclusions: The use of electronic control presents a small but real risk of death from fatal traumatic brain injury. Increased age represents an independent risk factor for such fatalities.
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http://dx.doi.org/10.1016/j.jflm.2016.07.001DOI Listing
October 2016