Use of Flexible Sensor to Characterize Biomechanics of Canine Skin

Background Suture materials and techniques are frequently evaluated in ex vivo studies by comparing tensile strengths. However, the direct measurement techniques to obtain the tensile forces in canine skin are not available, and, therefore, the conditions suture lines undergo is unknown. A soft elastomeric capacitor is used to monitor deformation in the skin over time by sensing strain. This sensor was applied to a sample of canine skin to evaluate its capacity to sense strain in the sample while loaded in a dynamic material testing machine. The measured strain of the sensor was compared with the strain measured by the dynamic testing machine. The sample of skin was evaluated with and without the sensor adhered. Results In this study, the soft elastomeric capacitor was able to measure strain and a correlation was made to stress using a modified Kelvin-Voigt model for the canine skin sample. The sensor significantly increases the stiffness of canine skin when applied which required the derivation of mechanical models for interpretation of the results. Conclusions Flexible sensors can be applied to canine skin to investigate the inherent biomechanical properties. These sensors need to be lightweight and highly elastic to avoid interference with the stress across a suture line. The sensor studied here serves as a prototype for future sensor development and has demonstrated that a lightweight highly elastic sensor is needed to decrease the effect on the sensor/skin construct. Further studies are required for biomechanical characterization of canine skin

Use of flexible sensor to characterize biomechanics of canine skin

Abstract Background Suture materials and techniques are frequently evaluated in ex vivo studies by comparing tensile strengths. However, the direct measurement techniques to obtain the tensile forces in canine skin are not available, and, therefore, the conditions suture lines undergo is unknown. A soft elastomeric capacitor is used to monitor deformation in the skin over time by sensing strain. This sensor was applied to a sample of canine skin to evaluate its capacity to sense strain in the sample while loaded in a dynamic material testing machine. The measured strain of the sensor was compared with the strain measured by the dynamic testing machine. The sample of skin was evaluated with and without the sensor adhered. Results In this study, the soft elastomeric capacitor was able to measure strain and a correlation was made to stress using a modified Kelvin-Voigt model for the canine skin sample. The sensor significantly increases the stiffness of canine skin when applied which required the derivation of mechanical models for interpretation of the results. Conclusions Flexible sensors can be applied to canine skin to investigate the inherent biomechanical properties. These sensors need to be lightweight and highly elastic to avoid interference with the stress across a suture line. The sensor studied here serves as a prototype for future sensor development and has demonstrated that a lightweight highly elastic sensor is needed to decrease the effect on the sensor/skin construct. Further studies are required for biomechanical characterization of canine skin

Numerical Investigation of Auxetic Textured Soft Strain Gauge for Monitoring Animal Skin

Recent advances in hyperelastic materials and self-sensing sensor designs have enabled the creation of dense compliant sensor networks for the cost-effective monitoring of structures. The authors have proposed a sensing skin based on soft polymer composites by developing soft elastomeric capacitor (SEC) technology that transduces geometric variations into a measurable change in capacitance. A limitation of the technology is in its low gauge factor and lack of sensing directionality. In this paper, we propose a corrugated SEC through surface texture, which provides improvements in its performance by significantly decreasing its transverse Poisson’s ratio, and thus improving its sensing directionality and gauge factor. We investigate patterns inspired by auxetic structures for enhanced unidirectional strain monitoring. Numerical models are constructed and validated to evaluate the performance of textured SECs, and to study their performance at monitoring strain on animal skin. Results show that the auxetic patterns can yield a significant increase in the overall gauge factor and decrease the stress experienced by the animal skin, with the re-entrant hexagonal honeycomb pattern outperforming all of the other patterns.This article is published as Liu, Han, Matthias Kollosche, Jin Yan, Eric M. Zellner, Sarah A. Bentil, Iris V. Rivero, Colin Wiersema, and Simon Laflamme. "Numerical investigation of auxetic textured soft strain gauge for monitoring animal skin." Sensors 20, no. 15 (2020): 4185. DOI: 10.3390/s20154185. Copyright 2020 by the authors. Attribution 4.0 International (CC BY 4.0). Posted with permission

Editorial: Errors in the Variables, Unobserved Heterogeneity, and Other Ways of Hiding Statistical Error

One research function is proposing new scientific theories; another is testing the falsifiable predictions of those theories. Eventually, sufficient observations reveal valid predictions. For the impatient, behold statistical methods, which attribute inconsistent predictions to either faulty data (e.g., measurement error) or faulty theories. Testing theories, however, differs from estimating unknown parameters in known relationships. When testing theories, it is sufficiently dangerous to cure inconsistencies by adding observed explanatory variables (i.e., beyond the theory), let alone unobserved explanatory variables. Adding ad hoc explanatory variables mimics experimental controls when experiments are impractical. Assuming unobservable variables is different, partly because realizations of unobserved variables are unavailable for validating estimates. When different statistical assumptions about error produce dramatically different conclusions, we should doubt the theory, the data, or both. Theory tests should be insensitive to assumptions about error, particularly adjustments for error from unobserved variables. These adjustments can fallaciously inflate support for wrong theories, partly by implicitly under-weighting observations inconsistent with the theory. Inconsistent estimates often convey an important message—the data are inconsistent with the theory! Although adjustments for unobserved variables and ex post information are extraordinarily useful when estimating known relationships, when testing theories, requiring researchers to make these adjustments is inappropriate.unobserved heterogeneity, scientific method, falsification, statistical validation, errors in the variables, Popper falsification

Combination propranolol and bepridil therapy in stable angina pectoris

The safety and efficacy of bepridil plus propranolol therapy were investigated in a placebo-controlled, parallel-design, double-blind trial in 56 patients who were not responding to propranolol alone. Patients entering the study were receiving an average propranolol dosage of 131 mg/day (range 20 to 240). For the first 2 weeks of the study they were given placebo in addition to their propranolol dose, and then were randomized to receive continued placebo plus propranolol or bepridil plus propranolol therapy. The bepridil dosage was adjusted over the 8 weeks of active treatment to an average of 273 mg/day (range 200 to 400). The double-blind treatment period was followed by a 3-week washout period during which all patients received propranolol and placebo. The effects of treatment on the frequency of angina attacks, nitroglycerin consumption, exercise performance (treadmill-modified Bruce protocol) and Holter electrocardiogram (ECG) were assessed. Propranolol and bepridil plasma levels also were obtained. Improved antianginal efficacy and reduced nitroglycerin consumption were noted when bepridil was added to propranolol (p \u3c 0.01). During 8 weeks of combination treatment, exercise tolerance increased 1.0 ± 1.2 minutes from a baseline of 7.3 ± 2.2 with bepridil plus propranolol compared with an increase of 0.02 ± 1.3 minutes from a baseline of 7.6 ± 2.9 with placebo plus propranolol (p \u3c 0.01). With bepridil plus propranolol, there were also increases in exercise time to onset of angina (p \u3c 0.04), exercise time to 1-mm electrocardiographic ST-segment depression (p \u3c 0.06) and total work (p \u3c 0.03) compared with placebo plus propranolol therapy. Resting heart rate was reduced a maximum of 2 beats/min with combination treatment compared with propranolol alone, and no differences in blood pressure between treatment groups were observed. There were no clinically significant rhythm changes on Holter ECG with combination treatment, and bepridil treatment had no effect on plasma propranolol levels. Bepridil did prolong the QTc interval on resting ECG by a mean of 37 ± 39 millisecond. Adverse effects were mild with bepridil plus propranolol and greater in frequency than those with placebo plus propranolol. With cessation of bepridil, patients returned toward the angina frequency and exercise tolerance levels seen at baseline with propranolol alone. The addition of bepridil to propranolol provided safe and effective antianginal therapy in patients whose angina was not controlled by propranolol alone. © 1985

Identification of Four Gene Variants Associated with Myocardial Infarction

Family history is a major risk factor for myocardial infarction (MI). However, known gene variants associated with MI cannot fully explain the genetic component of MI risk. We hypothesized that a gene-centric association study that was not limited to candidate genes could identify novel genetic associations with MI. We studied 11,053 single-nucleotide polymorphisms (SNPs) in 6,891 genes, focusing on SNPs that could influence gene function to increase the likelihood of identifying disease-causing gene variants. To minimize false-positive associations generated by multiple testing, two studies were used to identify a limited number of nominally associated SNPs; a third study tested the hypotheses that these SNPs are associated with MI. In the initial study (of 340 cases and 346 controls), 637 SNPs were associated with MI (P<.05); these were evaluated in a second study (of 445 cases and 606 controls), and 31 of the 637 SNPs were associated with MI (P<.05) and had the same risk allele as in the first study. For each of these 31 SNPs, we tested the hypothesis that it is associated with MI, using a third study (of 560 cases and 891 controls). We found that four of these gene variants were associated with MI (P<.05; false-discovery rate <10%) and had the same risk allele as in the first two studies. These gene variants encode the cytoskeletal protein palladin (KIAA0992 [odds ratio (OR) 1.40]), a tyrosine kinase (ROS1 [OR 1.75]), and two G protein–coupled receptors (TAS2R50 [OR 1.58] and OR13G1 [OR 1.40]); all ORs are for carriers of two versus zero risk alleles. These findings could lead to a better understanding of MI pathophysiology and improved patient risk assessment