Responses of the Transmembrane Potential of Myocardial Cells during a Shocks

Responses of Transmembrane Potential During a Shock. Introduction: The purpose of this investigation was to study the transmembrane potential changes (δV_m) during extracellular electrical field stimulation. Methods and Results: V_m was recorded in seven guinea pig papillary muscles in a tissue hath by a double-barrel microelectrode with one barrel in and the other just outside a cell while shocks were given across the bath. The short distance (15 to 30 μm) between the two microelectrode tips and alignment of the tips parallel to the shock electrodes eliminated the shock artifact. Following ten SI stimuli, an S2 shock field created by a 10-msec square wave was delivered during the action potential plateau or during diastole through shock electrodes 1 cm on either side of the tissue. Four shock strengths creating field strengths of 1.7 ± 0.1, 2.9 ± 0.2, 6.1 ± 0.6. and 8.8 ± 0.9 V/cm were given for the same impalement. Both shock polarities were given at each shock strength. For shocks delivered during the action potential plateau, the magnitudes of the peak δV_m caused by the above four potential gradients were 21.1 ± 8.2, 33.6 ± 13.6, 49.9 ± 24.2, and 52.3 ± 28.0 mV (P < 0.05 among the four groups) for the shocks causing depolarization and 37.9 ± 14.2,56.6 ± 16.4,83.1 ± 19.4. and 92.9 ± 29.1 mV (P < 0.05 among the four groups) for the shocks causing hyperpolarization. Though δV_m increased as potential gradients increased, the relationship was not linear. The magnitude of hyperpolarization was 1.9 ± 0.5 times that of depolarization when the shock polarity was reversed (P < 0.05). As potential gradients increased from 1.7 ± 0.1 to 8.8 ± 0.9 V/cm, the time constant of the membrane response decreased significantly from 3.5 ± 1.8 to 1.6 ± 0.7 msec for depolarizing shocks and from 6.0 ± 3.1 to 3.4 ± 1.9 msec for hyperpolarizing shocks (P < 0.01 vs depolarizing shocks). For shocks delivered during diastole, hyperpolarizing shocks induced triphasic changes in V_m during the shock, i.e., initial hyperpolarization, then depolarization, followed again by hyperpolarization. Conclusion: During the action potential plateau, the membrane response cannot be represented by a classic passive RC membrane model. During diastole, activation upstrokes occur even during hyperpolarization caused by shocks creating potential gradients between aproximately 2 and 9 V/cm.     

预激综合征旁路体表电位标测的研究进展

经过临床研究、动物实验、计算机模拟实验，体表电位标测现在已经成为一种可行性的临床诊断技术。不仅为外科手术及射频消融房室旁路提供精确定位，还进一步拓展了预激综合征的电生理知识。     

Study the Electrical Properties of Surface Mount Device Integrated Silver Coated Vectran Yarn

Smart textiles have attracted huge attention due to their potential applications for ease of life. Recently, smart textiles have been produced by means of incorporation of electronic components onto/into conductive metallic yarns. The development, characterizations, and electro-mechanical testing of surface mounted electronic device (SMD) integrated E-yarns is still limited. There is a vulnerability to short circuits as non-filament conductive yarns have protruding fibers. It is important to determine the best construction method and study the factors that influence the textile properties of the base yarn. This paper investigated the effects of different external factors, namely, strain, solder pad size, temperature, abrasion, and washing on the electrical resistance of SMD integrated silver-coated Vectran (SCV) yarn. For this, a Vectran E-yarn was fabricated by integrating the SMD resistor into a SCV yarn by applying a vapor phase reflow soldering method. The results showed that the conductive gauge length, strain, overlap solder pad size, temperature, abrasion, and washing had a significant effect on the electrical resistance property of the SCV E-yarn. In addition, based on the experiment, the E-yarn made from SCV conductive thread and 68 Ω SMD resistor had the maximum electrical resistance and power of 72.16 Ω and 0.29 W per 0.31 m length. Therefore, the structure of this E-yarn is also expected to bring great benefits to manufacturing wearable conductive tracks and sensors.     

体表电位标测评定经皮冠状动脉腔内成形术疗效的价值

报告７例冠心病患者经皮冠状动脉腔内成形术（ＰＴＣＡ）前、后体表电位标测（ＢＳＰＭ）的变化。结果表明：ＰＴＣＡ后Ｔ波等电位异常形态明显改善或恢复正常，ＳＴ－Ｔ标测计算指标和ＳＴ－Ｔ极小值位置ＰＴＣＡ前、后有明显改变。提示ＢＳＰＭ可用于ＰＴＣＡ近期疗效的无创伤性评定。     

Temporal Analysis of the Depolarization Wave of Healed Myocardial Infarction in Body Surface Potential Mapping

Background: We studied the ability of different time segments of the depolarization wave recorded with body surface potential mapping (BSPM) to detect and localize myocardial infarction (MI). Methods: BSPM was recorded in 24 patients with remote MI and in 24 healthy controls. Cine and contrast‐enhanced magnetic resonance imaging (MRI) was used as a reference method. Patients were grouped according to anatomical location of their MI. The QRS complex was divided into six temporally equal segments, for which time integrals were calculated. Results: The time segments of the QRS complex showed different MI detection capability depending on MI location. For anterior infarction the second segment of the QRS complex was the best in MI detection and the optimal area was on the right inferior quadrant of the thorax (time integral average ?1.5 ± 1.8 mVms patients, 1.0 ± 1.6 mVms controls, P = 0.002). For lateral infarction the first segment of the QRS complex performed best and the optimal area for MI detection was the left fourth intercostal area (time integral average 1.8 ± 1.0 mVms patients, 0.7 ± 0.5 mVms controls, P = 0.024). For inferior and posterior MI the mid‐phases of the QRS complex were the best and the optimal area was the mid‐inferior area of the thorax (time integral average ?6.2 ± 8.3 mVms patients, 3.3 ± 4.3 mVms controls, P = 0.002; ?9.1 ± 6.1 mVms patients, 0.6 ± 7.1 mVms controls, P = 0.001, respectively). Conclusions: Time segment analysis of the depolarization wave offers potential for improving the detection and localization of healed MI.     

Surface Charge of Red Blood Cells in Insulin-dependent Diabetic Patients with Incipient and Overt Nephropathy

The negative surface charge of red blood cells was studied in adults with insulin-dependent diabetes mellitus, using a chemical assay based on the binding of the cationic dye Alcian-blue 8GX to anionic sites on the cell surface. Twenty-one healthy non-diabetic adults, 21 normoalbuminuric diabetic patients, 25 diabetic patients with incipient nephropathy, and 19 diabetic patients with overt nephropathy were studied. The diabetic patients were matched for age, duration of diabetes, and glycaemic control. The red cell surface charge was nearly identical in the four groups studied. Our study does not suggest that loss of membrane negative charge is a generalized phenomenon in insulin-dependent diabetic patients with albuminuria.     

Surface Glycoprotein Patterns of B Type Chronic Lymphocytic Leukaemia Cells Correlate with the Clinical Activity of the Disease

The surface glycoprotein patterns of leukaemic B lymphocytes from 20 patients with clinically progressive or non-progressive chronic lymphocytic leukaemia (CLL) were investigated. Cells were labelled by the neuraminidase-galactose oxidase-tritiated sodium borohydride technique and the radioactive proteins were separated by polyacrylamide slab gel electrophoresis and visualized by fluorography. A total of 13 to 16 bands were detected. A common surface glycoprotein pattern for CLL cells was seen in all patients consisting of 7 proteins with the apparent molecular weights of 210, 200, 185, 150, 135, 110 and 90 kilodaltons, respectively. Interesting differences were, however, observed as cells from patients with progressive CLL in general lacked the glycoproteins 120, 72 and 67 K, which were found on cells from inactive CLL. The possible biological and clinical significance of these findings is discussed.     

Implications of Surface and Bulk Properties of Abutment Implants and Their Degradation in the Health of Periodontal Tissue

The aim of the current review was to investigate the implications of the surface and bulk properties of abutment implants and their degradation in relation to periodontal health. The success of dental implants is no longer a challenge for dentistry. The scientific literature presents several types of implants that are specific for each case. However, in cases of prosthetics components, such as abutments, further research is needed to improve the materials used to avoid bacterial adhesion and enhance contact with epithelial cells. The implanted surfaces of the abutments are composed of chemical elements that may degrade under different temperatures or be damaged by the forces applied onto them. This study showed that the resulting release of such chemical elements could cause inflammation in the periodontal tissue. At the same time, the surface characteristics can be altered, thus favoring biofilm development and further increasing the inflammation. Finally, if not treated, this inflammation can cause the loss of the implant.     

The Spike Glycoprotein of SARS-CoV-2 Binds to β1 Integrins Expressed on the Surface of Lung Epithelial Cells

The spike glycoprotein attached to the envelope of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to and exploits angiotensin-converting enzyme 2 (ACE2) as an entry receptor to infect pulmonary epithelial cells. A subset of integrins that recognize the arginyl–glycyl–aspartic acid (RGD) sequence in the cognate ligands has been predicted in silico to bind the spike glycoprotein and, thereby, to be exploited for viral infection. Here, we show experimental evidence that the β1 integrins predominantly expressed on human pulmonary epithelial cell lines and primary mouse alveolar epithelial cells bind to this spike protein. The cellular β1 integrins support adhesive interactions with the spike protein independently of ACE2, suggesting the possibility that the β1 integrins may function as an alternative receptor for SARS-CoV-2, which could be targeted for the prevention of viral infections.     

Atrial Electrical Remodeling by Rapid Pacing in the Isolated Rabbit Heart: Effects of Ca++ and K+ Channel Blockade

Introduction: Electrical remodeling describes atrial electrophysiologic changes that occur following atrial fibrillation. The mechanism(s) responsible for this phenomenon is not well understood. The purpose of this study was to examine the effects of rapid atrial pacing on atrial action potential duration, conduction time and refractoriness in the isolated rabbit heart. The effects of Ca⁺⁺ and K⁺ blockade in this model were also studied.Methods and Results: Monophasic action potential recordings were made from 12 epicardial atrial sites in 50 isolated perfused rabbit heart preparations. These recordings were analyzed for activation time (AT), 90% action potential duration (APD) and conduction times (CT) measured at a 250 msec cycle length. Atrial effective refractory periods (ERP) were determined at a 200 msec cycle length. All measurements were made at baseline and repeated after 2 hours of biatrial pacing at 250 msec (control group, n = 10) or 2 hours of rapid biatrial pacing (80 msec) in 4 groups: rapid pacing alone (rapid pacing group); rapid pacing in the presence of 0.1mM verapamil (verapamil group) for L-type Ca⁺⁺ channel blockade; rapid pacing with 1 mM 4-aminopyridine (4-AP group) for K⁺ channel blockade; and rapid pacing with 50 M nickel chloride (Ni⁺⁺ group) for T-type Ca⁺⁺ channel blockade (n = 10 each group). All baseline and post pacing measurements were taken in the presence of Ca⁺⁺ or K⁺ blockers for the respective groups.After rapid atrial pacing alone the average APD shortened by 8.2±10.4 msec compared to 3.6±12.5 msec shortening for control group (p = 0.002). The shortening of APD was uniform at all recording sites. For the rapid pacing group, CT was unchanged for right to left atrial conduction but shortened significantly for left to right atrial conduction (26.8±1.9 msec at baseline to 22.3±4.1 msec post pacing, p = 0.005). Conduction times were unchanged in the control group. The dispersion of repolarization was unchanged by rapid pacing alone. The decrease in APD from baseline to post rapid pacing was similar to the control group for those hearts treated with verapamil and 4-AP (1.5±12.3 and 4.7±10.4 msec, respectively, both p 0.18 vs control group). The decrease in APD was significantly greater for the Ni⁺⁺ group (11.8± 14.3 msec) than for either the control group or rapid pacing group (both p 0.023). The dispersion of repolarization was increased only in the 4-AP group post rapid pacing (41.7±6.2 msec at baseline to 53.5±9.6 msec post pacing, p = 0.01). ERPs were unchanged in any of the 5 groups except for a decrease in left atrial ERP in the Ni⁺⁺ group after rapid pacing (98±14 msec at baseline to 88±8 msec post rapid pacing, p = 0.005).Conclusions: In the isolated rabbit heart model: 1) atrial APD is shortened after rapid pacing; 2) the shortening of APD is attenuated by verapamil and 4-AP but exaggerated by Ni⁺⁺ 3) atrial conduction times are shortened in a direction specific manner after rapid pacing; and 4) shortening of ERP in this model is measured only in the presence of Ni⁺⁺. These findings suggest that both L-type Ca⁺⁺ and 4-AP sensitive channels may participate in atrial electrical remodeling.     

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe₃O₄ nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10⁻⁴ S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.     

Review of the Potential of the Ni/Cu Plating Technique for Crystalline Silicon Solar Cells

Developing a better method for the metallization of silicon solar cells is integral part of realizing superior efficiency. Currently, contact realization using screen printing is the leading technology in the silicon based photovoltaic industry, as it is simple and fast. However, the problem with metallization of this kind is that it has a lower aspect ratio and higher contact resistance, which limits solar cell efficiency. The mounting cost of silver pastes and decreasing silicon wafer thicknesses encourages silicon solar cell manufacturers to develop fresh metallization techniques involving a lower quantity of silver usage and not relying pressing process of screen printing. In recent times nickel/copper (Ni/Cu) based metal plating has emerged as a metallization method that may solve these issues. This paper offers a detailed review and understanding of a Ni/Cu based plating technique for silicon solar cells. The formation of a Ni seed layer by adopting various deposition techniques and a Cu conducting layer using a light induced plating (LIP) process are appraised. Unlike screen-printed metallization, a step involving patterning is crucial for opening the masking layer. Consequently, experimental procedures involving patterning methods are also explicated. Lastly, the issues of adhesion, back ground plating, process complexity and reliability for industrial applications are also addressed.     

Development and Investigation of an Inexpensive Low Frequency Vibration Platform for Enhancing the Performance of Electrical Discharge Machining Process

Difficulty in debris removal and the transport of fresh dielectric into discharge gap hinders the process performance of electrical discharge machining (EDM) process. Therefore, in this work, an economical low frequency vibration platform was developed to improve the performance of EDM through vibration assistance. The developed vibratory platform functions on an eccentric weight principle and generates a low frequency vibration in the range of 0–100 Hz. The performance of EDM was evaluated in terms of the average surface roughness (R_a), material removal rate (MRR), and tool wear rate (TWR) whilst varying the input machining parameters viz. the pulse-on-time (T_on), peak current (I_p), vibration frequency (VF), and tool rotational speed (TRS). The peak current was found to be the most significant parameter and contributed by 78.16%, 65.86%, and 59.52% to the R_a, MRR, and TWR, respectively. The low frequency work piece vibration contributed to an enhanced surface finish owing to an improved flushing at the discharge gap and debris removal. However, VF range below 100 Hz was not found to be suitable for the satisfactory improvement of the MRR and reduction of the TWR in an electrical discharge drilling operation at selected machining conditions.     

Effect Morphology and Surface Treatment of the Abutments of Dental Implants on the Dimension and Health of Peri-Implant Biological Space

Statement of the problem: The gingival configuration around implant abutments is of paramount importance for preserving the underlying marginal bone, and hence for the long-term success of dental implants. Objective: The objective was to study, clinically and histologically, the effects of the change in the morphology of abutments connected to the endosseous implant, and of their surface treatment. In particular, the objective was to ascertain the effect of changing the shape of the transepithelial pillar and the treatment of its surface on the dimensions, quality and health of the components of the peri-implant biological space, such as the dimensions of the epithelial and connective tissues of the biological space, the concentration of inflammatory cells and the density of collagen fibers. Methods: A clinical trial of 10 patients with a totally edentulous maxilla, who had four implants (IPX4010_GALIMPLANT^®, Sarria, Spain) inserted in the area of the first and second molars on both sides with computer-guided implant surgery, was conducted with the final purpose of assessing the quality of the peri-implant soft tissue attachment around the transepithelial abutments which were employed (aesthetic machined (RM), aesthetic anodized (RA), slim machined (SM) and slim anodized (SA)). At 8 weeks and following the collection of the samples (removal of the implant-abutment assembly with its surrounding hard and soft tissue) and their processing for subsequent histological and histomorphometric analysis in order to study the dimensions, quality and health of the peri-implant soft tissue area, the variables previously mentioned were determined according to the aims of the study. By using appropriate diameter trephine in order to obtain a useful fringe of soft tissue around the transepithelial pillars, ANOVA and chi-square tests were performed. Results: The SPSS statistical analysis ANOVA results revealed that the machined slim abutments have a better performance considering the variables analyzed with epithelial and connective attachment heights of 1.52 mm and 2.3 mm, respectively, and that connective density (density of collagen fibers) was high at 85.7% of the sample size affected by the design for the slim abutments and 92.9% of the high-density sample size affected by the surface treatment for the machined surface. Conclusions: All variables studied, despite the small sample size, showed the superiority of the slim machined abutment among the four groups.     

Surface Properties of Eggshell Powder and Its Influence on Cement Hydration

Using eggshell powder (EP) to replace partial cement in cement-based materials can abate pollution caused by eggshell discard and cement production. In this paper, the surface property of EP and its influence on cement hydration were studied. Quartz powder (QP) and limestone powder (LP) were used as references. First, the chemical composition of EP was characterized. Then, the surface charge properties of these materials were analyzed using zeta potential measurement. The interactions between EP surface and Ca²⁺ were discussed based on the zeta potential test. Afterward, a scanning electron microscope (SEM) was applied to observe the morphology of hydrates on the surfaces of these materials. The results indicated that, although the compositions of EP and LP are similar, the surface charge properties are significantly different. This is likely due to the existence of organic matter on the surface of EP and the difference in the atomic structure. As shown from the zeta potential test, EP exhibits similar interaction with Ca²⁺ as QP. The interactions between EP surface and Ca²⁺ are much weaker than that between LP and Ca²⁺. These weak interactions lead to the growth of C–S–H on the surface of EP particles less than that of LP particles. The chemical reactivity of EP can be improved by using heat treatment, electrical oven, etc. This study will provide theoretical support for the better use of EP in cement-based materials.     

Biocompatible Properties and Mineralization Potential of Premixed Calcium Silicate-Based Cements and Fast-Set Calcium Silicate-Based Cements on Human Bone Marrow-Derived Mesenchymal Stem Cells

Premixed calcium silicate-based cements (CSCs) and fast-set CSCs were developed for the convenience of retrograde filling during endodontic microsurgery. The aim of this study was to analyze the biocompatible properties and mineralization potential of premixed CSCs, such as Endocem MTA Premixed (EM Premixed) and EndoSequence BC RRM putty (EndoSequence), and fast-set RetroMTA on human bone marrow-derived mesenchymal stem cells (BMSCs) compared to ProRoot MTA. Using CCK-8, a significantly higher proliferation of BMSCs occurred only in the EM Premixed group on days 2 and 4 (p < 0.05). On day 6, the ProRoot MTA group had significantly higher cell proliferation than the control group (p < 0.05). Regardless of the experimental materials, all groups had complete cell migration by day 4. Alizarin Red-S staining and alkaline phosphatase assay demonstrated higher mineralization potential of all CSCs similar to ProRoot MTA (p < 0.05). The EndoSequence group showed more upregulation of SMAD1 and OSX gene expression than the other experimental groups (p < 0.05), and all experimental cements upregulated osteogenic gene expression more than the control group (p < 0.05). Therefore, using premixed CSCs and fast-set CSCs as retrograde filling cements may facilitate satisfactory biological responses and comparable osteogenic potential to ProRoot MTA.     

Tribological Characterization of the Heat-Assisted Single Point Incremental Forming Process Applied to the Ti6Al4V Alloy with the Definition of an Adhesion Parameter for the Tool Surface

Heat-assisted single point incremental forming or HA-SPIF has a great potential for producing one-piece batches of hard-to-form materials such as Ti6Al4V alloy for medical and aeronautical applications. One of the limitations of the process is the difficulty in achieving a reasonable surface finish, which makes essential the characterization of the tribological process in the tool–sheet contact. In fact, not much work can be found at this point in literature. In this research, a novel procedure for evaluating the adhesion on the tool surface is proposed and the influence of the temperature is determined. The surface finish of parts is analyzed, and the changes promoted by HA-SPIF appearing in the morphology of the external surface layer are characterized by SEM.     

Dependence of the Surface Morphology and Micromechanical and Sclerometric Properties of Al2O3 Layers on the Parameters of Anodizing Aluminum Alloy

The article presents the dependence of the morphology as well as micromechanical and sclerometric properties of Al₂O₃ layers on the parameters of anodizing of aluminum alloys. The oxide layers were produced on the EN AW-5251 aluminum alloy by means of a direct current anodizing in a three-component electrolyte. The input variables (current density and electrolyte temperature) were selected based on the overall design of the experiment. The current density was 1, 2, 3 A/dm², and the electrolyte temperature was 283, 293, 303 K. The surface morphology was examined using a scanning electron microscope (SEM), and then the microscopic images were analyzed using a graphics program. The micromechanical and sclerometric properties were examined by determining the H_IT hardness and three critical loads: Lc1 (critical load at which the first damage of the tested layers occurred-Hertz tensile cracks inside the crack), Lc2 (critical load at which the first cohesive damage of the layers occurred) and Lc3 (load at which the layers were completely damaged). Sclerometric tests with the use of scratch tests were supplemented with pictures from a scanning microscope, showing the scratches. The produced layers are characterized by a hardness above 3 GPa and a porosity of 4.9–10.3%. Such a range of porosity of the produced layers allows their wide application, both for sliding associations with polymers and for their modification.     

Effect of Substrate Temperature on the Structural,Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films

This study focuses on the effect of the substrate temperature (T_S) on the quality of VO₂ thin films prepared by DC magnetron sputtering. T_S was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that T_S below 500 °C favors the growth of V₂O₅ phase, whereas higher T_S (≥500 °C) facilitates the formation of the VO₂ phase. Optical characterization of the as-prepared VO₂ films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (T_t), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO₂ films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at T_S lower than 650 °C presents significant challenges.