Analysis of Influencing Parameters Enhancing the Plucking Efficiency of Piezoelectric Energy Harvesters.

The integration of energy harvesting systems into sensing technologies can result in novel autonomous sensor nodes, characterized by significant simplification and mass reduction. The use of piezoelectric energy harvesters (PEHs), particularly in cantilever form, is considered as one of the most promising approaches aimed at collecting ubiquitous low-level kinetic energy. Due to the random nature of most excitation environments, the narrow PEH operating frequency bandwidth implies, however, the need to introduce frequency up-conversion mechanisms, able to convert random excitation into the oscillation of the cantilever at its eigenfrequency. A first systematic study is performed in this work to investigate the effects of 3D-printed plectrum designs on the specific power outputs obtainable from FUC excited PEHs. Therefore, novel rotating plectra configurations with different design parameters, determined by using a design-of-experiment methodology and manufactured via fused deposition modeling, are used in an innovative experimental setup to pluck a rectangular PEH at different velocities. The obtained voltage outputs are analyzed via advanced numerical methods. A comprehensive insight into the effects of plectrum properties on the responses of the PEHs is attained, representing a new and important step towards the development of efficient harvesters aimed at a wide range of applications, from wearable devices to structural health monitoring systems.

Frequent accelerated idioventricular rhythm in an otherwise healthy child: a case report and review of literature.

BACKGROUND: Accelerated idioventricular rhythm (AIVR) is a wide QRS complex dysrhythmia that, as far as pediatric population is concerned, occurs mostly in children with underlying systemic or heart disease. Its clinical course is thought to be typically benign in otherwise healthy children and treatment to be completely needless. Existing guidelines/recommendations are based entirely on cases that had low daily burden of AIVR, and those referring to treatment itself are very unspecific. Pharmacologic therapy has been mostly unsuccessful and catheter ablation as a way of treatment has been only sporadically reported. This article is a case report with a literature review that aims to practically separate the age groups into newborn and older children and to emphasize the different clinical outcomes of children with occasional and frequent AIVR. There are only a few cases so far describing undesirable outcomes of this condition, and most of these patients had high daily burden of AIVR. To be more specific, among 38 healthy children older than 1 year reported in total, 6 had undesirable outcomes, short-term in terms of developing malignant arrhythmia or long-term in terms of developing cardiomyopathy/heart failure. CASE PRESENTATION: An 11-year-old boy had been referred to our center for a workup of incidentally discovered wide-complex arrhythmia. He was asymptomatic, with no underlying cardiac or systemic diseases. Continuous heart rate monitoring detected AIVR during most time of monitoring. In 24-h Holter-ECG, wide QRS complexes accounted for 73%. With parental consent, we conducted an electrophysiological study accompanied by radiofrequent ablation of ectopic focus, which lead to an instantaneous sinus rhythm that continued during the entire follow-up. CONCLUSION: AIVR is a rare dysrhythmia in the pediatric population, typically considered benign. Nevertheless, more than a few cases evidence its harmful potential, short-term in terms of developing malignant arrhythmia or long-term in terms of developing cardiomyopathy. Gathering more knowledge and experience along with conducting further studies is essential for the enhancement of understanding this condition, and selecting potentially vulnerable patients as well as their treatment.

Impact of CPAP Therapy on New Inflammation Biomarkers.

Obstructive sleep apnea (OSA) is a common sleep disorder leading to increased risk of developing cardiovascular diseases (CVDs) by supporting a low-grade chronic inflammation as one of the pathological mechanisms. The continuous positive airway pressure (CPAP) device is used as an effective treatment for moderate and severe OSA. Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), white blood cell-mean platelet volume ratio (WMR), C-reactive protein-albumin ratio (CAR) and fibrinogen-albumin ratio (FAR) are new potential inflammatory biomarkers that are widely available and were shown to be possibly favorable screening or follow-up tools for moderate- or severe-grade OSA, as well as indirect indicators for cardiovascular risk. Our study evaluated the impact of CPAP therapy in patients with severe OSA and acceptable therapy adherence on NLR, PLR, WMR, FAR and CAR. Of 57 patients who were initially enrolled and had no exclusion criteria, 37 had a satisfactory CPAP adherence (usage of ≥4 h per night) after a minimum of 6 months of therapy. There was a statistically significant difference in NLR (2.122 ± 0.745 before therapy vs. 1.888 ± 0.735 after therapy) and FAR (86.445 ± 18.763 before therapy vs. 77.321 ± 19.133 after therapy) suggesting a positive effect of the CPAP therapy on chronic inflammatory states, thereby possibly reducing cardiovascular risk.

Unveiling the Native Morphology of Extracellular Vesicles from Human Cerebrospinal Fluid by Atomic Force and Cryogenic Electron Microscopy.

Extracellular vesicles (EVs) are membranous structures in biofluids with enormous diagnostic/prognostic potential for application in liquid biopsies. Any such downstream application requires a detailed characterization of EV concentration, size and morphology. This study aimed to observe the native morphology of EVs in human cerebrospinal fluid after traumatic brain injury. Therefore, they were separated by gravity-driven size-exclusion chromatography (SEC) and investigated by atomic force microscopy (AFM) in liquid and cryogenic transmission electron microscopy (cryo-TEM). The enrichment of EVs in early SEC fractions was confirmed by immunoblot for transmembrane proteins CD9 and CD81. These fractions were then pooled, and the concentration and particle size distribution were determined by Tunable Resistive Pulse Sensing (around 1010 particles/mL, mode 100 nm) and Nanoparticle Tracking Analysis (around 109 particles/mL, mode 150 nm). Liquid AFM and cryo-TEM investigations showed mode sizes of about 60 and 90 nm, respectively, and various morphology features. AFM revealed round, concave, multilobed EV structures; and cryo-TEM identified single, double and multi-membrane EVs. By combining AFM for the surface morphology investigation and cryo-TEM for internal structure differentiation, EV morphological subpopulations in cerebrospinal fluid could be identified. These subpopulations should be further investigated because they could have different biological functions.

Disinfecting Action of Gaseous Ozone on OXA-48-Producing Klebsiella pneumoniae Biofilm In Vitro.

Klebsiella pneumoniae is an emerging multidrug-resistant pathogen that can contaminate hospital surfaces in the form of a biofilm which is hard to remove with standard disinfectants. Because of biofilm resistance to conservative disinfectants, the application of new disinfection technologies is becoming more frequent. Ozone gas has antimicrobial activity but there is lack of data on its action against K. pneumoniae biofilm. The aim of this study was to investigate the effects and mechanisms of action of gaseous ozone on the OXA-48-procuding K. pneumoniae biofilm. A 24 h biofilm of K. pneumoniae formed on ceramic tiles was subsequently exposed to different concentrations of ozone during one and two hours to determine the optimal ozone concentration. Afterwards, the total bacteria count, total biomass and oxidative stress levels were monitored. A total of 25 ppm of gaseous ozone was determined to be optimal ozone concentration and caused reduction in total bacteria number in all strains of K. pneumoniae for 2.0 log10 CFU/cm2, followed by reduction in total biomass up to 88.15%. Reactive oxygen species levels significantly increased after the ozone treatment at 182% for the representative K. pneumoniae NCTC 13442 strain. Ozone gas in the concentration of 25 ppm caused significant biofilm reduction but did not completely eradicate the K. pneumoniae biofilm formed on ceramics. In conclusion, ozone gas has great potential to be used as an additional hygiene measure in joint combat against biofilm in hospital environments.

Multiple Coronary Fistulas as a Rare Cause of Stable Angina Pectoris.

Congenital coronary artery-left ventricular multiple microfistulas (CA-LVMMFs) are rare anomalies in adults. They are more often found in female patients, and they usually originate from the distal segments of the coronary arteries, but they can originate from a proximal segments of a coronary arteries, and these patients are likely to be identified and treated in the pediatric age group. They are mostly asymptomatic. When symptoms and complications occur, they include angina, myocardial infarction, atrial heart failure, arrhythmias, and endocarditis. The management of CA-LVMMFs is controversial, but it is generally agreed that conservative medical management is the primary treatment of choice. Our case describes a rare form of CA-LVMMFs draining into the left ventricle in a female patient presenting with fatigue, atypical anginal symptoms, atrial fibrillation, and premature ventricular complexes, without concomitant obstructive coronary artery disease.

Ion Release and Surface Changes of Nickel-Titanium Archwires Induced by Changes in the pH Value of the Saliva-Significance for Human Health Risk Assessment.

The aim of this study was to explore whether changes in the salivary pH influence mechanical properties, surface roughness, and ion release from NiTi archwires with various surface coatings, and discuss the clinical significance of the findings. The uncoated, rhodium-coated, and nitrified NiTi wires were immersed into artificial saliva of different pH values (4.8, 5.1, 5.5, and 6.6). Released nickel and titanium ions were measured with inductively coupled plasma-optical emission spectroscopy at the end of 28 days. Atomic force microscopy was used to measure the arithmetic average surface roughness Ra, the root-mean-square roughness Rq, and the maximum height of the asperities RZ. The nanoindentation hardness (HIT) and Young's modulus (EIT) measurements were performed. The change in the pH of artificial saliva is inversely proportional to the release of titanium from both coated and uncoated wires, and the release of nickel from uncoated wires. The surface roughness parameters of both coated and uncoated wires are unaffected by the change in the pH of artificial saliva. The change in the pH of saliva has minor influence on the hardness and Young's modulus of elasticity of both coated and uncoated wires. The concentration of released metal ions measured was below the recommended upper limit for daily intake; nevertheless, hypersensitivity effects cannot be excluded, even at lower concentrations and at low pH.

Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference.

Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, and Veilonella parvula) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites ("warts"), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log10CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.

Perspectives of Microscopy Methods for Morphology Characterisation of Extracellular Vesicles from Human Biofluids.

Extracellular vesicles (EVs) are nanometric membranous structures secreted from almost every cell and present in biofluids. Because EV composition reflects the state of its parental tissue, EVs possess an enormous diagnostic/prognostic potential to reveal pathophysiological conditions. However, a prerequisite for such usage of EVs is their detailed characterisation, including visualisation which is mainly achieved by atomic force microscopy (AFM) and electron microscopy (EM). Here we summarise the EV preparation protocols for AFM and EM bringing out the main challenges in the imaging of EVs, both in their natural environment as biofluid constituents and in a saline solution after EV isolation. In addition, we discuss approaches for EV imaging and identify the potential benefits and disadvantages when different AFM and EM methods are applied, including numerous factors that influence the morphological characterisation, standardisation, or formation of artefacts. We also demonstrate the effects of some of these factors by using cerebrospinal fluid as an example of human biofluid with a simpler composition. Here presented comparison of approaches to EV imaging should help to estimate the current state in morphology research of EVs from human biofluids and to identify the most efficient pathways towards the standardisation of sample preparation and microscopy modes.

Clinical Paradox: Anterior Wall Myocardial Infarction with Predominant Inferior ST Elevation and No Variation in Coronary Anatomy in a PAI-1 Homozygote.

Changes of the ST segment are commonly used as predictors of the culprit vessel during an acute myocardial infarction. In case of combined ST elevation in both inferior and anterior leads, these changes can be due to a distal occlusion of a "wrapped" left anterior descending artery (LAD) or a two-vessel disease. Our case of anterior wall myocardial infarction with inferior ST elevation and anterior ST depression shows that electrocardiographic changes during acute myocardial infarction cannot always be explained by logical sequelae of the injury current, vessel anatomy, and their irrigation territory.

'Sandwich'-like hybrid ZnO thin films produced by a combination of atomic layer deposition and wet-chemistry using a mercapto silane as single organic precursor.

This study describes a straightforward preparation of hybrid organic-inorganic thin films containing a stable 'sandwich'-like structure of two atomic layer deposited (ALD) ZnO layers separated by a thin organosilane phase, which is built from a single organic component (3-mercaptopropyl)trimethoxysilane (MPTMS). Grafting of MPTMS on the first ALD ZnO layer was performed in solution and driven by the strong affinity of the terminal thiol functionality (-SH) towards ZnO. We demonstrate that under different reaction conditions, either MPTMS monolayers are prepared or a 5 nm thick cross-linked polymeric network is formed due to the self-condensation of silane, which covers the ALD ZnO surface. This film served as a soft template for the nucleation of an ALD ZnO top layer by creation of S-Zn and Si-O-Zn bonds at the upper interface, as confirmed by XPS measurements. An increase in surface roughness, as compared to the initial ZnO film, is observed after removal of the organic layer from the hybrid structure by calcination, which is accompanied by an improvement in UVA photocatalytic activity towards the degradation of methyl orange dye. Thus, MPTMS can be used as a sacrificial agent in combination with low temperature ALD processes for building rougher and photocatalytically efficient ZnO coatings.