Investigation of Fiber-Matrix Interface Strength via Single-Fiber Pull-Out Test in 3D-Printed Thermoset Composites: A Simplified Methodology.

The emergence of additive manufacturing technologies for fiber-reinforced thermoset composites has greatly bolstered their utilization, particularly within the aerospace industry. However, the ability to precisely measure the interface strength between the fiber and thermoset matrix in additively manufactured composites has been constrained by the cumbersome nature of single-fiber pull-out experiments and the need for costly instrumentation. This study aims to introduce a novel methodology for conducting single-fiber pull-out tests aimed at quantifying interface shear strength in additively manufactured thermoset composites. Our findings substantiate the viability of this approach, showcasing successful fiber embedding within composite test specimens and precise characterization of fiber pull-out strength using a conventional mechanical testing system. The test outcome revealed an average interfacial strength value of 2.4 MPa between carbon fiber and the thermoset epoxy matrix, aligning with similar studies in the existing literature. The outcome of this study offers an affordable and versatile test methodology to revolutionize composite material fabrication for superior mechanical performance.

Sand-Related Factors Influencing Nest Burrowing Potential of the Sand Martins.

Vertical embankments and mounds serve as suitable habitats for burrowing birds, such as the Sand Martin (Riparia riparia). Sand Martins have decreased in many countries during the last two decades, possibly because of the decline in suitable nest sites. Therefore, it is important to understand the factors affecting nest burrowing and nest hole characteristics for the Sand Martin. A smaller entrance hole would be beneficial for regulating the internal environment of the nest, whereas deeper nests are more advantageous against nest predators and parasites. We examined the general structure of Sand Martin colonies and determined if particle size, pH, or electrical conductivity (EC) of the soil and the location of the colony affects the morphology of Sand Martin nest holes. We hypothesized that the climate of near lakeshore and non-lakeshore differs; consequently, we predicted that Sand Martins would construct wider nest tunnel entrances in more humid environments near the lakeshore than further from the lake. We also hypothesized that a lower pH of clay loam soil would result in an increasing level of exchangeable aluminum (Al) and acidity, which in turn would promote soil aggregation. Because soils with a low EC are more stable and less prone to flooding or erosion, we predicted that Sand Martins in such soils would have deeper nesting burrows. A total of four colonies were located in the study area in Turkey. They contained 2510 burrows, of which 91.83% were used for breeding. The mean colony size was 627. We measured the soil and the nest burrow characteristics from the 80 nest bottoms used for breeding by the Sand Martin. The mean pH was 8.8, and the mean EC was 171. Tunnel depth was longer in nests with greater pH and EC and in lakeshore than in non-lakeshore colonies. The distance between nest holes increased with the EC, and nests were located nearer to each other in the lakeshore colonies than in non-lakeshore colonies. The width of the entrance opening increased with soil particle size and was wider in nests located at the lakeshore areas. Our results indicated that Sand Martins will avoid sites with too compact or loose soils for nesting, probably to avoid nest collapses. Vertical lakeshore embankments offer good nesting sites for Sand Martins and should, therefore, be protected. Because soil particle size, pH, EC, and distance from the lakeshore influenced the nest hole characteristics of the Sand Martin, conservation and management efforts should take these variables into account when maintaining or establishing suitable soil conditions for the Sand Martin.

A statistical approach on distribution and seasonal habitat use of waterfowl and shorebirds in Çildir Lake (Ardahan, Türkiye).

Wetlands are crucial habitats for both migrant and resident bird assemblages. The distribution and habitat preferences of birds in aquatic ecosystems are significantly influenced by environmental and ecological factors that critically impact the relevant habitats. In order to reveal the distribution and habitat preferences of the birds, many statistical models and methodologies are employed in ecology and conservation biology. Herein, we investigated the effects of year, season, habitat, and species variables on the distribution and population dynamics of waterfowls and shorebirds associated with the wetland. In this regard, field surveys were carried out in and around Çildir Lake (Ardahan, Türkiye) between April 2017 and September 2018 to examine the distribution of waterfowls and shorebirds and variations in population sizes. As an experimental design, a stratified random sampling design was used to assess bird fauna in the four dominant habitat types (open water surface, reeds, grasslands, and agricultural areas) in the study area. Accordingly, a total of 51 waterfowl and shorebird species were identified during the study period. Of the identified families, Anatidae (n = 18), Scolopacidae (n = 8), and Ardeidae (n = 8) were the most common families. Considering bird species, common coot Fulica atra and mallard Anas platyrhynchos were the most abundant species. The dependent variable (bird populations) was compared with the independent variables (year, season, habitat, and species). The population in 2018 decreased by 13% in comparison to the population in 2017 (p < 0.05). Once the reed area was considered as the reference, the population density in the water surface habitat increased by 65% (p < 0.001). In relation to seasonal reference, a 65% increase in population growth in spring was recorded in comparison to the growth in fall (p < 0.001). On the other hand, no statistical differences were noted in population growth in winter and summer ((p > 0.05). With respect to the reference species (Anas crecca), critical differences in species fluctuation were observed among species (p < 0.001). Consequently, the findings of the present study suggest that seasonal factor might be of the substantial factors linked to the habitat composition. However, more descriptive and predictive analytical methods are needed beyond classical regression approaches in habitat use and selection studies at bird ecology.

A bibliometric analysis: what do we know about metals(loids) accumulation in wild birds?

Metals and metalloids pollution is an important worldwide problem due to the social and ecological effects and therefore has been the subject of many disciplines and the adverse impacts have been documented. In this study, content analysis and trends of studies focused on heavy metal accumulation in birds were presented. For this purpose, a bibliometric network analysis of the studies that use the concepts of "pollution," "heavy metal," and "birds" together in the abstract, keywords, and titles of the papers was carried out. The purpose of choosing this research method was summarizing the relation between birds and environmental pollution in an understandable manner to determine metals(loids) pollution, which become an important environmental problem. Bibliometric data consisting of approximately 971 papers were evaluated with VOSviewer program using the network analysis method to answer the research questions. The results revealed that birds act as bioindicators in the determination of environmental pollution and that the contaminant metals deposited in the various tissues of birds provide preliminary information about environmental pollution. The most of bird studies emphasized that the metal accumulation was mostly in the liver, kidneys, and feathers and the accumulation caused serious problems in most of the vital activities of the birds. The USA is in the leading country in birds-heavy metal studies followed by Spain, Canada, and China. In addition, the mercury (Hg) was the most extensively studied heavy metal in these studies.

Investigation of Interlayer Interface Strength and Print Morphology Effects in Fused Deposition Modeling 3D-Printed PLA.

Fused deposition modeling polymer 3D printing has become a popular versatile additive manufacturing technology. However, there are limitations to the mechanical properties due to the layer-by-layer deposition approach. The relatively low strength of the interface between layers is the cause for potential microstructural weak points in such printed components. The interface strength of 3D-printed Polylactic Acid (PLA) polymer was determined through physical tensile testing in combination with microstructural finite element method (FEM) simulations. A custom tensile specimen was created to isolate the interlayer interfaces for direct testing of interface strength. Tensile tests resulted in an average 2.4 GPa stiffness and an average 22.8 MPa tensile strength for printed specimens, corresponding to a 32.4% and 47.8% reduction from the bulk filament stiffness and strength, respectively. Sectioned tensile specimens were observed under a digital microscope to examine microstructural features such as inter-layer gaps, extrusion cross-section, and voids. These were measured to create accurate FEM microstructural model geometries. The brittle fracture that occurred during the tensile testing was due to debonding of the interfaces. This was represented in Abaqus by using cohesive surfaces. Interface strength was inferred by varying the strength of the cohesive surfaces until the simulation mechanical response matched the physical tests. The resulting interface strength of the PLA polymer was 33.75 MPa on average, corresponding to a 22.5% reduction from bulk properties. Potential improvements to the overall strength of the 3D printed PLA were investigated in simulation by parameterizing improved gap morphologies. As the size of the interlayer gaps decreased, the stiffness and strength of the printed parts improved, whereas completely eliminating gaps resulted in a potential 16.1% improvement in material stiffness and 19.8% improvement in strength. These models show that significant improvements can be made to the overall printed part performance by optimizing the printing process and eliminating inner voids.

Effects of Using an Endotracheal Tube Introducer for Intubation During Mechanical Chest Compressions of a Manikin: Randomized, Prospective, Crossover Study.

BACKGROUND: Airway management methods during out-of-hospital cardiac arrest remain controversial. OBJECTIVES: This study aimed to compare the impact of using an endotracheal tube introducer with a Macintosh laryngoscope on the first-pass success rates of final-year medical students on a manikin during continuous chest compressions with a mechanical compression device. METHODS: Fifty-two final-year students of the faculty of medicine performed endotracheal intubations on a manikin using the Macintosh laryngoscope with and without the endotracheal tube introducer during chest compressions. First-pass success rates, the times of endotracheal intubations, the second endotracheal intubation attempt success rates, and the difficulty level of each method according to the participants' perceptions were measured. RESULTS: First-pass success rates did not differ using an endotracheal tube introducer as an adjunct to a Macintosh laryngoscope. Second endotracheal intubation attempt success rates also did not differ by endotracheal tube introducer use. The usage of an endotracheal tube introducer required significantly longer endotracheal intubation time than using only a Macintosh laryngoscope. The perception of difficulty was significantly lower with endotracheal tube introducer use. CONCLUSION: The use of an endotracheal tube introducer as an adjunct to a Macintosh laryngoscope is not associated with higher first-pass success rates during mechanical chest compressions in adult simulations performed by final-year medical students. © 2020 Elsevier Inc.

Recent Advances on Utilization of Bioprinting for Tumor Modeling.

Despite the recent rigorous studies towards a possible cure, cancer still remains as one of the most daunting problems faced by the humanity. Currently utilized two-dimensional cancer models are known to have various insuperable limitations such as insufficient biomimicry of the heterogeneous conditions of tumors and their three-dimensional structures. Discrepancies between the laboratory models and the actual tumor environment significantly impair a thorough comprehension of the carcinogenesis process and development of successful remedies against cancer. Modeling tumor microenvironments through bioprinting poses strong potential to minimize the effects of the aforementioned issues thanks to its freeform nature, adaptability, customizability, scalability and diversity. Numerous research studies involving three-dimensional modeling of various cancer types using bioprinting technologies have been reported, recently. In this review, we provide a broad summary of these studies to help better represent their potential and analyze their contribution to cancer research.

Intra-Cluster Distance Minimization in DNA Methylation Analysis Using an Advanced Tabu-Based Iterative k-Medoids Clustering Algorithm (T-CLUST).

Recent advances in DNA methylation profiling have paved the way for understanding the underlying epigenetic mechanisms of various diseases such as cancer. While conventional distance-based clustering algorithms (e.g., hierarchical and k-means clustering) have been heavily used in such profiling owing to their speed in conduct of high-throughput analysis, these methods commonly converge to suboptimal solutions and/or trivial clusters due to their greedy search nature. Hence, methodologies are needed to improve the quality of clusters formed by these algorithms without sacrificing from their speed. In this study, we introduce three related algorithms for a complete high-throughput methylation analysis: a variance-based dimension reduction algorithm to handle high-dimensionality in data, an outlier detection algorithm to identify the outliers of data, and an advanced Tabu-based iterative k-medoids clustering algorithm (T-CLUST) to reduce the impact of initial solutions on the performance of conventional k-medoids algorithm. The performance of the proposed algorithms is demonstrated on nine different real DNA methylation datasets obtained from the Gene Expression Omnibus DataSets database. The accuracy of the cluster identification obtained by our proposed algorithms is higher than those of hierarchical and k-means clustering, as well as the conventional methods. The algorithms are implemented in MATLAB, and available at: http://www.coe.miami.edu/simlab/tclust.html.

Nanoparticle-mediated targeted drug delivery for breast cancer treatment.

Breast cancer (BC) is the most common malignancy in women worldwide, and one of the deadliest after lung cancer. Currently, standard methods for cancer therapy including BC are surgery followed by chemotherapy or radiotherapy. However, both chemotherapy and radiotherapy often fail to treat BC due to the side effects that these therapies incur in normal tissues and organs. In recent years, various nanoparticles (NPs) have been discovered and synthesized to be able to selectively target tumor cells without causing any harm to the healthy cells or organs. Therefore, NPs-mediated targeted drug delivery systems (DDS) have become a promising technique to treat BC. In addition to their selectivity to target tumor cells and reduce side effects, NPs have other unique properties which make them desirable for cancer treatment such as low toxicity, good compatibility, ease of preparation, high photoluminescence (PL) for bioimaging in vivo, and high loadability of drugs due to their tunable surface functionalities. In this study, we summarize with a critical analysis of the most recent therapeutic studies involving various NPs-mediated DDS as alternatives for the traditional treatment approaches for BC. It will shed light on the significance of NPs-mediated DDS and serve as a guide to seeking for the ideal methodology for future targeted drug delivery for an efficient BC treatment.

Numerical simulations of cell flow and trapping within microfluidic channels for stiffness based cell isolation.

Analysis of rare cells in heterogenous mixtures is proven to be beneficial for regenerative medicine, cancer treatment and prenatal diagnostics. Scarcity of these cells, however, makes the isolation process extremely challenging. Efficiency in cell isolation is still low and therefore, novel cell isolation strategies with new biomarkers need exploration. In this study, we investigated the feasibility of using the mechanical stiffness difference to detect and isolate the rare cells from the surrounding cells without labelling them. Fluid and solid mechanics simulations have shown that cell isolation can be performed at high efficiency using stiffness-based isolation. Accuracy of the numerical simulations is established using microfluidic flow chamber experiments.

Nonsteroidal anti-inflammatory drug-induced acute respiratory distress syndrome.

Drug induced acute respiratory distress syndrome (ARDS) is a common clinical condition. Patients typically present with noncardiogenic pulmonary edema. Large number of ARDS cases reported induced by antineoplastic drugs and other drug intoxications. The pathophysiologic mechanisms of drug induced ARDS remains unknown. One of the postulated mechanisms of drug induced ARDS is anaphylaxis. We present a case of acute respiratory distress syndrome complicated by anaphylactic shock after use of two different nonsteroidal antiinflammatory drugs (NSAID). To the best of our knowledge, ARDS following normal doses of NSAID ingestion has not been reported previously. The case showed that ARDS may occur after ingestion of therapeutic doses of NSAID. NSAID ingestion should be considered in the differential diagnosis of patients with non-cardiogenic pulmonary edema.

Embedding Carbon Dots in Superabsorbent Polymers for Additive Manufacturing.

A type of orange carbon dots (O-CDs) synthesized via an ultrasonication route with citric acid and 1,2-phenylenediamine as precursors was embedded into sodium polyacrylate (SPA) as the ink for 3D printing. Characterizations of these spherical O-CDs revealed an ultra-small size (~2 nm) and excitation-independent, but solvent dependent, emission. The O-CDs were evenly distributed with low degree of aggregation in sodium polyacrylate (SPA), which was achieved due to the property that SPA can absorb water together with O-CDs. The 3D printed photoluminescent objective with the ink revealed a great potential for high yield application of these materials for additive manufacturing. This also represents the first time, bare CDs have been reported as a photoluminescent material in 3D printing, as well as the first time SPA has been reported as a material for 3D printing.

Protective effects of hesperidin in experimental testicular ischemia/reperfusion injury in rats.

INTRODUCTION: In this study, we aimed to determine the protective effects of hesperidin, a citrus flavonoid, in a model of testicular ischemia/reperfusion injury in rats. MATERIAL AND METHODS: Forty-two pubertal male Wistar-Albino rats were divided into six groups: group 1 - control; group 2 - 50 mg/kg hesperidin (low dose hesperidin) used without torsion (LH group); group 3 - 100 mg/kg hesperidin without torsion (HH group); group 4 - torsion/detorsion group (T/D); group 5 - T/D + 50 mg/kg hesperidin treatment group (T/D + LH); and group 6 - T/D + 100 mg/kg hesperidin treatment group (T/D + HH). Hesperidin was given to the treatment groups 30 min before detorsion. After the fourth hour of reperfusion, orchiectomy was performed on the rats under anesthesia. The tissue samples were examined histologically and biochemically. RESULTS: In the T/D group testicular malondialdehyde (MDA) levels were increased significantly (p < 0.001) whereas superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) levels were decreased compared to the control and other groups. However, hesperidin caused the effect of T/D to become closer to normal biochemical values. In addition, the histological examinations showed that T/D caused damage in the testis but hesperidin reduced this effect. The effects of hesperidin were found to be dose dependent. Thus, applying high doses would generate greater therapeutic effects. CONCLUSIONS: In a rat testicular T/D model we observed biochemical and histological damage due to ischemia. However, high and low dose applications of hesperidin were shown to have protective effects against this damage. Therefore, the aforementioned citrus flavonoid may provide positive results in cases of testicular torsion.

Scanning Ion Conductance Microscopic Study for Cellular Uptake of Cationic Conjugated Polymer Nanoparticles.

Positively charged conjugated polymer nanoparticles (CPNs) are emerging biomaterials exhibiting high levels of cellular entry. High rate of cellular entry efficiency is believed that the amphiphilic CPNs interact efficiently with the negatively charged hydrophobic cellular membranes. For the first time, the cell surface morphological changes of human cervical cancer cells treated with CPNs using a scanning probe microscopy technique, scanning ion conductance microscopy (SICM) are imaged. After 1 h of CPN incubation, distinct changes are observed in cell surface morphology such as interconnected protrusions and pits with sub-micrometer sizes, which are not observed from cells treated with positively charged polyethyleneimine (PEI) under the same treatment conditions. The change on cell surface morphology is quantified by surface roughness ratio, which is increased as CPN concentration increases, while the ratio first increases and then decreases as the incubation time increases. These results suggest that cells respond actively toward CPN with both positive charges on the side chain and the hydrophobicity from rigid aromatic backbone, which leads to subsequent endocytosis. In conclusion, it is demonstrated that SICM is a suitable imaging technique to reveal the dynamic alternations on the cell surface morphology at the early stage of nanoparticles endocytosis with high resolution.

Agonist leukadherin-1 increases CD11b/CD18-dependent adhesion via membrane tethers.

Integrin CD11b/CD18 is a key adhesion receptor that mediates leukocyte migration and immune functions. Leukadherin-1 (LA1) is a small molecule agonist that enhances CD11b/CD18-dependent cell adhesion to its ligand ICAM-1. Here, we used single-molecule force spectroscopy to investigate the biophysical mechanism by which LA1-activated CD11b/CD18 mediates leukocyte adhesion. Between the two distinct populations of CD11b/CD18:ICAM-1 complex that participate in cell adhesion, the cytoskeleton(CSK)-anchored elastic elements and the membrane tethers, we found that LA1 enhanced binding of CD11b/CD18 on K562 cells to ICAM-1 via the formation of long membrane tethers, whereas Mn(2+) additionally increased ICAM-1 binding via CSK-anchored bonds. LA1 activated wild-type and LFA1(-/-) neutrophils also showed longer detachment distances and time from ICAM-1-coated atomic force microscopy tips, but significantly lower detachment force, as compared to the Mn(2+)-activated cells, confirming that LA1 primarily increased membrane-tether bonds to enhance CD11b/CD18:ICAM-1 binding, whereas Mn(2+) induced additional CSK-anchored bond formation. The results suggest that the two types of agonists differentially activate integrins and couple them to the cellular machinery, providing what we feel are new insights into signal mechanotransduction by such agents.

Elongated membrane tethers, individually anchored by high affinity α4ß1/VCAM-1 complexes, are the quantal units of monocyte arrests.

The α4ß1 integrin facilitates both monocyte rolling and adhesion to the vascular endothelium and is physiologically activated by monocyte chemoattractant protein (MCP-1). The current study investigated the initial events in the adhesion of THP-1 cells to immobilized Vascular Cell Adhesion Molecule 1 (VCAM-1). Using AFM force measurements, cell adhesion was shown to be mediated by two populations of α4ß1/VCAM-1 complexes. A low affinity form of α4ß1 was anchored to the elastic elements of the cytoskeleton, while a higher affinity conformer was coupled to the viscous elements of the cell membrane. Within 100 ms of contact, THP-1 cells, stimulated by co-immobilized MCP-1, exhibited a tremendous increase in adhesion to VCAM-1. Enhanced cell adhesion was accompanied by a local decoupling of the cell membrane from the cytoskeleton and the formation of long membrane tethers. The tethers were individually anchored by multiple α4ß1/VCAM-1 complexes that prolonged the extension of the viscous tethers. In vivo, the formation of these membrane tethers may provide the quantal structural units for the arrest of rolling monocytes within the blood vessels.

Rearrangement of microtubule network under biochemical and mechanical stimulations.

Cells are constantly under the influence of various external forces in their physiological environment. These forces are countered by the viscoelastic properties of the cytoskeleton. To understand the response of the cytoskeleton to biochemical and mechanical stimuli, GFP-tubulin expressing CHO cells were investigated using scanning laser confocal microscopy. Cells treated with nocodazole revealed disruption in the microtubule network within minutes of treatment while keeping the cell shape intact. By contrast, trypsin, a proteolytic agent, altered the shape of CHO cells by breaking the peptide bonds at adhesion sites. CHO cells were also stimulated mechanically by applying an indentation force with an atomic force microscope (AFM) and by shear stress in a parallel plate flow chamber. Mechanical stimulation applied using AFM showed two distinct cytoskeletal responses to the applied force: an immediate response that resulted in the depolymerization and displacement of the microtubules out of the contact zone, and a slower response characterized by tubulin polymerization at the periphery of the indented area. Flow chamber experiments revealed that shear force did not induce formation of new microtubules in CHO cells and that detachment of adherent cells from the substrate occurred independent from the flow direction. Overall, the experimental system described here allows real-time characterization of dynamic changes in cell cytoskeleton in response to the mechano-chemical stimuli and, therefore, provides better understanding of the biophysical and functional properties of cells.

Anomalous relationship of coexisting ipsilateral recurrent and nonrecurrent inferior laryngeal nerves during thyroid surgery.

One of the most important complications of thyroid surgery is inferior laryngeal nerve injury. Variations of inferior laryngeal nerve may increase the risk of iatrogenic injury. Coexistence of ipsilateral nonrecurrent laryngeal nerve and recurrent laryngeal nerve is a very rare variation, and sufficient data are not available on the anatomical and functional relationship of the 2 branches and probable clinical outcomes resulting from the injury of one of them. Herein, we present a case with coexistence of nonrecurrent laryngeal nerve and ipsilateral recurrent laryngeal nerve and discuss the clinical importance of this rare variation.

Peptide tag forming a rapid covalent bond to a protein, through engineering a bacterial adhesin.

Protein interactions with peptides generally have low thermodynamic and mechanical stability. Streptococcus pyogenes fibronectin-binding protein FbaB contains a domain with a spontaneous isopeptide bond between Lys and Asp. By splitting this domain and rational engineering of the fragments, we obtained a peptide (SpyTag) which formed an amide bond to its protein partner (SpyCatcher) in minutes. Reaction occurred in high yield simply upon mixing and amidst diverse conditions of pH, temperature, and buffer. SpyTag could be fused at either terminus or internally and reacted specifically at the mammalian cell surface. Peptide binding was not reversed by boiling or competing peptide. Single-molecule dynamic force spectroscopy showed that SpyTag did not separate from SpyCatcher until the force exceeded 1 nN, where covalent bonds snap. The robust reaction conditions and irreversible linkage of SpyTag shed light on spontaneous isopeptide bond formation and should provide a targetable lock in cells and a stable module for new protein architectures.