Microscopy Methods Research Articles

The nontrivial effects of annealing on superconducting properties of Nb single crystals

The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 ∘C , 1400 ∘C , and near the melting point of niobium (2477 ∘C ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 ∘C . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 ∘C , measured, annealed at 1700 ∘C , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 ∘C . The clean gap was recovered after annealing at 1700 ∘C . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 ∘C , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from Γ=0.2 to about Γ=0.4 after annealing at 1400 ∘C . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.

Unveiling the abundance and potential impacts of microplastic contamination in commercial organic fertilizers/compost produced from different solid waste.

This study comprehensively investigated the abundance, morphologies, and polymer types of plastics, larger (1-5mm) and smaller (< 1mm) microplastics (MPs), in organic fertilizers using spectroscopic and microscopic methods. MPs abundance varied depending on the type of waste employed. MPs were detected in 80% of the investigated compost samples, while macro/meso plastics were found in only four samples. Compost from mixed municipal solid waste exhibited the highest MPs contamination (23100 ± 3615 items/kg dry weight), whereas compost produced from canteen waste had the lowest contamination (100 ± 65 items/kg dry weight). Smaller MPs were dominant in all samples. The estimated loads of MPs introduced into agricultural soil exceeded the previous studies. Common morphologies observed were sheet, film, fragment, and fiber, while dominant polymer types were polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS). Heavy metals, including Cr, Cu, Ni, and Pb, were identified in association with MPs. Results indicate that the utilization of appropriate waste for composting and upgrading fertilizer regulations is crucial to protect the environment and human health from smaller MPs.

Морфофункциональные изменения СОЖ откормочных свиней при хеликобактериозе

Abstract. The purpose is to study the features of morphofunctional changes in the gastric mucosa of fattening pigs in gastric ulcer disease and to establish a possible correlation between pathological changes and colonization of the gastric mucosa of H. suis. Methods. The study is based on pathoanatomic, microscopic, molecular genetic and histological research methods. Results. In 86 % of cases, significant pathomorphological changes in the gastric mucosa of pigs were detected during a pathoanatomical autopsy. Spiral-shaped microorganisms in smears were found in 28 %, H. suis DNA on the gastric mucosa – in 76 %. In the examined samples in which H. DNA was found. suis in the gastric mucosa, 76.3 % revealed various pathologies in the esophagus, 92% revealed various pathologies on the gastric mucosa. In 24 %, when H. suis DNA was not detected, 33.3 % showed no visible damage and 66.7 % revealed various pathologies. The results of the correlation between morphological changes in the gastric mucosa and its infection with helicobacter reached the limits of statistical reliability. Histological methods revealed that active chronic gastritis was detected in 48.0 %, inactive chronic gastritis was detected in 34.0 % and the norm (almost the norm) was found in 8.0 %. Chronic gastritis during exacerbation was reliably diagnosed in 55.2 % of cases when H. suis DNA was detected on the gastric mucosa. Chronic gastritis during remission was diagnosed in 34.2 % of cases when H. suis DNA was detected on the gastric mucosa. The results presented in the work reflect the undoubted connection between the presence of H. suis and the development of gastritis in pigs.

Microscopy methods map mobile genetic elements and their bacterial hosts.

Microscopy methods map mobile genetic elements and their bacterial hosts.

Real-time single-molecule observation of incipient collagen fibrillogenesis and remodeling

The hierarchic assembly of fibrillar collagen into an extensive and ordered supramolecular protein fibril is critical for extracellular matrix function and tissue mechanics. Despite decades of study, we still know very little about the complex process of fibrillogenesis, particularly at the earliest stages where observation of rapidly forming, nanoscale intermediates challenges the spatial and temporal resolution of most existing microscopy methods. Using video rate scanning atomic force microscopy (VRS-AFM), we can observe details of the first few minutes of collagen fibril formation and growth on a mica surface in solution. A defining feature of fibrillar collagens is a 67-nm periodic banding along the fibril driven by the organized assembly of individual monomers over multiple length scales. VRS-AFM videos show the concurrent growth and maturation of small fibrils from an initial uniform height to structures that display the canonical banding within seconds. Fibrils grow in a primarily unidirectional manner, with frayed ends of the growing tip latching onto adjacent fibrils. We find that, even at extremely early time points, remodeling of growing fibrils proceeds through bird-caging intermediates and propose that these dynamics may provide a pathway to mature hierarchic assembly. VRS-AFM provides a unique glimpse into the early emergence of banding and pathways for remodeling of the supramolecular assembly of collagen during the inception of fibrillogenesis.

Influence of plasma synthesis parameters on the magnetic, structural and photocatalytic properties of copper ferrite

CuFe2O4 cubic copper ferrite nanoparticles were synthesized by a new plasma method, the advantage of which is the short duration of processing and cost-effectiveness. To select optimal synthesis conditions, central compositional rotatable experimental planning was used. Using the methods of X-ray phase analysis, vibration magnetometry, electron microscopy, and UV spectroscopy, the sizes of crystallites, the intensity of peaks in X-ray diffraction patterns, dislocation density, saturation magnetization, coercive force, and the degree of degradation of 4-nitrophenol were determined. To study the effect of pH on the composition of the resulting copper ferrites, cyclic voltammetry was used. The kinetics of the ferritization process under the influence of a plasma discharge has also been studied. A mechanism for ferritization in the Cu2+-Fe2+-SO42--OH- system has been proposed.It was found that single-phase nanodispersed powders of cubic copper ferrites with a saturation magnetization Ms 78–93 Emu/g can be obtained by plasma treatment at 300 s and pH 12. Copper ferrite with an admixture of Cu2O is formed at pH = 8.The maximum values of the coercive force correspond to regimes in which the minimum dislocation density is observed. The saturation magnetization depends on the crystallite size. The crystallite size of the resulting powders is in the range of 225–500 A. The results showed that the processing time is the parameter that has the greatest impact on the structural and magnetic characteristics of copper ferrite; the pH of the reaction medium affects them to a lesser extent.

A Nafion/BiVO4-COOH-MWCNTs/GCE for the sensitive determination of Cd2+ and Pb2+ by DPASV

BiVO4 was hydrothermally prepared and then ultrasonically mixed with carboxylated multiwalled carbon nanotubes (COOH-MWCNTs) to yield a BiVO4-COOH-MWCNTs composite. The composite were cast-coated on a glassy carbon electrode (GCE) to yield a BiVO4-COOH-MWCNTs/GCE, and then a Nafion solution was cast-coated on the BiVO4-COOH-MWCNTs/GCE to yield a Nafion/BiVO4-COOH-MWCNTs/GCE. The related materials and electrodes were characterized by field emission scanning electron microscopy, X-ray diffractometer and electrochemical methods. Under the optimal experimental conditions, Cd2+ and Pb2+ were analyzed by differential pulse anodic stripping voltammetry on the Nafion/BiVO4-COOH-MWCNTs/GCE, giving a linear detection range (LDR) from 10.0 nM to 2.00 μM and a limit of detection (LOD, S/N = 3) of 0.5 nM for Cd2+, as well as a LDR from 10.0 nM to 1.00 μM and a LOD of 0.9 nM for Pb2+. The Nafion/BiVO4-COOH-MWCNTs/GCE exhibited good selectivity, stability and reproducibility and returned satisfactory results of determining Cd2+ and Pb2+ in seafood samples.

Imaging Single Prussian Blue Nanoparticles with Extraordinary Low-Spin Iron Capacity.

In attempts to obtain high-capacity Prussian blue nanomaterials, current efforts are predominantly focused on the particle-ensemble-level understanding of their structure-activity relationships. Complementarily, it would be insightful to screen out extraordinary individuals from the nanoparticle population. Using a simple and efficient technique of bright-field microscopy, this work enables, for the first time, quantitative characterization of the overall two-redox-center electrochemistry of single Prussian blue nanoparticles many at a time. Quantitative optical voltammograms with little interference from solvent breakdown and non-Faradaic electrode charging/discharging are extracted for each single nanoparticle, revealing clear heterogeneity among them. On this basis, the microscopic method allows a detailed comparative analysis between the two redox-active sites. It is found that while the synthesized nanoparticles show a similar specific capacity of the high-spin (HS-Fe) sites with STD/mean = 30%, most individual nanoparticles exhibit monodispersedly small capacities of the low-spin iron (LS-Fe) sites, only about of the HS-Fe capacity. Most importantly, it is discovered that there is always a small fraction (∼8%) of the single nanoparticles showing an impressively tripled LS-Fe capacity. Facilitated by optical imaging, the discovery of this easily overlooked extraordinary subpopulation confers alternative opportunities for targeted efforts for material chemists to improve synthesis and material design based on these unusual individuals, which in turn implies the general significance of nanoparticle screening.

Ubiquitous short-range order in multi-principal element alloys

Recent research in multi-principal element alloys (MPEAs) has increasingly focused on the role of short-range order (SRO) on material performance. However, the mechanisms of SRO formation and its precise control remain elusive, limiting the progress of SRO engineering. Here, leveraging advanced additive manufacturing techniques that produce samples with a wide range of cooling rates (up to 107 K s−1) and an enhanced semi-quantitative electron microscopy method, we characterize SRO in three CoCrNi-based face-centered-cubic (FCC) MPEAs. Surprisingly, irrespective of the processing and thermal treatment history, all samples exhibit similar levels of SRO. Atomistic simulations reveal that during solidification, prevalent local chemical order arises in the liquid-solid interface (solidification front) even under the extreme cooling rate of 1011 K s−1. This phenomenon stems from the swift atomic diffusion in the supercooled liquid, which matches or even surpasses the rate of solidification. Therefore, SRO is an inherent characteristic of most FCC MPEAs, insensitive to variations in cooling rates and even annealing treatments typically available in experiments.

Purification of Potential Antimicrobial Metabolites from Endophytic Fusarium oxysporum Isolated from Myrtus communis.

The rise of microbial resistance and emerging infections pose significant health threats. Natural products from endophytic fungi offer a promising source of novel compounds with the potential as major drug leads. This research aims to screen Myrtus communis and Moringa oleifera for endophytic fungi and screen their metabolites for antibacterial and antifungal potential. Six endophytic fungal strains were isolated using a potato dextrose agar (PDA) medium. The M. communis isolates were designated MC1, MC2, and MC3, and the M. oleifera isolates were named MO1, MO2, and MO3. Preliminary bioactivity testing revealed that the MC3 isolate exhibited significant growth inhibition against multidrug-resistant bacterial and fungal pathogens, including Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Candida glabrata. The MC3 isolate was identified as Fusarium oxysporum through morphological and microscopic methods. For metabolite production, the fungal strain was cultured in potato dextrose broth (PDB) medium at 28°C for 14days in a shaking incubator. The metabolites were purified using various chromatographic techniques, HPLC and GC-MS. The GC-MS analysis of the bioactive compound containing fungal strain (F. oxysporum) revealed multiple compounds at different retention times using the NIST-20 Library. Based on RSI values and probability indices, two compounds were targeted for further purification. Structure elucidation was performed using 1D and 2D nuclear magnetic resonance (NMR) experiments on a Varian 500 NMR machine. The compounds identified were ethyl iso-allocholate (C26H44O5, exact mass 436.32) and 1-monolinoleoyl glycerol trimethylsilyl ether (C27H56O4Si2, exact mass 500.37). The MS (NIST-20) library facilitated the investigation of the in silico antimicrobial activity of these compounds against the elastase virulence protein of P. aeruginosa and protease Sapp1p from C. parapsilosis. Both the compounds were docked with druggable proteins using the Glide induced fit docking (IFD) algorithm. The ethyl iso-allocholate and 1-monolinoleoyl glycerol trimethylsilyl ether compounds showed binding scores - 10.07kcalmol-1 and - 7.47kcalmol-1 against elastase, and - 8.16kcalmol-1 and - 6.89kcalmol-1 against aspartic protease, respectively. In vitro studies confirmed the inhibitory activity of these compounds against multidrug-resistant P. aeruginosa and E. faecalis. Ethyl iso-allocholate exhibited higher bioactivity against P. aeruginosa with inhibition rates of 41%, 27%, and 35% at concentrations of 1000, 500, and 250µgmL-1, respectively. These results suggest that bioactive compounds from F. oxysporum have the potential as antimicrobial agents, warranting further research.

Microcrack characteristics of granite under circumferential strain-controlled uniaxial compression test using UDEC-GBM

Rockburst is one of the significant challenges for underground excavation stability. The post-peak behaviour of rock controls the way it fails, and the released energy is potentially involved in the rockburst. However, understanding of both microscopic and macroscopic behaviours of brittle rock in the post-peak stage is limited due to the lack of proper loading methods and quantitative microscopic analysis methods. This study proposes a circumferential strain-controlled loading algorithm in UDEC to control the failure process, which has been verified against previous literature. By employing the improved geometry generation method, the microcrack evolution is quantitatively assessed. Energy analysis reveals that up to 80% of the input energy is stored in the granite prior to complete failure, which could be released if the rock fails at this moment. Conversely, after the complete failure, intragranular cracks account for the majority of energy dissipation, indicating its importance in post-peak stability. A small portion of the peak stored strain energy needs to be extracted to achieve a controlled failure process. Furthermore, it is found that the significant increases in the formation of intergranular shear and low-angled microcracks potentially feature the complete failure of the specimen. The proposed model offers a complementary method to systematically investigate the post-peak behaviour of rock, including the evolution of microcracks and energy.

Comparison of Foldscope to optical microscope to identify basic histology

Introduction: The teaching of basic histology is crucial in the training of healthcare professionals. Traditionally, the optical microscope is used, but it has limitations such as cost and the need for specific infrastructure. The Foldscope (FS), a low-cost and easy-to-handle tool, emerges as a promising alternative. Objective: To validate the efficacy of the FS in teaching basic histology for healthcare training, comparing it with the traditional method of binocular optical microscopy. Method: We used a kit of prepared histology slides, first examined with an optical microscope and then with the FS. We used a smartphone for image capture, ensuring comparative accuracy between the methods. Results: The FS could observe structures seen with a 10x objective in conventional microscopy but with less sharpness and some peripheral distortions. The applicability of the FS proved effective in observing structures of various tissues, such as the thyroid, arteries, veins, and neurons, although it has limitations for teaching muscular and testicular tissues. Conclusion: The FS is an innovative educational tool that bridges the gap between theory and practice in histology teaching. It is a complementary resource to the optical microscope, effectively identifying structures with about 100x magnification. However, it does not completely replace the optical microscope due to its limitations in magnification and image quality.

Aging drives cerebrovascular network remodeling and functional changes in the mouse brain

Aging is frequently associated with compromised cerebrovasculature and pericytes. However, we do not know how normal aging differentially impacts vascular structure and function in different brain areas. Here we utilize mesoscale microscopy methods and in vivo imaging to determine detailed changes in aged murine cerebrovascular networks. Whole-brain vascular tracing shows an overall ~10% decrease in vascular length and branching density with ~7% increase in vascular radii in aged brains. Light sheet imaging with 3D immunolabeling reveals increased arteriole tortuosity of aged brains. Notably, vasculature and pericyte densities show selective and significant reductions in the deep cortical layers, hippocampal network, and basal forebrain areas. We find increased blood extravasation, implying compromised blood-brain barrier function in aged brains. Moreover, in vivo imaging in awake mice demonstrates reduced baseline and on-demand blood oxygenation despite relatively intact neurovascular coupling. Collectively, we uncover regional vulnerabilities of cerebrovascular network and physiological changes that can mediate cognitive decline in normal aging.

Scanning Plasmon-Enhanced Microscopy for Simultaneous Optoelectrical Characterization.

Scanning microscopy methods are crucial for the advancement of nanoelectronics. However, the vertical nanoprobes in such techniques suffer limitations such as the fragility at the tip-sample interface, complex instrumentation, and the lack of in operando functionality in several cases. Here, we introduce scanning plasmon-enhanced microscopy (SPEM) and demonstrate its capabilities on MoS2 and WSe2 nanosheets. SPEM combines a nanoparticle-on-mirror (NPoM) configuration with a portable conductive cantilever, enabling simultaneous optical and electrical characterization. This distinguishes it from other current techniques that cannot provide both characterizations simultaneously. It offers a competitive optical resolution of 600 nm with local enhancement of optical signal up to 20,000 times. A single gold nanoparticle with a 15 nm radius forms pristine, nondamaging van der Waals contact, which allows observation of unexpected p-type behavior of MoS2 at the nanoscale. SPEM reconstructs the NPoM method by eliminating the need for extensive statistical analysis and offering excellent nanoscale mapping resolution of any selected region. It surpasses other scanning techniques in combining precise optical and electrical characterization, interactive simplicity, tip durability, and reproducibility, positioning it as the optimal tool for advancing nanoelectronics.

Field Application of an Innovative Approach to Assess Honeybee Health and Nutritional Status

Environment, forage quality, management practices, pathogens, and pesticides influence honeybee responses to stressors. This study proposes an innovative approach to assess colony health and performance using molecular diagnostic tools by correlating hemolymph proteins with common measures of colony strength, prevalent honeybee pathogens (Varroa destructor and Nosema spp.), and essential trace elements (iron, zinc and copper). Colonies were selected from four apiaries located in different environmental and foraging conditions in the province of Bologna (Italy). Hemolymph samples were taken from June to October 2019. The Varroa infestation of the colonies was estimated by assessing the natural mortality of the mites, while the bees were tested for Nosema spp. spores using a microscopic method. Hemolymph proteins were quantified and separated using SDS-PAGE, and colony performance was assessed by determining adult bees, total brood, honey, and pollen reserves. The biomarkers measured proved to be useful for monitoring changes in performance and trophic conditions during summer and early autumn. Significant correlations were found between hemolymph proteins and colony performance measures. A positive correlation between pollen reserves, vitellogenin, and hexamerin 70a highlights the importance of these proteins for successful overwintering. In October, Varroa infestation was negatively correlated with total proteins, vitellogenin, apolipophorin II, transferrin, and hexamerin 70a, with negative implications for overwintering; furthermore, Varroa infestation was also negatively correlated with iron content, potentially affecting iron homeostasis.

Metal-Organic Framework on Fullerene (MOFOF) as a Hierarchical Composite by the Integration of Coordination Chemistry and Supramolecular Chemistry.

There is a synergy between coordination chemistry and supramolecular chemistry that has led to the development of innovative hierarchical composites with diverse functionalities. Here, we present a novel approach for the synthesis and characterization of a metal-organic framework on fullerene (MOFOF) composites, achieved through the integration of coordination chemistry and supramolecular chemistry principles. The hierarchical nature of the MOFOF harnesses the inherent properties of metal-organic frameworks and fullerenes. The two-step synthesis procedure involves controlled assembly of fullerenes as tube-like nanostructures (fullerene nanotube: FNT), their surface functionalization, and the on-surface growth of the MOF (in this case, ZIF-67). The method permits the precise tuning of morphology, effective distribution of MOF-on-FNT, and tight compositional control. The materials were comprehensively structurally characterized using electron microscopy, spectroscopic techniques, and other methods to elucidate the unique features and interactions within the MOFOF composites. The main findings reveal that the novel synthesis and characterization of MOFOF composites demonstrate the successful integration of coordination chemistry and supramolecular chemistry for the designing and fabricating of advanced hierarchical composites with tailored properties, including micro- and mesopore channels, interfacial facets, and defect sites. These properties are expected to lead to numerous potential applications such as gas storage and separation, catalysis, sensing, energy storage, and environmental remediation. However, only the capability of acid vapor sensing was tested and is described here.

How to achieve nanometer flat surfaces: Pulsed electrochemical machining of bulk metallic glass

The Bulk Metallic Glass (BMG) Vitreloy 105 (Zr52.5Ti5Ni14.6Cu17.9Al10) as well as two crystalline reference materials of the same composition were machined with Pulsed Electrochemical Machining (PECM). One reference material was nano crystalline with an average grain size of 11 nm and the second one was a fine grain crystalline sample with an average grainsize of 110 nm. The goal was to achieve maximum surface quality in terms of roughness by utilizing a readily available industrial process. Samples were characterized by tactile profilometer, atomic force microscopy and electron microscopy methods. The results show superior surface quality of the amorphous samples over the reference materials with an average roughness depth as low as 1 nm. The observed dissolution mechanism of the BMG differs from the reference materials -as in contrast to the crystalline alloys that show a passive layer formation - no such surface layer other than the native oxide could be observed. The PECM procedure is found to be a promising post-processing step for BMGs with a resulting surface that can face even the most challenging surface quality requirements.

Phase retrieval via conjugate gradient minimization in double-plane lensless holographic microscopy

Optimization-based phase retrieval method for digital lensless holographic microscopy in the double-plane recording configuration is proposed. In our method the phase retrieval is framed as an optimization problem that can be efficiently and rigorously tackled with gradient decent tools. This is done with the conjugate gradient method that possesses excellent theoretical features such as global and fast convergence (compared to steepest descent) and relatively low computational cost (compared to second order optimizers). The proposed method is extensively tested with simulations and experimental measurements that show superiority of our method over the Gerchberg-Saxton algorithm, especially in terms of reconstruction of problematic low frequency components of viable phase information.

Advancing cellular insights: Super-resolution STORM imaging of cytoskeletal structures in human stem and cancer cells

Fluorescence microscopy is an important tool for cell biology and cancer research. Present-day approach of implementing advanced optical microscopy methods combined with immunofluorescence labelling of specific proteins in cells is now able to deliver optical super-resolution up to ∼25 nm. Here we perform super-resolved imaging using standard immunostaining protocol combined with easy stochastic optical reconstruction microscopy (easySTORM) to observe structural differences of two cytoskeleton elements, actin and tubulin in three different cell types namely human bone marrow-derived mesenchymal stem cells (MSCs), human glioblastoma (U87MG) and breast cancer (MDAMB-231) cells. The average width of the actin bundle obtained from STORM images of stem cells is observed to be larger than the same for U87MG and MDAMB-231 cells. No significant difference is however noticed in the width of the tubulin within the same cells. We also study the functional effect on the 2D migration potential of MDAMB-231 cells silenced for NICD1 and β-catenin. Although similar migration speed is observed for cells with the above two conditions compared to their control cells, easySTORM images show that widths of the actin in MDAMB-231 cells in β-catenin silenced is significantly lower than the same in control cells. Such minute differences however are not observable in widefield images. The outcome of our easySTORM investigation should benefit the researchers carrying out detailed investigations of the cellular structure and potential therapeutic applications.

Leveraging Methods in Microscopy for Exploring Structure-Property Relations of Ultrahigh Aspect Ratio Multiwalled Carbon Nanotubes Subject to Ball Milling and Compounding with Polymers

Leveraging Methods in Microscopy for Exploring Structure-Property Relations of Ultrahigh Aspect Ratio Multiwalled Carbon Nanotubes Subject to Ball Milling and Compounding with Polymers