Inoculation of heavy metal resistant bacteria alleviated heavy metal-induced oxidative stress biomarkers in spinach (Spinacia oleracea L.).

Most vegetable crops are severely affected by the uptake of heavy metals from the soil. Heavy metals in vegetable bodies generate reactive oxygen species (ROS) that unbalance the antioxidant defense system. This study was initiated to determine the physiological and biochemical characteristics of spinach plants grown on soil contaminated with heavy metals and responding to Bacillus cereus and Bacillus aerius were isolated from soil contaminated with heavy metals. Heavy metal contamination led to a significant reduction in seed germination, seedling biomass, protein, and total nitrogen content of spinach plants grown in contaminated soils compared to control soils. In contrast, a significant increase in the content of metallothioneins and antioxidant enzymes was observed. Plants inoculated with B. cereus and B. aerius significantly reduced the oxidative stress induced by heavy metals by improving seed germination (%), seedling growth, nitrogen, and protein content. The content of metallothioneins and the activities of antioxidant enzymes were reduced in spinach plants grown from seeds inoculated with bacterial strains. In addition, plants inoculated with, B. cereus and B. aerius showed greater stomata opening than plants grown on soil contaminated with heavy metals, whose stomata were almost closed. These results suggested that both bacterial strains enhanced plant growth by reducing oxidative stress caused by metals.

Macro-micro exploration on dynamic interaction between aflatoxigenic Aspergillus flavus and maize kernels using Vis/NIR hyperspectral imaging and SEM technology.

Aspergillus flavus and its toxic metabolites-aflatoxins infect and contaminate maize kernels, posing a threat to grain safety and human health. Due to the complexity of microbial growth and metabolic processes, dynamic mechanisms among fungal growth, nutrient depletion of maize kernels and aflatoxin production is still unclear. In this study, visible/near infrared (Vis/NIR) hyperspectral imaging (HSI) combined with the scanning electron microscope (SEM) was used to elucidate the critical organismal interaction at kernel (macro-) and microscopic levels. As kernel damage is the main entrance for fungal invasion, maize kernels with gradually aggravated damages from intact to pierced to halved kernels with A. flavus were cultured for 0-120 h. The spectral fingerprints of the A. flavus-maize kernel complex over time were analyzed with principal components analysis (PCA) of hyperspectral images, where the pseudo-color score maps and the loading plots of the first three PCs were used to investigate the dynamic process of fungal infection and to capture the subtle changes in the complex with different hardness of the maize matrix. The dynamic growth process of A. flavus and the interactions of fungus-maize complexes were explained on a microscopic level using SEM. Specifically, fungus morphology, e.g., hyphae, conidia, and conidiophore (stipe) was accurately captured on the microscopic level, and the interaction process between A. flavus and nutrient loss from the maize kernel tissues (i.e., embryo, and endosperm) was described. Furthermore, the growth stage discrimination models based on PLSDA with the results of CCRC = 100 %, CCRV = 97 %, CCRIV = 93 %, and the prediction models of AFB1 based on PLSR with satisfactory performance (R2C = 0.96, R2V = 0.95, R2IV = 0.93 and RPD = 3.58) were both achieved. In conclusion, the results from both macro-level (Vis/NIR-HSI) and micro-level (SEM) assessments revealed the dynamic organismal interactions in A. flavus-maize kernel complex, and the detailed data could be used for modeling, and quantitative prediction of aflatoxin, which would establish a theoretical foundation for the early detection of fungal or toxin contaminated grains to ensure food security.

The dam that fly ash built.

When the first concrete was poured in 1949 for the Hungry Horse Dam (Montana, USA), pozzolan cements had already been used in several major North American dams, including Grand Coulee on the Columbia River (diatomaceous earth explored but ultimately not used), Friant on the San Joaquin River and Altus on the North Fork Red River (pumicite) and Bonneville on the Columbia River and Davis on the Colorado River (calcined clay). But Hungry Horse Dam stands out as the first dam constructed using coal combustion fly ash. Utilising 2.4 million cubic metres of concrete, the dam is located on the South Fork Flathead River, one of the tributaries feeding one of the nation's major waterways, the Columbia River, and closely related to the adjacent Glacier National Park. In this respect, Hungry Horse is directly connected to two momentous periods in modern history - the massive adoption in the 1950s of coal as fuel for power plants, and the ongoing threats to fresh water supply and the rapid retreat of alpine glaciers due to global warming. Two concrete cores from this dam, one with fly ash and one without fly ash, are examined microscopically to explore the long-term suppression of alkali-aggregate reaction by fly ash. The core without fly ash exhibits clear evidence of alkali-aggregate reaction, manifested by sandstone coarse aggregate particles with darkened reaction rims. Sandstone coarse aggregate particles of the same lithology in the core with fly ash are without signs of alkali-aggregate reaction. A detailed examination of the darkened rims indicates that alkali-silica reaction products fill the narrow gaps between adjacent sand grains in the sandstone. This alkali-silica gel infilling allows for optical continuity between adjacent sand grains and is responsible for the classic darkened rim associated with the alkali-aggregate reaction.

The adsorption of 2-amino-1-methyl-6-phenyl-imidazolium [4, 5-B] pyridine (PhIP) by lactic acid bacteria 37X-15 and its peptidoglycan.

The heterocyclic amine 2-amino-1-methyl-6-phenyl-imidazolium [4, 5-B] pyridine (PhIP), commonly found in roasted meat products, is considered a potential carcinogen. This study is to explore the underlying mechanisms involved in the adsorption of PhIP by lactic acid bacteria 37X-15 and its peptidoglycan. The scanning electron microscope results suggested that the strain's adsorption on PhIP occurs on the cell wall, primarily composed of peptidoglycan. The fourier-transformed infrared spectroscopy results indicated that PhIP adsorption by both lactic acid bacteria 37X-15 and its peptidoglycan primarily involved OH and NH binding groups. Different adsorption conditions affected the adsorption rate of PhIP by peptidoglycan. The optimal values for each adsorption condition were 2 h, 37 °C, and pH 6 when the maximum adsorption rate reached. This study provides a new direction for the application of lactic acid bacteria and its peptidoglycan in food safety.

Comparison of Laboratory Diffraction Contrast Tomography and Electron Backscatter Diffraction Results: Application to Naturally Occurring Chromites.

Understanding how minerals are spatially distributed within natural materials and their textures is indispensable to understanding the fundamental processes of how these materials form and how they will behave from a mining engineering perspective. In the past few years, laboratory diffraction contrast tomography (LabDCT) has emerged as a nondestructive technique for 3D mapping of crystallographic orientations in polycrystalline samples. In this study, we demonstrate the application of LabDCT on both chromite sand and a complex chromitite sample from the Merensky Reef (Bushveld Complex, South Africa). Both samples were scanned using LabDCT and Electron Backscatter Diffraction (EBSD), and the obtained results were rigorously evaluated using a comprehensive set of qualitative and quantitative characterization techniques. The quality of LabDCT results was accessed by using the "completeness" value, while the inaccuracies were thoroughly discussed, along with proposed potential solutions. The results indicate that the grain orientations obtained from LabDCT are comparable to that of 2D EBSD but have the advantage of collecting true 3D size, shape, and textural information. This study highlights the significant contribution of LabDCT in the understanding of complex rock materials from an earth science perspective, particularly in characterizing mineral texture and crystallography in 3D.

In-vitro Antimicrobial Study of Non/irradiated Ylang-ylang Essential Oil Against Multi Drug Resistant Pathogens with Reference to Microscopic Morphological Alterations.

Essential oils have proven to possess great potential in the field of biomedicine due to their ability to effectively eradicate a diverse range of pathogenic microbes. In this study, the antimicrobial activity of ylang-ylang essential oil (YY-EO) was screened against twelve multidrug-resistant pathogens. The YY-EO was effective up to 536 µg/ml, with the highest inhibition zone in case of S. aureus MMCC21 and Escherichia coli MMCC24. The least effect on both Bacillus cereus MMCC11 and Klebsiella pneumonia MMCC16. The major components of the essential oil were identified using GC-MS analysis. Different gamma irradiation doses against the YY-EO were evaluated as a tool of natural decontamination. Moreover, the antimicrobial assay after irradiation proved no significant changes regarding the antimicrobial activity before and after irradiation of EO at the applied dose. The minimum inhibitory concentration (MIC) for the EO against the tested pathogens was detected. The possible morphological changes in some of the bacterial and yeast cells at the recognized MIC and 2MIC were detected using the scanning electron microscope (SEM). Results revealed a notable change in terms of both the microbial cell population and the morphology of the tested bacterial and yeast cells. The cytotoxicity of ylang-ylang EO was evaluated against normal skin tissue culture and showed a potential cytotoxic effect at concentrated doses. These results refer to the importance of YY-EO as a natural antimicrobial agent and the possible application of YY-EO as a surface decontaminant, but they also draw attention to the importance of the EO concentration used in different applications to avoid possible toxic effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01122-4.

Properties of three collagen scaffolds in comparison with native connective tissue: an in-vitro study.

PURPOSE: To evaluate collagen scaffolds (CS) in terms of their in vitro resorption behavior, surface structure, swelling behavior, and mechanical properties in physiologically simulated environments, compared with porcine native connective tissue. MATERIALS AND METHODS: Three test materials-one porcine collagen matrix (p-CM), two acellular dermal matrices (porcine = p-ADM, allogenic = a-ADM)-and porcine native connective tissue (p-CTG) as a control material were examined for resorption in four solutions using a high-precision scale. The solutions were artificial saliva (AS) and simulated body fluid (SBF), both with and without collagenase (0.5 U/ml at 37 °C). In addition, the surface structures of CS were analyzed using a scanning electron microscope (SEM) before and after exposure to AS or SBF. The swelling behavior of CS was evaluated by measuring volume change and liquid absorption capacity in phosphate-buffered saline (PBS). Finally, the mechanical properties of CS and p-CTG were investigated using cyclic compression testing in PBS. RESULTS: Solutions containing collagenase demonstrated high resorption rates with significant differences (p < 0.04) between the tested materials after 4 h, 8 h and 24 h, ranging from 54.1 to 100% after 24 h. SEM images revealed cross-linked collagen structures in all untreated specimens. Unlike a-ADM, the scaffolds of p-CM and p-ADM displayed a flake-like structure. The swelling ratio and fluid absorption capacity per area ranged from 13.4 to 25.5% among the test materials and showed following pattern: p-CM > a-ADM > p-ADM. P-CM exhibited higher elastic properties than p-ADM, whereas a-ADM, like p-CTG, were barely compressible and lost structural integrity under increasing pressure. CONCLUSIONS AND CLINICAL IMPLICATIONS: Collagen scaffolds vary significantly in their physical properties, such as resorption and swelling behavior and elastic properties, depending on their microstructure and composition. When clinically applied, these differences should be taken into consideration to achieve the desired outcomes.

Testing and Analysis of Ultra-High Toughness Cementitious Composite-Confined Recycled Aggregate Concrete under Axial Compression Loading.

In order to analyze the axial compressive properties of ultra-high-toughness cementitious composite (UHTCC)-confined recycled aggregate concrete (RAC), a batch of UHTCC-confined RAC components was designed and manufactured according to the requirements of GB/T50081-2002 specifications. After analyzing the surface failure phenomenon, load-displacement curves, scanning electron microscope (SEM), and parameter analysis of the specimen, the result shows that UHTCC-confined RAC is an effective confinement method, which can effectively improve the mechanical properties and control the degree of surface failure of RAC structures. Compared with the unconfined specimen, the maximum peak load of the UHTCC confinement layer with a thickness of 10 mm and 20 mm increased by 44.61% and 79.27%, respectively, meeting the requirements of engineering practice. Different fiber mixing amounts have different effects on improving the mechanical performance of RAC structural. The specific rule was steel fiber (SF) > polyvinyl alcohol fiber (PVAF) > polyvinyl alcohol fiber (PEF) > no fiber mixture, and the SF improves the axial compression properties of UHTCC most significantly. When there are strict requirements for improving the mechanical properties of the structure, SF should be added to UHTCC. On the contrary, PVAF should be added to UHTCC.

Effect of an In-Office Bleaching Agent with Surface Pre-Reacted Glass-Ionomer Filler on the Enamel Surface: A In-Vitro Study.

In-office bleaching with high concentrations of hydrogen peroxide (H2O2) agents causes undesirable alterations in the enamel. Surface pre-reacted glass-ionomer (S-PRG) filler is a functional material known for its acid-neutralizing and demineralization-inhibition properties. This study evaluates the effect of S-PRG filler incorporation in H2O2-based bleaching on the enamel surface. Bovine enamel surfaces were bleached using a bleaching paste formulated with a liquid (35% H2O2) and a powder containing 5% or 10% S-PRG filler. The surface roughness and the Vickers microhardness of the treated enamel surfaces were evaluated. The enamel surfaces were observed under a scanning electron microscope (SEM) and analyzed using energy dispersive X-ray (EDX) technology. The surfaces were challenged by citric acid and observed by SEM. The specimens bleached with the paste containing the S-PRG filler showed lower enamel surface roughness and higher microhardness values than did those bleached with the plain paste (0% S-PRG filler); meanwhile, there were no significant differences between the 5% or 10% S-PRG filler groups. The S-PRG filler groups showed enamel surface morphologies similar to those of the non-bleached enamel, according to SEM observation, and EDX analysis detected the presence of fluoride and strontium ions. The S-PRG filler groups showed a higher resistance to erosion. The S-PRG filler mitigated the detrimental effects of bleaching agents on the enamel surface and provided resistance to erosion.

Insights into spermatogenesis in the migratory locust, Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae), following histological and ultrastructural features of the testis.

The migratory locust, Locusta migratoria (Linnaeus, 1758), is one of the most destructive agricultural pests globally, and this species is particularly localized in several regions of Egypt. However, so far, very little attention has been paid to the characteristics of the testes. Furthermore, spermatogenesis requires careful analysis to characterize and track developmental episodes. We thus investigated, for the first time, the histological and ultrastructural properties of the testis in L. migratoria employing a light microscope, a scanning electron microscope (SEM), and a transmission electron microscope (TEM). Our results revealed that the testis comprises several follicles, emerging with distinct outer surface wrinkle patterns for each follicle throughout the length of the follicular wall. Furthermore, histological examination of the follicles showed that each has three developmental zones. Each zone has cysts with characteristic spermatogenic elements, beginning with the spermatogonia at the distal end of each follicle and ending with the spermatozoa at the proximal end. Moreover, spermatozoa are arranged in spermatozoa bundles called spermatodesms. Overall, this research provides novel insights into the structure of the testes of L. migratoria, which will significantly contribute to formulating effective pesticides against locusts.

A Retrofittable Photoelectron Gun for Low-Voltage Imaging Applications in the Scanning Electron Microscope.

Low-voltage scanning electron microscopy is a powerful tool for examining surface features and imaging beam-sensitive materials. Improving resolution during low-voltage imaging is then an important area of development. Decreasing the effect of chromatic aberration is one solution to improving the resolution and can be achieved by reducing the energy spread of the electron source. Our approach involves retrofitting a light source onto a thermionic lanthanum hexaboride (LaB6) electron gun as a cost-effective low energy-spread photoelectron emitter. The energy spread of the emitter's photoelectrons is theorized to be between 0.11 and 0.38 eV, depending on the photon energy of the ultraviolet (UV) light source. Proof-of-principle images have been recorded using this retrofitted photoelectron gun, and an analysis of its performance is presented.

Physicochemical Properties and Tissue Structure of High Kernel Elongation Rice (Oryza sativa L.) Varieties as Affected by Heat Treatment.

Heat treatment could affect the structure and properties of rice varieties. The present study was conducted in order to determine the effects of heat treatment on the physicochemical properties and tissue structure of Mahsuri Mutan, Basmati 370 and MR219 rice varieties. The three rice varieties were subjected to heat treatment (ageing) at 90 °C, using an oven, for 3 h. After the heat treatment, the samples were cooled at room temperature (25 °C) for 1 h. Physicochemical properties, such as alkali digestion value, water uptake ratio, solids in cooking water, high kernel elongation ratio and amylose contents, were determined. The procedure used in determining both apparent and absolute amylose involved measuring the iodine affinity of defatted whole starch. Ahigh-performance anion-exchange chromatograph was used to analyse branch chain length distribution of amylopectin quantitatively. The starch structure of the rice samples was observed under a scanning electron microscope. Data collected on physicochemical traits, heat treatment and control (ageing and non-ageing) were subjected to an analysis of variance using SAS software version 9.4. In this study, Mahsuri Mutan and Basmati 370 showed superior high kernel elongation as compared to their respective rice progenies. This study also found that heat treatment directly affected the increasingly high kernel elongation for both populations. The phenotypic correlation co-efficient indicated that there was a high positive correlation between high kernel elongation and water uptake ratio, implying that selection for water uptake ratio would increase the high kernel elongation characteristic. The heat treatment showed significant difference in all the physicochemical traits of the varieties studied. Heat treatment also affected the very long branch chains of starch, such as amylose. Observation under an electron microscope showed that the samples subjected to heat treatment had more cracks on the tissue structure compared to normal rice samples. The hexagon structure in Mahsuri Mutan produced a greater elongation effect on its kernel. The findings from this study could be useful to breeders in the selection and development of a new high kernel elongation rice variety.

A comparison of the impacts of different polysaccharides on the sono-physico-chemical consequences of ultrasonic-assisted modifications.

This study aimed to examine the sono-physico-chemical effects of ultrasound (UND) and its impact on the conjugate rates of morin (MOI) following the addition of polysaccharides in various conditions. In comparison to the control group, the incorporation of quaternary ammonium chitosan decreased the rate of MOI conjugation by 17.38%, but the addition of locust bean gum enhanced the grafting rate by 29.89%. Notably, the highest degree of myofibrillar protein (MRN) unfolding (fluorescence intensity: 114435.50), the most stable state (-44.98 mV), and the greatest specific surface area (393.06 cm2/cm3) were observed in the UMP/LBG group. The outcomes of atomic force microscopy and scanning electron microscopy revealed that the inclusion of locust bean gum led to a different microscopic morphology than the other two polysaccharides, which may be the primary cause of the strongest sono-physico-chemical effects of the system. This work demonstrated that acoustic settings can be tuned based on the characteristics of polysaccharides to maximize the advantages of sono-physico-chemical impacts in UND-assisted MOI processing.

Preliminary Study on the Effect of a Single High-Energy Electromagnetic Pulse on Morphology and Free Radical Generation in Human Mesenchymal Stem Cells.

The effect of nanosecond electromagnetic pulses on human health, and especially on forming free radicals in human cells, is the subject of continuous research and ongoing discussion. This work presents a preliminary study on the effect of a single high-energy electromagnetic pulse on morphology, viability, and free radical generation in human mesenchymal stem cells (hMSC). The cells were exposed to a single electromagnetic pulse with an electric field magnitude of ~1 MV/m and a pulse duration of ~120 ns generated from a 600 kV Marx generator. The cell viability and morphology at 2 h and 24 h after exposure were examined using confocal fluorescent microscopy and scanning electron microscopy (SEM), respectively. The number of free radicals was investigated with electron paramagnetic resonance (EPR). The microscopic observations and EPR measurements showed that the exposure to the high-energy electromagnetic pulse influenced neither the number of free radicals generated nor the morphology of hMSC in vitro compared to control samples.

A Novel Electrochemical Differentiation between Exosomal-RNA of Breast Cancer MCF7 and MCF7/ADR-Resistant Cells.

Cancer is considered one of the most burdensome diseases affecting lives and, hence, the economy. Breast cancer is one of the most common types of cancer. Patients with breast cancer are divided into two groups: one group responds to the chemotherapy, and the other group resists the chemotherapy. Unfortunately, the group which resists the chemotherapy is still suffering the pain associated with the severe side effects of the chemotherapy. Therefore, there is a critical need for a method to differentiate between both groups before the administration of the chemotherapy. Exosomes, the recently discovered nano-vesicles, are often used as cancer diagnostic biomarkers as their unique composition allows them to represent their parental cells, which makes them promising indicators for tumor prognosis. Exosomes contain proteins, lipids, and RNA that exist in most body fluids and are expelled by multiple cell types, including cancer cells. Furthermore, exosomal RNA has been significantly used as a promising biomarker for tumor prognosis. Herein, we have developed an electrochemical system that could successfully differentiate between MCF7 and MCF7/ADR depending on the exosomal RNA. The high sensitivity of the proposed electrochemical assay opens the door for further investigation that will address the other type of cancer cells.

Distribution, compositional characteristics, and historical pollution records of microplastics in tidal flats of South Korea.

Studies on distribution of microplastics (MPs) in sediments of tidal flats are relatively scarce compared to other coastal areas. In this study, spatial and vertical distributions and compositions of MPs in tidal flat sediments along the west coast of Korea were investigated. The abundance of MPs in surface and core sediments ranged from 20 to 325 and 14 to 483 particles per 50 g dry weight, respectively. Polypropylene (51%) and polyethylene (36%) were the most dominant MPs; the size was <0.3 mm, and the shape was mostly fragments followed by fibers. The abundance of MPs in sediments has increased rapidly since the 1970s, and recently showed a slight decrease. Surface morphology of MPs analyzed using a scanning electron microscope revealed that the MPs in tidal flats were highly weathered mechanically and/or oxidatively. The results of this study provide valid baseline data on distributions of MPs in tidal flats.

Scanning electron microscopic characterizations of the tongue of the Nubian goat (Capra aegagrus hircus): A specialized focus on its papillary system adaptation to Egyptian environmental conditions.

The current investigation was focused on describing the gross and scanning electron features of the Nubian goat (Capra aegagrus hircus) tongue, with new insights into its papillary adaptation to the Egyptian environment. The elongated tongue had a rostral free and the caudal fixed. The ventral apical surface is classified into the smaller rostral papillary region on the tip and the larger non-papillary region by the U-line of filiform papillae. Functionally, there are two papillary types: mechanical (filiform, conical and lentiform in addition to the longitudinal row of large conical papilla on the lateral of the body) and gustatory (fungiform and circumvallate). Filiform papillae were densely distributed on the dorsal surface of the apex and body, and on the lateral apical border and lateral surface of the body and root, in addition to the ventral surface of the tip. This filiform papillary system gives a raspy appearance to the dorsal surface. The conical and lentiform papillae were limited to the torus linguae. Circumvallate papillae are surrounded by an annular groove and slightly vallum. The lingual root was devoid of any papillae. Lingual papillary subtypes are filiform papillae (elongated and triangular), conical papillae (elongated and oval) and fungiform papillae (round and ovoid). The investigated Nubian goat may have developed a specialized papillary system due to regional differences in the distribution, structure and subtypes of the system, allowing it to adapt to the dried grasses and leaves of trees and bushes that are available in Upper Egypt's dry, hot climate.

Detection of In-Plane Movement in Electrically Actuated Microelectromechanical Systems Using a Scanning Electron Microscope.

The measurement of in-plane motion in microelectromechanical systems (MEMS) is a challenge for existing measurement techniques due to the small size of the moving devices and the low amplitude of motion. This paper studied the possibility of using images obtained using a scanning electron microscope (SEM) together with existing motion detection algorithms to characterize the motion of MEMS. SEM imaging has previously been used to detect motion in MEMS device. However, the differences in how SEM imaging and optical imaging capture motion, together with possible interference caused by electrical actuation, create doubts about how accurately motion could be detected in a SEM. In this work, it is shown that existing motion detection algorithms can be used to detect movement with an amplitude of 69 nm. In addition, the properties of SEM images, such as bright edges, complement these algorithms. Electrical actuation was found to cause error in the measurement, however, the error was limited to regions that were electrically connected to the actuating probes and minimal error could be detected in regions that were electrically insulated from the probes. These results show that an SEM is a powerful tool for characterizing low amplitude motion and electrical contacts in MEMS and allow for the detection of motion under 100 nm in amplitude.

In vitro controlled elemental analysis to evaluate the combined effect of acidulated phosphate fluoride with Er:YAG and diode lasers.

Background: Acidulated phosphate fluoride (APF) application is used for dental caries prevention. Combining APF with different laser wavelengths increases acid resistance in enamel. Aim: To assess the effects of Er:YAG (2940 nm) laser and diode (940 nm) laser after the application of APF on morphology and mineral content of enamel surfaces of human teeth in vitro. Materials and Methods: Twenty (20) freshly extracted third molar crowns were collected and split longitudinally into halves. Ten (10) halves were given to each of the following groups: group 1 (control), group 2 (application of 1.23% APF gel only), group 3 (diode laser; 1 W for 60 sec, contact mode after APF gel), and group 4 (Er:YAG; 80 mJ, 0.8 W, 10 Hz; in pulsed mode for 10 sec after APF gel). Specimens were morphologically examined by scanning electron microscope (SEM), and mineral content was analysed by energy dispersive X-ray (EDX). Collected data were statistically analysed by ANOVA. Results: Morphologic results were superior in group 3 followed by group 2 and group 1 with the least change in group 4. EDX of calcium (Ca), phosphorous (P), and Ca/P ratio weight % showed the highest value with no statistical significance between groups 2 and 1, and higher with statistical significance in groups 3 and 4 in descending order. Carbon weight % showed highest results in group 4 then 3, 2, and 1. Fluoride weight % showed highest statistical results in group 4 then 2, 3, and 1. Conclusion: The diode laser showed superior morphological results after APF application compared to the Er:YAG laser. The Er:YAG increased fluoride absorption on outer enamel surfaces.

Contexte: L'application de fluorure de phosphate acidulé (FPA) est utilisée pour la prévention des caries dentaires. La combinaison de FPA avec différentes longueurs d'onde de laser augmente la résistance de l'émail aux acides. Objectif: Évaluer les effets du laser erbium YAG (2940 nm) et du laser à diode (940 nm) après l'application de FPA sur la morphologie et le contenu minéral des surfaces de l'émail des dents humaines in vitro. Matériaux et méthodologies: Vingt (20) couronnes de troisième molaire fraîchement extraites ont été recueillies et divisées longitudinalement en moitiés. Dix (10) moitiés ont été données à chacun des groupes suivants : groupe 1 (contrôle), groupe 2 (application de gel de FPA à 1,23 % seulement), groupe 3 (laser à diode; 1 W pendant 60 secondes, mode contact après le gel de FPA), et groupe 4 (erbium YAG; 80 mJ, 0,8 W, 10 Hz kl ; en mode pulsé pendant 10 secondes après le gel de FPA). Les spécimens ont été examinés morphologiquement au microscope électronique à balayage (MEB), et le contenu minéral a été analysé par rayons X à dispersion d'énergie (EDX). Les données recueillies ont été analysées statistiquement par ANOVA. Résultats: Les résultats morphologiques étaient supérieurs dans le groupe 3, suivi par le groupe 2 et le groupe 1, avec le changement le moins important dans le groupe 4. Le pourcentage de l'EDX du calcium (Ca), du phosphore (P) et du rapport Ca/P en poids a montré la valeur la plus élevée sans signification statistique entre les groupes 2 et 1, et la plus élevée avec signification statistique dans les groupes 3 et 4 par ordre décroissant. Le pourcentage en poids de carbone a montré les résultats les plus élevés dans le groupe 4, ensuite 3, 2 et 1. Le pourcentage en poids de fluorure a montré les résultats statistiques les plus élevés dans le groupe 4 puis 2, 3 et 1. Conclusion: Le laser à diode a montré des résultats morphologiques supérieurs après l'application de FPA par rapport au laser erbium YAG. L'erbium YAG a augmenté l'absorption du fluorure sur les surfaces externes de l'émail.

Ion microsource integrated with scanning electron microscope for sample preparation.

The authors developed the Ar+ ion microsource, which can generate a filamentary ion beam of a few tens of µm at its half-power diameter with a target current up to 50 µA at - 4 kV extracting voltage. This comprises a ceramic discharge capillary of 1 mm in inner diameter and 10 mm long with a very small copper anode and a cathode outlet aperture of 0.5 mm in diameter at its ends. The arrangement has been examined in three alternative designs equipped with cathodes of different shapes and materials and two extraction voltage supply schemes, i.e., with the negatively biased sample and the earthed cathode or the earthed sample and the cathode at a floating positive potential (recommended solution). Numerous other factors were considered that can affect the standard SEM operation, such as excessive working gas leakage and jamming with discharge interferences, e.g., streamers. The microsource makes a compact structure that can be positioned above the sample inside a standard SEM without any changes to its original structure and collisions with standard modes of the SEM operation. Such a tool enables the removal of target microvolumes in chosen places, so it can be used for some technological purposes, such as making small apertures. However, its main goal is to uncover the bulk internal structure of the specimen, imaging it in a 3D form. Therefore, the microsource is placed on the movable arm and coupled with the semiconductor four-quadrant backscattered electron (BSE) detector, which enables 3D imaging of the uncovered structure with the multidetector method. This implies taking in one scan a set of images from four or five directions, using both material- and topography-sensitive channels of information (BSE and secondary electron SE), which facilitates their interpretation.