Variable Pressure Scanning Electron Research Articles

Characterization of Tableware from Fábrica de Loiça de Sacavém—Linking Analytical and Documental Research

Fábrica de Loiça de Sacavém (ca. 1858–1994) was among the first to produce white earthenware in Portugal, becoming one of the country’s leading ceramic manufacturers during the late 19th to early 20th centuries. Research on white earthenware has accompanied the growing interest in post-industrial archaeology but is still poorly explored compared to more ancient ceramic productions. This study focused on the ceramic body, glazes, and colourants of tableware produced by Fábrica de Loiça de Sacavém during the first 50 years of its activity (1859–1910). A multi-analytical approach was selected to investigate the chemical and mineralogical composition of the ceramic body, glaze, and pigments using optical microscopy, variable-pressure scanning electron microscope energy-dispersive X-ray spectroscopy (VP-SEM-EDS), μ-Raman spectroscopy, μ-X-ray Diffraction (μ-XRD), and reflectance spectroscopy (hyperspectral image analysis). The studied tableware was produced with a Ca-poor siliceous–aluminous white earthenware ceramic body covered with transparent alkali lead or lead borosilicate glaze, and most colourants were complex Cr-based pigments. These results are in agreement with the little documental evidence from this period found in the manufacturer’s archives.

DEFLECTION AND STRAINS PERFORMANCE OF KENAF FIBRE-REINFORCED CONCRETE BEAMS

There has been a need to find a lasting means to improve beams' deflection and strain performance without necessarily increasing the beam stirrups. The limitations of steel and other synthetic fibres have reduced their application. Given its tensile strength, renewability, sustainability, and affordability compared to steel and synthetic fibres, kenaf fibre development is of great interest in Malaysia. Therefore, this research work experimentally investigated the deflection and strain performance of Kenaf Fibre Reinforced concrete beams. The volume and length of kenaf fibre used were 0.75% and 25mm, respectively. Kenaf fibre was treated with 5% NaOH to improve its performance. The alkaline-treated and untreated kenaf fibres morphology was observed under a variable-pressure scanning electron microscope. It was discovered inclusion of kenaf fibre reduced the workability of concrete. Also, plain and KFR concrete morphology was observed under a variable-pressure scanning electron microscope. Four beams were designed to study the deflection and strain performance of the KFR concrete beam; one was well reinforced but without kenaf fibre. The stirrups spacings were increased by 25%, 50%, and 75% for the other three beams. The beams were tested under centre loading. Deflection and concrete strain at the centre and along the beam span were measured using LVDTs and concrete strain gauges for the four beams. Furthermore, the strains on the shear and bottom flexural reinforcements at the centre of the beam were measured using steel strain gauges. It was discovered that kenaf fibre enhanced the deflection and strain performance of beams between 25% and 50% stirrups deficiency.

Insight into the deep eutectic solvent pretreatment of oil palm empty fruit bunches: Effects of temperature, empty fruit bunch to solvent ratio, and time

This work aimed to comprehensively examine the pretreatment efficiency of oil palm empty fruit bunches (EFB) using two different types of deep eutectic solvent (DES) mixtures, i.e., choline chloride/imidazole (DES-I) and choline chloride/glycerol (DES-G) in terms of pretreated EFB structural composition and enzymatic hydrolysis. The influence of the pretreatment temperature (55 °C, 90 °C, 125 °C, 160 °C, and 195 °C), EFB to solvent ratio (1:5, 1:10, 1:15, and 1:20), and pretreatment time (2 h, 4 h, and 6 h) on the performance of pretreated EFB and the generated black liquor was examined. The optimal conditions for EFB pretreatment were 160 °C, 1:5 ratio, and 2 h using DES-I solvent, and 160 °C, 1:10 ratio and 4 h using DES-G solvent. The structural carbohydrates of empty fruit bunch pretreated with DES-I, DES-I EFB1 and DES-G, DES-G EFB2 increased to 66.1%, and 64.6%, respectively. The enzymatic hydrolysis of DES-I EFB1 resulted in higher glucan conversion (92.4%) compared to DES-G EFB2, indicating that DES-I solvent was more efficient than DES-G for EFB pretreatment. X-ray diffraction, Fourier transform infrared spectroscopy, and variable-pressure scanning electron microscopy confirmed the removal of lignin and hemicelluloses from EFB during pretreatment and enzymatic hydrolysis.

Bio-inspired self-healing of concrete cracks using new B. pseudomycoides species

Bio-inspired self-healing of concrete cracks has been widely exploited to improve concrete properties and thus increase concrete life span using different bacterial species in recent years. The most common bacterial species found in the present literature are B. sphaericus, Sporosarcina pasteurii, Spore-forming alkali-resistant bacteria, B. megaterium and B. subtilis, while there is no published research using B. pseudomycoides species to heal concrete cracks. Furthermore, the need for more in-depth information on the healing ratio in the deeper part of the concrete crack remains. In the present study, a new bacterial species, namely B. pseudomycoides strain HASS3, was isolated, identified and tested for its ability to heal artificially cracked concrete samples. Both variable-pressure scanning electron microscope (VP-SEM) and X-ray computed microtomography (X-ray μCT) were utilised to assess the evolution of the healing ratio along with the crack profile. VP-SEM results revealed that a crack mouth width of 0.4 mm was fully healed through microbial precipitation which was later identified as calcite and vaterite using XRD. In contrast, according to the X-ray μCT results, the maximum healing ratio in the deeper part of the crack was only 14% compared to the crack mouth. As such, it could be concluded that bacteria-based concrete self-healing could function as a sustainable strategy to heal cracks located in the concrete skin.

Study of hydrogen adsorption onto kenaf sorbent surface by metal impregnation method

The potential of kenaf ( Hibiscus cannabinus L. ) as hydrogen materials was investigated. Kenaf core from National Kenaf and Tobacco Board (NKTB), Kelantan, Malaysia have been synthesized and characterized to achieve the improvement on kenaf’s surface support, and then evaluated the hydrogen adsorption performance of the modified nickel-kenaf adsorbent (MK-Ni). Kenaf core have been transformed in particulate forms (size: 500 µm) for high performance adsorbents and impregnated into chemicals of Nickel Nitrate, Ni(NO 3 ) 2 in different concentrations. To improve the hydrogen adsorption, the surface was tailored using Formaldehyde (HCHO) and Potassium Hydroxide (KOH) before the process of metal impregnation. The modified kenaf and raw kenaf surface morphological structure were characterized by Variable-Pressure Scanning Electron Microscope (VPSEM) and the elements in kenaf sample was analyzed by using Energy Dispersive X-ray (EDX) spectroscopy. The hydrogen adsorption is compared with laboratory scale of hydrogen adsorption system by ultra-purity hydrogen gas (H 2 ) in ambient temperature. Two cyclic operation for delivery performance of hydrogen shows that modified nickel-kenaf with 0.4 M concentration in 4 bar pressure bed had better improvement in hydrogen adsorption performance.

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

Ca3Co4O9 is a p-type semiconducting material that is well-known for its thermoelectric (TE), magnetic, electronic, and electro-optic properties. In this study, sol-gel autoignition was used to prepare Ca3Co4O9 at different calcination temperatures (773, 873, 973, and 1073 K) and time (4, 6, 8, 10, 12, and 14 h) using starch as a fuel. The phase and microstructure of the prepared Ca3Co4O9 powder were investigated. Thermogravimetry.differential thermal analysis (TGA) confirms that the final weight loss occurred at 1073 K to form Ca3Co4O9 stable powder. The variable-pressure scanning electron microscopy (VP-SEM) images show that the size of powder particles increases from 1.15 to 1.47 μm as calcination time increases from 4 to 12 h, and the size remains almost constant thereafter. A similar pattern is also observed on the increment of the crystallite size and percentage of crystallinity with X-ray diffraction (XRD) analysis. The highest crystallinity is found about 92.9% when the powder was calcinated at 1073 K for 12 and 14 h with 458 and 460 Å crystallite size, respectively. Energy dispersive X-ray spectroscopy (EDS) analysis demonstrates that the calcinated powder has a high intensity of Ca, Co, and O with uniform distribution. High-resolution transmission electron microscopy (HRTEM) images prove that there is no distinct lattice distortion defect on the crystal structure.

Analysis of Stability in Time of Marginal Adaptation of Endosequence Root Repair Material on Biological Samples

Introduction: The introduction of mineral trioxide aggregate (MTA) and bioceramic sealers increased the success rate of endodontic surgery and perforation repair. The aim of this study was to evaluate the marginal adaptation at different times of endosequence root repair material (ERMM) in order to evaluate its dimensional stability using variable pressure-scanning electron microscope (VP-SEM). Material And Methods: Fourty-eight teeth were selected shaped up to a master apical size of 25. Then a 3 mm cut perpendicular to the long axis and a retrograde cavity preparation were performed. In order to obtain 2 mm thick sample a second cut was done and, in this disk, ERMM was inserted. The samples were stored at 37°. The samples were divided into four time-depending groups observed with VP-SEM at time 0 (Group 1) and after 2 (Group 2), 7 (Group 3) and 30 days (Group 4) after ERRM setting. Statistical analysis with one way-ANOVA test was performed (95%). Results: None of the four groups analyzed showed a complete marginal adaptation between dentin and ERRM. Instead, in all groups ERRM exhibited a completely preserved marginal adaptation to the dentin wall in all time-dependent groups. The mean (±SD) gap value was for time 0, 3.91 (±2.55) µm after 2 days, 4.32 (±2.69), after 7 days 4.49 (±2.53), and after 30 days 4.81 (±2.85) µm. No statistically significant difference was found between the four groups. Conclusions: The results of the present study demonstrate the dimensional stability over time of ERMM.

Stabilization of a Residual Soil Using Calcium and Magnesium Hydroxide Nanoparticles: A Quick Precipitation Method

The current study examines the potential of using calcium and magnesium hydroxide nanoparticles synthetized through a quick precipitation method as soil stabilizers for improving the engineering properties of tropical residual soil. The engineering properties of untreated and nanoparticles-treated soil were studied by carrying out a series of geotechnical tests including compaction, Atterberg limits, falling head permeability, and unconfined compressive strength (UCS). The stabilization mechanisms associated with soil–chemical reactions were further explored by performing microstructural analyses such as x-ray diffraction (XRD), variable-pressure scanning electron microscope (VP-SEM), and energy-dispersive x-ray spectroscopy (EDX). The findings revealed that the calcium hydroxide and magnesium hydroxide nanoparticles improved the geotechnical properties of residual soils in terms of reduced hydraulic conductivity and increased UCS. The percentage reduction of the hydraulic conductivity of magnesium and calcium hydroxide nanoparticles-treated soils compared to untreated soil after seven weeks of permeation were 85.14% and 98.70%, respectively. The magnesium and calcium hydroxide nanoparticles-treated soils subjected to 14 days of curing recorded a percentage increase in the UCS of 148.05% and 180.17%, respectively compared to untreated soil. Hence, it can be concluded that both magnesium and calcium hydroxide nanoparticles can be effectively utilized as environmental-friendly stabilizers.

Ni-based catalysts for steam reforming of tar model derived from biomass gasification

Tar formation during biomass gasification is a major barrier to utilise the produced syngas, which clogs processing equipment. In the present study, steam reforming of gasification-derived tar (phenol, toluene, naphthalene, and pyrene) was catalysed by Ni/dolomite, Ni/dolomite/Al2O3, Ni/dolomite/La2O3, Ni/dolomite/CeO2, and Ni/dolomite/ZrO2 for hydrogen production. The steam reforming experiment was conducted in a fixed bed reactor at 700 °C and the steam-to-carbon molar ratio of 1 under atmospheric pressure. After the catalytic test, the spent catalysts were characterised by thermogravimetric analysis and variable-pressure scanning electron microscope. The aim of this study is to investigate the catalytic activity of Ni-based catalysts in terms of tar conversion and their deactivation characteristic. The current results revealed that all the catalysts showed almost full conversion of tar (98.8%-99.9%) and considerably low amount of coke deposited in the form of amorphous and filamentous carbon (15.9-178.5 mg gcat-1). Among the catalysts studied, Ni/dolomite/La2O3 gave the highest catalytic activity for steam reforming of gasified biomass tar and lowest coke formation.

Lines, spots and trails: a microscopic and mineralogical study of antimonate-opacified glass beads from Lofkënd, Albania

This study focuses on a group of decorated glass beads (twelfth–tenth century BC), belonging to a larger assemblage that was excavated from the prehistoric burial tumulus at Lofkend, Albania. The bulk glass, opaque glass decorations, and corroded areas were examined and analyzed using variable pressure-scanning electron microscopy with energy-dispersive spectroscopy (VP-SEM-EDS) and X-ray diffraction (XRD). The four glass beads analyzed were made using a plant ash-based alkali and colored with an iron containing chromophore which gave the glass its dark green color. Calcium antimonate was the predominant white opacifier used. Sodium antimonate was found as the opacifier in one sample. Its occurrence is likely accidental and formed due to a low concentration of calcium in the glass. Lead antimonate was identified in one sample and, along with calcium antimonate which was also present, would have acted as an opacifier for the white glass.

Dimensional Changes of Tracheids during Drying of Radiata Pine (Pinus radiata D. Don) Compression Woods: A Study Using Variable-Pressure Scanning Electron Microscopy (VP-SEM).

Variable-pressure scanning electron microscopy was used to investigate the dimensional changes in longitudinal, tangential and radial directions, on wetting and drying, of tracheids of opposite wood (OW) and three grades of compression woods (CWs), including severe CW (SCW) and two grades of mild compression wood (MCW) (MCW1 and MCW2) in corewood of radiata pine (Pinus radiata) saplings. The CW was formed on the underside and OW on the upper side of slightly tilted stems. In the longitudinal direction, the shrinkage of SCW tracheids was ~300% greater than that of OW tracheids, with the shrinkage of the MCW1 and MCW2 tracheids being intermediate. Longitudinal swelling was also investigated and hysteresis was demonstrated for the tracheids of all corewood types, with the extent of hysteresis increasing with CW severity. A statistical association was found between longitudinal shrinkage and the content of lignin and galactosyl residues in the cell-wall matrix. The galactosyl residues are present mostly as (1→4)-β-galactans, which are known to have a high capacity for binding water and swell on hydration. The small proportions of (1→3)-β-glucans in the CWs have similar properties. These polysaccharides may play a functional role in the longitudinal shrinking and swelling of CW tracheids. Tangential shrinkage of tracheids was greater than radial shrinkage but both were greatest for OW and least for SCW, with the MCW1 and MCW2 being intermediate.

Microstructure, Mechanical Properties, and Shape Memory Effect of Annealed Cu-Al-Ni-xCo Shape Memory Alloys

In order to develop the main applications of Cu-based shape memory alloys (SMAs), the effect of annealing time and temperature on the microstructure, mechanical properties, and shape memory characteristics of Cu-Al-Ni-xCo SMAs (x is 0.38, 0.6, and 1.2 wt.%) were studied. A distinct consideration is lent to the microstructural changes, phase transformation, and mechanical properties, which might take place in accordance with the changes in the alloying element/composition and/or heat treatment implementation. Because of this, the microstructural changes were portrayed using a variable-pressure scanning electron microscope, energy-dispersive spectrometer, and x-ray diffraction. The strength and hardness were determined using a universal Instron testing machine and Vickers hardness testing machine, respectively. The shape memory test was carried out using specially designed with an insulated system. The results indicated that the phase transformation of Cu-Al-Ni-xCo SMAs can be changed by varying the annealing temperature and time, and subsequent annealing can cause an effective impact on the shape memory effect. Moreover, it was also realized that the annealing treatment is involved in controlling the presence of γ 2 phase precipitate, thereby, improving the mechanical properties. The highest fracture stress and strain of 860.94 MPa and 9.43%, respectively, were determined in the Cu-Al-Ni-0.6 wt.% Co SMAs after being annealed at 500 °C for 3 h. In particular, the Cu-Al-Ni-1.2 wt.% Co SMAs obtained 84.08% recovery, which is the highest strain recovery after being annealed at 500 °C for 3 h.

Inactivation of genes TEC1 and EFG1 in Candida albicans influences extracellular matrix composition and biofilm morphology

ABSTRACTBackground: Infections caused by Candida spp. have been associated with formation of a biofilm, i.e. a complex microstructure of cells adhering to a surface and embedded within an extracellular matrix (ECM).Methods: The ECMs of a wild-type (WT, SN425) and two Candida albicans mutant strains, Δ/Δ tec1 (CJN2330) and Δ/Δ efg1 (CJN2302), were evaluated. Colony-forming units (cfu), total biomass (mg), water-soluble polysaccharides (WSPs), alkali-soluble polysaccharides (ASPs), proteins (insoluble part of biofilms and matrix proteins), and extracellular DNA (eDNA) were quantified. Variable-pressure scanning electron microscopy and confocal scanning laser microscopy were performed. The biovolume (μm3/μm2) and maximum thickness (μm) of the biofilms were quantified using COMSTAT2.Results: ASP content was highest in WT (mean ± SD: 74.5 ± 22.0 µg), followed by Δ/Δ tec1 (44.0 ± 24.1 µg) and Δ/Δ efg1 (14.7 ± 5.0 µg). The protein correlated with ASPs (r = 0.666) and with matrix proteins (r = 0.670) in the WT strain. The population in Δ/Δ efg1 correlated with the protein (r = 0.734) and its biofilms exhibited the lowest biomass and biovolume, and maximum thickness. In Δ/Δ tec1, ASP correlated with eDNA (r = 0.678).Conclusion: ASP production may be linked to C. albicans cell filamentous morphology.

Visualization of Aspergillus fumigatus biofilms with Scanning Electron Microscopy and Variable Pressure-Scanning Electron Microscopy: A comparison of processing techniques

Aspergillus fumigatus biofilms consist of a three-dimensional network of cellular hyphae and extracellular matrix. They are involved in infections of immune-compromised individuals, particularly those with cystic fibrosis. These structures are associated with persistence of infection, resistance to host immunity, and antimicrobial resistance. Thorough understanding of structure and function is imperative in the design of therapeutic drugs. Optimization of processing parameters, including aldehyde fixation, heavy metal contrasting, drying techniques and Ionic Liquid treatment, was undertaken for an ultrastructural approach to understand cellular and extracellular biofilm components. Conventional and Variable Pressure Scanning Electron Microscopy were applied to analyze the structure of biofilms attached to plastic and formed at an air-liquid interface.

Boncuklu Höyük: The earliest ceramics on the Anatolian plateau

In this article 12 fired clay samples and an unfired marl sample from the late 9th and early 8th millennium cal BC site of Boncuklu Höyük (8300–7800calBC) in the Konya Plain, Turkey, were analysed by optical microscopy and SEM-EDX. The plant remains in the pottery fabrics were also examined in the variable pressure scanning electron microscope.Chemical analyses show that the same clays were used for multiple purposes, and more than one type of raw material was used to make the fired clay objects examined. Only one sherd showed signs of having added temper. The presence of scattered organic remains in the fabrics also suggests that the clay was minimally processed. Although the minerals present do not show any optical alteration, the shrinkage of the plant matter and the discolouring of bone inclusions suggested that all but one sample were fired, albeit at a relatively low temperature. These sherds are therefore regarded as among the earliest ceramic vessels known in southwest Asia, although the manufacturing technique was different to that used to make the contemporaneous PPNB ceramics found at Kfar HaHoresh in Israel.

Asbestos fibers in the gallbladder of patients affected by benign biliary tract diseases

This exploratory study aimed to evaluate the presence of asbestos fibers in the biliary tract of patients living in an asbestos-polluted area using scanning electron microscopy. Thin gallbladder sections were obtained from five patients who were operated on for gallbladder stones and the bile fluid of one of the patients was analyzed using variable-pressure scanning electron microscopy coupled with energy-dispersive spectroscopy. All patients were from Casale Monferrato, Italy, a well-known asbestos-polluted city, where the Eternit factory had operated since the beginning of the century until 1985. All the inorganic phases found in the gallbladder were analyzed for morphology and chemistry. Fibers and particles consistent with minerals defined by law as 'asbestos' were detected in three out of five patients. These findings suggest that asbestos fibers can be found in the gallbladder of patients exposed to asbestos, although how they reach the biliary tract remains unknown. Further studies to confirm these results are under way.

Interpenetrating polymer network hydrogel scaffolds for artificial cornea periphery.

Three-dimensional scaffolds based on inverted colloidal crystals (ICCs) were fabricated from sequentially polymerized interpenetrating polymer network (IPN) hydrogels of poly(ethyleneglycol) and poly(acrylic acid). This high-strength, high-water-content IPN hydrogel may be suitable for use in an artificial cornea application. Development of a highly porous, biointegrable region at the periphery of the artificial cornea device is critical to long-term retention of the implant. The ICC fabrication technique produced scaffolds with well-controlled, tunable pore and channel dimensions. When surface functionalized with extracellular matrix proteins, corneal fibroblasts were successfully cultured on IPN hydrogel scaffolds, demonstrating the feasibility of these gels as materials for the artificial cornea porous periphery. Porous hydrogels with and without cells were visualized non-invasively in the hydrated state using variable-pressure scanning electron microscopy.

Combination Prophylactic Therapy with Rifampin Increases Efficacy against an Experimental Staphylococcus epidermidis Subcutaneous Implant-Related Infection

The incidence of infections related to cardiac devices (such as permanent pacemakers) has been increasing out of proportion to implantation rates. As management of device infections typically requires explantation of the device, optimal prophylactic strategies are needed. Cefazolin and vancomycin are widely used as single agents for surgical prophylaxis against cardiac device-related infections. However, combination antibiotic prophylaxis may further reduce infectious complications. To model a localized subcutaneous implant-related infection, a bioluminescent strain of Staphylococcus epidermidis was inoculated onto a medical-procedure-grade titanium disc, which was placed into a subcutaneous pocket in the backs of mice. In vivo bioluminescence imaging, quantification of ex vivo CFU from the capsules and implants, variable-pressure scanning electron microscopy (VP-SEM), and neutrophil enhanced green fluorescent protein (EGFP) fluorescence in LysEGFP mice were employed to monitor the infection. This model was used to evaluate the efficacies of low- and high-dose cefazolin (50 and 200 mg/kg of body weight) and vancomycin (10 and 110 mg/kg) intravenous prophylaxis with or without rifampin (25 mg/kg). High-dose cefazolin and high-dose vancomycin treatment resulted in almost complete bacterial clearance, whereas both low-dose cefazolin and low-dose vancomycin reduced the in vivo and ex vivo bacterial burden only moderately. The addition of rifampin to low-dose cefazolin and vancomycin was highly effective in further reducing the CFU harvested from the implants. However, vancomycin-rifampin was more effective than cefazolin-rifampin in further reducing the CFU harvested from the surrounding tissue capsules. Future studies in humans will be required to determine whether the addition of rifampin has improved efficacy in preventing device-related infections in clinical practice.

Characterisation of calcium crystals in Abelia spp. using X-ray diffraction and electron microscopy

SummaryThe localisation, chemical composition, and morphology of calcium (Ca) oxalate crystals in the leaves and stems of Abelia mosanensis and of A. × grandiflora were analysed using a variable pressure-scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, a low temperature SEM (LT-SEM), and a transmission electron microscope (TEM). Foliar analyses of macro- and micro-elements were performed on the leaves and stems of A. mosanensis. A greater number of Ca oxalate crystals were observed in A. mosanensis than in A. × grandiflora. Three morphologically distinguishable types of crystals were observed: the prismatic crystals found inside the chloroplast, multifaceted star-like spherical and bladed aggregate crystals (druses) inside the vacuoles of the mesophyll cells, and small angular crystals (sand crystals) inside the cuticle. Semi-solid crystals that may drip and accumulate to become a solid Ca oxalate crystal were observed by LT-SEM, which indicated the growth of druses of Ca oxalate crystals. The growth of prismatic crystals and of druses were evident through the formation of crystalline lamellae. Micro-analysis indicated that the crystals were Ca oxalate and contained magnesium in A. mosanensis, or silicon in A. × grandiflora. Abelia stems with low foliar calcium concentrations showed no Ca oxalate crystal formation. This is the first report, to our knowledge, on the presence and possible growth of crystals of different morphologies and chemical compositions in Abelia.

Effect of Spinach Cultivar and Bacterial Adherence Factors on Survival of Escherichia coli O157:H7 on Spinach Leaves

Similar to phytopathogens, human bacterial pathogens have been shown to colonize the plant phylloplane. In addition to environmental factors, such as temperature, UV, relative humidity, etc., the plant cultivar and, specifically, the leaf blade morphological characteristics may affect the persistence of enteropathogens on leafy greens. This study was conducted to evaluate the effect of cultivar-dependent leaf topography and the role of strain phenotypic characteristics on Escherichia coli O157:H7 persistence on organic spinach. Spinach cultivars Emilia, Lazio, Space, and Waitiki were experimentally inoculated with the foodborne E. coli O157:H7 isolate EDL933 and its isogenic mutants deficient in cellulose, curli, or both curli and cellulose production. Leaves of 6-week-old plants were inoculated with 6.5 log CFU per leaf in a biosafety level 2 growth chamber. At 0, 1, 7, and 14 days, E. coli O157:H7 populations were determined by plating on selective medium and verified by laser scanning confocal microscopy. Leaf morphology (blade roughness and stoma density) was evaluated by low-temperature and variable-pressure scanning electron microscopy. E. coli O157:H7 persistence on spinach was significantly affected by cultivar and strain phenotypic characteristics, specifically, the expression of curli. Leaf blade roughness and stoma density influenced the persistence of E. coli O157:H7 on spinach. Cultivar Waitiki, which had the greatest leaf roughness, supported significantly higher E. coli O157:H7 populations than the other cultivars. These two morphological characteristics of spinach cultivars should be taken into consideration in developing intervention strategies to enhance the microbial safety of leafy greens.