Well-defined Pits Research Articles

Unveiling facet engineering of ultrathin Pt overlayers for enhanced ammonia oxidation reaction

Utilizing ammonia for hydrogen production via ammonia oxidation reaction (AOR) remains a challenge owing to insufficient electrode performance and high cost of noble metal. Herein, we performed repeated self-terminated electrodeposition (SED) of Pt on Ni substrate to obtain Pt/Ni electrodes. The electron-deficient Ni sites prefer *OH adsorption and serve as a reservoir for NH3 dehydrogenation, thereby promoting NH3 adsorption on Pt sites. Additionally, this iterative process enabled precise regulation of the Pt loading mass. Pt5/Ni electrode exhibited the highest catalytic activity for AOR. Subsequently, immersing this electrode in various acid solutions resulted in surface morphologies with numerous well-defined pits, driven by the adsorption of different electrolyte ions. Specifically, etching in HNO3 led to a higher Pt(100) density, further enhancing the electrode’s catalytic performance for AOR. Thus, this study offers a simple, fast, and spontaneous method for facet engineering ultrathin Pt overlayers on Ni substrate under ambient conditions.

First Mediterranean record of Micropilina minuta Warén, 1989 (Monoplacophora: Neopilinidae)

The lilliputian and elusive monoplacophoran Micropilina minuta Warén, 1989 is recorded for the first time from the Mediterranean basin upon various records of empty shells trawled between 270 and 700 m in the Tuscan Archipelago (northern Tyrrhenian Sea). Our data reveal that Micropilina minuta often co-occurs with the only other monoplacophoran previously recorded in the Mediterranean, Veleropilina reticulata (Seguenza G., 1876).Micropilina minuta Warén, originally described on material from Iceland, was later found in the lower Pleistocene of Archi (Reggio Calabria, Italy). Although some shells are definitely fresh, the absence of live collected specimens leaves open the possibility that the species is no longer living in the Mediterranean Sea.Micropilina minuta differs from V. reticulata for the more ovoidal outline, constricted toward the apex and the presence of about seven deep pits instead of shallow, not well-defined pits, on the apical cup.

Dawn of a New Age Fissure Sealant? A Study Evaluating the Clinical Performance of Embrace WetBond and ART Sealants: Results from a Randomized Controlled Clinical Trial.

Objectives The main purpose of this article is to evaluate the clinical performance of atraumatic restorative treatment (ART) sealant versus Embrace WetBond sealant in terms of retention and fissure caries prevention among a section of school children in the southern Indian state of Karnataka (ClinicalTrials.gov NCT02716558). Materials and Methods After obtaining consent from the parents and screening the children against the inclusion cum exclusion criteria, 90 school children whose mandibular first molars were caries free and with a well-defined pit and fissure system were recruited for this spilt mouth trial. The respective molars were allocated either to the ART sealant or the embrace group after the randomization process. The sealants were applied according to the manufacturer’s instructions and followed up at the end of 3rd, 6th, and 12th month, respectively. The outcome measures assessed were the retention and the caries preventive effects of the materials. Results At the end of the 6th month, about one-fourth of the sealants in either group remained totally intact, without evidence of caries. No significant differences were seen between the sealants either in terms of retention or caries preventive benefits at the end of 12 months. Statistical Analysis The chi-squared test was used to check differences in proportions. The significance value was set at <0.05. Kappa test was performed to assess the intraexaminer reproducibility with respect to retention and caries status. Conclusion The moisture-tolerant resin sealant could not replicate the physical properties usually associated with conventional resin sealants. The usage of ART sealants was deemed to be less cumbersome in an outreach setting as observed in this trial.

Su2002 Nonmyeloablative Stem Cell Therapy for Perianal Fistulizing Crohn's Disease: A Systematic Review of Safety and Efficacy

BODY: BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides volumetric images of tissue microstructure without requiring extrinsic contrast agents. Commercially available OCT systems have limited frame rates and typically use proximal rotation and pullback mechanisms to scan the imaging beam across the tissue. These two factors limit the ability to generate high quality en face images of aberrant mucosal surface patterns, which correlate with the presence and grade of dysplasias. In this study, we present a prototype ultrahigh speed 3D-OCT system with an advanced imaging probe using distal micromotor scanning. This system enables en face 3D-OCT images that visualize the mucosal surface patterns in a variety of GI structures in vivo. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) under a study protocol approved by the VABHS, Harvard Medical School and M.I.T. We used a prototype 3D-OCT system that has an imaging speed (axial scan rate) of 600 kHz, which is ~10 times faster than commercially available 3D-OCT imaging systems. Scanning of the imaging beam is performed using a micromotor at the distal end of the OCT probe. The probe was passed through the accessory channel of an Olympus double channel endoscope (GIF-2TH180) to allow coregistration of images with biopsies. RESULTS: The combined advantages of ultrahigh speed and distal scanning of the new 3D-OCT system and probe enables visualization of mucosal surface patterns with unprecedented clarity. Fig. 1(A) demonstrates a volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient. While cross sectional images give information on the layered architecture of the tissue, gastric folds and pit pattern can be visualized in the en face direction. Fig. 1(C) shows the squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE), where the squamous epithelium (SE) appears as a smooth layer, whereas the area with BE has a well-defined pit pattern architecture. Fig. 1(D) shows a region of the esophagus a BE patient immediately after radiofrequency ablation (RFA), where residual BE that is missed by the RFA application can be observed. CONCLUSIONS: This study demonstrates that ultrahigh speed 3D-OCT system with a distal scanning micromotor probe can generate cross-sectional and en face images from the same dataset, yielding a more comprehensive evaluation of tissue architecture. Moreover, imaging can be performed even after biopsies or ablations, and can survey margins of endoscopic resections which is not possible with confocal endomicroscopy using exogenous contrast agents. Therefore, this novel imaging system has the potential to greatly improve the clinical utility of 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-16, R44-CA101067-06, AFOSR FA9550-12-1-0499, and FA9550-10-10551. Figure 1: (A) Volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient showing cross sectional as well as en face visualization of the gastric folds and pit patterns. (B) Zoomed view of the en face image shown in (A). (C) Squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE) showing a region with smooth squamous epithelium and the BE region with well-defined pit patterns. (D) A region of a patient with BE immediately after radiofrequency ablation (RFA), where the encircled area shows BE glands that are likely missed by the RFA. Scale bars: 500um.

Su2001 The Role of the Histone Methyltransferase EZH2 in the Mouse Intestinal Epithelium

BODY: BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides volumetric images of tissue microstructure without requiring extrinsic contrast agents. Commercially available OCT systems have limited frame rates and typically use proximal rotation and pullback mechanisms to scan the imaging beam across the tissue. These two factors limit the ability to generate high quality en face images of aberrant mucosal surface patterns, which correlate with the presence and grade of dysplasias. In this study, we present a prototype ultrahigh speed 3D-OCT system with an advanced imaging probe using distal micromotor scanning. This system enables en face 3D-OCT images that visualize the mucosal surface patterns in a variety of GI structures in vivo. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) under a study protocol approved by the VABHS, Harvard Medical School and M.I.T. We used a prototype 3D-OCT system that has an imaging speed (axial scan rate) of 600 kHz, which is ~10 times faster than commercially available 3D-OCT imaging systems. Scanning of the imaging beam is performed using a micromotor at the distal end of the OCT probe. The probe was passed through the accessory channel of an Olympus double channel endoscope (GIF-2TH180) to allow coregistration of images with biopsies. RESULTS: The combined advantages of ultrahigh speed and distal scanning of the new 3D-OCT system and probe enables visualization of mucosal surface patterns with unprecedented clarity. Fig. 1(A) demonstrates a volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient. While cross sectional images give information on the layered architecture of the tissue, gastric folds and pit pattern can be visualized in the en face direction. Fig. 1(C) shows the squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE), where the squamous epithelium (SE) appears as a smooth layer, whereas the area with BE has a well-defined pit pattern architecture. Fig. 1(D) shows a region of the esophagus a BE patient immediately after radiofrequency ablation (RFA), where residual BE that is missed by the RFA application can be observed. CONCLUSIONS: This study demonstrates that ultrahigh speed 3D-OCT system with a distal scanning micromotor probe can generate cross-sectional and en face images from the same dataset, yielding a more comprehensive evaluation of tissue architecture. Moreover, imaging can be performed even after biopsies or ablations, and can survey margins of endoscopic resections which is not possible with confocal endomicroscopy using exogenous contrast agents. Therefore, this novel imaging system has the potential to greatly improve the clinical utility of 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-16, R44-CA101067-06, AFOSR FA9550-12-1-0499, and FA9550-10-10551. Figure 1: (A) Volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient showing cross sectional as well as en face visualization of the gastric folds and pit patterns. (B) Zoomed view of the en face image shown in (A). (C) Squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE) showing a region with smooth squamous epithelium and the BE region with well-defined pit patterns. (D) A region of a patient with BE immediately after radiofrequency ablation (RFA), where the encircled area shows BE glands that are likely missed by the RFA. Scale bars: 500um.

Biodegradation behavior of bacterial-based polyhydroxyalkanoate (PHA) and DDGS composites

The extensive use of plastics in agriculture has increased the need for development and implementation of polymer materials that can degrade in soils under natural conditions. The biodegradation behavior in soil of polyhydroxyalkanoate (PHA) composites with 10 wt% distiller's dried grains with solubles (DDGS) was characterized and compared to pure PHA over 24 weeks. Injection-molded samples were measured for degradation weight loss every 4 weeks, and the effects of degradation times on morphological, thermomechanical, and viscoelastic properties were evaluated by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), and small-amplitude oscillatory shear flow experiments. Incorporation of DDGS had a strong effect on biodegradation rate, mechanical properties, and production cost. Material weight loss increased linearly with increasing biodegradation time for both neat PHA and the PHA/DDGS 90/10 composites. Weight loss after 24 weeks was approximately six times greater for the PHA/DDGS 90/10 composites than for unaltered PHA under identical conditions. Rough surface morphology was observed in early biodegradation stages (≥8 weeks). With increasing biodegradation time, the composite surface eroded and was covered with well-defined pits that were evenly distributed, giving an areolate structure. Zero shear viscosity, Tg, gelation temperature, and cold crystallization temperature of the composites decreased linearly with increasing biodegradation time. Addition of DDGS to PHA establishes mechanical and biodegradation properties that can be utilized in sustainable plastics designed to end their lifecycle as organic matter in soil. Our results provide information that will guide development of PHA composites that fulfill application requirements then degrade harmlessly in soil.

Corrosion properties of electrodeposited cobalt in sulfate solutions containing chloride ions

Abstract The corrosion properties of electrodeposited pure cobalt were investigated in deaerated 0.5 M Na2SO4 solutions at pH 5, 7, 10 and 13 by using polarization techniques. The effect of chloride concentration (0.01 and 0.1 M NaCl) was also studied. The results showed that increasing pH shifted the anodic polarization curves to more negative potentials. At pH 5 and 7, cobalt exhibited active dissolution without any distinctive transition to passivation. However, at pH 10, the metal surface was partially passivated and anodic current increased sharply at approximately −0.2 VSCE and the corroded surface revealed several well-defined pits. On the other hand, at pH 13, a clear passivation region was observed within the potential range of −0.5 to 0.6 VSCE. With increasing chloride concentrations of 0, 0.01, and 0.1 M at pH 10, both the anodic current and the number of pits on the cobalt surface were gradually increased. X-ray photoelectron spectroscopic investigations showed that the cobalt surface was covered mostly with cobalt hydroxide after anodic polarization at pH 10 in 0.1 M NaCl.

Characterization of pitting corrosion in bare and sol–gel coated aluminum 2024-T3 alloy

The prevention of pitting corrosion in aerospace aluminum alloys by the application of protective sol–gel coatings requires a thorough understanding of pit formation kinetics and morphology developments in such surface coating systems. This study reports results of chemical and electrochemical methods of pitting corrosion tests for bare and sol–gel coated Al 2024-T3 alloy. Specific attention is focused on the characterization of pitting in samples coated with vinyl-silicate and epoxy-silicate sol–gel coatings. Specimens were exposed to a variety of chemically aggressive environments, based on 3–5% NaCl solutions with addition of HCl and H 2SO 4, including a standard CASS solution. The exposure of bare samples to these environments produced extensive surface corrosion, but pits were not observed for sol–gel coated samples. Anodic polarization tests with potentials above that required for pitting in bare samples were used to initiate pitting corrosion in sol–gel coated samples. A corrosion current monitoring test provided a method of controlling the pit formation process, which provides well-defined pits in terms of spatial density and geometry. A two-stage kinetic phase in pit development was observed and correlated with pit morphological developments in sol–gel coatings. An initial low current stage was associated with pit penetration through the coating to the surface and the secondary high current stage was associated with an active growth stage which grew in sub-coating surface interface regions. Results of this research provide a basis for designing and improving corrosion protection systems based on the application of sol–gel coatings.

The vomeronasal cavity in adult humans.

We observed the surface of the anterior part of the nasal septum of living subjects using an endoscope. In approximately 13% of 1842 patients without pathology of the septum, the vomeronasal pit was clearly observed on each side of the septum, and in 26% it was observed only on one side. The remaining observations indicated either the presence of putative pits or no visible evidence of a pit. However, repetitive observations on 764 subjects depicted changes over time, from nothing visible to well-defined pits and vice versa. Based on 130 subjects observed at least four times, we estimate that approximately 73% of the population exhibits at least one clearly defined pit on some days. By computer tomography, the vomeronasal cavities were located at the base of the most anterior part of the nasal septum. Histological studies indicated that the vomeronasal cavities consisted of a pit generally connected to a duct extending in a posterior direction under the nasal mucosa. Many glands were present around the duct, which contained mucus. There was no sign of the pumping elements found in other mammalian species. Most cells in the vomeronasal epithelium expressed keratin, a protein not expressed by olfactory neurons. Vomeronasal epithelial cells were not stained by an antibody against the olfactory marker protein, a protein expressed in vomeronasal receptor neurons of other mammals. Moreover, an antibody against protein S100, expressed in Schwann cells, failed to reveal the existence of vomeronasal nerve bundles that would indicate a neural connection with the brain. Positive staining was obtained with the same antibodies on specimens of human olfactory epithelium. The lack of neurons and vomeronasal nerve bundles, together with the results of other studies, suggests that the vomeronasal epithelium, unlike in other mammals, is not a sensory organ in adult humans.

Trace element analysis of scheelite by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) using a synthetic silicate glass standard

Concentrations of W and trace elements in scheelites (CaWO 4) associated with Archean lode-gold deposits in Western Australia were determiined by ArF (193 run) excimer laser ablation-ICP-MS with external calibration against a silicate glass standard reference material, NIST 610. The excimer laser beam drilled well-defined pits in both scheelite and silicate glass. With internal standardization against Ca alone, W measurements for the scheelites fall within 5% of the concentrations expected from electron microprobe measurements. A matrix effect between scheelite and silicate glass is apparent in the behaviour of W during; laser ablation: W is progressively fractionated from Ca in the glass but not in the scheelite. Proper data reduction, therefore, requires use of the early maximum count rates for W and Ca rather than the mean count rates during ablation. W isotopic ratios measured in the scheelites and an in-house generated silicate glass, ANU 252, are both within ∼2.5% of the accepted values for the natural ratios and are reproducible to ∼1%, if data for the first ∼11 s of ablation are excluded. Using the same data reduction techniques employed for W, concentrations of Sr, Y, Mo, REE and Pb, present at ppm levels in the scheelites, were measured with a precision of 4% or less. Measurements on Th and U, present at the 5–10 ppb level, and P, Mn, Nb and Ta are less precise (∼5–40%) and concentrations of Rb, Zr, Ba, Sn, Hf, TI and Bi are, for the most part, below detection limits. For Sr, Sm and Nd, replicate ELA-ICP-MS measurements made on 80-μm wide spots in scheelite largely encompass the concentrations determined by ID-TIMS on bulk samples. REE patterns determined by ELA-ICP-MS for the scheelites vary smoothly as a function of atomic number. Most of the patterns are hump-shaped but others are rather flat except for positive Eu anomalies. This suggests that the hydrothermal fluids that formed the scheelites did not have a common composition and source.

Laser ablation of organic polymers: Microscopic models for photochemical and thermal processes

Irradiation of organic polymers by short pulses of far-UV (e.g., 193 nm) laser light causes ablative photodecomposition (APD) of the material. This etching process occurs cleanly leaving behind a well-defined pit. Longer wavelength (e.g., 532 nm) laser light also ablates material from a polymeric solid. However, this process is distinct from APD in that the sample near the pit is distorted and melted. Microscopic models are presented here for both the photochemical and thermal processes. The photochemical model predicts that well-defined pits will be formed, that narrow angular distributions of the ablated material should be observed, and that the average perpendicular ejection velocity will be 1000–2000 m/s. The thermal model predicts melting or distortion of the solid and a broad angular distribution of the ejected material.

The effect of ion species on morphological structure development of ion bombarded (1131) single crystal Cu

Carefully prepared samples of (1131) oriented Cu single crystals were bombarded with 40 keV ions to fluences of the order of 10 19 cm −2. The ion species chosen were Ne, Ar, Kr, Xe, N and Cu, and thus represented a range of light to heavy, chemically inert species, a more chemically active species and the self ion species. Post-irradiation observation was performed by scanning electron microscopy at Copenhagen and subsequently at Salford. The results may be summarized as follows: 1. (1) All ion species lead to characteristic morphological surface changes including etch pit, and frequently, pyramid generation. 2. (2) The lighter ion species tend to produce lower pit densities and less well-defined pit habits and fewer, sometimes no pyramids. 3. (3) The heavier ions (including Cu +) produce denser arrays of all features and better geometrically defined features. 4. (4) N +, Ne + and Ar + ions produce a zone of surface blisters outside but surrounding the irradiated area but none within the irradiated area. 5. (5) Some signs of pyramid bending occur from one to a subsequent examination but there are no clear correlations with ion species and surface zone. 6. (6) The as-formed pyramids are in dense crystallographic array after Cu, Kr and Xe irradiation. These results are explained in terms of preferential sputtering of native and irradiation induced defect structures and differential atomic mobility of different ion species in the Cu. The Cu + irradiation results exhibit the lack of necessity of occluded gas for feature development whilst the N + results indicate that, for Cu, improved impurity depth profiling accuracy by sputter sectioning with such a chemically active species is unlikely.

Etching Studies on Photographic Grains

The application of preferential etching techniques to the study of crystalline imperfection in photographic emulsion grains is described. Both chemical etching and halogen evolution by print-out exposure in the absence of gelatin form well-defined pits in most cases. The concentration of chemical etch pits is dependent on the solvent used but is not sensitive to concentration or etch time over the range investigated. A general increase in etching on certain faces is found after intentionally straining the grains, but the effect is not sufficiently strong to establish a one-to-one relationship between etch pits and dislocations. In both silver bromide and silver bromoiodide grains, no evidence is found for the existence of any type of polycrystalline substructure. Experiments on pitting by print-out exposure indicate that iodide ions provide internal hole traps or recombination centers.