Water Adsorption Isotherm and Surface Conductivity of Boroaluminosilicate Glasses.

The surface resistivity of boroaluminosilicate display glasses, which may affect the downstream display panel manufacturing, varies with the relative humidity (RH) of the environment, but the origin of this RH dependence has not been well understood. We have measured the water adsorption behavior on Corning Eagle XG (Glass-E) and Lotus NXT (Glass-L) glass panels using Brewster angle transmission infrared spectroscopy. The IR spectra of adsorbed water were analyzed to obtain the effective thickness of adsorbed water, the distribution of hydrogen-bonding interactions among the adsorbed water molecules, and the isosteric heat of water adsorption. These characteristics were compared with the electrical conductivity (inverse of resistivity) of these two glasses [Appl. Surf. Sci. 2015, 356, 1189]. This comparison revealed the correlation between the conductivity and the water layer structure, which could explain the surface resistivity difference between Glass-E and Glass-L as a function of RH. This study also disputed the previous hypothesis that the water adsorption isotherm would be governed by the areal density of the surface hydroxyl group; instead, it suggested that the network modifier ions may also play a critical role, especially in the intermediate RH regime.

Prediction of glassy silica etching with hydrogen fluoride gas by kinetic Monte Carlo simulations.

Understanding the surface properties of glass during the hydrogen fluoride (HF)-based vapor etching process is essential to optimize treatment processes in semiconductor and glass industries. In this work, we investigate an etching process of fused glassy silica by HF gas with kinetic Monte Carlo (KMC) simulations. Detailed pathways of surface reactions between gas molecules and the silica surface with activation energy sets are explicitly implemented in the KMC algorithm for both dry and humid conditions. The KMC model successfully describes the etching of the silica surface with the evolution of surface morphology up to the micron regime. The simulation results show that the calculated etch rate and surface roughness are in good agreement with the experimental results, and the effect of humidity on the etch rate is also confirmed. Development of roughness is theoretically analyzed in terms of surface roughening phenomena, and it is predicted that the values of growth and roughening exponents are 0.19 and 0.33, respectively, suggesting that our model belongs to the Kardar-Parisi-Zhang universality class. Furthermore, the temporal evolution of surface chemistry, specifically surface hydroxyls and fluorine groups, is monitored. The surface density of fluorine moieties is 2.5 times higher than that of the hydroxyl groups, implying that the surface is well fluorinated during vapor etching.

Evaluating learning curves and competence in colorectal EMR among advanced endoscopy fellows: a pilot multicenter prospective trial using cumulative sum analysis.

BACKGROUND AND AIMS: Data on colorectal EMR (C-EMR) training are lacking. We aimed to evaluate C-EMR training among advanced endoscopy fellows (AEFs) by using a standardized assessment tool (STAT). METHODS: This multicenter prospective study used a STAT to grade AEF training in C-EMR during their 12-month fellowship. Cumulative sum analysis was used to establish learning curves and competence for cognitive and technical components of C-EMR and overall performance. Sensitivity analysis was performed by varying failure rates. AEFs completed a self-assessment questionnaire to assess their comfort level with performing C-EMR at the completion of their fellowship. RESULTS: Six AEFs (189 C-EMRs; mean per AEF, 31.5 ± 18.5) were included. Mean polyp size was 24.3 ± 12.6 mm, and mean procedure time was 22.6 ± 16.1 minutes. Learning curve analyses revealed that less than 50% of AEFs achieved competence for key cognitive and technical C-EMR endpoints. All 6 AEFs reported feeling comfortable performing C-EMR independently at the end of their training, although only 2 of them achieved competence in their overall performance. The minimum threshold to achieve competence in these 2 AEFs was 25 C-EMRs. CONCLUSIONS: A relatively low proportion of AEFs achieved competence on key cognitive and technical aspects of C-EMR during their 12-month fellowship. The relatively low number of C-EMRs performed by AEFs may be insufficient to achieve competence, in spite of their self-reported readiness for independent practice. These pilot data serve as an initial framework for competence threshold, and suggest the need for validated tools for formal C-EMR training assessment.

Nanoscale Structure and Dynamics of Water on Pt and Cu Surfaces from MD Simulations.

The interaction of liquid water with Pt(111) is investigated with classical molecular dynamics (MD) simulations, where the forces are determined using the third-generation charge optimized many-body (COMB3) interatomic potential. In cases of sub-monolayer water coverage, the parameterized empirical potential predicts experimentally observed and energetically favorable √37 and √39 reconstructed water structures with "575757" di-interstitial defects. At both sub-monolayer and multilayer water coverages, the structure of the first wetting layer of liquid water on Pt(111) exhibits a characteristic distribution where the molecules form two distinct buckled layers as a result of the interplay between water-metal adsorption and water-water hydrogen bonds. The dynamic spreading rate of water nanodroplets on large Pt surfaces (>200 nm2) characterized by molecular kinetic spreading theory is an order of magnitude slower than the molecular kinetic rate of the same droplet on close-packed Cu surfaces due to variation in molecular distributions at the water-metal interface. These nanoscale MD simulation predictions using the COMB3 interatomic potential demonstrate the capability of capturing both many-body interactions between H2O and Pt or Cu and hydrogen bonding in liquid water.

Applied Potentials in Variable-Charge Reactive Force Fields for Electrochemical Systems.

An atomic description of water dynamics and electrochemical properties at electrode-electrolyte interfaces is presented using molecular dynamics with the third generation of the charge-optimized many-body (COMB3) potential framework. Externally applied potentials in electrochemical applications were simulated by offsetting electronegativity on electrode atoms. This approach is incorporated into the variable charge scheme within COMB3 and is used to investigate electrochemical systems consisting of two Cu electrodes and a water electrolyte with varying concentrations of hydroxyls (OH-) and protons (H+). The interactions between the electronegativity offset method and the charge equilibration method in a variable charge scheme are analyzed. In addition, a charge equilibration method for electrochemical applications is proposed, where the externally applied potentials are treated by the electronegativity offset on the electrodes thus enforcing charge neutrality on the electrolyte. This method is able to qualitatively capture the relevant electrochemistry and predict consistently correct voltages with precalibration.

Effect of Surface Chemistry on Water Interaction with Cu(111).

The interfacial dynamics of water in contact with bare, oxidized, and hydroxylated copper surfaces are examined using classical molecular dynamics (MD) simulations. A third-generation charge-optimized many-body (COMB3) potential is used in the MD simulations to investigate the adsorption of water molecules on Cu(111), and the results are compared to the findings of density functional theory (DFT) calculations. The adsorption energies and structures predicted by COMB3 are generally consistent with those determined with DFT. The COMB3 potential is then used to investigate the wetting behavior of water nanodroplets on Cu(111) at 20, 130, and 300 K. At room temperature, the simulations predict that the spreading rate of the base radius, R0, of a water droplet with a diameter of about 1.5 nm exhibits a spreading rate of R0 ≈ t(0.16) and a final base radius of 3.5 nm. At 20 and 130 K, water droplets are predicted to retain their structure after adsorption on Cu(111) and to undergo minimal spreading in agreement with scanning tunneling microscopy data. When the same water droplet encounters a reconstructed, oxidized Cu(111) surface, the classical MD simulations predict wetting with a spreading rate of R ≈ t(0.14) and a final base radius of 3.0 nm. Similarly, our MD simulations predict a spreading rate of R ≈ t(0.14) and a final base radius of 2.5 nm when water encounters OH-covered Cu(111). These results indicate that oxidation and hydroxylation cause a reduction in the degree of spreading and final base radius that is directly associated with a decreased spreading rate for water nanodroplets on copper.

Mon2 is a negative regulator of the monomeric G protein, Arl1.

Using site-directed mutants of ARL1 predicted to alter nucleotide binding, we examined phenotypes associated with the loss of ARL1 , including effects on membrane traffic and K (+) homeostasis. The GTP-restricted allele, ARL[Q72L] , complemented the membrane traffic phenotype (CPY secretion), but not the K (+) homeostasis phenotypes (sensitivity to hygromycin B, steady-state levels of K (+) , and accumulation of (86) Rb (+) ), while the XTP-restricted mutant, ARL1[D130N] , complemented the ion phenotypes, but not the membrane traffic phenotype. A GDP-restricted allele, ARL1[T32N] , did not effectively complement either phenotype. These results are consistent with a model in which Arl1 has three different conformations in vivo. We also explored the relationship between ARL1 and MON2 using the synthetic lethal phenotype exhibited by these two genes and demonstrated that MON2 is a negative regulator of the GTP-restricted allele of ARL1 , ARL1[Q72L] . Finally, we constructed several new alleles predicted to alter binding of Arl1 to the sole GRIP domain containing protein in yeast, Imh1, and found that ARL1[F52G] and ARL1[Y82G] were unable to complement the loss of ARL1 with respect to either the membrane traffic or K (+) homeostasis phenotypes. Our study expands understanding of the roles of Arl1 in vivo.

Passivation of Mid-Gap Electronic States at Calcium Aluminosilicate Glass Surfaces upon Water Exposure: An Ab Initio Study.

When a clean glass surface is exposed to humid air, a thin water layer forms on the hydrophilic surface. Using ab initio molecular dynamics, we simulate the changes in the electronic structure of a CaO-Al2O3-SiO2 glass model upon vacuum fracture and subsequent exposure to H2O. When the glass is fractured, dangling bonds form, which lower the band gap of the surface by ∼1.8 eV compared to the bulk value due to mid-gap surface states. When H2O adsorbs onto the vacuum-fractured surface, the band gap increases to a value closer to that of the bulk band gap. Using two different hydroxylation methods, we find that the calculated band gap of the glass surface depends on the hydroxylation state. Surfaces with ∼4.5 OH/nm2 have smaller band gaps due to unfilled surface states, and surfaces with ∼2.5 OH/nm2 have larger band gaps with no apparent unfilled surface states. The resulting changes in the electronic structure, quantified by electron affinity and work function values, are hypothesized to play an important role in the electrostatic charge transfer based on the principles of surface state theory, which posit that the density of electronic surface states determines the amount of electronic charge transfer to or from material surfaces.

Adherence to quality indicators in endoscopic surveillance of Barrett's esophagus and correlation to dysplasia detection rates.

BACKGROUND AND AIMS: The American Gastroenterological Association introduced quality guidelines for the endoscopic management of Barrett's esophagus (BE) in 2015. Our aim was to determine if these guidelines are being followed and to correlate adherence with outcomes in surveillance endoscopy. METHODS: This is a retrospective study from December 2015 to June 2017. Charts were abstracted to determine if the recommended quality measures were successfully accomplished during surveillance endoscopic exams in BE. Five of the recommendations pertain to surveillance endoscopy. FINDINGS: One hundred and seventy-four patients with Barrett's esophagus who underwent endoscopic surveillance were included. Adherence to recommendations one (78%), two (70%), six (99%), and seven (95%) were generally observed (P<0.001) but not to recommendation five (41%). When recommendations one (documenting important landmarks) and two (documenting the Prague classification) were followed, there was a statistically significant increase in dysplasia detection compared with those that did not adhere to the recommendations (36% vs. 13%, P=0.006 and 36% vs. 19%, P=0.003). The odds of detecting dysplasia when recommendations one and two were followed were 3.7 (95% CI 1.37-10.2) and 2.4 (95% CI 1.1-5.2) respectively. Conversely, there was no statistical difference in dysplasia yield for adherers compared with non-adherers to statement five (if systematic biopsies were performed; 35% vs. 27%, P=0.3). CONCLUSION: Adherence to statements one and two resulted in higher dysplasia detection. This has implications for the use of quality indicators in BE management in endoscopy units.

Pneumobilia Resulting From Choledochoduodenal Fistula Secondary to Metastatic Colon Adenocarcinoma.

Pneumobilia, or air within the biliary tree, is a poor prognostic indicator in a patient without prior biliary sphincterotomy. Differential diagnosis includes infection with gas-forming organisms, choledochoenteric fistula in the setting of gallstones or penetrating ulcer disease, malignant invasion from a primary liver or biliary tract tumor, or metastatic disease. Treatment depends on etiology and patient factors, but often requires surgical intervention. We report a patient with gastrointestinal bleeding in whom pneumobilia was incidentally noted on abdominal plain film. Computed tomography and endoscopy revealed the biliary-enteric fistula to be caused by metastatic colon adenocarcinoma invading the biliary tree.

Preoperative Endoscopy Prior to Bariatric Surgery: a Systematic Review and Meta-Analysis of the Literature.

BACKGROUND: There is debate regarding preoperative endoscopy (EGD) in patients undergoing bariatric surgery. Some centers perform EGD routinely in all patients; others perform EGD selectively. The objective of this study was to perform a systematic review and meta-analysis of the existing literature to estimate how frequently preoperative EGD changes management. METHODS: Our review yielded 28 studies encompassing 6616 patients. Baseline characteristics including age and body mass index (BMI) were included. Patients were grouped based on EGD findings into two groups: Group 1-findings which did not significantly change management (e.g., mild/moderate duodenitis, Grade A/B esophagitis, mild/moderate gastritis, H. pylori infection, hiatal hernia <2 cm); Group 2-findings which delayed, altered, or cancelled surgery (e.g., severe duodenitis, Grade C/D esophagitis, gastric varices, hiatal hernia >2 cm, mass/carcinoma). A general estimating equation (GEE) model accounting for the correlated data within each study was used to calculate confidence intervals around the estimate of how frequently surgery was delayed or altered. RESULTS: Mean age was 41.4 ± 2.9 years, the majority was women, and mean preoperative BMI was 47 ± 3.2 kg/m2. Overall 92.4 % (n = 6112) had a normal EGD or findings that did not change clinical management and 7.6 % (n = 504); 95 % CI [4.6, 12.4 %] had findings that delayed/altered surgery. The revised estimate was 20.6 %; 95%CI [14.5, 28.2 %] if all esophagitis (regardless of grade) were categorized into Group 2. The approximate incidence of Barrett's esophagus and carcinoma were 0.1 and 0.08 %, respectively. CONCLUSION: A selective approach to preoperative EGD may be considered, based on the patients' symptoms, risk factors, and type of procedure planned.