Comparative simulation study of colloidal gels and glasses

Using computer simulations, we identify the mechanisms causing aggregation and structural arrest of colloidal suspensions interacting with a short-ranged attraction at moderate and high densities. Two different non-ergodicity transitions are observed. As the density is increased, a glass transition takes place, driven by excluded volume effects. In contrast, at moderate densities, gelation is approached as the strength of the attraction increases. At high density and interaction strength, both transitions merge, and a logarithmic decay in the correlation function is observed. All of these features are correctly predicted by mode coupling theory

Nonergodicity transitions in colloidal suspensions with attractive interactions

The colloidal gel and glass transitions are investigated using the idealized mode coupling theory (MCT) for model systems characterized by short-range attractive interactions. Results are presented for the adhesive hard sphere and hard core attractive Yukawa systems. According to MCT, the former system shows a critical glass transition concentration that increases significantly with introduction of a weak attraction. For the latter attractive Yukawa system, MCT predicts low temperature nonergodic states that extend to the critical and subcritical region. Several features of the MCT nonergodicity transition in this system agree qualitatively with experimental observations on the colloidal gel transition, suggesting that the gel transition is caused by a low temperature extension of the glass transition. The range of the attraction is shown to govern the way the glass transition line traverses the phase diagram relative to the critical point, analogous to findings for the fluid-solid freezing transition.Comment: 11 pages, 7 figures; to be published in Phys. Rev. E (1 May 1999

Higher order glass-transition singularities in colloidal systems with attractive interactions

The transition from a liquid to a glass in colloidal suspensions of particles interacting through a hard core plus an attractive square-well potential is studied within the mode-coupling-theory framework. When the width of the attractive potential is much shorter than the hard-core diameter, a reentrant behavior of the liquid-glass line, and a glass-glass-transition line are found in the temperature-density plane of the model. For small well-width values, the glass-glass-transition line terminates in a third order bifurcation point, i.e. in a A_3 (cusp) singularity. On increasing the square-well width, the glass-glass line disappears, giving rise to a fourth order A_4 (swallow-tail) singularity at a critical well width. Close to the A_3 and A_4 singularities the decay of the density correlators shows stretching of huge dynamical windows, in particular logarithmic time dependence.Comment: 19 pages, 12 figures, Phys. Rev. E, in prin

The Japanese Esophageal Society classification for prediction of superficial esophageal squamous cell neoplasia invasion depth:Validation in a Western population

Background: The Japan Esophageal Society proposed the JES microvessel classification to assess eligibility of early esophageal squamous cell neoplasia (ESCN) for endoscopic resection based on intrapapillary capillary loop assessment. We aimed to assess its diagnostic reproducibility and accuracy in Western ESCN patients. Methods: Intrapapillary capillary loops on endoscopic images of Western ESCN lesions (n = 113) collected between 2010 and 2022 were assessed by nine endoscopists, including three Japanese expert endoscopists, three Western expert endoscopists, and three residents-in-training, and graded according to the JES microvessel classification where microvessel type A corresponds with normality or low-grade intraepithelial neoplasia, and microvessel types B1, B2, and B3 correspond with high-grade intraepithelial neoplasia or invasion into the lamina propria, muscularis mucosae or superficial submucosa, and deep submucosa, respectively. Outcomes included overall accuracy in predicting ESCN invasion depth and interobserver agreement. Results: Good interobserver agreement was observed among expert endoscopists (Krippendorf's alpha 0.64, 95% CI 0.57–0.70), while agreement was moderate among residents-in-training (Krippendorf's alpha 0.58, 95% CI 0.52–0.72). Overall accuracy of the JES microvessel classification was 53% (95% CI 42–63), 52% (95% CI 41–62), and 44% (95% CI 34–55) for Japanese endoscopists, Western endoscopists, and residents-in-training, respectively. Sensitivity and specificity for vessel type A, B1, B2, and B3 across assessors were 0%–50% and 89%–100%, 55%–64% and 66%–77%, 42%–71% and 60%–76%, and 10%–24% and 92%–97%, respectively. Negative predictive value ranged between 80% and 85% for B3 vessels. Conclusion: Overall accuracy of the JES microvessel classification in Western ESCN patients is low, though absence of B3 vessels as assessed by experienced endoscopists may predict superficial ESCN amenable to endoscopic resection. Trial registry: www.trialregister.nl; NL8897 (6-9-2020).</p

B-NMR study of a buried Mn &-doped layer in a silicon host

Low temperature growth methods were used to encapsulate a buried Mn ¿-doping layer into a silicon host. A ¿-NMR investigation was performed of the magnetic properties in the temperature range 10-300 K using spin-polarized 8Li+. A depth-dependent broadening and shift of the NMR resonance was detected that is consistent with internal fields distributed at depths of 10-30 nm beneath the surface. At low temperatures, a negative relative shift occurred and the resonance was significantly broadened. At 300 K the line-shape could be described by a single Gaussian line, however, at 10 K the line is best approximated by a two component Lorentzian shape consisting of a broad and narrow component as anticipated for a diluted magnetic alloy. The overall magnitude of the resonance shift at both temperatures is small suggesting a weak interaction between the 8Li+ and the magnetic Mn environment