RESUMO
The mechanical and thermal properties of transition metal dichalcogenides (TMDs) are directly relevant to their applications in electronics, thermoelectric devices, and heat management systems. In this study, we use a machine learning (ML) approach to parametrize molecular dynamics (MD) force fields to predict the mechanical and thermal transport properties of a library of monolayered TMDs (MoS2, MoTe2, WSe2, WS2, and ReS2). The ML-trained force fields were then employed in equilibrium MD simulations to calculate the lattice thermal conductivities of the foregoing TMDs and to investigate how they are affected by small and large mechanical strains. Furthermore, using nonequilibrium MD, we studied thermal transport across grain boundaries. The presented approach provides a fast albeit accurate methodology to compute both mechanical and thermal properties of TMDs, especially for relatively large systems and spatially complex structures, where density functional theory computational cost is prohibitive.
RESUMO
BACKGROUND: Pseudoachalasia is a condition in which clinical and manometric signs of achalasia are mimicked by another abnormality, most often a malignancy. AIM: To identify risk factors that suggest presence of malignancy-associated pseudoachalasia. METHODS: In this retrospective cohort study, achalasia patients newly diagnosed by manometry were included. Patients with a normal initial endoscopy, clinical and manometric signs of achalasia who were afterwards found to have an underlying malignant cause were classified as pseudoachalasia. Clinical and diagnostic findings were compared between malignant pseudoachalasia and achalasia. RESULTS: We included 333 achalasia patients [180 male, median age 50 (38-62)]. Malignant pseudoachalasia was diagnosed in 18 patients (5.4%). Patients with malignancy-associated pseudoachalasia were older at time of diagnosis [67 (54-71) vs. 49 (37-60) years], had a shorter duration of symptoms [6 (5-10) vs. 25 (11-60) months] and lost more weight [12 (9-17) vs. 5 (0-12) kg). In 61% of the pseudoachalasia patients, the oesophagogastric junction (OGJ) was difficult or impossible to pass during endoscopy, compared to 23% in achalasia. Age ≥55 years (OR 5.93), duration of symptoms ≤12 months (OR 14.5), weight loss ≥10 kg (OR 6.73) and difficulty passing the OGJ during endoscopy (OR 6.06) were associated with a higher risk of malignant pseudoachalasia. CONCLUSIONS: Advanced age, short duration of symptoms, considerable weight loss and difficulty in passing the OGJ during endoscopy, are risk factors that suggest potential malignancy-associated pseudoachalasia. To exclude pseudoachalasia, additional investigations are warranted when two or more risk factors are present.
