Using first-principles calculations, we identify the mechanisms that lead to the lowest energy structures for the stable and metastable ͑GeTe͒ m ͑Sb 2 Te 3 ͒ n ͑GST͒ compounds, namely, strain energy release by the formation of superlattice structures along of the hexagonal ͓0001͔ direction and by maximizing the number of Te atoms surrounded by three Ge and three Sb atoms ͑3Ge-Te-3Sb rule͒ and Peierls-type bond dimerization. The intrinsic vacancies form ordered planes perpendicular to the stacking direction in both phases, which separate the GST building blocks. The 3Ge-Te-3Sb rule leads to the intermixing of Ge and Sb atoms in the ͑0001͒ planes for Ge 3 Sb 2 Te 6 and Ge 2 Sb 2 Te 5 , while only single atomic species in the ͑0001͒ planes satisfy this rule for the GeSb 2 Te 4 and GeSb 4 Te 7 compositions. Furthermore, we explain the volume expansion of the metastable phase with respect to the stable phase as a consequence of the different stacking sequence of the Te atoms in the stable and metastable phases, which leads to a smaller Coulomb repulsion in the stable phase. The calculated equilibrium lattice parameters are in excellent agreement with experimental results and differ by less than 1% from the lattice parameters derived from a combination of the GeTe and Sb 2 Te 3 parent compounds.

Fe doped GST has shown experimentally the ability to alter its magnetic properties by phase change. In this work, we use screened exchange hybrid functional to study the single neutral substitutional 3d transition metal (TM) in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over delocalization of the 3d states, we find that Fe on Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different than previous predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. In order to study the magnetic contrast, we use lower symmetry crystalline GeTe and GeSb2Te4 as the amorphous phases, respectively, which has been proposed to model the medium range disordering. We find that only Co substitution in r-GeSb2Te4 and s-GeSb2Te4 shows magnetic contrast. The experimental magnetic contrast for Fe doped GST may be due to additional TM-TM interaction, which is not included in our model. It can also be possible that these lower symmetry crystalline models are not sufficient to characterize the magnetic properties of real 3d TM doped amorphous GST.

Background/Aim: High-carbohydrate diets are generally provided to post-pancreatectomy cancer patients. Low energy density of this diet may obstruct proper energy intake and recovery. This study aimed to assess the effects of high-fat, high-energy ketogenic diet (KD) in these patients. Patients and Methods: After pancreatectomy, 9 patients were provided with general diet (GD) while 10 were served KD. Meal compliance, energy intake rate, meal satisfaction and presence of complications were monitored throughout hospital stay. Data on nutritional status, serum lipids and body composition were collected and compared between groups. Results: Meal compliance, energy intake rate and meal satisfaction score were higher in KD. There were no differences in complications, nutritional status and serum lipids. The decrease in body cell mass (BCM) was greater in GD. Conclusion: Postpancreatectomy cancer patients who consumed KD had a higher energy intake and BCM. These results suggest the potential use of KD as an adjuvant anti-cancer therapy. Pancreatic cancer accounts for 2.4% of the cancer incidence worldwide and has a particularly poor prognosis, resulting in 4.0% mortality. Gallbladder cancer accounts for 1.3% of all cancers with a mortality of 1.7% (1). Pancreatic cancer in South Korea was the eighth most common at 3% and gallbladder and other biliary cancers were the ninth most common at 2.9% in 2015 which, with regard to mortality, were ranked fifth with a rate of 7.2% and sixth with a rate of 5.6%, respectively. The five-year relative survival rate of pancreatic cancer was the lowest of all cancers at 10.8% (2). Radical resection is the only method that can completely cure pancreatobiliary cancer, as complete tumor removal can considerably reduce the risk of cancer recurrence and increase patient survival rates (3, 4). However, patients who undergo pancreatectomy are more susceptible to malnourishment and weight loss due to complications such as pancreatic fistula, delayed gastric emptying, dumping syndrome, impaired digestive enzyme secretion, dysfunctional nutrient absorption, diarrhea, and steatorrhea (5). Furthermore, delayed or reduced food intake after surgery due to difficulty in consuming food can also induce weight loss. This weight loss may subsequently impact cancer cachexia caused by malignant tumors, malnutrition, and reduced quality of life (6, 7). Multiple studies have reported that cancer patients experience at least 10% of their total weight loss within six months after surgery due to cancer cachexia and that death caused by serious weight loss accounts for 80% of deaths caused by pancreatic cancer (8). According to a 2015 Korean study, 60% of patients who undergo pancreatoduodenectomy experience at least two factors that hinder food intake and subsequent weight loss, suggesting the need to improve the standard meals provided after pancreatectomy (9). Recently, ketogenic diets (KD) have gained traction as a potential adjuvant anticancer therapy for targeting specific metabolic reactions of cancer tissu...

We investigated the optical properties of ultrathin MoS2 films (number of layers: N = 1, 2, 4, and 12) using Raman spectroscopy, photoluminescence (PL) spectroscopy, and spectroscopic ellipsometry. We estimated the layer thicknesses based on Raman spectra. We characterized the microstructural properties of a single-layer MoS2 film using atomic force microscopy. We measured the lowest-energy A and B excitons using PL spectroscopy. We measured the ellipsometric angles (Ψ and Δ) of MoS2 thin films using spectroscopic ellipsometry, and obtained the dielectric functions as the films' thickness changed from a single layer to multi-layers. We determined the films' optical gap energies from the absorption coefficients. Applying the standard critical point model to the second derivative of the dielectric function (d2ε(E)/dE2), we determined several critical point energies. The d2ε(E)/dE2 spectra showed doublet peaks around 3 eV corresponding to the C and D transitions, as well as doublet peaks around 2 eV corresponding to the A and B transitions. These doublet structures at 3 eV are attributed to the transitions in the Brillouin zone between the Γ and K points.