Elastocaloric Effect in Graphene Kirigami

Kirigami, a traditional Japanese art of paper-cutting, has recently been explored for its elastocaloric effect (ECE) in kirigami-based materials (KMs), where applying strain induces temperature changes. In this study, we investigate the ECE in a nanoscale graphene kirigami (GK) monolayer, representing the thinnest possible KM, to better understand this phenomenon. Through molecular dynamics simulations, we analyze the temperature change and coefficient of performance (COP) of the nanoscale GK architecture. Our findings reveal that while GKs lack the intricate temperature changes observed in macroscopic KMs, they exhibit a substantial temperature change of approximately 9.32 K (23 times higher than that of macroscopic KMs, which is about 0.4K) for heating and -3.50 K for cooling. Additionally, they demonstrate reasonable COP values of approximately 1.57 and 0.62, respectively. It is noteworthy that the one-atom-thick graphene configuration prevents the occurrence of the complex temperature distribution observed in macroscopic KMs.Comment: 14 pages, 06 figures, and 01 tabl

Abordagem dos pedículos glissonianos no manejo do trauma hepático

AIM:  To investigate a different approach in liver trauma, that preserves as much  liver parenchyma aspossible, exposing only the injured area to ischemia and reperfusion. MATHERIAL AND METHODS:Medline and pubMed search from 1980 to 2010 about the glissonian approach , including, liver, surgery,trauma, portal vein and hepatic artery as key-words .RESULTS: The glissonian approach is feasible, nottechnically demanding, and the key for the success is the knowledge of the anatomical landmarks  in theliver surface, to facilitate the surgeon to obtain a fast control of the injured area without compromising theliver flow to the non traumatic area.  CONCLUSION: The glissonian approach represents another toolthat can be performed in liver trauma setting to minimize complications related to the non-anatomicalremoval of parenchyma and blinded-ligaturesOBJETIVO: Investigar uma abordagem diferente no manejo do trauma hepático, que consiga preservaro máximo possível o parênquima do órgão, expondo apenas a área lesada à isquemia e posteriorreperfusão. METODOLOGIA: Pesquisa de artigos publicados nas bases de dados MedLine e pubMedno período de 1980 a 2010, sobre a abordagem dos pedículos glissonianos, e usando como palavrasde busca: fígado, cirurgia, trauma, veia porta e artéria hepática. RESULTADOS: A abordagem dos pedículosglissonianos é viável, não demanda de técnica cirúrgica elaborada, e a chave para o sucesso é ter umconhecimento anatômico do órgão, incluindo pontos importantes em sua superfície para que o cirurgião consiga obter o controle rápido de toda a área lesada sem comprometer o fluxo sanguíneo para asáreas sadias.  CONCLUSÃO: A abordagem glissoniana representa uma ferramenta que pode ser utilizada com segurança no cenário de um trauma hepático, para minimizar as complicações relacionadasa ressecção não anatômica do parênquima e ligaduras realizadas às cegas

Anterior Hepatic Transection for Caudate Lobectomy

Resection of the caudate lobe (segment I- dorsal sector, segment IX- right paracaval region, or both) is often technically difficult due to the lobe’s location deep in the hepatic parenchyma and because it is adjacent to the major hepatic vessels (e.g., the left and middle hepatic veins)

Sun-Graphyne: A New 2D Carbon Allotrope with Dirac Cones

Due to the success achieved by graphene, several 2D carbon-based allotropes were theoretically predicted and experimentally synthesized. Here, we propose a new 2D carbon allotrope named Sun-Graphyne (S-GY). We used density functional theory and reactive molecular dynamics simulations to investigate its mechanical, structural, electronic, and optical properties. The results showed that S-GY exhibits good dynamical and thermal stabilities. Its formation energy and elastic moduli are -8.57 eV/atom and 262.37 GPa, respectively. S-GY is a semi-metal and presents two Dirac cones in its band structure. This material is transparent, and its intense optical activity is limited to the infrared region. Remarkably, the band structure of S-GY remains practically unchanged at even moderate strain regimes. As far as we know, this is the first 2D carbon allotrope to exhibit this behaviour.Comment: 17 pages, and 11 figure

Quality Assessment of Photoplethysmography Signals For Cardiovascular Biomarkers Monitoring Using Wearable Devices

Photoplethysmography (PPG) is a non-invasive technology that measures changes in blood volume in the microvascular bed of tissue. It is commonly used in medical devices such as pulse oximeters and wrist worn heart rate monitors to monitor cardiovascular hemodynamics. PPG allows for the assessment of parameters (e.g., heart rate, pulse waveform, and peripheral perfusion) that can indicate conditions such as vasoconstriction or vasodilation, and provides information about microvascular blood flow, making it a valuable tool for monitoring cardiovascular health. However, PPG is subject to a number of sources of variations that can impact its accuracy and reliability, especially when using a wearable device for continuous monitoring, such as motion artifacts, skin pigmentation, and vasomotion. In this study, we extracted 27 statistical features from the PPG signal for training machine-learning models based on gradient boosting (XGBoost and CatBoost) and Random Forest (RF) algorithms to assess quality of PPG signals that were labeled as good or poor quality. We used the PPG time series from a publicly available dataset and evaluated the algorithm s performance using Sensitivity (Se), Positive Predicted Value (PPV), and F1-score (F1) metrics. Our model achieved Se, PPV, and F1-score of 94.4, 95.6, and 95.0 for XGBoost, 94.7, 95.9, and 95.3 for CatBoost, and 93.7, 91.3 and 92.5 for RF, respectively. Our findings are comparable to state-of-the-art reported in the literature but using a much simpler model, indicating that ML models are promising for developing remote, non-invasive, and continuous measurement devices.Comment: 9 page

Exploring the Elastic Properties and Fracture Patterns of Me-Graphene Monolayers and Nanotubes through Reactive Molecular Dynamics Simulations

Me-graphene (MeG) is a novel two-dimensional (2D) carbon allotrope. Due to its attractive electronic and structural properties, it is important to study the mechanical behavior of MeG in its monolayer and nanotube topologies. In this work, we conducted fully atomistic reactive molecular dynamics simulations using the Tersoff force field to investigate their mechanical properties and fracture patterns. Our results indicate that Young's modulus of MeG monolayers is about 414 GPa and in the range of 421-483 GPa for the nanotubes investigated here. MeG monolayers and MeGNTs directly undergo from elastic to complete fracture under critical strain without a plastic regime.Comment: 10 pages, 01 table, and 05 figure