633 research outputs found
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
Prioritizing patients for hip fracture surgery: the role of frailty and cardiac risk
IntroductionThe number of patients with hip fractures continues to rise as the average age of the population increases. Optimizing outcomes in this cohort is predicated on timely operative repair. The aim of this study was to determine if patients with hip fractures who are frail or have a higher cardiac risk suffer from an increased risk of in-hospital mortality when surgery is postponed >24 h.MethodsAll patients registered in the 2013–2021 TQIP dataset who were ≥65 years old and underwent surgical fixation of an isolated hip fracture caused by a ground-level fall were included. Adjustment for confounding was performed using inverse probability weighting (IPW) while stratifying for frailty with the Orthopedic Frailty Score (OFS) and cardiac risk using the Revised Cardiac Risk Index (RCRI). The outcome was presented as the absolute risk difference in in-hospital mortality.ResultsA total of 254,400 patients were included. After IPW, all confounders were balanced. A delay in surgery was associated with an increased risk of in-hospital mortality across all strata, and, as the degree of frailty and cardiac risk increased, so too did the risk of mortality. In patients with OFS ≥4, delaying surgery >24 h was associated with a 2.33 percentage point increase in the absolute mortality rate (95% CI: 0.57–4.09, p = 0.010), resulting in a number needed to harm (NNH) of 43. Furthermore, the absolute risk of mortality increased by 4.65 percentage points in patients with RCRI ≥4 who had their surgery delayed >24 h (95% CI: 0.90–8.40, p = 0.015), resulting in a NNH of 22. For patients with OFS 0 and RCRI 0, the corresponding NNHs when delaying surgery >24 h were 345 and 333, respectively.ConclusionDelaying surgery beyond 24 h from admission increases the risk of mortality for all geriatric hip fracture patients. The magnitude of the negative impact increases with the patient's level of cardiac risk and frailty. Operative intervention should not be delayed based on frailty or cardiac risk
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
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