Graphene twistronics have recently gained significant attention due their superconductive behavior as a consequence of their tunable electronic properties. Although the electronic properties of twisted graphene have been extensively studied, the mechanical properties and integrity of twisted trilayer graphene (tTLG) under loading is still elusive. We investigated the fracture mechanics of tTLG with a twist angle of ±1.53° utilizing molecular dynamics simulation. This twist angle was chosen because it is known to exhibit highly superconductive behavior. The results indicate that tTLG does not preserve the excellent mechanical properties typically associated with graphene, with toughness and fracture strain values much lower in comparison. The Young’s modulus was an exception with values relatively close to pristine graphene, whereas the tensile strength was found to be roughly half of the intrinsic strength of graphene. The fracture toughness, fracture strain and strength converge as the crack length increases, reaching 0.26 J/m3, 0.0217 and 39.9 GPa at a crack length of 8 nm, respectively. The Griffth critical strain energy is 19.98 J/m2 and the critical stress intensity factor Kc is 4.47 MPa M1/2, in good agreement with that of monolayer graphene in the experiment. Our atomic insights might be helpful in the material design of twisted trilayer graphene-based electronics.

Graphene is a type of 2D material with unique properties and promising applications. Fracture toughness and the tensile strength of a material with cracks are the most important parameters, as micro-cracks are inevitable in the real world. In this paper, we investigated the mechanical properties of triangular-cracked single-layer graphene via molecular dynamics (MD) simulations. The effect of the crack angle, size, temperature, and strain rate on the Young’s modulus, tensile strength, fracture toughness, and fracture strain were examined. We demonstrated that the most vulnerable triangle crack front angle is about 60°. A monitored increase in the crack angle under constant simulation conditions resulted in an enhancement of the mechanical properties. Minor effects on the mechanical properties were obtained under a constant crack shape, constant crack size, and various system sizes. Moreover, the linear elastic characteristics, including fracture toughness, were found to be remarkably influenced by the strain rate variations.

Background Most patients admitted to intensive care units (ICUs) with severe Corona Virus Disease 2019 (COVID-19) pneumonia receive antibacterial antibiotics with little evidence of bacterial infections. Objective This study was designed to review the profiles of patients with severe COVID-19 pneumonia requiring intensive care, the rate of bacterial coinfection, the antibiotics used, and their relation to patient outcomes (death or recovery). Methods This was a retrospective study that reviewed the medical records of all patients with confirmed COVID-19 (n = 120) severe pneumonia admitted directly from the emergency room to the intensive care unit, at a public hospital during the period from May 2020 to April 2021. The data collected included patients’ demographic and laboratory data, comorbidities, antibiotic treatment, and their outcome. Descriptive statistics, bivariate inferential analysis tests (chi-square and unpaired T-Tests) and multivariable binary logistic regression were performed. Results The mean age of the patients was 56.8 ± 16.5 years old, and among them, 74 (62.7%) were males. Of the included patients, 92 (77.0%) had comorbidities, 76 (63.3%) required mechanical ventilation and 30 (25%) died. All patients received empirical antibiotics for suspected bacterial coinfection. The most common antibiotics used were azithromycin (n = 97, 8%) and imipenem (n = 83, 9%). Ninety patients (75%) were on two empirical antibiotics. Early positive cultures for pathogens were found only in four patients (3.3%), whereas 36 (30%) patients had positive cultures 5–10 days after admission. The most frequently isolated pathogens were Acinetobacter baumannii (n = 16) and coagulase-negative Staphylococci (n = 14). In bivariate analysis empirical treatment with azithromycin resulted in a significantly lower mortality rate (p = 0.023), meanwhile mechanical ventilation, days of stay in intensive care unit, morbidities (e.g., lung disease), linezolid and, vancomycin use associated with mortality (p< 0.05). The adjusted logistic regression, controlling for age and gender, revealed that azithromycin antibiotic was more likely protective from mortality (OR= 0.22, 95%CI 0.06-0.85, p=0.028. However, patients with lung diseases and under mechanical ventilation were 35.21 and 19.57 more likely to die (95%CI =2.84-436.70, p=0.006; 95%CI=2.66-143.85, p=0.003, respectively). Conclusion Bacterial coinfection with severe COVID-19 pneumonia requiring intensive care was unlikely. The benefit of Azithromycin over other antibiotics could be attributed to its anti-inflammatory properties rather than its antibacterial effect.

Urinary tract infection (UTI) is the most common nosocomial infection. Indwelling catheters are found to be strongly associated with UTIs. In present study a total of 110 catheterized patients from general wards and ICU of Mayo Hospital Lahore were investigated for their microbial evaluation. Out of 110 urine samples 80 cultured positive of which 25 developed UTI symptoms while 55 were not having UTI symptoms implying 23% acquired catheter associated urinary tract infection (CAUTI) while 50% developed asymptomatic bacterial colonization. Among the isolates 49% Escherichia coli, 14% Psuedomonas aeruginosa, 7% Staphylococcus aureus, 7% Klebsiella pneumoniae, 10% Proteus species, 5% Enterobacter aerogens and 8% fungi and yeast were recovered. Out of 80 patients who were cultured positive 52 were females revealing high susceptibility of females towards acquiring UTI. 74% of patients were married showing higher rate in married. Prevalence of CAUTI was low in this hospital while asymptomatic colonization was 50%, duration of catheterization had strong influence on occurrence of infection as 36% with UTI were catheterized from 3 weeks and only 6% for 1-3 days. Socioeconomic status was not found to have major influence. Patients who needed to be catheterized for longer duration should be checked regularly for UTI symptoms to prevent complications that are life threatening and are difficult to treat.

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