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This paper presents a computational procedure for the determination of the dynamic behaviour of graphene with different types of defects. The lattice of graphene is modelled using the molecular structural mechanics (MSM) approach, where the C–C covalent bonds are replaced by equivalent beam elements. Cantilever and bridged boundary conditions are applied for the analysis. Four types of Stone–Wales (SW) defects such as S-W (555-8), S-W (555-888-3), S-W (555-77-8) and S-W (888-3), and two types of pinhole defects with 6 and 24 elements eliminated are examined on armchair, zigzag and chiral type of graphene sheet. The effect of the structural length of the sheet, chirality and defect type on the vibrational properties of graphene sheets is investigated. The computed results reveal that SW defects produce a high frequency to that of pristine graphene, whereas the effect of pinhole defects is significant as compared to SW defects. The computed results will be useful in nano-resonator-based sensor applications. [ABSTRACT FROM AUTHOR]

Graphene has been widely and extensively used in mass sensing applications. The present study focused on exploring the use of single-layer graphene (SLG) and double-layer graphene (DLG) as sensing devices. The dynamic analysis of SLG and DLG with different boundary conditions (BDs) and length was executed using the atomistic finite element method (AFEM). SLG and DLG sheets were modelled and considered as a space–frame structure similar to a 3D beam. Spring elements (Combin14) were used to identify the interlayer interactions between two graphene layers in the DLG sheet due to the van der Waals forces. Simulations were carried out to visualize the behavior of the SLG and DLG subjected to different BDs and when used as mass sensing devices. The variation in frequency was noted by changing the length and applied mass of the SLGs and DLGs. The quantity of the frequency was found to be highest in the armchair SLG (6, 6) for a 50 nm sheet length and lowest in the chiral SLG (16, 4) for a 20 nm sheet length in the bridged condition. When the mass was 0.1 Zg, the frequency for the zigzag SLG (20, 0) was higher in both cases. The results show that the length of the sheet and the various mass values have a significant impact on the dynamic properties. The present research will contribute to the ultra-high frequency nano-resonance applications. [ABSTRACT FROM AUTHOR]

Background: Stroke is major public health problem leading to increased morbidity and mortality. Stroke is one of the leading causes of death and disability in India. Carotid sonographic hemodynamic parameter Pulsatality Index by using carotid Doppler Ultrasound is associated with the future risk of development of cerebrovascular stroke. Material And Methods: The present cross sectional study was conducted on 25 hypertension with diabetes stroke (Group A) and 30 hypertension with diabetes controls (Group B). CCA peak systolic velocity, end diastolic velocity and Pulsatility Index were assessed in each group by Doppler ultrasound machine. BMI and W/H was measured according to WHO protocol. Blood pressure was measured by sphygmomanometer. Biochemical analysis like Lipid profile and HbA1c were done by autoanalyser machine. Result: CCA PSV in Group A was found to be 65.50±21.58 and 69.75±15.51 in left and right side respectively & 70.51±16.70 and 68.64±13.73 in Group B. CCA EDV in Group A was found to be 13.56±2.78 and 11.53±4.65 in left and right side respectively & 20.32±4.54 and 18.17±4.39 in Group B. The data was highly significant (p<0.0001). CCA MV in Group A was found to be 39.53±11.72 and 40.64±9.25 in left and right side respectively & 45.41±9.39 and 43.40±7.70 in Group B (p=0.04 & p=0.23 left and right side respectively). CCA PI in Group A was found to be 1.28±0.15 and 1.44±0.22 in left and right side respectively & 1.05±0.23 and 1.14±0.16 in Group B. The data was highly significant (p<0.0001).Age in Group A and B was found to be 62.20±9.60 and 54.66±9.01 respectively (p<0.004). BMI in Group A and Group B was found to be 28.27±1.17 and 26.35±1.45 respectively (p<0.0001). W/H in Group A and Group B was 0.88±0.04 and 0.86±0.02 respectively (p=0.01). Systolic and diastolic blood pressure in both the groups was found to be 148.16±15.21 & 138.72±6.91 and 87.60±5.94 & 83.86±6.23 which was statistically significant with p=0.003 & p=0.02. The difference between mean of two groups for HbA1c, HDL, LDL, total cholesterol and triglyceride in both the groups were 8.6±0.82 &7.45±0.56, 39.04±5.85 & 49.97±8.34, 143.20±6.40 &113.26±17.09, 226.28±8.28 & 201.90±21.83 & 195.68±9.69, 201.03±55.82 respectively in which HbA1c, HDL, LDL, Total cholesterol were statistically very significant(p<0.0001) and triglyceride was not statistically significant. Conclusion: In conclusion, among hemodynamic parameters that are measured by carotid Doppler ultrasound, Pulsatility Index may play a role for predicting cerebrovascular stroke in hypertension with diabetic patients. In this sense, we concluded that Pulsatility Index examination should be carried out in hypertension with diabetic patients by carotid Doppler ultrasonography. These findings need to be confirmed by a prospective study. [ABSTRACT FROM AUTHOR]

Background: Globally, smoking is considered to be associated with several public health problems including stroke. Common carotid artery (CCA) hemodynamic parameters peak systolic velocity (PSV), end diastolic velocity(EDV) and resistive Index(RI) have an association with the development of stroke. Material Method: The present study was conducted on 16 smokers with Stroke (Group A) and 22 hypertension with diabetic smokers non stroke patients (Group B). CCA peak systolic velocity, end diastolic velocity and resistive Index were assessed in each group by Doppler ultrasound machine. BMI and W/H was measured according to WHO protocol. Blood pressure was measured by sphygmomanometer. Lipid profile was done by autoanalyser machine. Result: CCA PSV in Group A was found to be 57.67±13.33 and 48.55±16.29 in right and left side respectively & 70.06±14.04 and 75.23±11.89 in Group B. The data was highly significant (p<0.0001). CCA EDV in Group A was found to be 10.43±5.97 and 10.43±4.57 in right and left side respectively & 18.79±2.89 and 21.76±2.68 in Group B. The data was highly significant (p<0.0001). CCA RI in Group A was found to be 0.82±0.09 and 0.80±0.09 in right and left side respectively & 0.72±0.03 and 0.70±0.04 in Group B. The data was highly significant (p<0.0001). Age in Group A and B was found to be 62.93±5.82 and 52.59±4.37 respectively (p<0.0001). BMI in Group A and Group B was found to be 28.30±3.10 and 28.43±2.11 respectively (p =0.87).W/H in Group A and Group B was 0.88±0.03 and 0.89±0.02 respectively (p=0.22). Systolic and diastolic blood pressure in both the groups was found to be 150.75±13.48 & 139.18±6.63 and 87.50±5.72 & 84.09±5.60 which was statistically significant with p=0.001 & p=0.07. The difference between mean of two groups for HbA1c, HDL, LDL, total cholesterol and triglyceride in both the groups were 8.70±0.71 &7.25±1.08, 36.93±5.20 & 46.00±5.13, 146.81±7.96 &116.63±13.91, 229.62±6.87 & 194.95±15.48 &155.81±38.38, 169.36±29.85 respectively in which HbA1c, HDL, LDL, Total cholesterol were statistically very significant(p<0.0001) and triglyceride was not statistically significant. Conclusion: Our finding revealed that Common carotid artery hemodynamic parameters PSV, and RI were increased in stroke patients as well as EDV decreased in these patients. Smoking has association of development of stroke in hypertensive and diabetic patients. Carotid Doppler sonography is useful diagnostic modality for predicting and preventing CV Stroke in smokers as well as patients with hypertension and diabetes mellitus. [ABSTRACT FROM AUTHOR]