Screened Interaction and Self-Energy in an Infinitesimally Polarized Electron Gas via the Kukkonen-Overhauser Method

The screened electron-electron interaction $W_{\sigma, \sigma'}$ and the electron self-energy in an infinitesimally polarized electron gas are derived by extending the approach of Kukkonen and Overhauser. Various quantities in the expression for $W_{\sigma, \sigma'}$ are identified in terms of the relevant response functions of the electron gas. The self-energy is obtained from $W_{\sigma, \sigma'}$ by making use of the GW method which in this case represents a consistent approximation. Contact with previous calculations is made.Comment: 7 page

Characterization of the Atherosclerotic Plaque Tissue

Cardiovascular diseases (CVD) are the leading causes of morbidity and mortality globally. Atherosclerosis is a chronic inflammatory CVD associated with the accumulation of plaque activated by the complex interactions between systemic, hemodynamic and biological factors. Thus, identification of plaque vulnerability is essential for the prevention of acute events and treatment of the disease. Despite, advanced imaging technologies, patient-specific computational simulations and availability of experimental data, there are still challenges in developing accurate risk stratification techniques. Therefore, this study aims to characterize the carotid plaque components structurally (histological analysis and immunostaining), mechanically (Nanoindentation tests) and chemically (Fourier Transform Infrared (FT-IR) micro-spectroscopy). The preliminary results showed that arterial remodelling is a dynamic interaction between mechanical forces and plaque progression. The biological content and composition of human atherosclerotic plaque tissue have been shown to significantly influence the mechanical response of samples. This data represents a step towards an enhanced understanding of the behaviour of human atherosclerotic plaque. Future large-scale experimental studies with more cross-sections along the length of the plaque could be used to develop a risk stratification technique

Numerical investigation of atherosclerotic plaque rupture using optical coherence tomography imaging and XFEM

Myocardial infarction contributes to most fatalities in which atherosclerotic plaque disruption is the underlying pathology. From the mechanics view point, the pulsatile blood flow in the arteries resembles a fatigue environment and generates stresses that affect the rupture of the atherosclerotic plaque. In this context, patient-specific optical coherence tomography (OCT) was used to develop the fatigue crack growth behavior. The impact of location specific morphological features and their relative effect on plaque life were discussed. EXtended Finite Element Method (XFEM) and Paris’ Law were employed to investigate the fatigue crack growth. Twelve 2D slices from six patients were reconstructed for studying the fatigue crack growth behavior. Our results indicate that plaque life decreases with an increase in pulse pressure and 53.5% of the total cracks initiated at various locations on the lumen lead to rupture. 73.7% of the rupture locations did not have calcifications. Correlation between the location specific morphology and the rupture indicates that for a 1 mm increase in the fibrous cap thickness there is a large decrease in the odds of rupture [0.163 (0.073; 0.363)], p-value < 0.0001; and for a 1 mm2 increase of the calcification area, there is a decrease in the odds of rupture by 0.719 (0.619; 0.835), p-value < 0.0001. In conclusion, the XFEM technique can be used to study the fatigue behavior of the atherosclerotic plaque that depends on the combined effects of plaque constituents and their morphology. It may help to better assess plaque vulnerability and make more accurate predictions for plaque rupture

Association of vaginal infections in Preterm labour

Background: Preterm labour is defined as onset of regular uterine contractions associated with cervical changes between 28-37 completed weeks of gestation. Prematurity is the cause of 85% neonatal morbidity and mortality. Preterm labour has multiple etiologies. Vaginal infections have been associated with increased risk for preterm labour. Screening for genitourinary infections antenatally, especially in high risk cases, prompt recognition and treatment decrease the incidence of preterm labour.Methods: Ours was a prospective and retrospective observational study done at Dr. Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation from April 2016 to February 2018 in the Department of Obstetrics and Gynaecology. The aim is to study the association of vaginal infections in preterm labour. A total of 116 women in preterm labor were studied. After clinical examination, CBP, CUE, Ultrasound, urine culture and sensitivity were done. Vaginal swab was taken from posterior fornix and sent for culture and sensitivity and gram staining .Culture and sensitivity were done in the Department of Microbiology at our Institute.Results: Out of 116 women in preterm labour, urinary tract infection was seen in 27.58% women. E. Coli was the commonest microorganism isolated in urine (15.51%). Vaginal infections were seen in 33.62% women. Candida was the commonest microorganism isolated in HVS cultures.Conclusions: Screening for genitourinary infections in pregnancy is necessary, especially in high risk cases. Early detection and prompt treatment of genitourinary infections decrease the incidence of preterm labor, thereby decreasing the neonatal morbidity and mortality associated with prematurity

Prediction of atherosclerotic plaque life – Perceptions from fatigue analysis

Cardiovascular diseases are the leading causes of morbidity and mortality globally. Heart disease and stroke contribute to most fatalities in which atherosclerotic plaque disruption is the underlying pathology. The pulsatile blood flow in the arteries generates mechanical stresses that affect the rupture of the atherosclerotic plaque. Fatigue failure being the accumulation of the damage due to repeated loading that occurs when the stresses are much lower than those needed to rupture the plaque with normal loading. Therefore, fracture mechanics concepts were used to investigate the impact of morphology and blood pressure on the plaque life. Incremental fatigue crack propagation simulations were performed on idealized geometries based on the maximum circumferential stress criteria by using a finite element solver. XFEM, which extends the standard finite element formulation by introducing additional enrichment functions was used to model the fatigue crack growth simulations. Paris’ Law was used to determine the fatigue crack growth rate. Cracks extended radially and fatigue crack growth rate increased with increase in pulse pressure. Further validation studies on the 3D printed arteries are necessary for better understanding the factors contributing to plaque rupture. The results could help in assessing the atherosclerotic plaque life under the fatigue environment of the cardiovascular system

Comment on ``Spin Dependent Hopping and Colossal Negative Magnetoresistance in Epitaxial Nd0.52Sr0.48MnO3Nd_{0.52}Sr_{0.48}MnO_{3} Films in Fields up to 50 T''

Recently Wagner et al. [Phys. Rev. Lett. Vol. 81, P. 3980 (1998)] proposed that Mott's original model be modified to incorporate a hopping barrier which depends on the misorientation between the spins of electrons at the initial and the final states in an elementary process. They further claimed that using the model they can explain the observed scaling behavior-- negative-magnetoresistivity scaling proportional to the Brillouin function $\cal{B}$ in the ferromagnetic state and to ${\cal{B}}^2$ in the paramagnetic state. In this comment we argue that the modification needed for Mott's original model is different from that proposed by Wagner et al. and further show that our picture will successfully explain the observed scaling in the two regimes.Comment: 1 pag

Evaluation of women with postcoital bleeding by clinical examination, papsmear, colposcopy and histopathology of cervix

Background: Postcoital bleeding refers to spotting or bleeding per vagina that occurs after intercourse and is not related to menstruation. Although there are multiple benign etiologies to this complaint, the most serious cause of postcoital bleeding is cervical cancer (3-5.5%). Cervical cancer is the most common and preventable genital cancer of women. It has a long premalignant phase and with an ideal screening test with good sensitivity and specificity, we can diagnose and treat premalignant cervical lesions, preventing cervical cancer. The present study is aimed to evaluate the women with postcoital bleeding by clinical examination, pap smear, colposcopy and guided biopsy to detect premalignant cervical lesions and carcinoma cervix.Methods: This was a prospective and retrospective study conducted from April, 2016 to March, 2018 for a period of 24 months in the Department of Obstetrics and Gynaecology on 100 women with postcoital bleeding at Dr. Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation (Dr. PSIMS&RF). After clinical examination, these women were subjected to pap smear, colposcopy and guided biopsy. The findings were correlated with histopathology of cervix. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of both papsmear and colposcopy were calculated.Results: Sensitivity of papsmear was 71.42%, specificity-86.20%, PPV-78.95%, NPV-80.64% and accuracy-80%. Sensitivity of colposcopy was 90.47%, specificity-89.65%, PPV-86.36%, NPV-92.85% and accuracy-90%.          Conclusions: These results establish colposcopy as an effective screening test for carcinoma cervix. Histopathology of suspected cervical lesion in colposcopy remains the gold standard for definitive diagnosis

Charge and Spin Response of the Spin--Polarized Electron Gas

The charge and spin response of a spin--polarized electron gas is investigated including terms beyond the random phase approximation. We evaluate the charge response, the longitudinal and transverse spin response, and the mixed spin--charge response self--consistently in terms of the susceptibility functions of a non--interacting system. Exchange--correlation effects between electrons of spin $\sigma$ and $\sigma^{'}$ are included following Kukkonen and Overhauser, by using spin--polarization dependent generalized Hubbard local field factors ${G_\sigma}^{\pm}$ and ${G_{\bar\sigma}}^{\pm}$. The general condition for charge--density and spin--density--wave excitations of the system is discussed.Comment: 4 pages, latex, no figure

Integrated nonlinear structural simulation of composite buildings in fire

The collapse of several tall composite buildings over the last two decades has shown that the performance of tall, composite and complex buildings in fire is a necessary design consideration that ought to go beyond simple code compliance. To this end, several advancements in the field of numerical simulation of both the fire and the thermomechanical response of structures have been made. In isolation, the practical benefit of these advancements is limited, and their true potential is only unlocked when the results of those numerical simulations are integrated. This paper starts by showcasing recent developments in the thermal and thermomechanical analysis of structures using OpenSees. Integration of these developments into a unified simulation environment combining fire simulation, heat transfer, and mechanical analysis is then introduced. Finally, a demonstration example based on the large compartment Cardington test is used to showcase the necessity and efficiency of the developed simulation environment for thermomechanical simulation of composite structures in fire