Fundamental Study of the Mechanical Failure of Silicon Based Electrodes for Li-Ion Batteries Using a Novel Multi-Physics Computational Modeling Framework

Li-ion batteries are the currently accepted flagship energy storage system with several cathode systems identified over the years. However, graphite has always remained the commercial anode material of choice. Silicon has been identified as the next-generation anode for Li-ion systems with a high theoretical capacity (4200 mAhg-1) compared to graphite (372 mAhg-1) and has been the focus of much research over the past decade. Silicon unfortunately, undergoes large volumetric expansion (312%) upon Li diffusion generating considerable diffusion-induced stresses. Presence of high stress leads to mechanical failure of Si resulting in capacity fade due to loss of electrical contact with the current collector impeding commercialization. The mechanical response of the electrode depends on the electrode properties comprising the active (Si) and passive components (current collector, mechanical supports). The objective of this thesis is to gain a mechanistic understanding of the interactions between the electrode components and their effect on the overall mechanical integrity of the Si based anode assembly, which can aid in the design of failure resistant, next-generation, high capacity anodes. To achieve this objective, a custom nonlinear finite element modeling software that can model coupled diffusion induced large elasto-plastic deformation of Si, surface electrochemical reaction kinetics and eventual mechanical failure response of the electrode system was utilized. This modeling framework is first used to understand the effect of passive components (current collector and Si-Cu interface properties) on the mechanical stability of an a-Si thin film anode system. To unlock the mechanisms behind the gradual interfacial delamination of the Si film from the underlying Cu current collector in an a-Si thin film anode system, a detailed parametric study is performed to analyze effect of the mechanical properties of the current collector and the Si-Cu interface on the delamination at Si-Cu interface. The knowledge gained from these studies is further bolstered by examining the mechanical stability of a-Si patterned thin film anodes upon insertion of a thin elastic buffer layer between a square Si thin film pattern and the current collector. Finally, the modeling framework is utilized to understand the effect of active material geometry in Si-carbon nanotube (CNT) heterostructured anodes

Prospective comparative study between colposcopy and histopathology for diagnosis of CIN and carcinoma cervix

Background: Cervical cancer develops from precursor lesions and detection of these lesions is of utmost importance. The detection of precancerous lesions is made with help of screening tests most important include PAP smear and colposcopy. So we conducted this study to understand the role of colposcopy in down staging of Carcinoma cervix.Methods: We performed a prospective study between Jan 2018 to Dec 2018 on 180 subjects chosen from patients who sought consultation for various gynaecological complaints between age group of 18-60 years. A Pap smear followed by a colposcopy was performed and colposcopic directed biopsies were taken and subjected to histolopathological examination.Results: Colposcopy had a sensitivity of 83.3%, specificity of 78.5%, PPV of 68.9% for CIN 1. It had a sensitivity of 90.9%, specificity of 95.2%, PPV of 83.33% for CIN 2 and 3 when co related with gold standard histopathology which is much higher as compared to Pap smear.Conclusions: Colposcopy is an effective tool in down staging of Carcinoma cervix

Modeling the delamination of amorphous-silicon thin film anode for lithium-ion battery

Sputter-deposited amorphous silicon thin films on metallic copper current collectors are widely studied as lithium-ion anode systems. Electrochemical results indicate these electrodes exhibit near theoretical capacity for first few cycles; however delamination at the thin film-current collector interface causes rapid capacity fade leading to poor cycling performance. Primary reason for this interfacial delamination is the mechanical stress generated due to colossal volume expansion of silicon during lithiation. The focus of the current study is to present a mechanistic understanding of the role of mechanical properties of the current collector on this characteristic delamination behavior during electrochemical cycling. Toward this end, we have developed a computational framework that accounts for the coupled diffusion induced large deformation in silicon, elasto-plastic deformation of the current collector, as well as the nucleation and propagation of interfacial delamination. We have also performed a detailed parametric study to investigate the effect of mechanical properties of the current collector on the delamination of the thin film-current collector interface. We have accordingly determined that current collectors with low elastic modulus such as graphite can completely suppress interfacial delamination. Our analysis thus provides a sound mechanistic approach for designing next generation Si thin film anodes with improved capacity retention. © 2013 Elsevier B.V. All rights reserved

Mastectomy and Contralateral Prophylactic Mastectomy Rates: An Institutional Review

Background. Breast conservation surgery (BCS) followed by radiation is as effective as mastectomy for long-term survival and is considered standard of care for early-stage breast cancer. An increasing number of patients are opting for cancer-side mastectomies (CM) and often contralateral prophylactic mastectomies (CPM). Our study investigates if there are increasing trends in our patient population toward CM and CPM and identifies common factors associated with those electing to have more extensive surgery. Methods. A retrospective analysis was performed on 812 breast cancer surgeries between January 2001 and December 2009 at The George Washington University Breast Care Center. BCS-eligible patients who elected to have BCS were compared with those who chose CM. Patients who underwent CM were compared with patients undergoing CM and CPM. Results. A personal or family history of breast cancer and larger tumor size were positively associated with choosing CM in BCS-eligible patients. A nonstatistically significant trend toward CM was seen in younger patients. Age, family history, fewer children, Caucasian race, and reconstructive surgery were positively associated with choosing CPM. Conclusion. Mastectomy rates at this institution have not shown the recent sharp increase observed by some authors. The association of age, race, family history, and parity with CPM has been corroborated in multiple studies. However, there is disagreement between statistically significant findings among investigators evaluating factors associated with CPM, and there is limited data in the literature characterizing BCS-eligible patients who chose CM. Larger prospective studies are necessary to further evaluate CM and CPM rates

Breast-specific gamma imaging influences surgical management in patients with breast cancer

Breast-specific gamma imaging (BSGI) is a physiologic breast imaging modality that provides more sensitive detection of breast lesions than mammography or ultrasound, and appears to have greater specificity than breast MRI. The purpose of this study was to evaluate how often BSGI changed surgical management in patients with breast cancer. Charts were reviewed from 218 consecutive eligible patients who had preoperative evaluation with BSGI or MRI before surgery for breast cancer from January 2008 to May 2010. Patients who were initially considered eligible for breast-conserving therapy (BCT) were evaluated to determine how many ultimately had mastectomies. Patients who underwent mastectomy because of personal choice or ineligibility for BCT were excluded. Management was changed to mastectomy in 11.9% of those who had BSGI and 28.9% of those who had MRI. Review of pathology demonstrated that all patients who underwent mastectomies were not candidates for breast conservation. 15.4% of patients who underwent BCT based on BSGI findings required a single re-excision due to positive surgical margins. 14.4% required mastectomy. In the MRI group, 18.8% required a single re-excision, and 6.3% required mastectomy. Evaluation with BSGI changed management to mastectomy in a substantial proportion of patients believed to be eligible for BCT following standard imaging. BSGI is effective in evaluation of extent of disease in patients with breast cancer, and is comparable to MRI in terms of its influence on surgical management. © 2013 Wiley Periodicals, Inc

Breast-specific gamma imaging influences surgical management in patients with breast cancer

Breast-specific gamma imaging (BSGI) is a physiologic breast imaging modality that provides more sensitive detection of breast lesions than mammography or ultrasound, and appears to have greater specificity than breast MRI. The purpose of this study was to evaluate how often BSGI changed surgical management in patients with breast cancer. Charts were reviewed from 218 consecutive eligible patients who had preoperative evaluation with BSGI or MRI before surgery for breast cancer from January 2008 to May 2010. Patients who were initially considered eligible for breast-conserving therapy (BCT) were evaluated to determine how many ultimately had mastectomies. Patients who underwent mastectomy because of personal choice or ineligibility for BCT were excluded. Management was changed to mastectomy in 11.9% of those who had BSGI and 28.9% of those who had MRI. Review of pathology demonstrated that all patients who underwent mastectomies were not candidates for breast conservation. 15.4% of patients who underwent BCT based on BSGI findings required a single re-excision due to positive surgical margins. 14.4% required mastectomy. In the MRI group, 18.8% required a single re-excision, and 6.3% required mastectomy. Evaluation with BSGI changed management to mastectomy in a substantial proportion of patients believed to be eligible for BCT following standard imaging. BSGI is effective in evaluation of extent of disease in patients with breast cancer, and is comparable to MRI in terms of its influence on surgical management. © 2013 Wiley Periodicals, Inc

Breast-specific gamma imaging influences surgical management in patients with breast cancer.

Breast-specific gamma imaging (BSGI) is a physiologic breast imaging modality that provides more sensitive detection of breast lesions than mammography or ultrasound, and appears to have greater specificity than breast MRI. The purpose of this study was to evaluate how often BSGI changed surgical management in patients with breast cancer. Charts were reviewed from 218 consecutive eligible patients who had preoperative evaluation with BSGI or MRI before surgery for breast cancer from January 2008 to May 2010. Patients who were initially considered eligible for breast-conserving therapy (BCT) were evaluated to determine how many ultimately had mastectomies. Patients who underwent mastectomy because of personal choice or ineligibility for BCT were excluded. Management was changed to mastectomy in 11.9% of those who had BSGI and 28.9% of those who had MRI. Review of pathology demonstrated that all patients who underwent mastectomies were not candidates for breast conservation. 15.4% of patients who underwent BCT based on BSGI findings required a single re-excision due to positive surgical margins. 14.4% required mastectomy. In the MRI group, 18.8% required a single re-excision, and 6.3% required mastectomy. Evaluation with BSGI changed management to mastectomy in a substantial proportion of patients believed to be eligible for BCT following standard imaging. BSGI is effective in evaluation of extent of disease in patients with breast cancer, and is comparable to MRI in terms of its influence on surgical management. © 2013 Wiley Periodicals, Inc