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1.  Enabling Ultrasensitive Photo-detection Through Control of Interface Properties in Molybdenum Disulfide Atomic Layers 
Scientific Reports  2016;6:39465.
The interfaces in devices made of two-dimensional materials such as MoS2 can effectively control their optoelectronic performance. However, the extent and nature of these deterministic interactions are not fully understood. Here, we investigate the role of substrate interfaces on the photodetector properties of MoS2 devices by studying its photocurrent properties on both SiO2 and self-assembled monolayer-modified substrates. Results indicate that while the photoresponsivity of the devices can be enhanced through control of device interfaces, response times are moderately compromised. We attribute this trade-off to the changes in the electrical contact resistance at the device metal-semiconductor interface. We demonstrate that the formation of charge carrier traps at the interface can dominate the device photoresponse properties. The capture and emission rates of deeply trapped charge carriers in the substrate-semiconductor-metal regions are strongly influenced by exposure to light and can dynamically dope the contact regions and thus perturb the photodetector properties. As a result, interface-modified photodetectors have significantly lower dark-currents and higher on-currents. Through appropriate interfacial design, a record high device responsivity of 4.5 × 103 A/W at 7 V is achieved, indicative of the large signal gain in the devices and exemplifying an important design strategy that enables highly responsive two-dimensional photodetectors.
PMCID: PMC5172306  PMID: 27995992
2.  Variations of transesophageal echocardiography practices in India: A survey by Indian College of Cardiac Anaesthesia 
Annals of Cardiac Anaesthesia  2016;19(4):646-652.
Use of perioperative transesophageal echocardiography (TEE) has expanded in India. Despite attempts to standardize the practice of TEE in cardiac surgical procedures, variation in practice and application exists. This is the first online survey by Indian College of Cardiac Anaesthesia, research and academic wing of the Indian Association of Cardiovascular Thoracic Anaesthesiologists (IACTA).
We hypothesized that variations in practice of intraoperative TEE exist among centers and this survey aimed at analyzing them.
Settings and Design:
This is an online survey conducted among members of the IACTA.
Subjects and Methods:
All members of IACTA were contacted using online questionnaire fielded using SurveyMonkey™ software. There were 21 questions over four pages evaluating infrastructure, documentation of TEE, experience and accreditation of anesthesiologist performing TEE, and finally impact of TEE on clinical practice. Questions were also asked about national TEE workshop conducted by the IACTA, and suggestions were invited by members on overseas training.
Response rate was 29.7% (382/1222). 53.9% were from high-volume centers (>500 cases annually). TEE machine/probe was available to 75.9% of the respondents and those in high-volume centers had easier (86.9%) access. There was poor documentation of preoperative consent (23.3%) as well as TEE findings (66%). Only 18.2% of responders were board qualified. Almost 90% of the responders felt surgeons respected their TEE diagnosis. Around half of the responders felt that new intraoperative findings by TEE were considered in decision-making in most of the cases and 70% of the responders reported that surgical plan was altered based on TEE finding more than 10 times in the last year. Despite this, only 5% of the responders in this survey were monetarily awarded for performing impactful skill of TEE. Majority (57%) felt that there is no need for overseas training for Indian cardiac anesthesiologists.
In this survey of members of the IACTA, use of TEE has increased substantially, but still a lot of variations in practice patterns exist in India. There is urgent need for improving TEE certification and upgrade documentation standards, motivate use of TTE across all centers, promote awareness and usefulness of TEE use among surgical fraternity, monitor impact of TEE, and support separate remuneration policy in India.
PMCID: PMC5070324  PMID: 27716695
Current practices in India; Indian College of Cardiac Anaesthesia; Transesophageal echocardiography survey
3.  Anesthetic implications of subxiphoid coronary artery bypass surgery 
Annals of Cardiac Anaesthesia  2016;19(3):433-438.
Minimal invasive surgeries are carried out to benefit the patient with less pain, blood loss, mechanical ventilation and hospital stay; a smaller scar is not the aim. Minimal invasive cardiac surgeries are carried out via small sternotomy, small thoracotomy and via robotic arms. Subxiphoid route is a novel method and avoids sternotomy.
This case series is an attempt to understand the anesthetic modifications required. Secondly, whether it is feasible to carry out subxiphoid coronary artery bypass surgery.
Elective patients scheduled to undergo subxiphoid coronary artery bypass surgery were chosen. The surgeries were conducted under general anesthesia with left lung isolation via either endobronchial tube or bronchial blocker.
We conducted ten (seven males and 3 females) coronary artery bypass graft surgeries via subxiphoid technique. The mean EuroSCORE was 1.7 and the mean ejection fraction was 53.6. Eight patients underwent surgery via endobronchial tube, while, in the remaining two lung isolation was obtained using bronchial blocker. Mean blood loss intraoperatively was 300 ± 42 ml and postoperatively 2000 ± 95 ml. The pain score on the postoperative day ‘0’ was 4.3 ± 0.6 and 2.3 ± 0.7 on the day of discharge. Length of stay in the hospital was 4.8 ± 0.9 days. There were no complications, blood transfusions, conversion to cardiopulmonary bypass. The modifications in the anesthetic and surgical techniques are, use of left lung isolation using either endobronchial tube or bronchial blocker, increased duration for conduit harvesting, grafting, requirement of transesophageal echocardiography monitoring in addition to hemodynamic monitoring. Other minor requirements are transcutaneous pacing and defibrillator pads, a wedge under the chest to ‘lift’ up the chest, sparing right femoral artery and vein (to serve as vascular access) for an unlikely event of conversion to cardiopulmonary bypass. Any anesthesiologist wishing to start this technique must be aware of these modifications.
Subxiphoid route is safe to carry out coronary artery bypass graft surgery using the minimal invasive cardiac surgery. It is reproducible and has undeniable benefits. We plan to conduct such surgeries in awake patients under thoracic epidural anesthesia thus making it even less invasive and amenable for fast tracking.
PMCID: PMC4971971  PMID: 27397447
Minimal invasive coronary artery bypass surgery; Off-pump coronary artery bypass surgery; Subxiphoid coronary artery bypass graft
4.  Intraoperative conversion to on-pump coronary artery bypass grafting is independently associated with higher mortality in patients undergoing off-pump coronary artery bypass grafting: A propensity-matched analysis 
Annals of Cardiac Anaesthesia  2016;19(3):475-480.
One of the main limitations of off-pump coronary artery bypass grafting (OPCAB) is the occasional need for intraoperative conversion (IOC) to on-pump coronary artery bypass grafting. IOC is associated with a significantly increased risk of mortality and postoperative morbidity. The impact of IOC on outcome cannot be assessed by a randomized control design.
The objective of this study was to analyze the incidence, risk factors, and impact of IOC on the outcome in patients undergoing OPCAB.
Settings and Design:
Three tertiary care level hospitals; retrospective observational study.
Subjects and Methods:
This retrospective observational study included 1971 consecutive patients undergoing OPCAB from January 2012 to October 2015 at three tertiary care level hospitals by four surgeons. The incidence, patient characteristics, cause of IOC, and its impact on outcome were studied.
Statistical Analysis Used:
The cohort was divided into two groups according to IOC. Univariate logistic regression was performed to describe the predictors of IOC. Variables that were found to be significant in univariate analysis were introduced into multivariate model, and adjusted odds ratio (OR) was calculated. To further assess the independent effect of IOC on mortality, propensity score matching with a 5:1 ratio of non-IOC to IOC was performed.
The overall all-cause in-hospital mortality was 2.6%. IOC was needed in 128 (6.49%) patients. The mortality in the IOC group was significantly higher than non-IOC group (21 of 128 [16.4%] vs. 31 of 1843 [1.7%], P = 0.0001). The most common cause for IOC was hemodynamic disturbances during grafting to the obtuse marginal artery (51/128; 40%). On multivariate logistic regression analysis, left main disease, pulmonary hypertension, and mitral regurgitation independently predicted IOC. We obtained a propensity-matched sample of 692 patients (No IOC 570; IOC 122), and IOC had OR of 16.26 (confidence interval 6.3–41; P < 0.0001) for mortality in matched population.
Emergency IOC increases odds for mortality by 16-fold. Hence, identification of patients at higher risk of IOC may improve the outcome.
PMCID: PMC4971976  PMID: 27397452
Off-pump coronary artery bypass grafting; Intraoperative conversion; Mortality; Propensity matched analysis
5.  Monitoring diastolic dysfunction using a simplified algorithm in patients undergoing off-pump coronary artery bypass grafting surgery 
Annals of Cardiac Anaesthesia  2016;19(2):231-239.
Left ventricle diastolic dysfunction (LVDD) is gaining importance as useful marker of mortality and morbidity in cardiac surgical patients. Different algorithms have been proposed for the intraoperative grading of DD. Knowledge of the particular grade of DD has clinical implications with the potential to modify therapy, but there is a paucity of literature on the role of diastolic function evaluation during off-pump coronary artery bypass grafting (OPCABG) surgery.
The aim of this study was to monitor changes in LVDD using simplified algorithm proposed by Swaminathan et al. in patients undergoing OPCABG.
Settings and Design:
The study was conducted in a tertiary care level hospital; this was a prospective, observational study.
Subjects and Methods:
Fifty consecutive patients undergoing OPCABG were enrolled. Hemodynamic and echocardiographic parameters were measured at 6 stages in every patient namely after anesthetic induction (baseline), during left internal mammary artery (LIMA) to left anterior descending (LAD) grafting (LIMA → LAD), saphenous vein graft (SVG) to obtuse marginal (OM) grafting (SVG → OM), SVG to posterior descending artery (PDA) grafting (SVG → PDA), during proximal anastomosis of SVG to aorta, and postprotamine. The patients were classified in grades of LVDD as per simplified algorithm proposed by Swaminathan et al. using only intraoperatively measured E and E’.
The success rate of measurement and classification of LVDD was 98.92% (277 out of 280 measurements). The grades of LVDD varied significantly as per surgical steps with maximum downgrading occurring during OM and LAD grafting. During OM grafting, none of the patients had normal diastolic function while 29% of patients exhibited restrictive pattern (Grade 3 LVDD). Patients with normal baseline LV diastolic function also exhibited downgrading during OM and LAD grafting. Postprotamine, 37% of patients with normal baseline diastolic function continued to exhibit some degree of DD.
The LVDD changes dynamically during various stages of OPCABG, which can be successfully monitored with simplified algorithm.
PMCID: PMC4900366  PMID: 27052062
Diastolic dysfunction; Left ventricle; Off-pump coronary artery bypass grafting
6.  Patient prosthesis mismatch after aortic valve replacement: An Indian perspective 
Annals of Cardiac Anaesthesia  2016;19(1):84-88.
Perioperative period.
Occurrence of PPM after AVR, factors associated with PPM, impact on mortality.
Settings and Design:
Teritary Care Referral Cardiac Centre.
Materials and Methods:
A retrospective analysis of AVR procedures at a single centre over 4 years was conducted. Demographic, echocardiographic and outcome data were collected from institute database. Rahimtoola criteria of indexed effective orifice area (iEOA) were used to stratify patients into PPM categories. Patients with and without PPM were compared for associated factors.
Statistical Analysis Used:
Independent t-test, chi-square test, logistic regression analysis, ROC-AUC, Youden index.
606 patients with complete data were analysed for PPM. The incidence of mild, moderate and severe PPM was 6.1% (37), 2.5% (15) and 0.5% (3) respectively. There was no impact of PPM on all-cause in-hospital mortality. PPM was observed more with Aortic Stenosis (AS) compared to Aortic Regurgitation (AR) as etiology. Aortic annulus indexed to BSA (iAA) had a very good predictive ability for PPM at <16mm/m2 BSA.
PPM has lower incidence after AVR in this Indian population and does not increase early mortality. Patients with AS and iAA<16mm/m2BSA should be cautiously dealt with to prevent PPM.
PMCID: PMC4900404  PMID: 26750679
Aortic annulus indexed to body surface area; Aortic valve replacement; Patient prosthesis mismatch
7.  Weight-for-age standard score - distribution and effect on in-hospital mortality: A retrospective analysis in pediatric cardiac surgery 
Annals of Cardiac Anaesthesia  2015;18(3):367-372.
To study the distribution of weight for age standard score (Z score) in pediatric cardiac surgery and its effect on in-hospital mortality.
WHO recommends Standard Score (Z score) to quantify and describe anthropometric data. The distribution of weight for age Z score and its effect on mortality in congenital heart surgery has not been studied.
All patients of younger than 5 years who underwent cardiac surgery from July 2007 to June 2013, under single surgical unit at our institute were enrolled. Z score for weight for age was calculated. Patients were classified according to Z score and mortality across the classes was compared. Discrimination and calibration of the for Z score model was assessed. Improvement in predictability of mortality after addition of Z score to Aristotle Comprehensive Complexity (ACC) score was analyzed.
The median Z score was -3.2 (Interquartile range -4.24 to -1.91] with weight (mean±SD) of 8.4 ± 3.38 kg. Overall mortality was 11.5%. 71% and 52.59% of patients had Z score < -2 and < -3 respectively. Lower Z score classes were associated with progressively increasing mortality. Z score as continuous variable was associated with O.R. of 0.622 (95% CI- 0.527 to 0.733, P < 0.0001) for in-hospital mortality and remained significant predictor even after adjusting for age, gender, bypass duration and ACC score. Addition of Z score to ACC score improved its predictability for in-hosptial mortality (δC - 0.0661 [95% CI - 0.017 to 0.0595, P = 0.0169], IDI- 3.83% [95% CI - 0.017 to 0.0595, P = 0.00042]).
Z scores were lower in our cohort and were associated with in-hospital mortality. Addition of Z score to ACC score significantly improves predictive ability for in-hospital mortality.
PMCID: PMC4881691  PMID: 26139742
Aristotle comprehensive complexity score; Congenital heart surgery; Weight-for-age; Z score
8.  Propensity-matched analysis of association between preoperative anemia and in-hospital mortality in cardiac surgical patients undergoing valvular heart surgeries 
Annals of Cardiac Anaesthesia  2015;18(3):373-379.
Anaemia is associated with increased post-operative morbidity and mortality. We retrospectively assess the relationship between preoperative anaemia and in-hospital mortality in valvular cardiac surgical population.
Materials and Methods:
Data from consecutive adult patients who underwent valvular repair/replacement at our institute from January 2010 to April 2014 were collected from hospital records. Anaemia was defined according to WHO criteria (hemoglobin <13g/dl for males and <12g/dl for females). 1:1 matching was done for anemic and non-anemic patients based on propensity for potentially confounding variables. Logistic regression was used to evaluate the relationship between anaemia and in-hospital mortality. MatchIt package for R software was used for propensity matching and SPSS 16.0.0 was used for statistical analysis.
2449 patients undergoing valvular surgery with or without coronary artery grafting were included. Anaemia was present in 37.1% (33.91% among males & 40.88% among females). Unadjusted OR for mortality was 1.6 in anemic group (95% Confidence Interval [95% CI] – 1.041-2.570; p=0.033). 1:1 matching was done on the basis of propensity score for anaemia (866 pairs). Balancing was confirmed using standardized differences. Anaemia had an OR of 1.8 for mortality (95% CI- 1.042 to 3.094, P=0.035). Hematocrit of < 20 on bypass was associated with higher mortality.
Preoperative anaemia is an independent risk factor associated with in-hospital mortality in patients undergoing valvular heart surgery.
PMCID: PMC4881714  PMID: 26139743
Preoperative Anemia and Cardiac Surgery; Propensity Matching; Valvular Heart Disease
9.  Update on the classification of hemangioma 
Despite the fact that a biological classification of congenital vascular tumors and malformations was first published in 1982 by Mulliken and Glowacki, significant confusion still prevails due to the indiscriminate and interchangeable use of the terms hemangioma and vascular malformation. Hemangiomas are true neoplasms of endothelial cells and should be differentiated from vascular malformations which are localized defects of vascular morphogenesis. On an analysis of various scientific articles and latest edition of medical text books an inappropriate use of various terms for vascular lesions was found, contributing further towards the confusion. The widely accepted International Society for the Study of Vascular Anomalies (ISSVA) classification differentiates lesions with proliferative endothelium from lesions with structural anomalies and has been very helpful in standardizing the terminologies. In addition to overcoming obstacles in communication when describing a vascular lesion, it is important that we adhere to the correct terminology, as the therapeutic guidelines, management and follow-up of these lesions differ.
PMCID: PMC4211219  PMID: 25364160
Classification; congenital hemangioma; hemangioma; infantile hemangioma; international society for the study of vascular anomalies; vascular malformation
10.  Imaging ultra thin layers with helium ion microscopy: Utilizing the channeling contrast mechanism 
Background: Helium ion microscopy is a new high-performance alternative to classical scanning electron microscopy. It provides superior resolution and high surface sensitivity by using secondary electrons.
Results: We report on a new contrast mechanism that extends the high surface sensitivity that is usually achieved in secondary electron images, to backscattered helium images. We demonstrate how thin organic and inorganic layers as well as self-assembled monolayers can be visualized on heavier element substrates by changes in the backscatter yield. Thin layers of light elements on heavy substrates should have a negligible direct influence on backscatter yields. However, using simple geometric calculations of the opaque crystal fraction, the contrast that is observed in the images can be interpreted in terms of changes in the channeling probability.
Conclusion: The suppression of ion channeling into crystalline matter by adsorbed thin films provides a new contrast mechanism for HIM. This dechanneling contrast is particularly well suited for the visualization of ultrathin layers of light elements on heavier substrates. Our results also highlight the importance of proper vacuum conditions for channeling-based experimental methods.
PMCID: PMC3458595  PMID: 23019545
channeling; contrast mechanism; helium ion microscopy; ion scattering; thin layers
11.  Gnathic osteosarcomas: Review of literature and report of two cases in maxilla 
Primary neoplasms of the skeleton are rare, accounting for 0.2% of overall human tumor burden. Osteosarcoma (OS) accounts for 15–35% of all primary bone tumors, while gnathic osteosarcomas (GOS) represent 4–8% of all osteosarcomas. GOS shows a predilection for men, a peak incidence of 33 years, and affects the mandible more than the maxilla. We review the scientific literature for a better understanding of the clinical, radiographic, and histopathological features of GOS, along with its etiology, staging, treatment protocol, prognosis, and survival. Evidence from molecular research suggests that it is a differentiation disease that disrupts osteoblasts differentiation from mesenchymal stem cells. The classical radiographic finding of a “sunburst” appearance is appreciated only in 50% of GOS. The universally accepted staging system is not commonly used due to the rarity with which they metastasize to the regional lymph nodes. A number of distinct histopathological subtypes have been described, of which osteoblastic GOS are most common. The treatment protocol is multimodal consisting of preoperative chemotherapy followed by surgery and postoperative chemotherapy, and has a 60-70% five-year survival rate. We present two case reports of osteosarcoma involving the maxillary that were initially misdiagnosed as peripheral giant cell granuloma and osteoma of the maxilla, respectively. These case reports demonstrate the diverse clinical, radiographic, and histopathological features that can be encountered in GOS.
PMCID: PMC3329700  PMID: 22529570
Bone tumor; gnathic; jaw; maxilla; metastasis; osteogenic sarcoma; osteosarcoma; prognosis; recurrence; staging; treatment

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