Long term study of the light curve of PKS 1510-089 in GeV energies

We have analyzed data from the Flat Spectrum Radio Quasar PKS 1510-089 collected over a period of 8 years from August 2008 to December 2016 with the Fermi-LAT. We have identified several flares of this highly variable source, studied their temporal and spectral properties in detail and compared with previous works on flares of PKS 1510-089. Five major flares and few sub-flares/sub-structures have been identified in our study. The fastest variability time is found to be 1.30$\pm$0.18 hr between MJD 55852.063 and 55852.188 where we estimate the minimum size of the emission region to be $4.85 \times 10^{15}$ cm. In most of the flares the spectral energy distributions are better fitted with Logparabolic distribution compared to simple Power law or Power law with exponential cut-offs. This has strong physics implications regarding the nature of the high energy gamma-ray emission region.Comment: 29 pages, 29 figures, Accepted in Ap

An investigation of the impact of enterprise social media in leading an enterprise transformation

Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2013."February 2013." Cataloged from PDF version of thesis.Includes bibliographical references (p. 108-112).Historically, 70% of change initiatives in organizations and businesses fail. Change involves people. Throughout decades, as the generations change, we've seen a major change in the leader's approach and the medium they have used to connect with people. It is predicted that enterprise social media will become the main communications channel for 20% of business users by 2014. Investigation in this thesis shows the extent to which corporate leaders have used enterprise social media to bring a change in an organization. This research is an examination of how enterprise social media can deliver value in bringing an enterprise transformation. Fundamentals that have been laid out by Dr. Kotter to implement change in the organizations by the corporate leaders still hold. This thesis includes a practical examination of the effectiveness of using enterprise social media for each of the Dr. Kotter's 8-stages for leading change. To investigate the impact of enterprise social media in enterprise transformation, several full scale and brief interviews were conducted with key stakeholders in small, medium, and large scaled organizations. In addition to the standard Lean Advancement Initiative (LAI) suite of tools, the effectiveness of social media was evaluated in various stages using Kaplan's Balanced Scorecard, Force Field Analysis, Matrix Scorecard, System Dynamics Model, and a Weighted Scoring Card. Analysis suggests that based on the existing set of enterprise social tools, enterprise social media can play a key role in 3 of the 8 steps of leading change described by Dr. Kotter. Currently, enterprise social media can provide limited advantages in 5 of the 8 steps of leading change. Going forward, with the emerging set of enterprise social tools that are more integrated into business processes, the role of enterprise social media in bringing an enterprise transformation is expected to increase significantly.by Raj (Pratik) Rajani.S.M

Fermi-Large Area Telescope observations of the brightest Gamma-ray flare ever detected from CTA 102

We present a multi-wavelength study of the FSRQ CTA 102 using Fermi-LAT and simultaneous Swift-XRT/UVOT observations. The Fermi-LAT telescope detected one of the brightest flares from this object during Sep, 2016 to Mar, 2017. In the 190 days of observation period the source underwent four major flares. A detailed analysis of the temporal and spectral properties of these flares indicates the flare at MJD 57751.594 has a $\gamma$-ray flux of (30.12$\pm$4.48)$\times 10^{-6}$ ph cm$^{-2}$ s$^{-1}$ (from 90 minutes binning) in the energy range of 0.1--300 GeV. This has been found to be the highest flux ever detected from CTA 102. Time dependent leptonic modelling of the pre-flare, rising state, flares and decaying state has been done. A single emission region of size $6.5\times 10^{16}$ cm has been used in our work to explain the multi-wavelength spectral energy distributions. During flares the luminosity in electrons increases nearly seventy times compared to the pre-flare state.Comment: 19 pages, 7 figures, Accepted for Publication in Ap

Multiwavelength temporal and spectral study of TeV blazar 1ES 1727+502 during 2014 to 2021

One of the most important questions in blazar physics is the origin of broadband emission and fast-flux variation. In this work, we studied the broadband temporal and spectral properties of a TeV blazar 1ES 1727+502 and explore the one-zone synchrotron-self Compton (SSC) model to fit the broadband spectral energy distribution (SED). We collected the long-term (2014-2021) multiband data which includes both the low and high flux states of the source. The entire light curve is divided into three segments of different flux states and the best-fit parameters obtained by broadband SED modeling corresponding to three flux states were then compared. The TeV blazar 1ES 1727+502 has been observed to show the brightest flaring episode in X-ray followed by optical-UV and gamma-ray. The fractional variability estimated during various segments behaves differently in multiple wavebands, suggesting a complex nature of emission in this source. This source has shown a range of variability time from days scale to month scale during this long period of observations between 2014-2021. A "harder-when-brighter" trend is not prominent in X-ray but seen in optical-UV and an opposite trend is observed in gamma-ray. The complex nature of correlation among various bands is observed. The SED modeling suggests that the one-zone SSC emission model can reproduce the broadband spectrum in the energy range from optical-UV to very high energy gamma-ray.Comment: 14 pages, 8 figure, 2 table. Accepted for publication in MNRA

Association between maxillary and mandibular apical base lengths and severity of dental crowding or spacing in Class II malocclusion subjects : an in-vitro study

Anterior crowding/ spacing are one of the major problems that inspire patients to undergo orthodontic treatment. Several factors associated with anterior crowding/ spacing includes arch width and length, mesio-distal tooth diameter and proportions. The aim of the present study was to evaluate the relationship of maxillary and mandibular base lengths to the amount of anterior dental crowding/ spacing in patients with complete class II malocclusions. A retrospective study was done with 152 patients who were divided into four groups according to the severity of pre-treatment dental crowding/spacing present in the mandibular arch. Measurements were performed on the pre-treatment dental casts and lateral cephalograms. Statistical analysis was done using t-test and chi-square test. Subjects with complete class II malocclusion and moderate to severe mandibular crowding [?3mm] have significantly smaller base lengths as compared to the subjects with slight crowding or spacing [<3mm]. There exists an inverse correlation between maxillary and mandibular base lengths and the severity of dental crowding and direct correlation with spacing

Evaluation of cardioprotective effect of Aegle marmelos on doxorubicin induced cardiotoxicity: an experimental study

Background: Aegle marmelos (A. marmelos), a medicinal herb, is widely used in the Indian system of medicine for treatment of various ailments. The methanolic extract of A. marmelos leaves had shown antioxidant effect. However, so far aqueous extract of A. marmelos is not scientifically evaluated for its cardio protective potential. Hence the present study was designed to find out cardio protective role of A. marmelos against doxorubicin induced cardiotoxicity.Methods: Thirty rats were randomized into five major groups (n=6). Group I received only 2ml/100g/day normal saline p.o., group II received 2ml/100g/day of normal saline p.o. followed by doxorubicin on 21st day, group III received carvedilol 30 mg/kg/day p.o., Group IV received A. marmelos 250mg/kg/day p.o. and Group V received A. marmelos 500mg/kg/day p.o. for 21days. Doxorubicin 20mg/kg i.p. single dose was given to induce cardiotoxicity in rats of group II, III, IV and V respectively on last day of experiment. Animals were sacrificed 48 hours after doxorubicin administration. Cardiac serum markers creatinine phosphokinase MB, lactate dehydrogenase, serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase were analysed biochemically. Histopathological changes were studied under light microscope.Results: All cardiac serum marker levels were found significantly (p<0.001) increased in doxorubicin group while A. marmelos pre-treated group displayed significant (p<0.001) reduction in rise of these parameters in a dose dependent manner indicating cardio protection. Histological observations further correlated the cardio protective effect of A. marmelos.Conclusions: The present study concluded that aqueous extract of A. marmelos possesses cardio protective potential against doxorubicin induced cardiotoxicity

Multi-wavelength study of TeV blazar 1ES 1218+304 using gamma-ray, X-ray and optical observations

We report the multi-wavelength study for a high-synchrotron-peaked BL Lac 1ES 1218+304 using near-simultaneous data obtained during the period from January 1, 2018, to May 31, 2021 (MJD 58119-59365) from various instruments including Fermi-LAT, Swift-XRT, AstroSat, and optical from Swift-UVOT $\&$ TUBITAK observatory in Turkey. The source was reported to be flaring in TeV $\gamma$-ray band during 2019, but no significant variation is observed with Fermi-LAT. A sub-hour variability is seen in the SXT light curve, suggesting a compact emission region for their variability. However, hour scale variability is observed in the $\gamma$-ray light curve. A "softer-when-brighter" trend is observed in $\gamma$-rays, and an opposite trend is seen in X-rays suggesting both emissions are produced via two different processes as expected from an HBL source. We have chosen the two epochs in January 2019 to study and compare their physical parameters. A joint fit of SXT and LAXPC provides a constraint on the synchrotron peak, roughly estimated to be $\sim$1.6 keV. A clear shift in the synchrotron peak is observed from $\sim$1 keV to above 10 keV revealing its extreme nature or behaving like an EHBL-type source. The optical observation provides color-index variation as "blue-when-brighter". The broadband SED is fitted with a single-zone SSC model, and their parameters are discussed in the context of a TeV blazar and the possible mechanism behind the broadband emission.Comment: 13 pages, 10 figures, 5 tables, Accepted for publication in MNRA

Preliminary experience of fractionated stereotactic radiosurgery with extend system of Gamma Knife

Purpose: The purpose of this study is to present multisession stereotactic radiosurgery with initial experience using custom made extend system (ES) of Gamma Knife.Methods: The ES is comprised of a carbon fiber frame also called extend frame, vacuum head rest cushion, patient surveillance unit and a configurable front piece with dental impression tray. The extend frame is a rigid connection between patient's head and patient positioning system (PPS) of Gamma Knife. A dental impression of patient was created and attached to the frontal piece of extend system. The treatment setup involves positioning the patient within the extend frame using patient specific headrest cushion and front piece. The reference patient’s head position was recorded through measurements of repositioning check tool (RCT) apertures using a high precision digital probe before computed tomography (CT) scan. The RCT measurements taken before treatment were compared with recorded reference position to ensure appropriate patient treatment position. Volumetric magnetic resonance (MR) scan was co-registered with stereotactic CT scan on Leksell Gamma plan. Fused MR to CT images on Gamma Plan was utilized to delineate regions of interest and prepare a precise treatment plan. The presented study includes positional reproducibility check and dosimetric evaluation of ten patients treated with ES.Results: Forty-three fractions on ten patients with prescribed treatment format were delivered successfully. An average tumor volume of 11.26 cm3 (range, 340 mm3 to 59.12 cm3) was treated with ES. The mean tumor coverage of 91.91% (range, 90% to 95%) was able to achieve at 50% prescription isodose without compromising adjacent normal structure radiation dose tolerances. The mean inter-fraction positional variation of 0.69 mm influences an inherent strength of immobilization technique. Follow-up of seven patients at a median interval of 16 months (range, 9 months to 26 months) showed evidence of 100% radiographic control with improved clinical results.Conclusion: Conjugative clinical outcome shows the efficacy of fractionation in various clinical indications

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care