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Partha Sona Maji,Partha Roy Chaudhuri 한국광학회 2014 Current Optics and Photonics Vol.18 No.3
In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangularlattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of d/, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction (d/). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length (LD) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.
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Partha Mandal,Barrett P. O’Donnell,Eric Reuben Smith,Osamah Al-Bayati,Adam Khalil,Serena Jen,Mario Vela,Jorge Lopera 소화기인터벤션의학회 2022 Gastrointestinal Intervention Vol.11 No.1
Background: This study investigated the incidence and clinical outcomes of portal and hepatic vein thrombosis (VT) on imaging after transjugular intrahepatic portosystemic shunt (TIPS). Methods: A retrospective review of records at a single liver transplant center between 2010 and 2018 revealed 423 patients who underwent TIPS. Contrast-enhanced computed tomography and magnetic resonance images within 1 year post-TIPS were available for 138 patients and compared to assess the imaging findings of VT and liver infarction. The associations of VT with overall survival, patient characteristics, stent size, pre- and post- TIPS Model for End-Stage Liver Disease (MELD) scores, and post-TIPS hepatic encephalopathy at 90 days were analyzed. Results: The prevalence of VT on imaging within 1 year was 63.0% (n = 87). VT within the right portal vein was more common: 41 cases were in the right portal vein, 25 in the posterior portal vein, and two in the anterior right portal vein. Ten patients had VT in the left portal vein. Four had VT in the main portal vein (MPV), and one had shunt thrombosis extending into the superior mesenteric vein. Hepatic VT was seen in the right hepatic vein in 17 patients and in the middle hepatic vein in six patients. VT was associated with liver infarction (n = 9, P = 0.018). There was no relationship between VT and sex, age, cirrhosis etiology, indication for TIPS, stent size, or hepatic encephalopathy at 90 days. VT in the MPV had poorer survival (P < 0.001). Older age (P = 0.028) and higher pre-TIPS MELD score (P = 0.049) were poor prognostic factors. VT was not treated. Conclusion: Portal and hepatic VTs were common imaging findings after TIPS without worsened clinical outcomes unless VT involved the MPV. VT may cause liver infarction, but infarcts were not independently associated with poorer survival.
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Partha Sengupta,Subrata Chakraborty 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.1
The prediction error variances for frequencies are usually considered as unknown in the Bayesian system identification process. However, the error variances for mode shapes are taken as known to reduce the dimension of an identification problem. The present study attempts to explore the effectiveness of Bayesian approach of model parameters updating using Markov Chain Monte Carlo (MCMC) technique considering the prediction error variances for both the frequencies and mode shapes. To remove the ergodicity of Markov Chain, the posterior distribution is obtained by Gaussian Random walk over the proposal distribution. The prior distributions of prediction error variances of modal evidences are implemented through inverse gamma distribution to assess the effectiveness of estimation of posterior values of model parameters. The issue of incomplete data that makes the problem ill-conditioned and the associated singularity problem is prudently dealt in by adopting a regularization technique. The proposed approach is demonstrated numerically by considering an eight-storey frame model with both complete and incomplete modal data sets. Further, to study the effectiveness of the proposed approach, a comparative study with regard to accuracy and computational efficacy of the proposed approach is made with the Sequential Monte Carlo approach of model parameter updating.
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Total Synthesis of Azasugar 1,4-Dideoxy-1,4-imino-D-galacitol
Partha Sarathi Sadhu,Amlipur Santhoshi,Vaidya Jayathirtha Rao,강한영,강성호 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.11
A new highly stereoselective synthesis of pyrrolidine azasugar 1,4-dideoxy-1,4-imino-D-galacitol is being reported herein. The synthesis was achieved in a linear sequence and inexpensive chiral source (+)-diethyl tartarate was used as the starting material. The key step involved during the synthesis was Pd catalysed amino cyclization of alkenylamine, Bose modified Mitsunobu reaction and Sharpless asymmetric dihydroxylation.
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Partha Pal,Sundeep Lakhtakia 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.2
Advanced malignant hilar biliary obstruction (MHBO) with inaccessible papilla poses a significant challenge to endoscopists, as drainage of multiple liver segments may be warranted. Transpapillary drainage may not be feasible in patients with surgically altered anatomy, duodenal stenosis, prior duodenal self-expanding metal stent, and after initial transpapillary drainage, but require re-intervention for draining separated liver segments. Endoscopic ultrasound-guided biliary drainage (EUS-BD) and percutaneous trans-hepatic biliary drainage are the feasible options in this scenario. The major advantages of EUS-BD over percutaneous trans-hepatic biliary drainage include a reduction in patient discomfort and internal drainage away from the tumor, thus reducing the possibility of tissue or tumor ingrowth. With innovations, EUS-BD is helpful not only for bilateral communicating MHBO but also for non-communicating systems with bridging hilar stents or isolated right intra-hepatic duct drainage by hepatico-duodenostomy. EUS-guided multi-stent drainage with specially designed cannulas and guidewires has become a reality. A combined approach with endoscopic retrograde cholangiopancreatography for re-intervention, interventional radiology, and intraductal tumor ablative therapies has been reported. Stent migration and bile leakage can be minimized with proper stent selection and technique, and stent blocks can be managed with EUS-guided interventions in a majority of cases. Future comparative studies are required to establish the role of EUS-guided interventions in MHBO as rescue or primary therapy.
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Partha Sarati Das,Kyeong-Hwa Kim 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.11
New voltage-based on-line fault detection and faulty switch identification algorithms under multiple open-switches in a grid-connected wind power converter are proposed in this paper. The proposed algorithms are based on the three-phase voltages which are calculated by using the DC link voltage and switching times determined from the space vector PWM scheme. From the calculated three-phase voltages, the absolute of average phase voltage and normalized three-phase RMS voltages are obtained to be used for the fault detection and faulty switch identification algorithms in three-phase AC/DC PWM converter. To determine faulty switches, three-phase voltages and RMS currents are taken as faulty switch localization variables. The complete diagnosis is carried out by a simple method during operation, which does not require any additional sensors. Therefore, the proposed methods are cost-effective and easy to use. To verify the validity and performance of the proposed algorithms, the simulation is carried out using the PSIM software for twenty-one cases of faults including multiple open-switches. As a result, the proposed scheme can effectively detect the occurrence of fault as well as faulty switches for these conditions independent of operating conditions.
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Partha Mandal,Barrett P. O’Donnell,Eric Reuben Smith,Osamah Al-Bayati,Adam Khalil,Serena Jen,Mario Vela,Jorge Lopera 소화기인터벤션의학회 2022 International journal of gastrointestinal interven Vol.11 No.1
Background: This study investigated the incidence and clinical outcomes of portal and hepatic vein thrombosis (VT) on imaging after transjugular intrahepatic portosystemic shunt (TIPS). Methods: A retrospective review of records at a single liver transplant center between 2010 and 2018 revealed 423 patients who underwent TIPS. Contrast-enhanced computed tomography and magnetic resonance images within 1 year post-TIPS were available for 138 patients and compared to assess the imaging findings of VT and liver infarction. The associations of VT with overall survival, patient characteristics, stent size, pre- and post- TIPS Model for End-Stage Liver Disease (MELD) scores, and post-TIPS hepatic encephalopathy at 90 days were analyzed. Results: The prevalence of VT on imaging within 1 year was 63.0% (n = 87). VT within the right portal vein was more common: 41 cases were in the right portal vein, 25 in the posterior portal vein, and two in the anterior right portal vein. Ten patients had VT in the left portal vein. Four had VT in the main portal vein (MPV), and one had shunt thrombosis extending into the superior mesenteric vein. Hepatic VT was seen in the right hepatic vein in 17 patients and in the middle hepatic vein in six patients. VT was associated with liver infarction (n = 9, P = 0.018). There was no relationship between VT and sex, age, cirrhosis etiology, indication for TIPS, stent size, or hepatic encephalopathy at 90 days. VT in the MPV had poorer survival (P < 0.001). Older age (P = 0.028) and higher pre-TIPS MELD score (P = 0.049) were poor prognostic factors. VT was not treated. Conclusion: Portal and hepatic VTs were common imaging findings after TIPS without worsened clinical outcomes unless VT involved the MPV. VT may cause liver infarction, but infarcts were not independently associated with poorer survival.
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