Showing 1–24 of 24 results for author: Paul, P

Optimizing Objective Model Calibration Approaches using Single Column Models

Authors: Pappu Paul, Cristian Proistosescu

Abstract: Sub-grid scale parameterizations in atmospheric models involve numerous uncertain parameters that must be tuned to align simulations with observations. Here, we propose a framework for assessing objective tuning frameworks using the Single Column Atmosphere Model (SCAM), which retains key physical parameterizations of general circulation models (GCMs) while greatly reducing computational cost. We… ▽ More Sub-grid scale parameterizations in atmospheric models involve numerous uncertain parameters that must be tuned to align simulations with observations. Here, we propose a framework for assessing objective tuning frameworks using the Single Column Atmosphere Model (SCAM), which retains key physical parameterizations of general circulation models (GCMs) while greatly reducing computational cost. We conduct a perfect-model experiment where we run SCAM with a known "true" parameter set to generate synthetic observations that mimic Atmospheric Radiation Measurement (ARM) Intensive Observation Periods. Perturbed parameter ensembles are constructed by varying microphysics, convection, and aerosol parameters, and cloud-radiation fields are evaluated over the Southern Great Plains. We find that point estimates find solutions that greatly reduce model-observation misfit without recovering the true parameter values. In contrast, a Bayesian framework using a Gaussian Process emulator with Markov Chain Monte Carlo sampling yields tighter constraints on some parameters and more consistent recovery across experiments and variables. The perfect model framework allows to assess which observables yield most information, which parameters are recoverable given a certain set of observations, and what is the minimum observational record needed. Although this study focuses on a single location with synthetic observations, such experiments provide a controlled setting to evaluate and identify robust calibration frameworks, which can then be extended to multiple locations and real observations with greater confidence. △ Less

Submitted 4 April, 2026; originally announced April 2026.

Comments: 22 pages, 6 figures

Pulsed Laser Template Engineering- PLATEN

Authors: Dhiman Biswas, Junyeob Song, Francisco Guzman, Levi Brown, Yiwei Ju, Nisha Geng, Pralay Paul, Sumit Goswami, Casey Kerr, Sreehari Puthan Purayil, Ben Summers, Preston Larson, Binbin Weng, Bin Wang, Horst Hahn, Xiaoxing Pan, Alisa Javadi, Henri Lezec, Thirumalai Venkatesan

Abstract: Thin films of functional inorganic materials, particularly oxides, play a vital role in optoelectronics, enabling applications that range from active optical components to MEMS-based architectures. Achieving high aspect ratio patterning of these functional materials remains a significant challenge, as many of their constituent elements do not readily form volatile compounds required for convention… ▽ More Thin films of functional inorganic materials, particularly oxides, play a vital role in optoelectronics, enabling applications that range from active optical components to MEMS-based architectures. Achieving high aspect ratio patterning of these functional materials remains a significant challenge, as many of their constituent elements do not readily form volatile compounds required for conventional reactive ion etch processes. We introduce a novel approach, Pulsed Laser Template ENgineering (PLATEN), which offers a more accessible route for patterning materials that are typically difficult to etch. This technique involves depositing functional films using the Pulsed Laser Deposition (PLD) process onto silicon substrates that have been pre-patterned using reactive ion etching to create high aspect ratio features. Due to the highly forward-directed nature of the PLD process, the deposited films replicate closely the topography of the patterned silicon, without coatings the sidewalls. This process remains effective even at feature sizes down to approximately 50 nm. The oxide films replicate the underlying silicon pattern to a thickness of 80 nm. For thickness beyond 80 nm the patterns develop a waist at the midpoint which scales with film thickness and is not dependent on the feature size. In this paper, we present a detailed analysis of the PLATEN process, including deviations from ideal pattern replication in sub-micron features as a function of film thickness, and demonstrate near single crystalline growth of oxides on the patterned silicon substrate, demonstrating the potential of PLATEN technique for active opto-electronic materials. △ Less

Submitted 26 March, 2026; originally announced March 2026.

The forgotten role of wave dynamics in modulating the low cloud response to warm pool warming

Authors: Cristian Proistosescu, Pappu Paul, Nicholas J. Lutsko, Andrew I. L. Williams, Malte F. Stuecker

Abstract: The Pattern Effect describes the dependence of top-of-atmosphere radiation anomalies on changes in the pattern of sea surface temperatures. The emerging consensus in the field explains the impact of Pacific warm pool temperature on radiation using Convective Quasi-Equilibrium Weak Temperature Gradient (QE-WTG) theory: warm pool warming leads to increase in free-tropospheric temperatures across the… ▽ More The Pattern Effect describes the dependence of top-of-atmosphere radiation anomalies on changes in the pattern of sea surface temperatures. The emerging consensus in the field explains the impact of Pacific warm pool temperature on radiation using Convective Quasi-Equilibrium Weak Temperature Gradient (QE-WTG) theory: warm pool warming leads to increase in free-tropospheric temperatures across the tropics, a strengthening of inversion, increased cloud cover in the East Pacific low cloud decks, and negative radiative anomalies. Here we call on overlooked past results and new simulations from the Energy Exascale Earth System model to show that Rossby waves dominate the low-cloud response over the subtropical East Pacific low cloud decks, leading to decrease cloud cover in the low cloud decks. While the global radiative response is negative and consistent with QE-WTG, it is dominated by the response of the deep tropics, rather than the subtropical low cloud decks. △ Less

Submitted 25 March, 2026; originally announced March 2026.

Applying the ACE2 Emulator to SST Green's Functions for the E3SMv3 Global Atmosphere Model

Authors: Elynn Wu, Finn Rebassoo, Pappu Paul, Cristian Proistosescu, Jacqueline Nugent, Daniel McCoy, Peter Caldwell, Christopher S. Bretherton

Abstract: Green's functions are a useful technique for interpreting atmospheric state responses to changes in the spatial pattern of sea surface temperature (SST). Here we train version 2 of the Ai2 Climate Emulator (ACE2) on reference historical SST simulations of the US Department of Energy's EAMv3 global atmosphere model. We compare how well the SST Green's functions generated by ACE2 match those of EAMv… ▽ More Green's functions are a useful technique for interpreting atmospheric state responses to changes in the spatial pattern of sea surface temperature (SST). Here we train version 2 of the Ai2 Climate Emulator (ACE2) on reference historical SST simulations of the US Department of Energy's EAMv3 global atmosphere model. We compare how well the SST Green's functions generated by ACE2 match those of EAMv3, following the protocol of the Green's Function Model Intercomparison Project (GFMIP). The spatial patterns of top-of-atmosphere (TOA) radiative response from the individual GFMIP SST patch simulations are similar for ACE and the EAMv3 reference. The derived sensitivity of global net TOA radiation sensitivity to SST patch location is qualitatively similar in ACE as in EAMv3, but there are statistically significant discrepancies for some SST patches, especially over the subtropical northeast Pacific. These discrepancies may reflect insufficient diversity in the SST patterns sampled over the course of the EAMv3 AMIP simulation used for training ACE. Both ACE and EAMv3 Green's functions reconstruct the historical record of the global annual-mean TOA radiative flux from a reference EAMv3 AMIP simulation reasonably well. Notably, under our configuration and compute resources, ACE achieves these results approximately 100 times faster in wall-clock time compared to EAMv3, highlighting its potential as a powerful and efficient tool for tackling other computationally intensive problems in climate science. △ Less

Submitted 27 May, 2025; v1 submitted 13 May, 2025; originally announced May 2025.

Developing New Analysis Tools for Near Surface Radio-based Neutrino Detectors

Authors: ARIANNA Collaboration, A. Anker, P. Baldi, S. W. Barwick, J. Beise, D. Z. Besson, P. Chen, G. Gaswint, C. Glaser, A. Hallgren, J. C. Hanson, S. R. Klein, S. A. Kleinfelder, R. Lahmann, J. Liu, J. Nam, A. Nelles, M. P. Paul, C. Persichilli, I. Plaisier, R. Rice-Smith, J. Tatar, K. Terveer, S. -H Wang, L. Zhao

Abstract: The ARIANNA experiment is an Askaryan radio detector designed to measure high-energy neutrino induced cascades within the Antarctic ice. Ultra-high-energy neutrinos above $10^{16}$ eV have an extremely low flux, so experimental data captured at trigger level need to be classified correctly to retain more neutrino signal. We first describe two new physics-based neutrino selection methods, (the updo… ▽ More The ARIANNA experiment is an Askaryan radio detector designed to measure high-energy neutrino induced cascades within the Antarctic ice. Ultra-high-energy neutrinos above $10^{16}$ eV have an extremely low flux, so experimental data captured at trigger level need to be classified correctly to retain more neutrino signal. We first describe two new physics-based neutrino selection methods, (the updown and dipole cut) that extend the previously published analysis to a specialized ARIANNA station with 8 antenna channels, which is double the number used in the prior analysis. For a standard trigger with a threshold signal to noise ratio at 4.4, the new cuts produce a neutrino efficiency of > 95% per station-year, while rejecting 99.93% of the background (corresponding to 53 remaining experimental background events). When the new cuts are combined with a previously developed cut using neutrino waveform templates, all background is removed at no change of efficiency. In addition, the neutrino efficiency is extrapolated to 1,000 station-years, obtaining 91%. This work then introduces a new selection method (deep learning (DL) cut) to augment the identification of neutrino events by using DL methods and compares the efficiency to the physics-based analysis. The DL cut gives 99% signal efficiency per station-year of operation while rejecting 99.997% of the background (corresponding to 2 remaining experimental background events), which are then removed by the waveform template cut at no significant change in efficiency. The results of the DL cut were verified using measured cosmic rays which shows the simulations do not introduce artifacts with respect to experimental data. The paper demonstrates the background rejection and signal efficiency of near surface antennas meets the requirements of a large scale future array, as considered in baseline design of the radio component of IceCube-Gen2. △ Less

Submitted 26 September, 2023; v1 submitted 14 July, 2023; originally announced July 2023.

Comments: 29 pages, 16 figures, 3 tables

Enhanced Surface Second Harmonic Generation in Nanolaminates

Authors: Fatemeh Abtahi, Pallabi Paul, Sebastian Beer, Athira Kuppadakkath, Anton Pakhomov, Adriana Szeghalmi, Stefan Nolte, Frank Setzpfandt, Falk Eilenberger

Abstract: Second-harmonic generation (SHG) is a second-order nonlinear optical process that is not allowed in media with inversion sym-metry. However, due to the broken symmetry at the surface, surface SHG still occurs, but is generally small. We experimentally investi-gate the surface SHG in periodic stacks of alternating, subwave-length dielectric layers, which have a large number of surfaces, thus enhanc… ▽ More Second-harmonic generation (SHG) is a second-order nonlinear optical process that is not allowed in media with inversion sym-metry. However, due to the broken symmetry at the surface, surface SHG still occurs, but is generally small. We experimentally investi-gate the surface SHG in periodic stacks of alternating, subwave-length dielectric layers, which have a large number of surfaces, thus enhancing surface SHG considerably. To this end, multilayer stacks of SiO2/TiO2 were grown by Plasma Enhanced Atomic Layer Deposition (PEALD) on fused silica substrates. With this technique individual layers of a thickness of less than 2 nm can be fabricated. We experimentally show that under large angles of incidence (> 20 degrees) there is substantial SHG, well beyond the level, which can be observed from simple interfaces. We perform this experiment for samples with different periods and thickness of SiO2/TiO2 and our results are in agreement with theoretical calculations. △ Less

Submitted 19 January, 2023; originally announced January 2023.

Atomically Thin Metal-Dielectric Heterostructures by Atomic Layer Deposition

Authors: Pallabi Paul, Paul Schmitt, Vilborg Vala Sigurjonsdottir, Kevin Hanemann, Nadja Felde, Sven Schroeder, Felix Otto, Marco Gruenewald, Torsten Fritz, Vladimir Roddatis, Andreas Tuennermann, Adriana Szeghalmi

Abstract: Heterostructures increasingly attracted attention over the past several years to enable various optoelectronic and photonic applications. In this work, atomically thin interfaces of Ir/Al2O3 heterostructures compatible with micro-optoelectronic technologies are reported. Their structural and optical properties were determined by spectroscopic and microscopic techniques (XRR, XPS, HRTEM, spectrosco… ▽ More Heterostructures increasingly attracted attention over the past several years to enable various optoelectronic and photonic applications. In this work, atomically thin interfaces of Ir/Al2O3 heterostructures compatible with micro-optoelectronic technologies are reported. Their structural and optical properties were determined by spectroscopic and microscopic techniques (XRR, XPS, HRTEM, spectroscopic ellipsometry, and UV/VIS/NIR spectrophotometry). The XRR and HRTEM analyses reveal a layer-by-layer growth mechanism of Ir in atomic scale heterostructures, which is different from the typical island-type growth of metals on dielectrics. Alongside, XPS investigations imply the formation of Ir-O-Al bonding at the interfaces for lower Ir concentrations, in contrast to the nanoparticle core-shell structure formation. Precisely tuning the ratio of the constituents ensures the control of the dispersion profile along with a transition from effective dielectric to metallic heterostructures. The Ir coating thickness was varied ranging from a few Å to films of about 7 nm in the heterostructures. The transition has been observed in the structures containing individual Ir coating thicknesses of about 2-4 nm. Following this, show epsilon-near-zero metamaterials with tunable dielectric constants by precisely varying the composition of such heterostructures. Overall, a comprehensive study on structural and optical properties of the metal-dielectric interface of Ir/Al2O3 heterostructures was addressed indicating an extension of the material portfolio available for optical system design. △ Less

Submitted 16 December, 2022; originally announced December 2022.

Heterostructure films of SiO$_2$ and HfO$_2$ for high power laser optics prepared by plasma-enhanced atomic layer deposition

Authors: Shawon Alam, Pallabi Paul, Vivek Beladiya, Olaf Stenzel, Marcus Trost, Steffen Wilbrandt, Sven Schroeder, Gabor Matthaeus, Stefan Nolte, Sebastian Riese, Felix Otto, Torsten Fritz, Alexander Gottwald, Adriana Szeghalmi

Abstract: Absorption losses and laser-induced damage threshold (LIDT) are considered as the major constraint for the development of optical coatings for high-power laser optics. Such coatings require paramount properties like low losses due to optical absorption, high mechanical stability, and enhanced damage resistance to withstand high-intensity laser pulses. In this work, heterostructure films were devel… ▽ More Absorption losses and laser-induced damage threshold (LIDT) are considered as the major constraint for the development of optical coatings for high-power laser optics. Such coatings require paramount properties like low losses due to optical absorption, high mechanical stability, and enhanced damage resistance to withstand high-intensity laser pulses. In this work, heterostructure films were developed by the intermixing of SiO$_2$ and HfO$_2$ using plasma-enhanced atomic layer deposition (PEALD) technique. Thin film characterization techniques such as spectroscopic ellipsometry, spectrophotometry, substrate curvature measurements, x-ray reflectivity, and Fourier transform infrared spectroscopy were employed for extracting optical constants, spectral inter-pretation, residual stress, layer formation, and functional groups present in the heterostructures, respectively. These heterostructures demonstrate tunable refractive index, bandgap, and improved optical losses and LIDT properties. The films were incorporated into antireflection coatings (multilayer stacks and graded index coatings) and the LIDT was determined at 355 nm wavelength by the R-on-1 method. Optical absorptions at the reported wavelengths were characterized using photothermal common-path interferometry and laser-induced deflection techniques. △ Less

Submitted 16 December, 2022; originally announced December 2022.

Nonlinear polarization holography of nanoscale iridium films

Authors: Mouli Hazra, Pallabi Paul, Doyeong Kim, Christin David, Stefanie Gräfe, Ulf Peschel, Matthias Kübel, Adriana Szeghalmi, Adrian N. Pfeiffer

Abstract: The phasing problem of heterodyne-detected nonlinear spectroscopy states that the relative time delay between the exciting pulses and a local oscillator must be known with subcycle precision to separate absorptive and dispersive contributions. Here, a solution to this problem is presented which is the time-domain analogue of holographic interferometry, in which the comparison of two holograms reve… ▽ More The phasing problem of heterodyne-detected nonlinear spectroscopy states that the relative time delay between the exciting pulses and a local oscillator must be known with subcycle precision to separate absorptive and dispersive contributions. Here, a solution to this problem is presented which is the time-domain analogue of holographic interferometry, in which the comparison of two holograms reveals changes of an objects size and position with interferometric precision (i.e. to fractions of a wavelength of light). The introduced method, called nonlinear polarization holography, provides equivalent information as attosecond nonlinear polarization spectroscopy but has the advantage of being all-optical instead of using an attosecond streak camera. Nonlinear polarization holography is used here to retrieve the time-domain nonlinear response of a nanoscale iridium film to an ultrashort femtosecond pulse. Using density matrix calculations it is shown that the knowledge of the nonlinear response with subcycle precision allows to distinguish excitation and relaxation mechanisms of low-energetic electrons that depend on the nanoscale structure of the iridium film. △ Less

Submitted 7 November, 2022; originally announced November 2022.

Linear and Nonlinear Optical Properties of Iridium Nanoparticles by Atomic Layer deposition

Authors: Paul Schmitt, Pallabi Paul, Weiwei Li, Zilong Wang, Christin David, Navid Daryakar, Kevin Hanemann, Nadja Felde, Anne-Sophie Munser, Matthias F. Kling, Sven Schroeder, Andreas Tuennermann, Adriana Szeghalmi

Abstract: Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical applications. While noble metal nanoparticles, na… ▽ More Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical applications. While noble metal nanoparticles, nanostructures, and thin films of Ag and Au were widely studied, iridium (Ir) nanoparticles and ultra-thin films have not been investigated yet. Here, we present a combined theoretical and experimental study on the linear and nonlinear optical properties of Ir nanoparticles deposited by atomic layer deposition (ALD). Linear optical constants, i.e., the effective refractive index n and extinction coefficient k, were evaluated at different growth stages of nanoparticle formation. Both linear and nonlinear optical properties of these Ir ALD coatings were calculated theoretically using Bruggeman and Maxwell-Garnett theories. The third-order susceptibility of Ir nanoparticle samples was experimentally investigated using the Z-scan technique. Overall, our studies demonstrate the potential of ultrathin Ir NPs as an alternative nonlinear optical material at an atomic scale. △ Less

Submitted 11 October, 2022; originally announced October 2022.

Direct Growth of Monolayer MoS$_2$ on Nanostructured Silicon Waveguides

Authors: Athira Kuppadakkath, Emad Najafidehaghani, Ziyang Gan, Alessandro Tuniz, Gia Quyet Ngo, Heiko Knopf, Franz J. F. Löchner, Fatemeh Abtahi, Tobias Bucher, Sai Shradha, Thomas Käsebier, Stefano Palomba, Nadja Felde, Pallabi Paul, Tobias Ullsperger, Sven Schröder, Adriana Szeghalmi, Thomas Pertsch, Isabelle Staude, Uwe Zeitner, Antony George, Andrey Turchanin, Falk Eilenberger

Abstract: We report for the first time the direct growth of Molybdenum disulfide (MoS$_2$) monolayers on nanostructured silicon-on-insulator waveguides. Our results indicate the possibility of utilizing the Chemical Vapour Deposition (CVD) on nanostructured photonic devices in a scalable process. Direct growth of 2D material on nanostructures rectifies many drawbacks of the transfer-based approaches. We sho… ▽ More We report for the first time the direct growth of Molybdenum disulfide (MoS$_2$) monolayers on nanostructured silicon-on-insulator waveguides. Our results indicate the possibility of utilizing the Chemical Vapour Deposition (CVD) on nanostructured photonic devices in a scalable process. Direct growth of 2D material on nanostructures rectifies many drawbacks of the transfer-based approaches. We show that the van der Waals materials grow conformally across the curves, edges, and the silicon-SiO$_2$ interface of the waveguide structure. Here, the waveguide structure used as a growth substrate is complex not just in terms of its geometry but also due to the two materials (Si and SiO$_2$) involved. A transfer-free method like this yields a novel approach for functionalizing nanostructured, integrated optical architectures with an optically active direct semiconductor. △ Less

Submitted 27 May, 2022; originally announced June 2022.

Effect of Functional Group on Electrical Switching Behaviour of an Imidazole Derivative in Langmuir-Blodgett Film

Authors: Bapi Dey, Sudip Suklabaidya, Swapan Majumdar, Pabitra Kumar Paul, Debajyoti Bhattacharjee, Syed Arshad Hussain

Abstract: Here we report the design and synthesis of an imidazole derivative namely 1-benzyl-2,4,5-triaryl imidazole and its switching behaviour assembled onto Langmuir-Blodgett films. Monolayer characteristic of imidazole at the air-water interface has been studied by surface pressure vs area per molecule isotherm, hysteresis analysis and insitu Brewster Angle Microscopy . These studies indicated the forma… ▽ More Here we report the design and synthesis of an imidazole derivative namely 1-benzyl-2,4,5-triaryl imidazole and its switching behaviour assembled onto Langmuir-Blodgett films. Monolayer characteristic of imidazole at the air-water interface has been studied by surface pressure vs area per molecule isotherm, hysteresis analysis and insitu Brewster Angle Microscopy . These studies indicated the formation of stable floating Langmuir film at the water subphase. Atomic Force Microscopy investigation confirmed the successful deposition of the Langmuir film onto solid substrate. Device consisted of 60 layers LB films of imidazole showed resistive bipolar switching behaviour irrespective of the first applied bias voltage polarity. Observed bipolar switching has been explained in terms of reduction oxidation process. Due to the presence of strong reducible group C double bond N in the imidazole core, reduction oxidation process takes place easily during bias. Presence of sharp reduction and oxidation peaks in the Cyclic Voltammetry measurement of 2 also supported this hypothesis. Presence of benzyl group with the imidazole core played the crucial rule in the reduction oxidation process and hence the switching behaviour. When benzyl group was replaced by a H then bipolar switching was not observed. In that case oxidizable group NH opposed the reduction process during bias. This type of bipolar switching is very promising for future technological applications in organic electronics. △ Less

Submitted 27 July, 2019; originally announced July 2019.

Comments: 26 pages 7 figures

Original Ti:Sa 10 kHz Front-end design delivering 17 fs, 170 mrad CEP stabilized pulses up to 5 W

Authors: A. Golinelli, X. Chen, E. Gontier, B. Bussière, O. Tcherbakoff, M. Natile, P. D'Oliveira, P. -M. Paul, J. -F. Hergott

Abstract: We present a compact 10 kHz Ti:Sa front-end relying on an original double-crystal regenerative amplifier design. This new configuration optimizes the thermal heat load management, allowing producing a 110 nm large spectrum and maintaining a good beam profile quality. The front-end delivers up to 5 W after compression, 17 fs pulses with a 170 mrad shot-to-shot residual CEP noise. We present a compact 10 kHz Ti:Sa front-end relying on an original double-crystal regenerative amplifier design. This new configuration optimizes the thermal heat load management, allowing producing a 110 nm large spectrum and maintaining a good beam profile quality. The front-end delivers up to 5 W after compression, 17 fs pulses with a 170 mrad shot-to-shot residual CEP noise. △ Less

Submitted 25 February, 2019; originally announced February 2019.

Comments: 5 figures, 1 equation

Role of EV+0.98 eV trap in light soaking-induced short circuit current instability in CIGS solar cells

Authors: P. K. Paul, T. Jarmar, L. Stolt, A. Rockett, A. R. Arehart

Abstract: Light-induced instabilities/degradation in Cu(In,Ga)Se2 (CIGS) solar cells are a prevalent and urgent issue to resolve to improve performance, uniformity, and reliability. Here, mechanisms contributing to light-induced instabilities are identified focusing on an observed short circuit current (JSC) reduction. External quantum efficiency measurements before and after light soaking identified a redu… ▽ More Light-induced instabilities/degradation in Cu(In,Ga)Se2 (CIGS) solar cells are a prevalent and urgent issue to resolve to improve performance, uniformity, and reliability. Here, mechanisms contributing to light-induced instabilities are identified focusing on an observed short circuit current (JSC) reduction. External quantum efficiency measurements before and after light soaking identified a reduction in long wavelength photon carrier collection efficiency in the CIGS absorber layer. Using deep level optical spectroscopy (DLOS), the concentration of CIGS EV+0.98 eV deep level is correlated with the amount of JSC degradation, Finally, capacitance voltage (C-V) measurements reveal light induces a large reduction in the depletion depth and reduction of carrier collection and are all correlated with the JSC reduction. Finally, the EV+0.53 eV trap concentrations are shown to correlate with VOC instability but not the JSC reduction confirming that multiple trap-induced mechanism are responsible for the light-induced instabilities. △ Less

Submitted 24 May, 2018; originally announced June 2018.

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

Authors: P. K. Paul, J. Bailey, G. Zapalac, A. R. Arehart

Abstract: In this work, methods to determine more accurate doping profiles in semiconductors is explored where trap-induced artifacts such as hysteresis and doping artifacts are observed. Specifically in CIGS, it is shown that this fast capacitance-voltage (C-V) approach presented here allows for accurate doping profile measurement even at room temperature, which is typically not possible due to the large r… ▽ More In this work, methods to determine more accurate doping profiles in semiconductors is explored where trap-induced artifacts such as hysteresis and doping artifacts are observed. Specifically in CIGS, it is shown that this fast capacitance-voltage (C-V) approach presented here allows for accurate doping profile measurement even at room temperature, which is typically not possible due to the large ratio of trap concentration to doping. Using deep level transient spectroscopy (DLTS) measurement, the deep trap responsible for the abnormal C-V measurement above 200 K is identified. Importantly, this fast C-V can be used for fast evaluation on the production line to monitor the true doping concentration, and even estimate the trap concentration. Additionally, the influence of high conductance on the apparent doping profile at different temperature is investigated. △ Less

Submitted 13 July, 2017; v1 submitted 29 June, 2017; originally announced June 2017.

Extracellular biosynthesis of silver nanoparticles from Plant Growth Promoting Rhizobacteria Pseudomonas sp

Authors: Archana Yadav, T. Theivasanthi, P. K. Paul, K. C. Upadhyay

Abstract: Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. In the present study, extracellular synthesis of silver nanoparticles using culture supernatant of plant growth promoting rhizobacterium, Pseudomonas sp.ARS22. The biosynthesis of AgNPs by Pseudomonas sp.ARS22 was monitored by UVvisible spec… ▽ More Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. In the present study, extracellular synthesis of silver nanoparticles using culture supernatant of plant growth promoting rhizobacterium, Pseudomonas sp.ARS22. The biosynthesis of AgNPs by Pseudomonas sp.ARS22 was monitored by UVvisible spectrum that showed the surface plasmon resonance peak at 410 nm, an important characteristic of AgNPs. Furthermore, the morphological, elemental, functional and thermal characterization of arsAgNPs was carried out using the electron and atomic microscopies, FTIR spectroscopy and Atomic Force microscopy, respectively. The arsAgNPs were spherical in shape. The DebyeScherrer equation was used to calculate particle sizes and the silver nanoparticles of approximate size 10 to 30 nm were observed. The process of reduction is extracellular, which makes it an easier method for the synthesis of silver nanoparticles. △ Less

Submitted 6 November, 2015; originally announced November 2015.

Comments: 10 pages and 4 figures

Journal ref: Int.J.Curr.Microbiol.App.Sci (2015) 4(8): 1057-1068

The Intermediate Neutrino Program

Authors: C. Adams, J. R. Alonso, A. M. Ankowski, J. A. Asaadi, J. Ashenfelter, S. N. Axani, K. Babu, C. Backhouse, H. R. Band, P. S. Barbeau, N. Barros, A. Bernstein, M. Betancourt, M. Bishai, E. Blucher, J. Bouffard, N. Bowden, S. Brice, C. Bryan, L. Camilleri, J. Cao, J. Carlson, R. E. Carr, A. Chatterjee, M. Chen , et al. (164 additional authors not shown)

Abstract: The US neutrino community gathered at the Workshop on the Intermediate Neutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 to explore opportunities in neutrino physics over the next five to ten years. Scientists from particle, astroparticle and nuclear physics participated in the workshop. The workshop examined promising opportunities for neutrino physics in the intermedia… ▽ More The US neutrino community gathered at the Workshop on the Intermediate Neutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 to explore opportunities in neutrino physics over the next five to ten years. Scientists from particle, astroparticle and nuclear physics participated in the workshop. The workshop examined promising opportunities for neutrino physics in the intermediate term, including possible new small to mid-scale experiments, US contributions to large experiments, upgrades to existing experiments, R&D plans and theory. The workshop was organized into two sets of parallel working group sessions, divided by physics topics and technology. Physics working groups covered topics on Sterile Neutrinos, Neutrino Mixing, Neutrino Interactions, Neutrino Properties and Astrophysical Neutrinos. Technology sessions were organized into Theory, Short-Baseline Accelerator Neutrinos, Reactor Neutrinos, Detector R&D and Source, Cyclotron and Meson Decay at Rest sessions.This report summarizes discussion and conclusions from the workshop. △ Less

Submitted 1 April, 2015; v1 submitted 23 March, 2015; originally announced March 2015.

Comments: pdfLaTeX, 31 pages, 1 figure, minor modification to 0nuBB discussion

Sensing of DNA conformation based on change in FRET efficiency between laser dyes

Authors: Dibyendu Dey, Jaba Saha, Arpan Datta Roy, D. Bhattacharjee, Sangram Sinha, P. K. Paul, Santanu Chakraborty, Syed Arshad Hussain

Abstract: This communication reports the effect of DNA conformation on fluorescence resonance energy transfer (FRET) efficiency between two laser dyes in layer by layer (LbL) self assembled film. The dyes Acraflavine and Rhodamine B were attached onto the negative phosphate backbones of DNA in LbL film through electrostatic attraction. Then FRET between these dyes was investigated. Increase in pH or tempera… ▽ More This communication reports the effect of DNA conformation on fluorescence resonance energy transfer (FRET) efficiency between two laser dyes in layer by layer (LbL) self assembled film. The dyes Acraflavine and Rhodamine B were attached onto the negative phosphate backbones of DNA in LbL film through electrostatic attraction. Then FRET between these dyes was investigated. Increase in pH or temperature causes the denaturation of DNA followed by coil formation of single stranded DNA. As a result the FRET efficiency also changed along with it. These observations demonstrated that by observing the change in FRET efficiency between two laser dyes in presence of DNA it is possible to detect the altered DNA conformation in the changed environment. △ Less

Submitted 16 September, 2014; originally announced September 2014.

Comments: 28 pages, 5 figures

Journal ref: Sens Act B 204 (2014) 746

Inflationary phase and role of dark energy: Revisited

Authors: Indranath Bhattacharyya, Saibal Ray, Prasenjit Paul

Abstract: The inflationary phase of the Universe is explored by proposing a toy model related to the scalar field, termed as {\it inflaton}. The potential part of the energy density in the said era is assumed to have a constant vacuum energy density part and a variable part containing the inflaton. The prime idea of the proposed model constructed in the framework of the closed Universe is based on a fact th… ▽ More The inflationary phase of the Universe is explored by proposing a toy model related to the scalar field, termed as {\it inflaton}. The potential part of the energy density in the said era is assumed to have a constant vacuum energy density part and a variable part containing the inflaton. The prime idea of the proposed model constructed in the framework of the closed Universe is based on a fact that the inflaton is the root cause of the orientation of the space. According to this model the expansion of the Universe in the inflationary epoch is not approximately rather exactly exponential in nature and thus it can solve some of the fundamental puzzles, viz. flatness as well as horizon problems. It is also predicted that the constant energy density part in the potential may be associated to the dark energy, which is eventually different from the vacuum energy, at least in the inflationary phase of the Universe. However, the model keeps room for the end of inflationary era. △ Less

Submitted 21 May, 2019; v1 submitted 16 May, 2013; originally announced May 2013.

Comments: 6 pages, 1 figure, Major changes in the assumption and textual version

The T2K ND280 Off-Axis Pi-Zero Detector

Authors: S. Assylbekov, B. E. Berger, H. Berns, D. Beznosko, A. Bodek, R. Bradford, N. Buchanan, H. Budd, Y. Caffari, K. Connolly, I. Danko, R. Das, S. Davis, M. Day, S. Dytman, M. Dziomba, R. Flight, D. Forbush, K. Gilje, D. Hansen, J. Hignight, J. Imber, R. A. Johnson, C. K. Jung, V. Kravtsov , et al. (31 additional authors not shown)

Abstract: The Pi-Zero detector (PØD) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the PØD is to measure the relevant cross sections for neutrino interactions that generate pi-zero's, especially the cross section for neutral current pi-zero interactions, which are one of the dominant sources of backg… ▽ More The Pi-Zero detector (PØD) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the PØD is to measure the relevant cross sections for neutrino interactions that generate pi-zero's, especially the cross section for neutral current pi-zero interactions, which are one of the dominant sources of background to the electron neutrino appearance signal in T2K. The PØD is composed of layers of plastic scintillator alternating with water bags and brass sheets or lead sheets and is one of the first detectors to use Multi-Pixel Photon Counters (MPPCs) on a large scale. △ Less

Submitted 28 June, 2012; v1 submitted 21 November, 2011; originally announced November 2011.

Comments: 17 pages, submitted to NIM A

Journal ref: Nuclear Instruments and Methods in Physics Research A, 686 (2012) 48-63

Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector

Authors: K. Abe, N. Abgrall, Y. Ajima, H. Aihara, J. B. Albert, C. Andreopoulos, B. Andrieu, M. D. Anerella, S. Aoki, O. Araoka, J. Argyriades, A. Ariga, T. Ariga, S. Assylbekov, D. Autiero, A. Badertscher, M. Barbi, G. J. Barker, G. Barr, M. Bass, M. Batkiewicz, F. Bay, S. Bentham, V. Berardi, B. E. Berger , et al. (407 additional authors not shown)

Abstract: Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure o… ▽ More Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision. △ Less

Submitted 14 November, 2011; originally announced November 2011.

Comments: 32 pages, 27 figures, submitted to Nucl. Instr. and Meth. A

A New Computationally Efficient Measure of Topological Redundancy of Biological and Social Networks

Authors: Reka Albert, Bhaskar DasGupta, Anthony Gitter, Gamze Gursoy, Rashmi Hegde, Pradyut Paul, Gowri Sangeetha Sivanathan, Eduardo Sontag

Abstract: It is well-known that biological and social interaction networks have a varying degree of redundancy, though a consensus of the precise cause of this is so far lacking. In this paper, we introduce a topological redundancy measure for labeled directed networks that is formal, computationally efficient and applicable to a variety of directed networks such as cellular signaling, metabolic and social… ▽ More It is well-known that biological and social interaction networks have a varying degree of redundancy, though a consensus of the precise cause of this is so far lacking. In this paper, we introduce a topological redundancy measure for labeled directed networks that is formal, computationally efficient and applicable to a variety of directed networks such as cellular signaling, metabolic and social interaction networks. We demonstrate the computational efficiency of our measure by computing its value and statistical significance on a number of biological and social networks with up to several thousands of nodes and edges. Our results suggest a number of interesting observations: (1) social networks are more redundant that their biological counterparts, (2) transcriptional networks are less redundant than signaling networks, (3) the topological redundancy of the C. elegans metabolic network is largely due to its inclusion of currency metabolites, and (4) the redundancy of signaling networks is highly (negatively) correlated with the monotonicity of their dynamics. △ Less

Submitted 5 November, 2011; v1 submitted 30 August, 2011; originally announced August 2011.

Comments: 18 pages

MSC Class: 68R10; 05C85; 05C82; 05C20; 05C40; 91D30; 92C42; 93C15; 37N25 ACM Class: J.3; J.4; F.2.2; G.2.1; G.2.2; G.2.3

Journal ref: Physical Review E, 84 (3), 036117, 2011

The T2K Experiment

Authors: T2K Collaboration, K. Abe, N. Abgrall, H. Aihara, Y. Ajima, J. B. Albert, D. Allan, P. -A. Amaudruz, C. Andreopoulos, B. Andrieu, M. D. Anerella, C. Angelsen, S. Aoki, O. Araoka, J. Argyriades, A. Ariga, T. Ariga, S. Assylbekov, J. P. A. M. de André, D. Autiero, A. Badertscher, O. Ballester, M. Barbi, G. J. Barker, P. Baron , et al. (499 additional authors not shown)

Abstract: The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ_{13} by observing ν_e appearance in a ν_μ beam. It also aims to make a precision measurement of the known oscillation parameters, Δm^{2}_{23} and sin^{2} 2θ_{23}, via ν_μ disappearance studies. Other goals of the experiment include various neutrino cross… ▽ More The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ_{13} by observing ν_e appearance in a ν_μ beam. It also aims to make a precision measurement of the known oscillation parameters, Δm^{2}_{23} and sin^{2} 2θ_{23}, via ν_μ disappearance studies. Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem. △ Less

Submitted 8 June, 2011; v1 submitted 6 June, 2011; originally announced June 2011.

Comments: 33 pages, 32 figures, Submitted and accepted by NIM A. Editor: Prof. Chang Kee Jung, Department of Physics and Astronomy, SUNY Stony Brook, chang.jung@sunysb.edu, 631-632-8108 Submit Edited to remove line numbers

Maximizing bandgaps in two-dimensional photonic crystals: a variational algorithm

Authors: Prabasaj Paul, Francis C. Ndi

Abstract: We present an algorithm for the maximization of photonic bandgaps in two-dimensional crystals. Once the translational symmetries of the underlying structure have been imposed, our algorithm finds a global maximal (and complete, if one exists) bandgap. Additionally, we prove two remarkable results related to maximal bandgaps: the so-called `maximum contrast' rule, and about the location in the Br… ▽ More We present an algorithm for the maximization of photonic bandgaps in two-dimensional crystals. Once the translational symmetries of the underlying structure have been imposed, our algorithm finds a global maximal (and complete, if one exists) bandgap. Additionally, we prove two remarkable results related to maximal bandgaps: the so-called `maximum contrast' rule, and about the location in the Brillouin zone of band edges. △ Less

Submitted 30 May, 2002; originally announced May 2002.

Comments: 4 pages