49 results on '"Mukherjee, Bhaskar"'
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2. Stable infinite-temperature eigenstates in SU(2)-symmetric nonintegrable models
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Turner, Christopher J., Szyniszewski, Marcin, Mukherjee, Bhaskar, Melendrez, Ronald, Changlani, Hitesh J., and Pal, Arijeet
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Quantum Physics ,Condensed Matter - Quantum Gases ,Condensed Matter - Strongly Correlated Electrons - Abstract
Nonintegrable many-body quantum systems typically thermalize at long times through the mechanism of quantum chaos. However, some exceptional systems, such as those harboring quantum scars, break thermalization, serving as testbeds for foundational problems of quantum statistical physics. Here, we investigate a class of nonintegrable bond-staggered models that is endowed with a large number of zero-energy eigenstates and possesses a non-Abelian internal symmetry. We use character theory to give a lower bound on the zero-energy degeneracy, which matches exact diagonalization results, and is found to grow exponentially with the system size. We also show that few-magnon zero-energy states have an exact analytical description, allowing us to build a basis of low-entangled fixed-separation states, which is stable to most perturbations found in experiments. This remarkable dynamical stability of special states elucidates our understanding of nonequilibrium processes in non-Abelian chaotic quantum models., Comment: 10 pages, 7 figures
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- 2024
3. Emergent strong zero mode through local Floquet engineering
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Mukherjee, Bhaskar, Melendrez, Ronald, Szyniszewski, Marcin, Changlani, Hitesh J., and Pal, Arijeet
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Statistical Mechanics ,Quantum Physics - Abstract
Periodically driven quantum systems host exotic phenomena which often do not have any analog in undriven systems. Floquet prethermalization and dynamical freezing of certain observables, via the emergence of conservation laws, are realized by controlling the drive frequency. These dynamical regimes can be leveraged to construct quantum memories and have potential applications in quantum information processing. Solid state and cold atom experimental architectures have opened avenues for implementing local Floquet engineering which can achieve spatially modulated quantum control of states. Here, we uncover the novel memory effects of local periodic driving in a nonintegrable spin-half staggered Heisenberg chain. For a boundary-driven protocol at the dynamical freezing frequency, we show the formation of an approximate strong zero mode, a prethermal quasi-local operator, due to the emergence of a discrete global $\mathbb{Z}_2$ symmetry. This is captured by constructing an accurate effective Floquet Hamiltonian using a higher-order partially resummed Floquet-Magnus expansion. The lifetime of the boundary spin can be exponentially enhanced by enlarging the set of suitably chosen driven sites. We demonstrate that in the asymptotic limit, achieved by increasing the number of driven sites, a strong zero mode emerges, where the lifetime of the boundary spin grows exponentially with system size. The non-local processes in the Floquet Hamiltonian play a pivotal role in the total freezing of the boundary spin in the thermodynamic limit. The novel dynamics of the boundary spin is accompanied by a rich structure of entanglement in the Floquet eigenstates where specific bipartitions yield an area-law scaling while the entanglement for random bipartitions scales as a volume-law., Comment: 22 pages, 15 figures, 1 table
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- 2023
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4. Quantum state complexity meets many-body scars
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Nandy, Sourav, Mukherjee, Bhaskar, Bhattacharyya, Arpan, and Banerjee, Aritra
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Quantum Physics ,Condensed Matter - Quantum Gases ,Condensed Matter - Statistical Mechanics ,Condensed Matter - Strongly Correlated Electrons ,High Energy Physics - Theory - Abstract
Scar eigenstates in a many-body system refers to a small subset of non-thermal finite energy density eigenstates embedded into an otherwise thermal spectrum. This novel non-thermal behaviour has been seen in recent experiments simulating a one-dimensional PXP model with a kinetically-constrained local Hilbert space realized by a chain of Rydberg atoms. We probe these small sets of special eigenstates starting from particular initial states by computing the spread complexity associated to time evolution of the PXP hamiltonian. Since the scar subspace in this model is embedded only loosely, the scar states form a weakly broken representation of the Lie Algebra. We demonstrate why a careful usage of the Forward Scattering Approximation (or similar strategies thereof) is required to extract an appropriate set of Lanczos coefficients in this case as the consequence of this approximate symmetry. This leads to a well defined notion of a closed Krylov subspace and consequently, that of spread complexity. We show how the spread complexity shows approximate revivals starting from both $|\mathbb{Z}_2\rangle$ and $|\mathbb{Z}_3\rangle$ states and how these revivals can be made more accurate by adding optimal perturbations to the bare Hamiltonian. We also investigate the case of the vacuum as the initial state, where revivals can be stabilized using an iterative process of adding few-body terms., Comment: 19 pages, 11 figures
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- 2023
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5. Real space thermalization of locally driven quantum magnets
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Melendrez, Ronald, Mukherjee, Bhaskar, Sharma, Prakash, Pal, Arijeet, and Changlani, Hitesh J.
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Statistical Mechanics ,Quantum Physics - Abstract
Thermalization and its breakdown in isolated systems has led to a deeper understanding of non-equilibrium quantum states and their dependence on initial conditions. This is prominently highlighted by the existence of quantum scars, special athermal states with an underlying effective superspin structure, embedded in an otherwise chaotic many-body spectrum. Spin $XXZ$ models and their variants in one and higher dimension have been shown to host exact quantum scars, exhibiting perfect revivals of spin helix states that are realizable in synthetic and condensed matter systems. Motivated by these advances, we propose experimentally accessible local, time-dependent protocols to explore the spatial thermalization profile and highlight how different parts of the system thermalize and affect the fate of the superspin. We identify distinct parametric regimes for the ferromagnetic ($X$-polarized) initial state based on the interplay between the driven spin and the rest, including local athermal behavior where the driven spin effectively decouples, acting like a "cold" spot while being instrumental in heating up the other spins. We develop a real and Floquet space picture that explains our numerical observations, and make predictions that can be tested in various experimental setups., Comment: 4+ pages, 4 figures. 2 pages of Supplemental Material
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- 2022
6. Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
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Chattopadhyay, Anwesha, Mukherjee, Bhaskar, Sengupta, K., and Sen, Arnab
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Condensed Matter - Statistical Mechanics - Abstract
We introduce a disorder-free model of $S=1/2$ spins on the square lattice in a constrained Hilbert space where two up-spins are not allowed simultaneously on any two neighboring sites of the lattice. The interactions are given by ring-exchange terms on elementary plaquettes that conserve both the total magnetization as well as dipole moment. We show that this model provides a tractable example of strong Hilbert space fragmentation in two dimensions with typical initial states evading thermalization with respect to the full Hilbert space. Given any product state, the system can be decomposed into disjoint spatial regions made of edge and/or vertex sharing plaquettes that we dub as ``quantum drums''. These quantum drums come in many shapes and sizes and specifying the plaquettes that belong to a drum fixes its spectrum. The spectra of some small drums is calculated analytically. We study two bigger quasi-one-dimensional drums numerically, dubbed ``wire'' and a ``junction of two wires'' respectively. We find that these possess a chaotic spectrum but also support distinct families of quantum many-body scars that cause periodic revivals from different initial states. The wire is shown to be equivalent to the one-dimensional PXP chain with open boundaries, a paradigmatic model for quantum many-body scarring; while the junction of two wires represents a distinct constrained model., Comment: v3: 57 pages, 30 figs; resubmission to SciPost Physics
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- 2022
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7. Driving quantum many-body scars in the PXP model
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Hudomal, Ana, Desaules, Jean-Yves, Mukherjee, Bhaskar, Su, Guo-Xian, Halimeh, Jad C., and Papić, Zlatko
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Condensed Matter - Quantum Gases ,Condensed Matter - Strongly Correlated Electrons ,Quantum Physics - Abstract
Periodic driving has been established as a powerful technique for engineering novel phases of matter and intrinsically out-of-equilibrium phenomena such as time crystals. Recent work by Bluvstein et al. [Science 371, 1355 (2021)] has demonstrated that periodic driving can also lead to a significant enhancement of quantum many-body scarring, whereby certain non-integrable systems can display persistent quantum revivals from special initial states. Nevertheless, the mechanisms behind driving-induced scar enhancement remain poorly understood. Here we report a detailed study of the effect of periodic driving on the PXP model describing Rydberg atoms in the presence of a strong Rydberg blockade - the canonical static model of quantum many-body scarring. We show that periodic modulation of the chemical potential gives rise to a rich phase diagram, with at least two distinct types of scarring regimes that we distinguish by examining their Floquet spectra. We formulate a toy model, based on a sequence of square pulses, that accurately captures the details of the scarred dynamics and allows for analytical treatment in the large-amplitude and high-frequency driving regimes. Finally, we point out that driving with a spatially inhomogeneous chemical potential allows to stabilize quantum revivals from arbitrary initial states in the PXP model, via a mechanism similar to prethermalization., Comment: 21 pages, 17 figures
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- 2022
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8. Periodically driven Rydberg chains with staggered detuning
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Mukherjee, Bhaskar, Sen, Arnab, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons ,Quantum Physics - Abstract
We study the stroboscopic dynamics of a periodically driven finite Rydberg chain with staggered ($\Delta$) and time-dependent uniform ($\lambda(t)$) detuning terms using exact diagonalization (ED). We show that at intermediate drive frequencies ($\omega_D$), the presence of a finite $\Delta$ results in violation of the eigenstate thermalization hypothesis (ETH) via clustering of Floquet eigenstates. Such clustering is lost at special commensurate drive frequencies for which $\hbar \omega_d=n \Delta$ ($n \in Z$) leading to restoration of ergodicity. The violation of ETH in these driven finite-sized chains is also evident from the dynamical freezing displayed by the density-density correlation function at specific $\omega_D$. Such a correlator exhibits stable oscillations with perfect revivals when driven close to the freezing frequencies for initial all spin-down ($|0\rangle$) or Neel ($|{\mathbb Z}_2\rangle$, with up-spins on even sites) states. The amplitudes of these oscillations vanish at the freezing frequencies and reduces upon increasing $\Delta$; their frequencies, however, remains pinned to $\Delta/\hbar$ in the large $\Delta$ limit. In contrast, for the $|{\bar {\mathbb Z}_2}\rangle$ (time-reversed partner of $|{\mathbb Z}_2\rangle$) initial state, we find complete absence of such oscillations leading to freezing for a range of $\omega_D$; this range increases with $\Delta$. We also study the properties of quantum many-body scars in the Floquet spectrum of the model as a function of $\Delta$ and show the existence of novel mid-spectrum scars at large $\Delta$. We supplement our numerical results with those from an analytic Floquet Hamiltonian computed using Floquet perturbation theory (FPT) and also provide a semi-analytic computation of the quantum scar states within a forward scattering approximation (FSA)., Comment: v1; 19 pages, 19 figs
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- 2021
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9. Minimal model for Hilbert space fragmentation with local constraints
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Mukherjee, Bhaskar, Banerjee, Debasish, Sengupta, K., and Sen, Arnab
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Condensed Matter - Strongly Correlated Electrons ,High Energy Physics - Lattice ,Quantum Physics - Abstract
Motivated by previous works on a Floquet version of the PXP model [Mukherjee {\it et al.} Phys. Rev. B 102, 075123 (2020), Mukherjee {\it et al.} Phys. Rev. B 101, 245107 (2020)], we study a one-dimensional spin-$1/2$ lattice model with three-spin interactions in the same constrained Hilbert space (where all configurations with two adjacent $S^z=\uparrow$ spins are excluded). We show that this model possesses an extensive fragmentation of the Hilbert space which leads to a breakdown of thermalization upon unitary evolution starting from a large class of simple initial states. Despite the non-integrable nature of the Hamiltonian, many of its high-energy eigenstates admit a quasiparticle description. A class of these, which we dub as "bubble eigenstates", have integer eigenvalues (including mid-spectrum zero modes) and strictly localized quasiparticles while another class contains mobile quasiparticles leading to a dispersion in momentum space. Other anomalous eigenstates that arise due to a {\it secondary} fragmentation mechanism, including those that lead to flat bands in momentum space due to destructive quantum interference, are also discussed. The consequences of adding a (non-commuting) staggered magnetic field and a PXP term respectively to this model, where the former preserves the Hilbert space fragmentation while the latter destroys it, are discussed. A Floquet version with time-dependent staggered field also evades thermalization with additional features like freezing of exponentially many states at special drive frequencies. Finally, we map the model to a $U(1)$ lattice gauge theory coupled to dynamical fermions and discuss the interpretation of some of these anomalous states in this language. A class of gauge-invariant states show reduced mobility of the elementary charged excitations with only certain charge-neutral objects being mobile suggesting a connection to fractons., Comment: v3; 22 pages, 11 figures, corrected some typos, close to published version
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- 2021
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10. Constraint-induced breaking and restoration of ergodicity in spin-1 PXP models
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Mukherjee, Bhaskar, Cai, Zi, and Liu, W. Vincent
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Quantum Physics ,Condensed Matter - Statistical Mechanics - Abstract
Eigenstate Thermalization Hypothesis(ETH) has played a pivotal role in understanding ergodicity and its breaking in isolated quantum many-body systems. Recent experiment on 51-atom Rydberg quantum simulator and subsequent theoretical analysis have shown that hardcore kinetic constraint can lead to weak ergodicity breaking. In this work, we demonstrate, using 1d spin-1 PXP chains, that miscellaneous type of ergodicity can be realized by adjusting the hardcore constraints between different components of nearest neighbor spins. This includes ETH violation due to emergent shattering of Hilbert space into exponentially many subsectors of various sizes, a novel form of non-integrability with an extensive number of local conserved quantities and strong ergodicity. We analyze these different forms of ergodicity and study their impact on the non-equilibrium dynamics of a Z2 initial state. We use forward scattering approximation (FSA) to understand the amount of Z2-oscillation present in these models. Our work shows that not only ergodicity breaking but an appropriate choice of constraints can lead to restoration of ergodicity as well.
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- 2021
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11. Order by disorder in frustration-free systems: a Quantum Monte Carlo study of a two-dimensional PXP model
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Yue, Mingxi, Wang, Zijian, Mukherjee, Bhaskar, and Cai, Zi
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Quantum Gases - Abstract
In this study, an order by disorder mechanism has been proposed in a two-dimensional PXP model, where the extensive degeneracy of the classical ground-state manifold is due to strict occupation constraints instead of geometrical frustrations. By performing an unbias large-scale quantum monte carlos simulation, we find that local quantum fluctuations, which usually work against long-range ordering, lift the macroscopic classical degeneracy and give rise to a compressible ground state with charge-density-wave long-range order. A simple trial wavefunction has been proposed to capture the essence of the ground-state of the two-dimensional PXP model. The finite temperature properties of this model have also been studied, and we find a thermal phase transition with an universality class of two-dimensional Ising model., Comment: 4 pages
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- 2021
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12. A Floquet perturbation theory for periodically driven weakly-interacting fermions
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Ghosh, Roopayan, Mukherjee, Bhaskar, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We compute the Floquet Hamiltonian $H_F$ for weakly interacting fermions subjected to a continuous periodic drive using a Floquet perturbation theory (FPT) with the interaction amplitude being the perturbation parameter. This allows us to address the dynamics of the system at intermediate drive frequencies $\hbar \omega_D \ge V_0 \ll {\mathcal J}_0$, where ${\mathcal J}_0$ is the amplitude of the kinetic term, $\omega_D$ is the drive frequency, and $V_0$ is the typical interaction strength between the fermions. We compute, for random initial states, the fidelity $F$ between wavefunctions after a drive cycle obtained using $H_F$ and that obtained using exact diagonalization (ED). We find that FPT yields a substantially larger value of $F$ compared to its Magnus counterpart for $V_0\le \hbar \omega_D$ and $V_0\ll {\mathcal J}_0$. We use the $H_F$ obtained to study the nature of the steady state of an weakly interacting fermion chain; we find a wide range of $\omega_D$ which leads to subthermal or superthermal steady states for finite chains. The driven fermionic chain displays perfect dynamical localization for $V_0=0$; we address the fate of this dynamical localization in the steady state of a finite interacting chain and show that there is a crossover between localized and delocalized steady states. We discuss the implication of our results for thermodynamically large chains and chart out experiments which can test our theory., Comment: 11 pages,8 figures
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- 2020
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13. Dynamics of the vacuum state in a periodically driven Rydberg chain
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Mukherjee, Bhaskar, Sen, Arnab, Sen, Diptiman, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons ,Quantum Physics - Abstract
We study the dynamics of the periodically driven Rydberg chain starting from the state with zero Rydberg excitations (vacuum state denoted by $|0\rangle$) using a square pulse protocol in the high drive amplitude limit. We show, using exact diagonalization for finite system sizes ($L\le 26$), that the Floquet Hamiltonian of the system, within a range of drive frequencies which we chart out, hosts a set of quantum scars which have large overlap with the $|0\rangle$ state. These scars are distinct from their counterparts having high overlap with the maximal Rydberg excitation state ($|\mathbb{Z}_2\rangle$); they coexist with the latter class of scars and lead to persistent coherent oscillations of the density-density correlator starting from the $|0\rangle$ state. We also identify special drive frequencies at which the system undergoes perfect dynamic freezing and provide an analytic explanation for this phenomenon. Finally, we demonstrate that for a wide range of drive frequencies, the system reaches a steady state with sub-thermal values of the density-density correlator. The presence of such sub-thermal steady states, which are absent for dynamics starting from the $|\mathbb{Z}_2\rangle$ state, imply a weak violation of the eigenstate thermalization hypothesis in finite sized Rydberg chains distinct from that due to the scar-induced persistent oscillations reported earlier. We conjecture that in the thermodynamic limit such states may exist as pre-thermal steady states that show anomalously slow relaxation. We supplement our numerical results by deriving an analytic expression for the Floquet Hamiltonian using a Floquet perturbation theory in the high amplitude limit which provides an analytic, albeit qualitative, understanding of these phenomena at arbitrary drive frequencies. We discuss experiments which can test our theory., Comment: 18 pages and 17 figures including appendices
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- 2020
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14. Restoring coherence via aperiodic drives in a many-body quantum system
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Mukherjee, Bhaskar, Sen, Arnab, Sen, Diptiman, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons ,Quantum Physics - Abstract
We study the unitary dynamics of randomly or quasi-periodically driven tilted Bose-Hubbard (tBH) model in one dimension deep inside its Mott phase starting from a $\mathbb{Z}_2$ symmetry-broken state. The randomness is implemented via a telegraph noise protocol in the drive period while the quasi-periodic drive is chosen to correspond to a Thue-Morse sequence. The periodically driven tBH model (with a square pulse protocol characterized by a time period $T$) is known to exhibit transitions from dynamical regimes with long-time coherent oscillations to those with rapid thermalization. Here we show that starting from a regime where the periodic drive leads to rapid thermalization, a random drive, which consists of a random sequence of square pulses with period $T+\alpha dT$, where $\alpha=\pm 1$ is a random number and $dT$ is the amplitude of the noise, restores long-time coherent oscillations for special values of $dT$. A similar phenomenon can be seen for a quasi-periodic drive following a Thue-Morse sequence where such coherent behavior is shown to occur for a larger number of points in the $(T, dT)$ plane due to the additional structure of the drive protocol. We chart out the dynamics of the system in the presence of such aperiodic drives, provide a qualitative analytical understanding of this phenomenon, point out the role of quantum scars behind it, and discuss experiments which can test our theory., Comment: v2; 10 pages, 11 Figs; references corrected
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- 2020
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15. Collapse and revival of quantum many-body scars via Floquet engineering
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Mukherjee, Bhaskar, Nandy, Sourav, Sen, Arnab, Sen, Diptiman, and Sengupta, K.
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Quantum Physics ,Condensed Matter - Quantum Gases ,Condensed Matter - Statistical Mechanics - Abstract
The presence of quantum scars, athermal eigenstates of a many-body Hamiltonian with finite energy density, leads to absence of ergodicity and long-time coherent dynamics in closed quantum systems starting from simple initial states. Such non-ergodic coherent dynamics, where the system does not explore its entire phase space, has been experimentally observed in a chain of ultracold Rydberg atoms. We show, via study of a periodically driven Rydberg chain, that the drive frequency acts as a tuning parameter for several reentrant transitions between ergodic and non-ergodic regimes. The former regime shows rapid thermalization of correlation functions and absence of scars in the spectrum of the system's Floquet Hamiltonian. The latter regime, in contrast, has scars in its Floquet spectrum which control the long-time coherent dynamics of correlation functions. Our results open a new possibility of drive frequency-induced tuning between ergodic and non-ergodic dynamics in experimentally realizable disorder-free quantum many-body systems., Comment: v2; 14 pages and 8 figures including supplementary material. Expanded version with additional results and discussions; a co-author added
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- 2019
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16. Floquet topological transition by unpolarized light
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Mukherjee, Bhaskar
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Condensed Matter - Other Condensed Matter - Abstract
We study Floquet topological transition in irradiated graphene when the polarization of incident light changes randomly with time. We numerically confirm that the noise averaged time evolution operator approaches a steady value in the limit of exact Trotter decomposition of the whole period where incident light has different polarization at each interval of the decomposition. This steady limit is found to coincide with time-evolution operator calculated from the noise-averaged Hamiltonian. We observe that at the six corners (Dirac($K$) point) of the hexagonal Brillouin zone of graphene random Gaussian noise strongly modifies the phaseband structure induced by circularly polarized light whereas in zone-center ($\Gamma$ point) even a strong noise isn't able to do the same. This can be understood by analyzing the deterministic noise averaged Hamiltonian which has a different Fourier structure as well as lesser no of symmetries compared to the noise-free one. In 1D systems noise is found to renormalize the drive amplitude only., Comment: 8 Pages, 8 figures
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- 2018
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17. Comparing Research Topics through Metatags Analysis: A Multi-module Machine Algorithm Approaches Using Real World Data on Digital Humanities
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Mukherjee, Bhaskar, primary, Majhi, Debasis, additional, Tiwari, Priya, additional, and Chaudhary, Saloni, additional
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- 2024
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18. Cerebral Venous Sinus Thrombosis Complicating Herpes Zoster Ophthalmicus Ophthalmoplegia
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Ali, Meithem, primary, Obiechina, Nonyelum, additional, Ling, Kay Teck, additional, Nandi, Angela, additional, and Mukherjee, Bhaskar, additional
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- 2024
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19. Low-frequency phase diagram of irradiated graphene and periodically driven spin-1/2 $XY$ chain
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Mukherjee, Bhaskar, Mohan, Priyanka, Sen, Diptiman, and Sengupta, K.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We study the Floquet phase diagram of two-dimensional Dirac materials such as graphene and the one-dimensional (1D) spin-1/2 $XY$ model in a transverse field in the presence of periodic time-varying terms in their Hamiltonians in the low drive frequency ($\omega$) regime where standard $1/\omega$ perturbative expansions fail. For graphene, such periodic time dependent terms are generated via the application of external radiation of amplitude $A_0$ and time period $T = 2\pi/\omega$, while for the 1D $XY$ model, they result from a two-rate drive protocol with time-dependent magnetic field and nearest-neighbor couplings between the spins. Using the adiabatic-impulse method, we provide several semi-analytic criteria for the occurrence of changes in the topology of the phase bands of such systems. For irradiated graphene, we point out the role of the symmetries of $H(t)$ and $U$ behind such topology changes. Our analysis reveals that at low frequencies, phase band topology changes may also happen at $t= T/3, 2T/3$ (apart from $t=T$). We chart out the phase diagrams at $t=T/3, 2T/3,\, {\rm and }\, T$ as a function of $A_0$ and $T$ using exact numerics, and compare them with the prediction of the adiabatic-impulse method. We show that several characteristics of these phase diagrams can be analytically understood from results obtained using the adiabatic-impulse method and point out the crucial contribution of the high-symmetry points in the graphene Brillouin zone to these diagrams. Finally we study the 1D $XY$ model with a two-rate driving protocol using the adiabatic-impulse method and exact numerics revealing a phase band crossing at $t=T/2$ and $k=\pi/2$. We also study the anomalous end modes generated by such a drive. We suggest experiments to test our theory., Comment: v1; 26 pages, 19 Figs
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- 2017
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20. Bosons with incommensurate potential and spin-orbit coupling
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Ray, Sayak, Mukherjee, Bhaskar, Sinha, S., and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We chart out the phase diagram of ultracold `spin-half' bosons in a one-dimensional optical lattice in the presence of Aubry-Andr\'e (AA) potential and with spin-orbit (SO) and Raman couplings investigating the transition from superfluid (SF) to localized phases and the existence of density wave phase for nearest-neighbor interaction (NNI). We show that the presence of SO coupling and AA potential leads to a novel spin-split momentum distribution of the bosons in the localized phase near the boundary with the SF phase, which can act as a signature of such a transition. We also obtain the level statistics of the bosons in the superfluid phase with finite NNI and demonstrate its change from Gaussian Unitary Ensemble (GUE) to Gaussian Orthogonal Ensemble (GOE) as a function of the Raman coupling. We discuss experiments which can test our theory., Comment: 4 pages, 4 Figs, Supplementary material; v1
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- 2017
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21. Signatures and conditions for phase band crossings in periodically driven integrable systems
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Mukherjee, Bhaskar, Sen, Arnab, Sen, Diptiman, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We present generic conditions for phase band crossings for a class of periodically driven integrable systems represented by free fermionic models subjected to arbitrary periodic drive protocols characterized by a frequency $\omega_D$. These models provide a representation for the Ising and $XY$ models in $d=1$, the Kitaev model in $d=2$, several kinds of superconductors, and Dirac fermions in graphene and atop topological insulator surfaces. Our results demonstrate that the presence of a critical point/region in the system Hamiltonian (which is traversed at a finite rate during the dynamics) may change the conditions for phase band crossings that occur at the critical modes. We also show that for $d>1$, phase band crossings leave their imprint on the equal-time off-diagonal fermionic correlation functions of these models; the Fourier transforms of such correlation functions, $F_{\vec k_0}( \omega_0)$, have maxima and minima at specific frequencies which can be directly related to $\omega_D$ and the time at which the phase bands cross at $\vec k = \vec k_0$. We discuss the significance of our results in the contexts of generic Hamiltonians with $N>2$ phase bands and the underlying symmetry of the driven Hamiltonian., Comment: v1; 7 figs, 12 pages
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- 2016
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22. Tuning towards dynamic freezing using a two-rate protocol
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Kar, Satyaki, Mukherjee, Bhaskar, and Sengupta, K.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We study periodically driven closed quantum systems where two parameters of the system Hamiltonian are driven with frequencies $\omega_1$ and $\omega_2=r \omega_1$. We show that such drives may be used to tune towards dynamics induced freezing where the wavefunction of the state of the system after a drive cycle at time $T= 2\pi/\omega_1$ has almost perfect overlap with the initial state. We locate regions in the $(\omega_1 ,r)$ plane where the freezing is near exact for a class of integrable and a specific non-integrable model. The integrable models that we study encompass Ising and XY models in $d=1$, Kitaev model in $d=2$, and Dirac fermions in graphene and atop a topological insulator surface whereas the non-integrable model studied involves the experimentally realized one-dimensional (1D) tilted Bose-Hubbard model in an optical lattice. In addition, we compute the relevant correlation functions of such driven systems and describe their characteristics in the region of $(\omega_1,r)$ plane where the freezing is near-exact. We supplement our numerical analysis with semi-analytic results for integrable driven systems within adiabatic-impulse approximation and discuss experiments which may test our theory., Comment: v1: 9 pages 9 figs
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- 2016
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23. Inflammatory Markers in Patients With Major Depressive Disorder: A Prospective, Clinic-Based, Cohort Study From India
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Mandal, Sucharita, primary, Spoorthy, Mamidipalli Sai, additional, Godi, Sangha Mitra, additional, Nanda, Rachita, additional, Mukherjee, Bhaskar, additional, and Mishra, Nihar Ranjan, additional
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- 2023
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24. Strong Hilbert space fragmentation via emergent quantum drums in two dimensions
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Chattopadhyay, Anwesha, primary, Mukherjee, Bhaskar, additional, Sengupta, Krishnendu, additional, and Sen, Arnab, additional
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- 2023
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25. Comparing research trends through author-provided keywords with machine extracted terms: A ML algorithm approach using publications data on neurological disorders
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Tiwari, Priya, primary, Chaudhary, Saloni, additional, Majhi, Debasis, additional, and Mukherjee, Bhaskar, additional
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- 2023
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26. Measuring scientific value of Indian journals beyond impact factor: a case with physics–chemistry–biology journals
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Mukherjee, Bhaskar
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- 2018
27. Automatic extraction of significant terms from the title and abstract of scientific papers using the machine learning algorithm: A multiple module approach.
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Mukherjee, Bhaskar and Majhi, Debasis
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MACHINE learning , *NATURAL language processing , *TERMS & phrases , *KEYWORDS - Abstract
Keyword extraction is the task of identifying important terms or phrase that are most representative of the source document. Although the process of automatic extraction of keywords from title is an old method, it was mainly for extraction from a single web document. Our approach differs from previous research works on keyword extraction in several aspects. For those who are non-expert of the scientific fields, understating scientific research trends is difficult. The purpose of this study is to develop an automatic method of obtaining overviews of a scientific field for non-experts by capturing research trends. This empirical study excavates significant term extraction using Natural Language Processing (NLP) tools. More than 15000 titles saved in a .csv file was our dataset and scripts written in Python were our process to compare how far significant terms of scientific title corpus are similar or different to the terms available in the abstract of that same scientific article corpus. A light-weight unsupervised title extractor, Yet Another Keyword Extractor (YAKE) was used to extract the results. Based on our analysis, it can be concluded that these algorithms can be used for other fields too by the non-experts of that subject field to perform automatic extraction of significant words and understanding trends. Our algorithm could be a solution to reduce the labour-intensive manual indexing process. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
28. Evaluating the research performance of women scientists in Indian research laboratories based on Scopus citation database: A bibliometric analysis
- Author
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Mukherjee, Bhaskar, primary
- Published
- 2022
- Full Text
- View/download PDF
29. Perceptions of engineering faculty members regarding research collaborations.
- Author
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Mukherjee, Bhaskar and Tiwari, Priya
- Subjects
- *
ACADEMIC-industrial collaboration , *ENGINEERING teachers , *CITATION analysis - Abstract
The purpose of this study is to connect the perceptions and understanding of the collaboration of faculty members of NIRF ranked top-performing engineering institutes with the publication they have. The quantitative bibliometric analysis along with the enquiry with authors show that national collaboration, mainly with academic authors of same or other institution, still is a preferred. Despite international collaboration leading to more average citations, there is no significant gain seen. Scholars collaborate for many reasons, but mostly to gain popularity among peers or to receive citation benefits. Collaboration with private or government organizations, although uncommon, is primarily used to test newly developed ideas or to provide consultancy. Most of the respondents believe that funding is important for research collaborations and low commitment of team members to the shared goal is a major barrier in collaboration. We argue that as the share of University-Industry-Government research collaborations is low, a strong congruence between knowledge capital and entrepreneurial capital is needed to develop an entrepreneurial university. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
30. Constraint-induced breaking and restoration of ergodicity in spin-1 PXP models
- Author
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Mukherjee, Bhaskar, primary, Cai, Zi, additional, and Liu, W. Vincent, additional
- Published
- 2021
- Full Text
- View/download PDF
31. A TLD-Microdosimeter for aerospace usage: Results relevant to airline pilots undertook long-haul intercontinental flights during March–May 2017
- Author
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Mukherjee, Bhaskar, Woda, Clemens, and Mares, Vladimir
- Published
- 2020
- Full Text
- View/download PDF
32. How collaborative is Indian academia? A case study of top three ranked institutions.
- Author
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Mukherjee, Bhaskar and Singh, Ankit
- Subjects
- *
BIBLIOMETRICS , *EMPLOYMENT , *PEARSON correlation (Statistics) - Abstract
The present study employs bibliometric methods to examine the pattern of existing collaboration in India's top three ranked academic institutes using publications indexed in the Web of Science for the period 2000 to 2020. The results show although the number of collaborations and the degree of collaboration have increased over time, however, the collaboration coefficient remains almost the same in the three institutes. The lesser negative Pearson correlation between authors and articles with a higher positive Pearson correlation between articles and citations for JNU publications suggests that collaboration with a smaller group is more successful than a larger group for gaining citations. Collaborative publications of Banaras Hindu University (36%) and Indian Institute of Science (33%) are more inclined towards authors of the same department, while for Jawaharlal Nehru University, it is with other authors from different universities (41%). The foreign collaboration for all three institutes is almost the same. The network visualization of collaboration in three institutes suggests that the collaborative research in IISc is more diverse than JNU or BHU and in national collaboration, distance between two national organizations also play an important role for strong collaboration. Overall, theoretical aspects of physics lead in collaborative publications followed by chemical sciences. Agricultural biotechnology, clinical medicine, polymer sciences and nanoscience are some emerging disciplines where organizations are increasing their participation through collaborative research. [ABSTRACT FROM AUTHOR]
- Published
- 2022
33. Not All Facial Droops Are Stroke: Miller Fisher Syndrome Presenting as a Stroke Mimic
- Author
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Kamarul Bahrin, Muhammad Hafiz, primary, Abidi, Syed Muhammad Ali, additional, Ling, Kayteck, additional, and Mukherjee, Bhaskar, additional
- Published
- 2020
- Full Text
- View/download PDF
34. Analysis of Global Research Trends in Coronaviruses: A Bibliometric Investigation
- Author
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Mukherjee, Bhaskar, primary
- Published
- 2020
- Full Text
- View/download PDF
35. Response to letter to the editor: Perspectives, attitude and practice of lithium prescription among psychiatrists in India
- Author
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Mamidipalli, SpoorthySai, primary, Mandal, Sucharita, additional, Mukherjee, Bhaskar, additional, and Suchandra, KHari Hara, additional
- Published
- 2020
- Full Text
- View/download PDF
36. Publication pattern expressed by scientific position, service tenure, and age -- A comparative analysis with working women scientists of science and technology laboratories of India.
- Author
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Mukherjee, Bhaskar
- Subjects
- *
WOMEN scientists , *COMPARATIVE studies , *SCIENTOMETRICS - Abstract
This study investigates the effect of scientific position, service tenure, and age of women scientists of various research laboratories of the Ministry of Science and Technology, Government of India on the research productivity. Drawing on a sample of 902 women scientists of various research laboratories, with their 22,617 publications extracted from Web of Science & Scopus databases, the results show that CSIR scientists have more women per laboratory, DST women scientists have more publication per scientists and DBT women scientists received more citations. The majority of the publications were published by scientists who have post-doctoral or doctorate degrees and most of the papers were published by the women scientists between age 31 and 40. However, per scientist publication reveals that there is a continuous increase of publication with the increase of service and physical age. Therefore, better funding opportunities for young researchers and retaining experienced women scientists for more years may be important to increase women's participation in science. [ABSTRACT FROM AUTHOR]
- Published
- 2021
37. KOLI-2018 - a real-time Gamma Dosimeter for XFEL usingRadiochromic Film
- Author
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Hoffmann, Markus and Mukherjee, Bhaskar
- Abstract
29 pp. (2019)., Sensitive electronics equipment ist installed in the XFEL main linac tunnel. Although it is sufficiently shielded, it is mandatory to carefully observe the dose rate by radiation produced by the accelerating cavities and beam losses. In the undulator sections of the XFEL highly intense synchroton light could damage the undulator magnets. Gamma doses of 1 to 100 Gy per year are expected. We evaluate a new simple and relatively cheap dosimeter system based on the DESY patent Nr. 10 2007 056989, which can measure the integral gamma dose independant of the pulse structure of the accelerator up to 50 Gy. This dosimeter type (called gamma cube) can be readout remotely at any time to perform an online dosimetry on gamma radiation induced by multiple effects including beam losses. We describe the technical details of a prototype setup and present measurements on the acuracy of the measurement.
- Published
- 2019
38. Inconsistencies in the retrieval of Indic names in Web of Science: a case study of women authors.
- Author
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Mukherjee, Bhaskar and Gangopadhyay, Subrata
- Subjects
- *
WOMEN authors , *BIBLIOGRAPHICAL searching - Abstract
The present study is an attempt to show the variations in search results retrieved for Indic women names in the Web of Science database. A sample of almost 50 women names was identified from official websites of scientific organizations of India. The names were explored through the 'Basic' as well as 'Author' Search field of Web of Science. The results show a wide variation in search results for Author search and Basic search. Several cases were observed where two author records on the same name and affiliation with a different set of publications came in search results. The study suggests that for getting accurate results searching through hyperlinked author names available in the bibliographic details of an author's publication led to best results. The study further suggests that while submitting publication, journals may ask the authors to input primary element, secondary element, and auxiliary-element of author's names instead of surname/last name and first name/given-name/forename. Additional Tab asking how the author would like to render his/her name in the article may be added to the journal submission page so that indexing databases can correctly capture records. [ABSTRACT FROM AUTHOR]
- Published
- 2021
39. Correlation between serum progesterone level on the day of ovulation trigger during In vitro fertilization and its effect on treatment outcome
- Author
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Talwar, Pankaj, primary, Nagaraja, N, additional, Mukherjee, Bhaskar, additional, and Chakrabarty, BarunKumar, additional
- Published
- 2019
- Full Text
- View/download PDF
40. Perspectives, attitude, and practice of lithium prescription among psychiatrists in India
- Author
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Mamidipalli, SpoorthySai, primary, Mandal, Sucharita, additional, Mukherjee, Bhaskar, additional, and Hara, SuchandraK Hari, additional
- Published
- 2019
- Full Text
- View/download PDF
41. Perspectives, attitude, and practice of lithium prescription among psychiatrists in India.
- Author
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Mandal, Sucharita, Mamidipalli, Spoorthy Sai, Mukherjee, Bhaskar, and Hari Hara, Suchandra K.
- Subjects
INTELLECT ,INTERNET ,LITHIUM ,MEDICAL prescriptions ,PATIENT compliance ,PSYCHIATRISTS ,QUESTIONNAIRES ,COMORBIDITY ,PSYCHOSOCIAL factors ,DESCRIPTIVE statistics - Abstract
The article discusses perspectives, attitude, and practice of lithium prescription among psychiatrists in India. Topics include Lithium remains the medication that has approved by the Food and Drug Administration for maintenance treatment of bipolar disorder; and lithium as an augmenting agent for treatment‑resistant depression, around 50% of the psychiatrists have comfortable in prescribing lithium.
- Published
- 2019
- Full Text
- View/download PDF
42. Measuring Scientific Value of Indian Journals Beyond Impact Factor:A Case with Physics–Chemistry–Biology Journals
- Author
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Mukherjee, Bhaskar, primary
- Published
- 2018
- Full Text
- View/download PDF
43. A Case of Early Onset Subacute Sclerosing Panencephalitis Presented as Juvenile Myoclonic Epilepsy
- Author
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Bhattacharyya, Ranjan, primary, Mukherjee, Bhaskar, additional, and Bhattacharyya, Sumita, additional
- Published
- 2017
- Full Text
- View/download PDF
44. Correlation between Serum Progesterone Level on the Day of Ovulation Trigger During In vitro Fertilization and Its Effect on Treatment Outcome.
- Author
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N., Nagaraja, Talwar, Pankaj, Mukherjee, Bhaskar, and Chakrabarty, Barun Kumar
- Subjects
FERTILIZATION in vitro ,OVULATION ,PROGESTERONE ,GONADOTROPIN ,INDUCED ovulation ,CHORIONIC gonadotropins ,TREATMENT effectiveness ,OVUM donation - Abstract
Background: Premature luteinization (PL) is defined as a premature rise in serum progesterone concentration on or before the day of ovulation trigger with human chorionic gonadotropin. The incidence of PL varies between 5% and 30% during in vitro fertilization and embryo transfer (IVF-ET). Materials and Methods: The prospective observational study comprising 380 patients undergoing IVF-ET. Blood samples were collected for serum progesterone level estimation on the day of ovulation trigger. Ovum pickup was done 36 h later and serum progesterone levels were correlated with IVF-ET outcome. Study Outcome: To correlate serum progesterone level on the day of ovulation trigger during IVF and its effect on treatment outcome. Results: Mean serum progesterone level in the positive pregnancy group and negative pregnancy group was 0.892 ± 0.752 ng/ml and 0.91 ± 0.688 ng/ml, respectively (P = 0.961). The overall incidence of PL was 12.8% with 12.7% and 13.6% in the agonist and antagonist protocol respectively (P = 0.9001). PL incidence was 13.5% and 13.4% in positive pregnancy and negative pregnancy group (P = 0.223). Conclusion: PL has been associated with 12.8% of the IVF cycles. There was no statistically significant difference observed in the incidence of PL between different IVF stimulation protocols. PL does not seem to affect IVF outcome. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
45. Congenital erythropoietic porphyria: Insight into the molecular basis of the disease
- Author
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Harith, ArunKumar, primary, Arora, Sandeep, additional, Kapoor, Seema, additional, and Mukherjee, Bhaskar, additional
- Published
- 2016
- Full Text
- View/download PDF
46. 'Military Superbug' Acinetobacter Baumanii Induced Sepsis in Craniofacial Gunshot Injuries.
- Author
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Khan, I. Danish, Gupta, Rajiv Mohan, Sen, Sourav, Sahni, Ajay Kumar, Khan, Shazia, Jindal, Ashok Kumar, Mukherjee, Bhaskar, Sashindran, V. K., Hashmi, Syed Asif, and Rajmohan, K. S.
- Subjects
ACINETOBACTER infections ,EMERGENCY medical services ,GUNSHOT wounds ,MILITARY medicine ,SEPSIS ,TREATMENT effectiveness - Abstract
Background Craniofacial gunshot injuries encountered during counter-insurgency/counter-terrorism operations are involved in a situational complexity requiring astute battlefield care, evacuation, operative management and critical life support. Secondary infections by 'military superbug' Acinetobacter baumanii complicating to sepsis can jeopardize survival. Cases Two combatants sustained craniofacial gunshot injuries during counter-insurgency/counter-terrorism operations in hilly jungle terrain of South-Asia. Having survived through initial assault of the gunshot and resuscitation, they were tactically evacuated on ventilator support to tertiary care. In the backdrop of tissue devitalization, hemodynamic and renal compromise, extensive surgical and critical care interventions, secondary infection by multidrug resistant Acinetobacter baumanii led to sepsis and demise. Conclusions Craniofacial gunshot wounds in the battlefield can initiate a domino effect leading to physiological complications which can predispose to secondary infections, leading to sepsis and demise. Acinetobacter baumanii known to survive in environmental reservoirs, can cause bacteremia and sepsis in gunshot, warfare injuries and natural disasters. A prudent emphasis on secondary and opportunistic infections in battlefield and hospital care is mandated to optimize outcome in gunshot injuries. [ABSTRACT FROM AUTHOR]
- Published
- 2018
47. LIS journals in India: Current status and some improvement measures.
- Author
-
Mukherjee, Bhaskar and Vishwakarma, Priyanka
- Subjects
- *
LIBRARY science periodicals , *INFORMATION science periodicals , *PERIODICAL publishing , *PUBLISHING , *CITATION analysis , *SUBSCRIPTIONS to serial publications , *BIBLIOGRAPHIC databases - Abstract
The paper identifies the present status of journal publishing in India in the field of library & information science. Identification of journals were made by consulting various sources. The characteristics of the journals have been studied on various parameters like number of years of existence, type of publisher, accessibility, references and citation characteristics, etc. Of the total 72 identified journals, it was observed that almost 70% journals started their publication from 2000 onwards. About 81% journals are available on subscription basis. Print as well as online format for dissemination of research have been adopted by 59% journals, however, 30% journals are still available only in print form. It is seen that private or profit-making (59%) organizations are more interested to publish LIS journals than non-profit making organizations (41%). One of the major drawbacks of Indian LIS journals is there poor visibility and limited coverage in various bibliographical databases. More than 54% journals are not indexed in any important bibliographic database and only 6 journals are indexed in LISA, LISTA or ILSA. The citation statistics of these journals are not satisfactory as 42 journals did not receive any citations for their articles published during 2011-2013. At the end, the study suggests a few measures for improving the quality of journal in LIS domain. [ABSTRACT FROM AUTHOR]
- Published
- 2014
48. Response to letter to the editor: Perspectives, attitude and practice of lithium prescription among psychiatrists in India.
- Author
-
Mandal, Sucharita, Mamidipalli, Spoorthy, Mukherjee, Bhaskar, and Suchandra, K
- Subjects
DRUG prescribing ,EXPERIMENTAL design ,LITHIUM ,MEDICAL prescriptions ,SURVEYS ,PHYSICIAN practice patterns - Published
- 2020
- Full Text
- View/download PDF
49. Correlation between Serum Progesterone Level on the Day of Ovulation Trigger During In vitro Fertilization and Its Effect on Treatment Outcome.
- Author
-
Nagaraja N, Talwar P, Mukherjee B, and Chakrabarty BK
- Abstract
Background: Premature luteinization (PL) is defined as a premature rise in serum progesterone concentration on or before the day of ovulation trigger with human chorionic gonadotropin. The incidence of PL varies between 5% and 30% during in vitro fertilization and embryo transfer (IVF-ET)., Materials and Methods: The prospective observational study comprising 380 patients undergoing IVF-ET. Blood samples were collected for serum progesterone level estimation on the day of ovulation trigger. Ovum pickup was done 36 h later and serum progesterone levels were correlated with IVF-ET outcome., Study Outcome: To correlate serum progesterone level on the day of ovulation trigger during IVF and its effect on treatment outcome., Results: Mean serum progesterone level in the positive pregnancy group and negative pregnancy group was 0.892 ± 0.752 ng/ml and 0.91 ± 0.688 ng/ml, respectively ( P = 0.961). The overall incidence of PL was 12.8% with 12.7% and 13.6% in the agonist and antagonist protocol respectively ( P = 0.9001). PL incidence was 13.5% and 13.4% in positive pregnancy and negative pregnancy group ( P = 0.223)., Conclusion: PL has been associated with 12.8% of the IVF cycles. There was no statistically significant difference observed in the incidence of PL between different IVF stimulation protocols. PL does not seem to affect IVF outcome., Competing Interests: There are no conflicts of interest.
- Published
- 2019
- Full Text
- View/download PDF
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