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  1. Article ; Online: An adaptive excitation source for high-speed multiphoton microscopy.

    Li, Bo / Wu, Chunyan / Wang, Mengran / Charan, Kriti / Xu, Chris

    Nature methods

    2019  Volume 17, Issue 2, Page(s) 163–166

    Abstract: Optical imaging is important for understanding brain function. However, established methods with high spatiotemporal resolution are limited by the potential for laser damage to living tissues. We describe an adaptive femtosecond excitation source that ... ...

    Abstract Optical imaging is important for understanding brain function. However, established methods with high spatiotemporal resolution are limited by the potential for laser damage to living tissues. We describe an adaptive femtosecond excitation source that only illuminates the region of interest, which leads to a 30-fold reduction in the power requirement for two- or three-photon imaging of brain activity in awake mice for improved high-speed longitudinal neuroimaging.
    MeSH term(s) Action Potentials ; Animals ; Mice ; Microscopy/methods ; Neuroimaging/methods ; Neurons/physiology ; Photons
    Language English
    Publishing date 2019-12-02
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 2169522-2
    ISSN 1548-7105 ; 1548-7091
    ISSN (online) 1548-7105
    ISSN 1548-7091
    DOI 10.1038/s41592-019-0663-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Predictive Value of Chest CT Score in Assessing Disease Severity and Short-term Mortality in COVID-19 Pneumonia at a Tertiary Care Centre in Northern India

    Pradeep Kumar Roul / Ashish Kaushik / Poonam Sherwani / Kriti Yadav / Aditi Saini / O Budha Charan Singh / Anjum Syed / Prasan Kumar Panda

    Journal of Clinical and Diagnostic Research, Vol 16, Iss 3, Pp TC05-TC

    A Prospective Observational Study

    2022  Volume 11

    Abstract: Introduction: Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection, also known as Coronavirus Disease-2019 (COVID-19) is the global pandemic, first described in Wuhan city of China in December 2019. Its diagnosis depends upon real time ... ...

    Abstract Introduction: Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection, also known as Coronavirus Disease-2019 (COVID-19) is the global pandemic, first described in Wuhan city of China in December 2019. Its diagnosis depends upon real time Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). On chest Computerised Tomography (CT), it is almost similar to other viral pneumonia with extensive parenchymal involvement. Semiquantitative scores depicting this extensiveness of involvement could correlate with disease severity, laboratory parameters, mortality like Intensive Care Unit (ICU) admission, requirements of ventilatory support and longer hospital stay. Aim: To define the role of chest CT score in determining disease severity, predicting poor prognosis and mortality of COVID-19 pneumonia in short-term follow-up. Materials and Methods: This prospective study enrolled 547 admitted real time RT-PCR positive patients for COVID-19 at All India Institute of Medical Sciences, Rishikesh, India from 15th April 2021 to 31st May 2021. All patients were assigned semi-quantitative CT scores based on the extent of lung parenchymal involvement of 20 lung regions in chest CT. Finally, 205 patients were enrolled for the final analysis. Clinical severity was matched with chest CT scoring and laboratory findings. Survival curves along with univariate and multivariate analysis was applied to define the role of CT scoring in predicting short-term prognosis. Results: Total 205 subjects were included in the study, of which the chest CT score showed a significant association with clinical severities (p-value <0.001). CT score was correlating significantly with increased serum C-Reactive Protein (CRP) (p-value=0.001) and D-dimer (p-value=0.01), and decreased lymphocyte count (p-value <0.001). A CT score ≥31 was found to be associated with an increased risk of mortality in both univariate and multivariate analysis {Odd Ratio (OR)=276.8; 95% Confidence Interval (CI)=45.21-1695.43; p-value <0.001}. Conclusion: ...
    Keywords coronavirus disease-19 ; computed tomography severity score ; ground glass opacity ; Medicine ; R
    Subject code 610
    Language English
    Publishing date 2022-03-01T00:00:00Z
    Publisher JCDR Research and Publications Private Limited
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article: Fiber-based tunable repetition rate source for deep tissue two-photon fluorescence microscopy.

    Charan, Kriti / Li, Bo / Wang, Mengran / Lin, Charles P / Xu, Chris

    Biomedical optics express

    2018  Volume 9, Issue 5, Page(s) 2304–2311

    Abstract: Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We ... ...

    Abstract Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We show that the ideal repetition rate for deep two-photon imaging in the mouse brain is between 1 and 10 MHz, and we present a fiber-based source with an arbitrarily tunable repetition rate within this range. The performance of the new source is compared to a mode-locked Ti:Sapphire (Ti:S) laser for
    Language English
    Publishing date 2018-04-23
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2572216-5
    ISSN 2156-7085
    ISSN 2156-7085
    DOI 10.1364/BOE.9.002304
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Investigation of the long wavelength limit of soliton self-frequency shift in a silica fiber.

    Li, Bo / Wang, Mengran / Charan, Kriti / Li, Ming-Jun / Xu, Chris

    Optics express

    2018  Volume 26, Issue 15, Page(s) 19637–19647

    Abstract: We explore the long wavelength limit of soliton self-frequency shift in silica-based fibers experimentally and using numerical simulation. We found that the longest wavelength soliton generated by soliton self-frequency shift is approximately 2500 nm ... ...

    Abstract We explore the long wavelength limit of soliton self-frequency shift in silica-based fibers experimentally and using numerical simulation. We found that the longest wavelength soliton generated by soliton self-frequency shift is approximately 2500 nm because the soliton loses its energy rapidly at wavelength beyond 2400 nm due to material absorption by silica and water. We demonstrate 1580-2520 nm wavelength-tunable, high-pulse energy soliton generation using soliton self-frequency shift in a large-mode-area silica fiber pumped by a compact fiber source. Soliton pulses with pulse width of ~100 fs and pulse energy up to 73 nJ were obtained. Second harmonic generation of the solitons enables a wavelength-tunable femtosecond source from 950 nm to 1260 nm, with pulse energy up to 21 nJ. Using such energetic pulses, we demonstrate in vivo two-photon excited fluorescence imaging of vasculature and neurons in a mouse brain at wavelength beyond the tuning range of a mode-locked Ti:Sapphire lasers.
    Language English
    Publishing date 2018-08-16
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.26.019637
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Characterization and adaptive compression of a multi-soliton laser source.

    Rasskazov, Gennady / Ryabtsev, Anton / Charan, Kriti / Wang, Tianyu / Xu, Chris / Dantus, Marcos

    Optics express

    2017  Volume 25, Issue 1, Page(s) 320–329

    Abstract: Ultrashort pulse generation in the 1600 nm wavelength region is required for deep-tissue biomedical imaging. We report on the characterization and adaptive compression of a multi-soliton output spanning >300 nm from a large-mode area photonic-crystal ... ...

    Abstract Ultrashort pulse generation in the 1600 nm wavelength region is required for deep-tissue biomedical imaging. We report on the characterization and adaptive compression of a multi-soliton output spanning >300 nm from a large-mode area photonic-crystal fiber rod for two separate laser setups. Sub-30 fs pulses are generated by first compressing of each soliton individually, and then followed by coherently combining all of the pulses in the train, which are separated by hundreds of femtoseconds. Simulations of the source, together with amplitude and phase coherence measurements are provided.
    Language English
    Publishing date 2017-01-13
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.25.000320
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Nonresonant background suppression for coherent anti-Stokes Raman scattering microscopy using a multi-wavelength time-lens source.

    Li, Bo / Charan, Kriti / Wang, Ke / Rojo, Tomás / Sinefeld, David / Xu, Chris

    Optics express

    2016  Volume 24, Issue 23, Page(s) 26687–26695

    Abstract: We demonstrate a robust, all-fiber, two-wavelength time-lens source for background-free coherent anti-Stokes Raman scattering imaging. The time-lens source generates two picosecond pulse trains simultaneously: one at 1064 nm and the other tunable between ...

    Abstract We demonstrate a robust, all-fiber, two-wavelength time-lens source for background-free coherent anti-Stokes Raman scattering imaging. The time-lens source generates two picosecond pulse trains simultaneously: one at 1064 nm and the other tunable between 1040 nm and 1075 nm (~400 mW for each wavelength). When synchronized to a mode-locked Ti:Sapphire laser, the two wavelengths are used to obtain on- and off-resonance coherent anti-Stokes Raman scattering images. Real-time subtraction of the nonresonant background in the coherent anti-Stokes Raman scattering image is achieved by the synchronization of the pixel clock and the time-lens source. Background-free coherent anti-Stokes Raman scattering imaging of sebaceous glands in ex vivo mouse tissue is demonstrated.
    Language English
    Publishing date 2016-11-09
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.24.026687
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Three-photon excited fluorescence imaging of unstained tissue using a GRIN lens endoscope.

    Huland, David M / Charan, Kriti / Ouzounov, Dimitre G / Jones, Jason S / Nishimura, Nozomi / Xu, Chris

    Biomedical optics express

    2013  Volume 4, Issue 5, Page(s) 652–658

    Abstract: We present a compact and portable three-photon gradient index (GRIN) lens endoscope system suitable for imaging of unstained tissues, potentially deep within the body, using a GRIN lens system of 1 mm diameter and 8 cm length. The lateral and axial ... ...

    Abstract We present a compact and portable three-photon gradient index (GRIN) lens endoscope system suitable for imaging of unstained tissues, potentially deep within the body, using a GRIN lens system of 1 mm diameter and 8 cm length. The lateral and axial resolution in water is 1.0 μm and 9.5 μm, respectively. The ~200 μm diameter field of view is imaged at 2 frames/s using a fiber-based excitation source at 1040 nm. Ex vivo imaging is demonstrated with unstained mouse lung at 5.9 mW average power. These results demonstrate the feasibility of three-photon GRIN lens endoscopy for optical biopsy.
    Language English
    Publishing date 2013-04-01
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2572216-5
    ISSN 2156-7085
    ISSN 2156-7085
    DOI 10.1364/BOE.4.000652
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: Intermodal four-wave mixing in a higher-order-mode fiber.

    Cheng, Ji / Pedersen, Martin E V / Charan, Kriti / Wang, Ke / Xu, Chris / Grüner-Nielsen, Lars / Jakobsen, Dan

    Applied physics letters

    2012  Volume 101, Issue 16, Page(s) 161106

    Abstract: We demonstrate a high-efficiency intermodal four-wave-mixing process in an all-fiber system, comprising a picosecond fiber laser and a high-order-mode (HOM) fiber. Two pump photons in the LP(01) mode of the fiber can generate an anti-Stokes photon in the ...

    Abstract We demonstrate a high-efficiency intermodal four-wave-mixing process in an all-fiber system, comprising a picosecond fiber laser and a high-order-mode (HOM) fiber. Two pump photons in the LP(01) mode of the fiber can generate an anti-Stokes photon in the LP(01) mode and a Stokes photon in the LP(02) mode. The wavelength dependent mode profiles of the HOM fiber produce significant spatial overlap between the modes involved. The anti-Stokes wave at 941 nm is generated with 20% conversion efficiency with input pulse energy of 20 nJ. The guidance of the anti-Stokes and Stokes waves in the HOM fiber enhances system stability.
    Language English
    Publishing date 2012-10-16
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1469436-0
    ISSN 1077-3118 ; 0003-6951
    ISSN (online) 1077-3118
    ISSN 0003-6951
    DOI 10.1063/1.4759038
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  9. Article ; Online: Intermodal Čerenkov radiation in a higher-order-mode fiber.

    Cheng, Ji / Pedersen, Martin E V / Charan, Kriti / Wang, Ke / Xu, Chris / Grüner-Nielsen, Lars / Jakobsen, Dan

    Optics letters

    2012  Volume 37, Issue 21, Page(s) 4410–4412

    Abstract: We demonstrate an intermodal Čerenkov radiation effect in a higher-order-mode (HOM) fiber with a mode crossing (i.e., two guided modes having the same propagation constant at the same wavelength). A frequency-shifted soliton in the vicinity of the mode- ... ...

    Abstract We demonstrate an intermodal Čerenkov radiation effect in a higher-order-mode (HOM) fiber with a mode crossing (i.e., two guided modes having the same propagation constant at the same wavelength). A frequency-shifted soliton in the vicinity of the mode-crossing wavelength emits a phase-matched dispersive wave in a different propagation mode. We develop a theoretical explanation for this nonlinear optical effect and demonstrate that the mode crossing in HOM fibers can be utilized to achieve simultaneous wavelength and mode conversion; the strength of this intermodal nonlinear interaction can be tuned by controlled fiber bending.
    MeSH term(s) Nonlinear Dynamics ; Optical Fibers ; Optical Phenomena ; Silicon Dioxide ; Spectrum Analysis
    Chemical Substances Silicon Dioxide (7631-86-9)
    Language English
    Publishing date 2012-11-01
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.37.004410
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  10. Article ; Online: Time-lens based hyperspectral stimulated Raman scattering imaging and quantitative spectral analysis.

    Wang, Ke / Zhang, Delong / Charan, Kriti / Slipchenko, Mikhail N / Wang, Ping / Xu, Chris / Cheng, Ji-Xin

    Journal of biophotonics

    2013  Volume 6, Issue 10, Page(s) 815–820

    Abstract: We demonstrate a hyperspectral stimulated Raman scattering (SRS) microscope through spectral-transformed excitation. The 1064 nm Stokes pulse was from a synchronized time-lens source, generated through time-domain phase modulation of a continuous wave ( ... ...

    Abstract We demonstrate a hyperspectral stimulated Raman scattering (SRS) microscope through spectral-transformed excitation. The 1064 nm Stokes pulse was from a synchronized time-lens source, generated through time-domain phase modulation of a continuous wave (CW) laser. The tunable pump pulse was from linear spectral filtering of a femtosecond laser output with an intra-pulse spectral scanning pulse shaper. By electronically modulating the time-lens source at 2.29 MHz, hyperspectral stimulated Raman loss (SRL) images were obtained on a laser-scanning microscope. Using this microscope, DMSO in aqueous solution with a concentration down to 28 mM could be detected at 2 μs time constant. Hyperspectral SRL images of prostate cancer cells were obtained. Multivariate curve resolution analysis was further applied to decompose the SRL images into concentration maps of CH₂ and CH₃ bonds. This method offers exciting potential in label-free imaging of live cells using fingerprint Raman bands.
    MeSH term(s) Cell Line, Tumor ; Dimethyl Sulfoxide ; Humans ; Lasers ; Lenses ; Molecular Imaging/instrumentation ; Molecular Imaging/methods ; Multivariate Analysis ; Spectrum Analysis, Raman/instrumentation ; Spectrum Analysis, Raman/methods ; Time Factors
    Chemical Substances Dimethyl Sulfoxide (YOW8V9698H)
    Language English
    Publishing date 2013-07-10
    Publishing country Germany
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2390063-5
    ISSN 1864-0648 ; 1864-063X
    ISSN (online) 1864-0648
    ISSN 1864-063X
    DOI 10.1002/jbio.201300005
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