Demonstration of Dynamics of Nanosecond Discharge in Liquid Water Using Four-Channel Time-Resolved ICCD Microscopy

The microscopic physical mechanisms of micro-discharges produced in liquid waters by nanosecond high-voltage pulses are quite complex phenomena, and relevant coherent experimentally supported theoretical descriptions are yet to be provided. In this study, by combining a long-distance microscope with a four-channel image splitter fitted with four synchronised intensified charge-coupled device detectors, we obtained and analysed sequences of microscopic discharge images acquired with sub-nanosecond temporal resolution during a single event. We tracked luminous filaments either through monochromatic images at two specific wavelengths (532 and 656 nm) or through broadband integrated UV–vis–near infrared (NIR) discharge emission. An analysis of the sequences of images capturing discharge filaments in subsequent time windows facilitated the tracking of movement of the luminous fronts during their expansion. The velocity of expansion progressively decreased from the maximum of ~2.3 × 105 m/s observed close to the anode pin until the propagation stopped due to the drop in the anode potential. We demonstrate the basic features characterising the development of the luminous discharge filaments. Our study provides an important insight into the dynamics of micro-discharges during the primary and successive reflected high-voltage pulses in de-ionised water.

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Sub-nanosecond time resolved light emission study for diffuse discharges in air under steep high voltage pulses

Plasma Sources Science and Technology ◽

10.1088/0963-0252/25/5/054005 ◽

2016 ◽

Vol 25 (5) ◽

pp. 054005 ◽

Cited By ~ 34

Author(s):

P Tardiveau ◽

L Magne ◽

E Marode ◽

K Ouaras ◽

P Jeanney ◽

...

Keyword(s):

High Voltage ◽

Light Emission ◽

Time Resolved ◽

Voltage Pulses ◽

Emission Study

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Dynamics of human neurovascular coupling resolved in the millisecond range using dc-magnetoencephalography and time-resolved near-infrared spectroscopy

Klinische Neurophysiologie ◽

10.1055/s-2008-1072924 ◽

2008 ◽

Vol 39 (01) ◽

Author(s):

S Leistner ◽

T Sander-Thoemmes ◽

H Wabnitz ◽

M Burghoff ◽

L Trahms ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Neurovascular Coupling ◽

Time Resolved ◽

Millisecond Range

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Spatiotemporal tracing of pandemic spread from infection data

Scientific Reports ◽

10.1038/s41598-021-97207-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Satyaki Roy ◽

Preetom Biswas ◽

Preetam Ghosh

Keyword(s):

New York ◽

Network Inference ◽

Spatial Interaction ◽

Time Windows ◽

New York State ◽

Mitigation Measures ◽

Contact Tracing ◽

Long Distance ◽

Spatiotemporal Models ◽

Spread Of Infection

AbstractCOVID-19, a global pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 virus, has claimed millions of lives worldwide. Amid soaring contagion due to newer strains of the virus, it is imperative to design dynamic, spatiotemporal models to contain the spread of infection during future outbreaks of the same or variants of the virus. The reliance on existing prediction and contact tracing approaches on prior knowledge of inter- or intra-zone mobility renders them impracticable. We present a spatiotemporal approach that employs a network inference approach with sliding time windows solely on the date and number of daily infection numbers of zones within a geographical region to generate temporal networks capturing the influence of each zone on another. It helps analyze the spatial interaction among the hotspot or spreader zones and highly affected zones based on the flow of network contagion traffic. We apply the proposed approach to the daily infection counts of New York State as well as the states of USA to show that it effectively measures the phase shifts in the pandemic timeline. It identifies the spreaders and affected zones at different time points and helps infer the trajectory of the pandemic spread across the country. A small set of zones periodically exhibit a very high outflow of contagion traffic over time, suggesting that they act as the key spreaders of infection. Moreover, the strong influence between the majority of non-neighbor regions suggests that the overall spread of infection is a result of the unavoidable long-distance trips by a large number of people as opposed to the shorter trips at a county level, thereby informing future mitigation measures and public policies.

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Real-time observation of tetrapyrrole binding to an engineered bacterial phytochrome

Communications Chemistry ◽

10.1038/s42004-020-00437-3 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Yusaku Hontani ◽

Mikhail Baloban ◽

Francisco Velazquez Escobar ◽

Swetta A. Jansen ◽

Daria M. Shcherbakova ◽

...

Keyword(s):

Real Time ◽

Rational Design ◽

Near Infrared ◽

Fluorescent Proteins ◽

Covalent Bond ◽

Binding Pocket ◽

Tissue Imaging ◽

Covalent Attachment ◽

Time Resolved

AbstractNear-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes are widely used for structural and functional deep-tissue imaging in vivo. To fluoresce, NIR FPs covalently bind a chromophore, such as biliverdin IXa tetrapyrrole. The efficiency of biliverdin binding directly affects the fluorescence properties, rendering understanding of its molecular mechanism of major importance. miRFP proteins constitute a family of bright monomeric NIR FPs that comprise a Per-ARNT-Sim (PAS) and cGMP-specific phosphodiesterases - Adenylyl cyclases - FhlA (GAF) domain. Here, we structurally analyze biliverdin binding to miRFPs in real time using time-resolved stimulated Raman spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. Biliverdin undergoes isomerization, localization to its binding pocket, and pyrrolenine nitrogen protonation in <1 min, followed by hydrogen bond rearrangement in ~2 min. The covalent attachment to a cysteine in the GAF domain was detected in 4.3 min and 19 min in miRFP670 and its C20A mutant, respectively. In miRFP670, a second C–S covalent bond formation to a cysteine in the PAS domain occurred in 14 min, providing a rigid tetrapyrrole structure with high brightness. Our findings provide insights for the rational design of NIR FPs and a novel method to assess cofactor binding to light-sensitive proteins.

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Giant enhancement of THz-frequency optical nonlinearity by phonon polariton in ionic crystals

Nature Communications ◽

10.1038/s41467-021-23526-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yao Lu ◽

Qi Zhang ◽

Qiang Wu ◽

Zhigang Chen ◽

Xueming Liu ◽

...

Keyword(s):

Near Infrared ◽

Optical Nonlinearity ◽

Ionic Crystals ◽

Nonlinear Optical Susceptibility ◽

Time Resolved ◽

Light Coupling ◽

Tremendous Progress ◽

Fundamental Research ◽

Ionic Contribution ◽

Time Resolved Imaging

AbstractThe field of nonlinear optics has grown substantially in past decades, leading to tremendous progress in fundamental research and revolutionized applications. Traditionally, the optical nonlinearity for a light wave at frequencies beyond near-infrared is observed with very high peak intensity, as in most materials only the electronic nonlinearity dominates while ionic contribution is negligible. However, it was shown that the ionic contribution to nonlinearity can be much larger than the electronic one in microwave experiments. In the terahertz (THz) regime, phonon polariton may assist to substantially trigger the ionic nonlinearity of the crystals, so as to enhance even more the nonlinear optical susceptibility. Here, we experimentally demonstrate a giant second-order optical nonlinearity at THz frequency, orders of magnitude higher than that in the visible and microwave regimes. Different from previous work, the phonon-light coupling is achieved under a phase-matching setting, and the dynamic process of nonlinear THz generation is directly observed in a thin-film waveguide using a time-resolved imaging technique. Furthermore, a nonlinear modification to the Huang equations is proposed to explain the observed nonlinearity enhancement. This work brings about an effective approach to achieve high nonlinearity in ionic crystals, promising for applications in THz nonlinear technologies.

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Susceptibility of 100Base-T1 Communication Lines to Coupled Fast Switching High-Voltage Pulses

2020 International Symposium on Electromagnetic Compatibility - EMC EUROPE ◽

10.1109/emceurope48519.2020.9245650 ◽

2020 ◽

Author(s):

S. Jeschke ◽

J. Loos ◽

M. Kleinen ◽

O. Kurt ◽

J. Barenfanger ◽

...

Keyword(s):

High Voltage ◽

Fast Switching ◽

Voltage Pulses ◽

Communication Lines

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Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties

International Journal of Molecular Sciences ◽

10.3390/ijms22094465 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4465

Author(s):

Krystian Mokrzynski ◽

Shosuke Ito ◽

Kazumasa Wakamatsu ◽

Theodore G. Camenish ◽

Tadeusz Sarna ◽

...

Keyword(s):

Chemical Composition ◽

Singlet Oxygen ◽

Near Infrared ◽

Paramagnetic Resonance ◽

Time Resolved ◽

W Band ◽

Epr Oximetry ◽

X Band ◽

Hair Samples ◽

Electron Paramagnetic

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.

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A Versatile Setup for Time-Resolved Functional Near Infrared Spectroscopy Based on Fast-Gated Single-Photon Avalanche Diode and on Four-Wave Mixing Laser

Applied Sciences ◽

10.3390/app9112366 ◽

2019 ◽

Vol 9 (11) ◽

pp. 2366 ◽

Cited By ~ 2

Author(s):

Laura Di Sieno ◽

Alberto Dalla Mora ◽

Alessandro Torricelli ◽

Lorenzo Spinelli ◽

Rebecca Re ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Single Photon ◽

Wave Mixing ◽

Functional Near Infrared Spectroscopy ◽

Time Resolved ◽

Diffusive Medium ◽

Spectroscopy System

In this paper, a time-domain fast gated near-infrared spectroscopy system is presented. The system is composed of a fiber-based laser providing two pulsed sources and two fast gated detectors. The system is characterized on phantoms and was tested in vivo, showing how the gating approach can improve the contrast and contrast-to-noise-ratio for detection of absorption perturbation inside a diffusive medium, regardless of source-detector separation.

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