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Photoacoustics Apr 2023Longitudinal acoustic modes in planar thin gold films are excited and detected by a combination of ultrafast pump-probe photoacoustic spectroscopy and a surface plasmon...
Longitudinal acoustic modes in planar thin gold films are excited and detected by a combination of ultrafast pump-probe photoacoustic spectroscopy and a surface plasmon resonance (SPR) technique. The resulting high sensitivity allows the detection of acoustic modes up to the 7th harmonic (258 GHz) with sub-pm amplitude sensing capabilities. This makes a comparison of damping times of individual modes possible. Further, the dynamics of the real and imaginary part of the dielectric function and the film's thickness variation are separated by using the dependence of the amplitudes of the acoustic modes on the detection angle and the surface plasmon resonance. We find that longitudinal acoustic modes in the gold films mainly affect the real part of the dielectric function and highlight the importance to consider thickness related effects in acousto-plasmonic sensing.
PubMed: 36936710
DOI: 10.1016/j.pacs.2023.100464 -
Biochemistry and Biophysics Reports Jul 2016Electropermeabilization of cell membranes by micro- and nanosecond-duration stimuli has been studied extensively, whereas effects of picosecond electric pulses (psEP)...
Electropermeabilization of cell membranes by micro- and nanosecond-duration stimuli has been studied extensively, whereas effects of picosecond electric pulses (psEP) remain essentially unexplored. We utilized whole-cell patch clamp and Di-8-ANEPPS voltage-sensitive dye measurements to characterize plasma membrane effects of 500 ps stimuli in rat hippocampal neurons (RHN), NG108, and CHO cells. Even a single 500-ps pulse at 190 kV/cm increased membrane conductance and depolarized cells. These effects were augmented by applying brief psEP bursts (5-125 pulses), whereas the rate of pulse delivery (8Hz - 1 kHz) played little role. psEP-treated cells displayed large inward current at negative membrane potentials but modest or no conductance changes at positive potentials. A 1-kHz burst of 25 pulses increased the whole-cell conductance in the range (-100) - (-60) mV to 22-26 nS in RHN and NG108 cells (from 3 and 0.7 nS, respectively), but only to 5 nS in CHO (from 0.3 nS). The conductance increase was reversible within about 2 min. Such pattern of cell permeabilization, with characteristic inward rectification and slow recovery, was similar to earlier reported effects of 60- and 600-ns pulses, pointing to the similarity of structural membrane rearrangements in spite of a different membrane charging mechanism.
PubMed: 27482547
DOI: 10.1016/j.bbrep.2016.05.002 -
Lasers in Surgery and Medicine Jan 2018The picosecond 755 nm alexandrite laser using a diffractive lens array has demonstrated consistent clinical efficacy for improving the appearance of acne scarring and...
OBJECTIVE
The picosecond 755 nm alexandrite laser using a diffractive lens array has demonstrated consistent clinical efficacy for improving the appearance of acne scarring and wrinkles amongst other benefits. This small pilot study is to assess the difference, if any, in clinical benefit if a higher than the standard protocol for number of pulses delivered to a tissue area is used compared to the standard protocol guidelines.
METHOD
Seven subjects received treatment to one side of the face with a standard protocol number of laser pulses with the other side of the face receiving higher than standard number of pulses from the same 755 nm picosecond laser using an additional diffractive lens array. Photographs at final follow up were compared to baseline by two blinded Board Certified Dermatologists and assessed for improvements to acne scarring using a 6-point grading score, for wrinkles using the Fitzpatrick Wrinkle & Elastosis 3-point grading scale and a Global Aesthetic Improvement Scale assessment. Subjects also completed a satisfaction questionnaire.
RESULTS
For the acne scarring subjects, the average improvement from baseline to final follow up was 4.0 +/- 1.0 for the standard treated side and 4.5 +/- 0.5 for the high pulse side. There was no statistically significant difference between the two treated sides (P > 0.05, n = 3 paired t-test). For the wrinkle subjects, the average grading of the standard pulse side improved from 2.0 +/- 0.82 to 1.75 +/- 1.0 from baseline to final follow-up. The high pulse side improved from 1.5 +/- 1.0 to 1.125 +/- 0.25 from baseline to final follow-up. There was no statistically significant difference between the improvement of the standard and high pulse treatment sides (P > 0.05, n = 4 paired t-test). The comparison of baseline to final follow-up images of each subject found both sides to be Much or Very Much improved with no statistically significant difference between the standard and high pulse sides (P > 0.05, n = 7 paired t-test). Six of the seven subjects did not note any difference between the effect on different sides of the face and four of the seven rated their overall improvement after treatment as Good, three subjects as Reasonable and one subject with Slight Improvement. All subjects found the treatment comfortable and easy to tolerate and there was no increased incidence of side effects other than the mild occurrences typically observed for this type of treatment.
CONCLUSION
This is a small pilot study with limited subject numbers and further data is needed to be able to make firm conclusions of observed trends, which suggest that the use of higher than standard suggested protocol number of pulses with the diffractive lens array and the 755 nm picosecond laser does not appear to offer any additional benefit over that that can already be achieved with the standard number of pulses, but also does not increase risk of detrimental post treatment effects either. Lasers Surg. Med. 50:51-55, 2018. © 2017 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
Topics: Acne Vulgaris; Adult; Aged; Cicatrix; Face; Female; Follow-Up Studies; Humans; Lasers, Solid-State; Low-Level Light Therapy; Male; Middle Aged; Patient Satisfaction; Pilot Projects; Skin Aging; Time Factors; Treatment Outcome
PubMed: 29140537
DOI: 10.1002/lsm.22763 -
Photoacoustics Jun 2023Colored Picosecond Acoustics (CPA) and Spectroscopic Ellipsometry (SE) are combined to measure elastic and thermoelastic properties of polymer thin-film resins deposited...
Colored Picosecond Acoustics (CPA) and Spectroscopic Ellipsometry (SE) are combined to measure elastic and thermoelastic properties of polymer thin-film resins deposited on 300 mm wafers. Film thickness and refractive index are measured using SE. Sound velocity and thickness are measured using CPA from the refractive index. Comparing the two thicknesses allows checking consistency between both approaches. The same combination is then applied at various temperatures from 19° to 180°C. As the sample is heated, both thickness and sound velocity change. By monitoring these contributions separately, the Temperature Coefficient on sound Velocity (TCV) and the Coefficient on Thermal Expansion are deduced. The protocol is applied to five industrial samples made of different thin-film resins currently used by microelectronic industry. Young's modulus varies from resin to resin by up to 20%. TCV is large on each resin and varies from one resin to another up to 57%.
PubMed: 37152401
DOI: 10.1016/j.pacs.2023.100498 -
BioRxiv : the Preprint Server For... Nov 2023Water inside biological ion channels regulates the key properties of these proteins such as selectivity, ion conductance, and gating. In this Article we measure the...
Water inside biological ion channels regulates the key properties of these proteins such as selectivity, ion conductance, and gating. In this Article we measure the picosecond spectral diffusion of amide I vibrations of an isotope labeled KcsA potassium channel using two-dimensional infrared (2D IR) spectroscopy. By combining waiting time (100 - 2000 fs) 2D IR measurements of the KcsA channel including CO isotope labeled Val76 and Gly77 residues with molecular dynamics simulations, we elucidated the site-specific dynamics of water and K ions inside the selectivity filter of KcsA. We observe inhomogeneous 2D lineshapes with extremely slow spectral diffusion. Our simulations quantitatively reproduce the experiments and show that water is the only component with any appreciable dynamics, whereas K ions and the protein are essentially static on a picosecond timescale. By analyzing simulated and experimental vibrational frequencies, we find that water in the selectivity filter can be oriented to form hydrogen bonds with adjacent, or non-adjacent carbonyl groups with the reorientation timescales being three times slower and comparable to that of water molecules in liquid, respectively. Water molecules can reside in the cavity sufficiently far from carbonyls and behave essentially like "free" gas-phase-like water with fast reorientation times. Remarkably, no interconversion between these configurations were observed on a picosecond timescale. These dynamics are in stark contrast with liquid water that remains highly dynamic even in the presence of ions at high concentrations.
PubMed: 38014355
DOI: 10.1101/2023.11.16.567415 -
Journal of the American Chemical Society Jul 2017Proteins are dynamic entities and populate ensembles of conformations. Transitions between states within a conformational ensemble occur over a broad spectrum of...
Proteins are dynamic entities and populate ensembles of conformations. Transitions between states within a conformational ensemble occur over a broad spectrum of amplitude and time scales, and are often related to biological function. Whereas solid-state NMR (SSNMR) spectroscopy has recently been used to characterize conformational ensembles of proteins in the microcrystalline states, its applications to membrane proteins remain limited. Here we use SSNMR to study conformational dynamics of a seven-helical transmembrane (TM) protein, Anabaena Sensory Rhodopsin (ASR) reconstituted in lipids. We report on site-specific measurements of the N longitudinal R and rotating frame R relaxation rates at two fields of 600 and 800 MHz and at two temperatures of 7 and 30 °C. Quantitative analysis of the R and R values and of their field and temperature dependencies provides evidence of motions on at least two time scales. We modeled these motions as fast local motions and slower collective motions of TM helices and of structured loops, and used the simple model-free and extended model-free analyses to fit the data and estimate the amplitudes, time scales and activation energies. Faster picosecond (tens to hundreds of picoseconds) local motions occur throughout the protein and are dominant in the middle portions of the TM helices. In contrast, the amplitudes of the slower collective motions occurring on the nanosecond (tens to hundreds of nanoseconds) time scales, are smaller in the central parts of helices, but increase toward their cytoplasmic sides as well as in the interhelical loops. ASR interacts with a soluble transducer protein on its cytoplasmic surface, and its binding affinity is modulated by light. The larger amplitude of motions on the cytoplasmic side of the TM helices correlates with the ability of ASR to undergo large conformational changes in the process of binding/unbinding the transducer.
Topics: Anabaena; Molecular Dynamics Simulation; Nuclear Magnetic Resonance, Biomolecular; Protein Conformation, alpha-Helical; Sensory Rhodopsins
PubMed: 28613900
DOI: 10.1021/jacs.7b03974 -
Proceedings of the National Academy of... Sep 2023The dynamics of lattice vibrations govern many material processes, such as acoustic wave propagation, displacive phase transitions, and ballistic thermal transport. The...
The dynamics of lattice vibrations govern many material processes, such as acoustic wave propagation, displacive phase transitions, and ballistic thermal transport. The maximum velocity of these processes and their effects is determined by the speed of sound, which therefore defines the temporal resolution (picoseconds) needed to resolve these phenomena on their characteristic length scales (nanometers). Here, we present an X-ray microscope capable of imaging acoustic waves with subpicosecond resolution within mm-sized crystals. We directly visualize the generation, propagation, branching, and energy dissipation of longitudinal and transverse acoustic waves in diamond, demonstrating how mechanical energy thermalizes from picosecond to microsecond timescales. Bulk characterization techniques capable of resolving this level of structural detail have previously been available on millisecond time scales-orders of magnitude too slow to capture these fundamental phenomena in solid-state physics and geoscience. As such, the reported results provide broad insights into the interaction of acoustic waves with the structure of materials, and the availability of ultrafast time-resolved dark-field X-ray microscopy opens a vista of new opportunities for 3D imaging of materials dynamics on their intrinsic submicrosecond time scales.
PubMed: 37725646
DOI: 10.1073/pnas.2307049120 -
Scientific Reports Dec 2019Phase change memory (PCM) offers remarkable features such as high-speed and non-volatility for universal memory. Yet, simultaneously achieving better thermal stability...
Phase change memory (PCM) offers remarkable features such as high-speed and non-volatility for universal memory. Yet, simultaneously achieving better thermal stability and fast switching remains a key challenge. Thus, exploring novel materials with improved characteristics is of utmost importance. We report here, a unique property-portfolio of high thermal stability and picosecond threshold switching characteristics in InSbTe (IST) PCM devices. Our experimental findings reveal an improved thermal stability of amorphous IST compared to most other phase change materials. Furthermore, voltage dependent threshold switching and current-voltage characteristics corroborate an extremely fast, yet low electric field threshold switching operation within an exceptionally small delay time of less than 50 picoseconds. The combination of low electric field and high speed switching with improved thermal stability of IST makes the material attractive for next-generation high-speed, non-volatile memory applications.
PubMed: 31848416
DOI: 10.1038/s41598-019-55874-5 -
Annals of Translational Medicine May 2021Laser treatment of acne scars is common, but quality evidence on its efficacy is still needed. Our study aimed to compare picosecond laser and non-ablative fractional...
Comparison of fractionated frequency-doubled 1,064/532 nm picosecond Nd:YAG lasers and non-ablative fractional 1,540 nm Er: glass in the treatment of facial atrophic scars: a randomized, split-face, double-blind trial.
BACKGROUND
Laser treatment of acne scars is common, but quality evidence on its efficacy is still needed. Our study aimed to compare picosecond laser and non-ablative fractional laser's efficacy and safety in treating acne atrophic scars.
METHODS
This was a randomized, split-face double-blind trial recruiting patients with acne atrophic scars. Facial halves were randomly divided and treated with fractionated frequency-doubled 1,064/532 nm picosecond Nd:YAG laser or non-ablative fractional 1,540 nm Er: glass laser. ECCA score (echelle d'evaluation clinique des cicatrices d'acne) and skin flatness measured with a non-invasive phaseshift rapid in vivo measurement of skin (PRIMOS) system were evaluated one month after the last treatment.
RESULTS
Twenty-two Fitzpatrick skin type IV patients were included in this study, with an average age of 29.68 years, an average duration of acne scars of 8.8 years. Picosecond laser impacted all acne scar types (before and after treatment; P=0.000 for all types, P<0.001 for V-type, P=0.002 for U-type, and P=0.021 for M-type) and more pronounced effect on ECCA score than non-ablative laser for V-type and U-type acne scars. After treatment, each treatment site's height was significantly lower than that before treatment (P=0.041) in the picosecond group but not in the non-ablative group (P=0.785). The reported erythema rate was higher in patients treated with a picosecond laser, while edema, exudation, purpura, pain, and long-term AEs were similar between the groups.
CONCLUSIONS
Fractionated frequency-doubled 1,064/532 nm Picosecond Nd: YAG laser showed better efficacy in treating acne atrophic scars than the alternative and provided satisfactory safety with added improvement in pores and the glossiness of the skin.
REGISTRATION NUMBER
ChiCTR2100045982 (comparison of fractionated frequency-doubled 1,064/532 nm picosecond Nd: YAG lasers and nonablative fractional 1,540 nm Er: glass in the treatment of facial atrophic scar: a randomized, split-face, double-blind controlled trial).
PubMed: 34164496
DOI: 10.21037/atm-21-1715 -
Proceedings of the National Academy of... Apr 2022Intense light–matter interactions and unique structural and electrical properties make van der Waals heterostructures composed by graphene (Gr) and monolayer...
Intense light–matter interactions and unique structural and electrical properties make van der Waals heterostructures composed by graphene (Gr) and monolayer transition metal dichalcogenides (TMD) promising building blocks for tunneling transistors and flexible electronics, as well as optoelectronic devices, including photodetectors, photovoltaics, and quantum light emitting devices (QLEDs), bright and narrow-line emitters using minimal amounts of active absorber material. The performance of such devices is critically ruled by interlayer interactions which are still poorly understood in many respects. Specifically, two classes of coupling mechanisms have been proposed, charge transfer (CT) and energy transfer (ET), but their relative efficiency and the underlying physics are open questions. Here, building on a time-resolved Raman scattering experiment, we determine the electronic temperature profile of Gr in response to TMD photoexcitation, tracking the picosecond dynamics of the G and 2D Raman bands. Compelling evidence for a dominant role of the ET process accomplished within a characteristic time of ∼4 ps is provided. Our results suggest the existence of an intermediate process between the observed picosecond ET and the generation of a net charge underlying the slower electric signals detected in optoelectronic applications.
PubMed: 35380900
DOI: 10.1073/pnas.2119726119