scholarly journals Thermal laser ablation with tunable lesion size reveals multiple origins of seizure-like convulsions in Caenorhabditis elegans

2021 ◽  
Author(s):  
Anthony D. Fouad ◽  
Alice Liu ◽  
Angelica Du ◽  
Priya D. Bhirgoo ◽  
Christopher Fang-Yen
Keyword(s):  
Laser Ablation ◽  
Ventral Nerve Cord ◽  
High Spatial Resolution ◽  
Laser System ◽  
Laser Pulses ◽  
Lesion Size ◽  
Single Neurons ◽  
C Elegans ◽  
Multiple Origins ◽  
Important Means

AbstractLaser microsurgery has long been an important means of assessing the functions of specific cells and tissues. Most laser ablation systems use short, highly focused laser pulses to create plasma-mediated lesions with dimensions on the order of the wavelength of light. While the small size of the lesion enables ablation with high spatial resolution, it also makes it difficult to ablate larger structures. We developed an infrared laser ablation system capable of thermally lesioning tissues with spot sizes tunable by the duration and amplitude of laser pulses. We used our laser system in the roundworm C. elegans to kill single neurons and to sever the dorsal and ventral nerve cords, structures that are difficult to lesion using a plasma-based ablation system. We used these ablations to investigate the source of convulsions in a gain-of-function mutant for the acetylcholine receptor ACR-2. Severing the ventral nerve cord caused convulsions to occur independently anterior and posterior to the lesion, suggesting that convulsions can arise independently from distinct subsets of the motor circuit.

scholarly journals Thermal laser ablation with tunable lesion size reveals multiple origins of seizure-like convulsions in Caenorhabditis elegans

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anthony D. Fouad ◽  
Alice Liu ◽  
Angelica Du ◽  
Priya D. Bhirgoo ◽  
Christopher Fang-Yen
Keyword(s):  
Laser Ablation ◽  
Ventral Nerve Cord ◽  
High Spatial Resolution ◽  
Laser System ◽  
Laser Pulses ◽  
Lesion Size ◽  
Single Neurons ◽  
C Elegans ◽  
Multiple Origins ◽  
Important Means

AbstractLaser microsurgery has long been an important means of assessing the functions of specific cells and tissues. Most laser ablation systems use short, highly focused laser pulses to create plasma-mediated lesions with dimensions on the order of the wavelength of light. While the small size of the lesion enables ablation with high spatial resolution, it also makes it difficult to ablate larger structures. We developed an infrared laser ablation system capable of thermally lesioning tissues with spot sizes tunable by the duration and amplitude of laser pulses. We used our laser system in the roundworm C. elegans to kill single neurons and to sever the dorsal and ventral nerve cords, structures that are difficult to lesion using a plasma-based ablation system. We used these ablations to investigate the source of convulsions in a gain-of-function mutant for the acetylcholine receptor ACR-2. Severing the ventral nerve cord caused convulsions to occur independently anterior and posterior to the lesion, suggesting that convulsions can arise independently from distinct subsets of the motor circuit.

Femtosecond Laser Ablation of Titanium and Silicon

2000 ◽  
Author(s):  
Mengqi Ye ◽  
Costas P. Grigoropoulos
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Fluence ◽  
Laser System ◽  
Femtosecond Laser Ablation ◽  
Laser Pulses ◽  
Femtosecond Laser Irradiation ◽  
Nanosecond Laser ◽  
Iccd Camera ◽  
Plume Emission

Abstract Femtosecond laser ablation of titanium and silicon samples has been studied via time-of-flight (TOF), emission spectroscopy and microscopy measurement. Laser pulses of around 100 fs (FWHM) at λ = 800 nm were delivered by a Ti:sapphire femtosecond laser system. A vacuum chamber with a base pressure of 10−7 torr was built for ion TOF measurement. These ion TOF spectra were utilized to determine the velocity distribution of the ejected ions. While nanosecond laser ablation typically generates ions of a few tens of eV, femtosecond laser irradiation even at moderate energy densities can produce energetic ions with energies of up to a few keV. The most probable energy of these fast ions is proportional to the laser fluence. The structure and number of peaks of the TOF spectra varies with the laser fluence. Images of plume emission were captured by an intensified CCD (ICCD) camera. The plume emission spectrum was analyzed by a spectrometer. Laser ablated craters were measured by an interferometric microscope and a scanning electron microscope (SEM). Ablation yield was expressed as a function of laser fluence, and number of shots.

scholarly journals Mutations Affecting Nerve Attachment of Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Genetic Loci ◽  
Muscle Attachment ◽  
C Elegans ◽  
Ventral Cord ◽  
Excretory Canal

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.

Fabrication and Characterization of Si Nano-Columns by Femtosecond Laser

2012 ◽  
Vol 16 ◽  
pp. 15-20 ◽  
Author(s):  
Omid Tayefeh Ghalehbeygi ◽  
Vural Kara ◽  
Levent Trabzon ◽  
Selcuk Akturk ◽  
Huseyin Kizil
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Beam ◽  
Chemical Etching ◽  
Silicon Surface ◽  
Laser Pulses ◽  
Laser Beam Profile ◽  
Fs Laser ◽  
Fabrication And Characterization

We fabricated Si Nano-columns by a femtosecond laser with various wavelengths and process parameters, whilst the specimen was submerged in water. The experiments were carried out by three types of wavelengths i.e. 1030 nm, 515nm, 343nm, with 500 fs laser pulses. The scales of these spikes are much smaller than micro spikes that are constructed by laser irradiation of silicon surface in vacuum or gases like SF6, Cl2. The Si nano-columns of 300 nm or less in width were characterized by SEM measurements. The formation of these Si Nano-columns that were revealed by SEM observation, indicates chemical etching with laser ablation occurred when surface exposed by laser beam. We observed 200 nm spikes height at the center of laser beam profile and the ones uniform in height at lateral incident area.

scholarly journals The time-resolved hard X-ray diffraction endstation KMC-3 XPP at BESSY II

2021 ◽  
Vol 28 (3) ◽  
Author(s):  
Matthias Rössle ◽  
Wolfram Leitenberger ◽  
Matthias Reinhardt ◽  
Azize Koç ◽  
Jan Pudell ◽  
...  
Keyword(s):  
Storage Ring ◽  
Single Photon ◽  
Laser System ◽  
High Vacuum ◽  
Laser Pulses ◽  
Pixel Detector ◽  
X Ray Diffraction ◽  
Optical Pump ◽  
Time Resolved ◽  
X Ray

The time-resolved hard X-ray diffraction endstation KMC-3 XPP for optical pump/X-ray probe experiments at the electron storage ring BESSY II is dedicated to investigating the structural response of thin film samples and heterostructures after their excitation with ultrashort laser pulses and/or electric field pulses. It enables experiments with access to symmetric and asymmetric Bragg reflections via a four-circle diffractometer and it is possible to keep the sample in high vacuum and vary the sample temperature between ∼15 K and 350 K. The femtosecond laser system permanently installed at the beamline allows for optical excitation of the sample at 1028 nm. A non-linear optical setup enables the sample excitation also at 514 nm and 343 nm. A time-resolution of 17 ps is achieved with the `low-α' operation mode of the storage ring and an electronic variation of the delay between optical pump and hard X-ray probe pulse conveniently accesses picosecond to microsecond timescales. Direct time-resolved detection of the diffracted hard X-ray synchrotron pulses use a gated area pixel detector or a fast point detector in single photon counting mode. The range of experiments that are reliably conducted at the endstation and that detect structural dynamics of samples excited by laser pulses or electric fields are presented.

scholarly journals Preparation and Characterization of Lead Oxide Nanoparticles by Laser Ablation as Antibacterial Agent

2017 ◽  
Vol 14 (4) ◽  
pp. 801-807
Author(s):  
Baghdad Science Journal
Keyword(s):  
Laser Ablation ◽  
Lead Oxide ◽  
Laser Energy ◽  
Laser Pulses ◽  
Diffusion Method ◽  
Lead Target ◽  
Oxide Nanoparticles ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

In this work, lead oxide nanoparticles were prepared by laser ablation of lead target immersed in deionized water by using pulsed Nd:YAG laser with laser energy 400 mJ/pulse and different laser pulses. The chemical bonding of lead oxide nps was investigated by Fourier Transform Infrared (FTIR); surface morphology and optical properties were investigated by Scanning Electron Microscope (SEM) and UV-Visible spectroscopy respectively, and the size effect of lead oxide nanoparticles was studied on its antibacterial action against two types of bacteria Gram-negitive (Escherichia coli) and Gram-positive (Staphylococcusaurus) by diffusion method. The antibacterial property results show that the antibacterial activity of the Lead oxide NPs was inversely proportional to the size of the nanoparticles in both Gram-negative and Gram-positive, and also it has been found that Gram-positive bacteria possess have greater sensitivity and less resistance to the lead oxide nanoparticles compared with Gram-negative bacteria.

scholarly journals Laser ablation of silicon with THz bursts of femtosecond pulses: an experimental and theoretical investigation

2021 ◽  
Author(s):  
Caterina Gaudiuso ◽  
Pavel N. Terekhin ◽  
Annalisa Volpe ◽  
Stefan Nolte ◽  
Bärbel Rethfeld ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Thermal Load ◽  
Laser Pulses ◽  
Ablation Rate ◽  
Pulse Mode ◽  
Femtosecond Laser Pulses ◽  
Photon Absorption ◽  
Burst Frequency ◽  
Two Photon Absorption ◽  
Theoretical Investigations

Abstract In this work, we performed an experimental investigation supported by a theoretical analysis, to improve knowledge on the laser ablation of silicon with THz bursts of femtosecond laser pulses. Laser ablated craters have been created using 200 fs pulses at a wavelength of 1030 nm on silicon samples systematically varying the burst features and comparing to the Normal Pulse Mode (NPM). Using bursts in general allowed reducing the thermal load to the material, however, at the expense of the ablation rate. The higher the number of pulses in the bursts and the lower the intra-burst frequency, the lower is the specific ablation rate. However, bursts at 2 THz led to a higher specific ablation rate compared to NPM, in a narrow window of parameters. Theoretical investigations based on the numerical solution of the density-dependent two temperature model revealed that lower lattice temperatures are reached with more pulses and lower intra-burst frequencies, thus supporting the experimental evidence of the lower thermal load in Burst Mode (BM). This is ascribed to the weaker transient drop of reflectivity, which suggests that with bursts less energy is transferred from the laser to the material. This also explains the trends of the specific ablation rates. Moreover, we found that two-photon absorption plays a fundamental role during BM processing in the THz frequency range.

scholarly journals Demonstration of laser pulse amplification by stimulated Brillouin scattering

2014 ◽  
Vol 2 ◽  
Author(s):  
E. Guillaume ◽  
K. Humphrey ◽  
H. Nakamura ◽  
R. M. G. M. Trines ◽  
R. Heathcote ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Plasma Density ◽  
Brillouin Scattering ◽  
Laser System ◽  
Laser Pulses ◽  
Seed Pulse ◽  
Central Wavelength ◽  
Demonstration Experiment ◽  
Stimulated Brillouin ◽  
Underdense Plasma

Abstract The energy transfer by stimulated Brillouin backscatter from a long pump pulse (15 ps) to a short seed pulse (1 ps) has been investigated in a proof-of-principle demonstration experiment. The two pulses were both amplified in different beamlines of a Nd:glass laser system, had a central wavelength of 1054 nm and a spectral bandwidth of 2 nm, and crossed each other in an underdense plasma in a counter-propagating geometry, off-set by $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}10^\circ $ . It is shown that the energy transfer and the wavelength of the generated Brillouin peak depend on the plasma density, the intensity of the laser pulses, and the competition between two-plasmon decay and stimulated Raman scatter instabilities. The highest obtained energy transfer from pump to probe pulse is 2.5%, at a plasma density of $0.17 n_{cr}$ , and this energy transfer increases significantly with plasma density. Therefore, our results suggest that much higher efficiencies can be obtained when higher densities (above $0.25 n_{cr}$ ) are used.

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