Time and space-resolved spectroscopic and imaging study of a laser-produced swine muscle tissue plasma

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/We investigated the optical emission and imaging features of plasmas produced by a high-power transversely excited atmospheric CO2 laser pulses on a swine muscle tissue sample in different vacuum conditions. The analyzed plasma shows electronically excited neutral Na, K, C, Mg, H, Ca, N, and O atoms, ionized C+, C2+, C3+, Mg+, Mg2+, N+, N2+, Ca+, O+, and O2+ species and molecular band systems of CN, C2, CH, NH, OH and CaOH. Time-resolved 2D emission spectroscopy is employed to study the expanded distribution of several species ejected during ablation. The expansion of the plume front was analyzed using Shock wave and Drag models. Laser-produced plasmas (LPPs) are currently a topic of great interest in fundamental and applied areas such as fabrication of thin films by pulsed laser deposition, production of nanoparticles, spectrochemical analysis through laserinduced breakdown spectroscopy (LIBS) [1], ion source etc. Beyond traditional applications of LIBS, recent progresses lead to analysis of biological warfare agents and animal tissues. In this work, we present a spatial and temporal analysis of the LPP plume generated on a biological tissue target. Time-resolved 2D emission spectroscopy is used to study the expanded distribution of different species ejected during ablation. Fig. 1 shows a schematic overview of the temporal history of the LPP sample. The temporal shape of the CO2 laser pulse is also shown. Inset plots illustrate some spaceresolved spectral images observed at different delays for a gate width time of 100 ns. The recorded spectral intensity is indicated by a pseudo- color. By tracking the maximum brightness displacement for different plasma species gives their average expansion velocities. The expansion velocities of the ionized species towards the longitudinal direction are found to be increasing with degree of ionization. Plasma parameters such as electron density and temperature were measured from the spatial-temporal analysis of different specific species. We used the imaging data to create positiontime plots (Fig. 2) of the shockwave front at several background air pressures. The solid line represents the shockwave model fit. These images provide very useful information about the expansion and internal structure of the plasmaplume. Surface morphology of irradiated surface showed that increasing the pressure of the ambient gas, decreased the ablated mass. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Time (¿s) Plume front position, R (mm) R ¿¿(¿¿¿¿ ¿¿¿¿)¿t¿¿¿¿¿¿¿¿ 0.0 5.0x105 1.0x106 1.5x106 2.0x106 2.5x106 3.0x106 Velocity (cm/s) Fig. 2. R-t plot and velocities for the expanding plume front in vacuum (0.01 Pa). Insets show two images (0 and 4 ¿s) at 1.1 GW/cm2 incident laser power density. Acknowledgments We gratefully acknowledge the support received by the project: CTQ2013-43086. References [1] J. J. Camacho et al 2013 Spectrochimica Acta Part B 88 203. Fig. 1. Schematic overview of the temporal and spatial evolution of the LPP sample. 1 E-mail: [email protected] XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015) IOP Publishing Journal of Physics: Conference Series 635 (2015) 042005 doi:10.1088/1742-6596/635/4/042005Peer Reviewe

Mathematical Modeling of the Parabolic Trough Collector Field of the TCP-100 Research Plant

The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016 Oulu (Finlandia)There are two main drawbacks when operating solar energy systems: a) the resulting energy costs are not yet competitive and b) solar energy is not always available when needed. In order to improve the overall solar plants efficiency, advances control techniques play an important role. In order to develop efficient and robust control techniques, the use of accurate mathematical models is crucial. In this paper, the mathematical modeling of the new TCP100 parabolic trough collector (PTC) research facility at the Plataforma Solar de Almería is presented. Some simulations are shown to demonstrate the adequate behavior of the model compared to the facility design conditions.Junta de Andalucía P11-TEP-8129Unión Europea FP7-ICT-ICT-2013.3.4-611281Ministerio de Economía y Competitividadt DPI2014-56364-C2-2-

Micro-Raman and Raman Imaging studies of glassy material produced by continuous wave (CW) CO2 laser irradiation of lime/pozzolan mortar

ICCC 2015, Beijing, China, 13~16 October 2015; http://iccc2015.csp.escience.cn/dct/page/1This work describes the distribution of the portlandite over the surface of the lime/pozzolan mortar and the mineral composition of the glassy material formed when the mortar was irradiated with continuous-wave-CO2 (CW-CO2) laser. Both Micro-Raman and Raman mapping have been used for structural studies. Lime/pozzolan/sand 1/1/2 mortars, 5 years at room temperature, were irradiated with CW-CO2 laser (Synrad Firestar t80, Mukilteo, WA) operating at a wavelength of 10.591 ¿m, 10P(20) CO2 laser line. Laser output: 8W, 18W and 38W (Synrad PW-250 (Mukilteo, WA)). The laser beam was focused by means of a NaCl lens of 10 cm focal length and the irradiation time was 5 seconds. Raman spectra were collected with a Raman Spectrometer (Renishaw Invia) equipped with a CCD camera, using 532 nm (Nd:YAG) excitation line. The laser on the sample was 5 mW and the integration time was 10 seconds. For mapping measurements, an area of 80 ¿m x 80 ¿m was chosen in the internal part of the glass. The step size was 5 ¿m with an individual grid size of 25 ¿m2. Glazing, vaporization and spalling process can produce over an irradiated surface with a high power laser beam. When the power density of the irradiating laser beam is high enough to raise the temperature beyond the glass transition, a glassy surface layer is formed. However, if surface temperatures are below that melting point, the vaporization of water can be produce over the material surface. Due to the small diffusivity of water vapour, its transport is hindered and an overpressure is attained. Hydraulic building materials have about 4-10% bounded water, after irradiation with the CW-CO2 laser, water vapour spread out in a vaporization front reacting with the CaO present in the sample and producing Ca(OH)2, besides a glassy surface.Peer Reviewe

WKB formalism and a lower limit for the energy eigenstates of bound states for some potentials

In the present work the conditions appearing in the WKB approximation formalism of quantum mechanics are analyzed. It is shown that, in general, a careful definition of an approximation method requires the introduction of two length parameters, one of them always considered in the text books on quantum mechanics, whereas the second one is usually neglected. Afterwards we define a particular family of potentials and prove, resorting to the aforementioned length parameters, that we may find an energy which is a lower bound to the ground energy of the system. The idea is applied to the case of a harmonic oscillator and also to a particle freely falling in a homogeneous gravitational field, and in both cases the consistency of our method is corroborated. This approach, together with the Rayleigh--Ritz formalism, allows us to define an energy interval in which the ground energy of any potential, belonging to our family, must lie.Comment: Accepted in Modern Physics Letters

Laser-induced breakdown spectroscopy of trisilane using infrared C O2 laser pulses

The plasma produced in trisilane (Si3 H8) at room temperature and pressures ranging from 50 to 103 Pa by laser-induced breakdown (LIB) has been investigated. The ultraviolet-visible-near infrared emission generated by high-power IR C O2 laser pulses in Si3 H8 has been studied by means of optical emission spectroscopy. Optical breakdown threshold intensities in trisilane at 10.591 μm for laser pulse lengths of 100 ns have been measured as a function of gas pressure. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited atomic H and Si and ionic fragments Si+, Si2+, and Si3+. An excitation temperature Texc =5600±300 K was calculated by means of H atomic lines assuming local thermodynamic equilibrium. The physical processes leading to LIB of trisilane in the power density range 0.28 GW cm-2 <J<3.99 GW cm-2 have been analyzed. From our experimental observations we can propose that, although the first electrons must appear via multiphoton ionization, electron cascade is the main mechanism responsible for the breakdown in trisilane. © 2007 American Institute of Physics.This work was partially supported by the Spanish MEC Project No. CTQ2007-60177/BQU. It is a pleasure to acknowledge the excellent technical support of A. Magro. This work is dedicated in memory of Professor Antonio Pardo Martinez.Peer Reviewe

Optical Breakdown in Gases Induced by High-power IR CO2 Laser Pulses

This chapter reviews some fundamentals of laser-induced breakdown spectroscopy (LIBS) and describes some experimental studies developed in our laboratory on gases such as nitrogen, oxygen and air. LIBS of these gases at different pressures, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), was excited by using a high-power transverse excitation atmospheric (TEA) CO2 laser (¿=9.621 or 10.591 ¿m; tFWHM=64 ns; and different laser power densities). The spectra of the generated plasmas are dominated by emission of strong atomic, ionic species and molecular bands. Excitation temperatures are estimated from the intensities of atomic and ionic lines. Electron number densities are deduced from the Stark broadening of several ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the gas pressure and laser irradiance. Optical breakdown threshold intensities in different gases have been experimentally measured. The physical processes leading to laser-induced breakdown of gases have been analyzed. Plasma characteristics of LIBS in air are examined in detail on the emission lines of N+, O+ and C by using time-resolved optical-emission spectroscopy (OES) technique. The results show a faster decay of continuum and ionic spectral species than of neutral atomic and molecular ones. The velocity and kinetic energy distributions for the different species are obtained from time-of-flight (TOF) OES measurements. Excitation temperatures and electron densities in the laser-induced plasma are estimated from the analysis of spectral data at various times from the laser pulse incidence. Temporal evolution of electron density has been used for the estimation of the three-body recombination rate constant.Peer Reviewe

Temporal evolution of the laser-induced plasma generated by IR CO 2 pulsed laser on carbon targets

Time-resolved optical emission analysis was carried out for the plasma plume, produced by high-power tunable IR CO2 pulsed laser ablation of graphite, at λ=10.591 μm and in a regime of relatively high laser fluences (123-402 J/ cm2). Wavelength-dispersed spectra of the plasma plume, at medium-vacuum conditions (4 Pa) and at 9.0 mm from the target, show ionized species (C+, C2+, C3+, C4+, N2 +, N+, and O+), neutral atoms (C, H, N, and O), and neutral diatomic molecules (C2, CN, OH, CH, and N2). In this work, we focus our attention on the temporal evolution of different atomic/ionic and molecular species over a broad spectral range from 190 to 1000 nm. The results show a faster decay for ionic fragments than for neutral atomic and molecular species. The velocity and kinetic energy distributions for different species were obtained from time-of-flight measurements using time-resolved optical emission spectroscopy. Possible mechanisms for the production of these distributions are discussed. Excitation temperature, electron density, and vibrational temperature in the laser-induced plasma were estimated from the analysis of spectral data at various times from the laser pulse incidence. © 2009 American Institute of Physics.Peer Reviewe

Optimization of Amino Acid Sequence of Fmoc-Dipeptides for Interaction with Lipid Membranes

Fmoc-dipeptides appear as highly relevant building blocks in smart hydrogels and nanovehicles for biological applications. The interactions of the Fmocdipeptides with the cell membrane determine the efficiency of the nanomaterials based on the Fmoc-dipeptides’ internalization of nanovehicles for drug delivery. Here, we aim to understand the interplay of the interactions between the Fmoc-dipeptides and a phospholipid surface as a function of the amino acid sequence. The DMPA (1,2-dimyristoyl-snglycero- 3-phosphate) phospholipid in Langmuir monolayers was used as a model cell surface. A set of seven derivatives of Fmoc-dipeptides with a broad range of hydrophobicity were included. Mixed monolayers composed of DMPA/Fmoc-dipeptides in an equimolar ratio were built and characterized in situ at the air/water interface. Surface pressure−molecular area isotherms (π−A), Brewster angle microscopy (BAM), and UV−vis reflection spectroscopy (ΔR) were combined to provide a holistic picture of the interactions of the Fmoc-dipeptide with the phospholipid molecules. An increase in the hydrophobicity led to enhanced interaction of the Fmoc-dipeptide and DMPA molecules. The compression of the mixed monolayer could displace a significant fraction of the Fmoc-dipeptide from the monolayer. High hydrophobicity promoted self-assembly of the Fmoc-dipeptides over interaction with the phospholipid surface. The interplay of these two phenomena was analyzed as a function of the amino acid sequence of the Fmoc-dipeptides. The toxicity effect of Fmoc-FF could be observed and detailed at the molecular level. This study suggests that the adjustment of the hydrophobicity of the Fmoc-dipeptides within a defined range might optimize their efficiency for interaction with the lipid membranes. A semiquantitative guide for the chemical design of Fmoc-dipeptides for biological applications is proposed herein

Folding of cytosine-based nucleolipid monolayer by guanine recognition at the air-water interface

Monolayers of a cytosine-based nucleolipid (1,2-dipalmitoyl-sn-glycero-3-(cytidine diphosphate) (ammonium salt), CDP-DG) at basic subphase have been prepared at the air-water interface both in absence and presence of guanine. The formation of the complementary base pairing is demonstrated by combining surface experimental techniques, i.e., surface pressure (π)–area (A), Brewster angle microscopy (BAM), infrared spectroscopy (PM-IRRAS) and computer simulations. A folding of the cytosine-based nucleolipid molecules forming monolayer at the air-water interface occurs during the guanine recognition as absorbate host and is kept during several compression-expansion processes under set experimental conditions. The specificity between nitrogenous bases has been also registered. Finally, mixed monolayers of CDP-DG and a phospholipid (1,2-dimyristoyl-sn-glycero-3-phosphate (sodium salt), DMPA) has been studied and a molecular segregation of the DMPA molecules has been inferred by the additivity rule