UV and IR laser ablation under MALDI conditions is described for two typical solid UV and IR matrices. 2,5-Dihydroxy benzoic acid (2,5-DHB) as a UV and IR matrix and succinic acid (SA) as an IR ...matrix were investigated systematically by light and electron microscopy, and by mass spectrometry. Large single crystals of 2,5-DHB and SA with and without protein incorporated were used for the experiments. The UV MALDI experiments were performed with a flat-top laser beam profile. Within a limited fluence range, these exposures resulted in the formation of typical cone structures, occurring after several hundred laser shots onto a given spot. Such structures had originally been described for materials processing of polymers and ceramics with excimer lasers. For the IR exposures, a Gaussian laser beam profile was used. The much lower absorption of matrix compounds at IR wavelengths compared with the absorption of matrix compounds at UV wavelengths results in a much larger penetration depth of the IR laser light into the matrix solid and consequently in a much higher ablation depth and amount of ablated material. This large volume of material, ablated per single exposure, prevents the formation of specific surface structures in IR MALDI. The amount of matrix material ablated per laser shot was measured with a laser profilometer to about 10 000 μm
3. This determines the amount of consumed protein per laser shot to about 1 fmol under typical IR MALDI conditions.
In this survey paper, a brief survey has been performed about the free space optical communication (FSO), which has emerged as an innovative hot topic in the field of research. This paper inspected ...about the features and challenges faced by FSO communication. Here, it is focused about atmospheric turbulence, one of the main challenge FSO has to encounter during the propagation of laser beams through free space. The survey has also been undergone regarding the various modulation schemes, and various laser optical beam profile that can be used in FSO as optical source of propagation. The analysed techniques employed for the process of modulation are Amplitude shift keying(ASK), Binary phase shift keying(BPSK), Quadrature phase shift keying(QPSK), Pulse position modulation(PPM), Pulse amplitude modulation(PAM), Pulse width modulation(PWM). Also, investigated about the effect of different types of aberrations such a tilt, astigmatism, coma, and spherical aberrations present in a turbulent atmosphere on different laser beam profiles such as Bessel Gaussian (BG) beam, Laguerre-Gaussian (LG) beam, Hermite-Gaussian (HG) beam, Helical beam.
During laser irradiation of biological tissue, a number of physical processes take place that determine temperature elevation and thermal damage rates. Some of those important to laser-tissue ...interaction are: 1) propagation of light in scattering media; 2) transformation of laser light into photochemical, acoustic, or thermal energy; 3) tissue-tissue and tissue-environment heat and mass transfer; 4) and the occurrence of low-energy phase transformations responsible for structural alterations. The aim of this study was to formulate a finite-element model (FEM) able to predict the temperature distribution in a slab of porcine nasal cartilage during laser irradiation. The FEM incorporates heat diffusion, light propagation in tissue, and water evaporation from the surfaces of the slab. Numerical results were compared to experimental temperature distributions where surface and internal temperatures were measured while heating cartilage using a pulsed Nd: YAG laser (/spl lambda/ = 1.32 /spl mu/m). Rectangular specimens, 1-4-mm thick, were secured perpendicular to the laser beam and irradiated for 1-15 s using different laser-beam powers (1-10 W).
We present a theoretical and experimental investigation of a very simple binary Diffractive Optical element referred as a phase slit. The latter is made up of two transparent plates of glass in which ...a phase step has been patterned using ion beam etching. The two phase steps are set parallel and are able to slide each on the other so that one can adjust continuously the width of the phase shifting zone that suffers an incident Gaussian beam. It is shown that the phase slit is able to make a 1-D transformation of a Gaussian beam either into a uniform profile or a hollow profile having a central depression whose depth can be continuously adjusted just by changing the width of the slit.
Techniques for flow cytometer alignment Jett, James H; Martin, John C; Habbersett, Robert C
Current protocols in cytometry,
October 2009, Letnik:
Chapter 1
Journal Article
This unit provides essential knowledge for correctly using any flow cytometer to ensure that data collected are accurate and reliable. Two levels of system alignment are described: routine alignment ...checks and complete alignment, both of which can be applied to a variety of instrument configurations.
The effect of the laser pulse width has been investigated for matrix-assisted laser desorption/ionization (MALDI) of analyte and matrix ions as well as for (photoionized) neutral matrix molecules by ...comparing two nitrogen lasers (337 nm) with 0.55 and 3 ns pulse widths as commonly used for MALDI mass spectrometry. A homogeneous “flat-top” laser beam profile was used in these experiments. Neither did the threshold fluences (minimum incident laser energy per unit area for producing a spectrum) change, nor was there a difference in the increase in ion signal intensity with laser fluence between the two lasers. Also, no significant differences were found in the mass spectra. The results show that the desorption/ionization process is essentially determined by the energy supplied in the studied pulse width range, rather than by the rate of energy flow into the sample.
Sn
29Se
56Sb
10Co
5 amorphous thin films were prepared on the polymer substrates, and was irradiated at room temperature by Nd:YAG pulsed laser in air, with the wavelength of 532
nm, pulse width of ...90
ns after equilibration. Irradiation-induced surface morphological modifications were characterized using Secco-etching aided scanning electron microscopy (SEM). Complementary information was obtained from X-ray diffraction (XRD) spectrum and energy dispersive X-ray spectrum (EDS). The experimental results demonstrated that the grain size distribution was closely related to the laser beam profile. As a function of laser fluence, the average grain size evolution was also studied, which may not be interpreted by the conventional crystallography theories, and was related to some threshold effects.
Analysis of international ultraviolet explorer (IUE) and Voyager ultraviolet spectrometer (UVS) spectra of the Jovian auroral emission indicates that the Jovian auroral brightness is modulated in ...longitude (brighter near 180° in the north and 20° in the south) and that there is a color ratio asymmetry associated with this brightening. The purpose of this study is to investigate the origin of this apparent asymmetry. To that end, we use a series of six typical images of the north auroral region taken in the H2 Lyman bands with the faint object camera (FOC) aboard the Hubble space telescope (HST) and which cover a full Jovian rotation. Although the images do not display any strong brightening near 180°, once we have simulated the signal IUE would see through its aperture, we find the characteristic longitudinal modulation. We attribute most of this modulation to a combination of viewing geometry effects near the east and west ansae of the auroral oval (already taken into account in previous studies) and of the spatial degradation of the source by the IUE instrument function (never considered so far), and we suggest qualitatively that these effects may also affect the color ratio asymmetry. Nevertheless, part of the asymmetry seems to be due to an intrinsic modulation associated with a bright feature crossing the polar cap along the 160° meridian (transpolar emission) and present in most of the images. We then use a series of FOC images taken during an atypically strong auroral event, and we show that the same effects can again account for the anomalous brightness variations observed simultaneously with IUE.
Thermal and fluid behavior are governing factors for the via processing of semiconducting substrates. In order to investigate the fundamentals, nanosecond (ns) time-resolved visualization of ns-pulse ...Nd:YAG laser ablation of SiC substrate has been performed for various conditions. Time-resolved visualizations have been conducted by using a ultra high speed camera with the frame rate of 200 million frames/second for the first time to reveal the ablation process in a single event with the temporal resolution of 5 ns. Both self-emitting light from the ablation plume and the shadow image due to the refractive index profile are visualized. The results show unique features for each spatial beam profiles (Gaussian, quasi-flat top, annular) with different beam energy. Combined with the previous experimental observations, the results help modeling the thermo-fluid numerical modeling of the ablation process.
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