Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Laser induced breakdown spectroscopy (LIBS) is basically an emission spectroscopy technique where atoms and ions are primarily formed in their excited states as a result of interaction between a tightly focused laser beam and the material sample. The interaction between matter and high-density photons generates a plasma plume, which evolves with time and may eventually acquire thermodynamic equilibrium. One of the important features of this technique is that it does not require any sample preparation, unlike conventional spectroscopic analytical techniques. Samples in the form of solids, liquids, gels, gases, plasmas and biological materials (like teeth, leaf or blood) can be studied with almost equal ease.LIBS has rapidly developed into a major analytical technology with the capability of detecting all chemical elements in a sample, of real- time response, and of close-contact or stand-off analysis of targets. The present book has been written by active specialists in this field, it includes the basic principles, the latest developments in instrumentation and the applications of LIBS. It will be useful to analytical chemists and spectroscopists as an important source of information and also to graduate students and researchers engaged in the fields of combustion, environmental science, and planetary and space exploration. It features: recent research work, possible future applications and LIBS Principles.

Chapter 12 – Laser-Induced Breakdown Spectroscopy: Advanced Analytical Technique

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Good practices in LIBS analysis: Review and advices

Chemometrics: A Textbook

The recent progress made in developing laser-induced breakdown spectroscopy (LIBS) has transformed LIBS from an elemental analysis technique to one that can be applied for the reagentless analysis of molecularly complex biological materials or clinical specimens. Rapid advances in the LIBS technology have spawned a growing number of recently published articles in peer-reviewed journals which have consistently demonstrated the capability of LIBS to rapidly detect, biochemically characterize and analyse, and/or accurately identify various biological, biomedical or clinical samples. These analyses are inherently real-time, require no sample preparation, and offer high sensitivity and specificity. This overview of the biomedical applications of LIBS is meant to summarize the research that has been performed to date, as well as to suggest to health care providers several possible specific future applications which, if successfully implemented, would be significantly beneficial to humankind.

Laser-induced breakdown spectroscopy (LIBS): an overview of recent progress and future potential for biomedical applications.

We report on a pump–probe mode-mismatched thermal-lens Z-scan method for the measurement of small absorption coefficients. In this method the pump light beam is focused into the sample to induce a thermal lens, which is tested by a collimated probe-light beam. Comparison between mode-matched and mode-mismatched Z-scan schemes is performed by use of a Fresnel-diffraction approximation model. This method is used to measure the absorption of distilled water and optical glass in the near-infrared and visible regions of the spectrum.

Pump–probe mode-mismatched thermal-lens Z scan

We describe a calibrated two-beam mode-mismatched thermal lens experiment aimed at determination of the absorption coefficient and the photothermal parameters of a nearly transparent material. The use of a collimated probe beam in the presence of a focused excitation beam optimizes the thermal lens experiment. The signal becomes independent from the Rayleigh parameters and waist positions of the beams. We apply this method to determine the absolute value of the thermal diffusivity and absorption coefficient of distilled water at 533 nm.

Optimizing and calibrating a mode-mismatched thermal lens experiment for low absorption measurement

The authors would like to thank Fondo Nacional para Ciencia y la Tecnolog´ia, Fonacit, Caracas,
Venezuela (Grant G97000593), the Latin American Center of Physics (CLAF) and the ICTP.

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Absorption coefficient of nearly transparent liquids measured using thermal lens spectrometry

Absorption and scattering cross-section extinction values of silver nanoparticles

A recently developed dual-beam configuration that optimizes the thermal lens technique has been used to obtain the absorption spectrum of pure water from 350 to 528 nm. Our results indicate the minimum linear absorption coefficient smaller than 2×10−5 cm−1 between 360 and 400 nm. This value is lower than previous literature data, and it is blueshifted. Absorption coefficients as small as 2×10−7 cm−1 can be measured for water using 1 W of excitation power. A detection limit of ~6×10−9 cm−1(P=1 W) for CCl4 was estimated, which represents, to the best of our knowledge, the highest sensitivity obtained in small absorption measurements in liquids.

Aristides Marcano

Papers

Pump–probe mode-mismatched thermal-lens Z scan

Optimizing and calibrating a mode-mismatched thermal lens experiment for low absorption measurement

Absorption coefficient of nearly transparent liquids measured using thermal lens spectrometry

Absorption and scattering cross-section extinction values of silver nanoparticles

Ultrasensitive thermal lens spectroscopy of water.