Acquisition Of Spectroscopic Data Research Articles

Chemical imaging of pharmaceutical granules by Raman global illumination and near-infrared mapping platforms

Raman global illumination and near-infrared (NIR) mapping instruments were used to chemically image pharmaceutical granules obtained by the wet granulation process in order to determine whether the API was mixed with the major excipient or granulates on its own. The granules were randomly distributed onto a microscope slide and an average area of about 3.5 mm × 3.5 mm, covering 50–100 granules, was analyzed by both instruments. Light microscopy images of the separated granules were collected before the spectroscopic data acquisition. Both Raman and NIR signals of API and major excipient (mannitol) were easily detected by both techniques which allowed the chemical structure of the granules to be characterised. Most of the granules were found to contain both API and mannitol but pure mannitol and a few pure API granules were also identified. Raman global illumination was found to provide a comprehensive insight into chemical structure of the granules being able to more clearly determine the API in comparison with NIR mapping. Owing to the differences in shapes of the particles and reflection characteristics, visual microscopy and methods based on reflection can be potentially useful for analyzing this particular formulation.

Micro-X-ray absorption near edge structure as a suitable probe to monitor live organisms

X-ray spectroscopies are very powerful tools to determine the chemistry of complex dilute solutes in abiotic and biotic systems. We have assayed their suitability to monitor the chemistry of complex solutions in a live biotic system. The impact of the probe on cells was quantified for 4 different cellular organisms differing in their resistance level to environmental stresses. We show that none of the organisms tested can survive the radiation doses needed for the acquisition of meaningful spectroscopic data. Therefore, on one hand, X-ray spectroscopy cannot be applied to the monitoring of single cells, and cellular damages have to be taken into account in the interpretation of the evolution of such systems. On the other hand, due to the limited extension of X-ray induced cellular damages in the culture volume, it is possible to probe a population of live cells provided that the culture to beam probe ratio is large enough to minimize the impact of mortality on the evolution of the biological system. Our results suggest that it could be possible to probe the volume in the close vicinity of a cell without affecting its activity. Using this setup we could monitor the reduction of selenite by the X-ray sensitive bacterium, Agrobacterium tumefaciens strain C58, for 24 h. This method has a great potential to monitor the respiration of various metals, such as iron, manganese and arsenic, in situ under relevant environmental conditions by live microorganisms.

Nondestructive multispectral reflectoscopy between 800 and 1900nm: An instrument for the investigation of the stratigraphy in paintings

In the present work, a powerful tool for the investigation of paintings is presented. This permits the tuneable multispectral real time imaging between 200 and 5000 nm and the simultaneous multispectral acquisition of spectroscopic data from the same region. We propose the term infrared reflectoscopy for tuneable infrared imaging in paintings (Chryssonlakis and Chassery, The Application of Physicochemical Methods of Analysis and Image Processing Techniques to Painted Works of Art, Erasmus Project ICP-88-006-6, Athens, June, 1989) for a technique that is effective especially when the spectroscopic data acquisition is performed between 800 and 1900 nm. Elements such as underdrawings, old damage that is not visible to the naked eye, later interventions or overpaintings, hidden signatures, nonvisible inscriptions, and authenticity features can thus be detected with the overlying paint layers becoming successively "transparent" due to the deep infrared penetration. The spectroscopic data are collected from each point of the studied area with a 5 nm step through grey level measurement, after adequate infrared reflectance (%R) and curve calibration. The detection limits of the infrared detector as well as the power distribution of the radiation coming out through the micrometer slit assembly of the monochromator in use are also taken into account. Inorganic pigments can thus be identified and their physicochemical properties directly compared to the corresponding infrared images at each wavelength within the optimum region. In order to check its effectiveness, this method was applied on an experimental portable icon of a known stratigraphy.

Phase‐rotation in in‐vivo localized spectroscopy

AbstractPhase‐rotation is an alternative method to phase‐cycling in acquisition of magnetic resonance spectroscopic data. However, there has only been two papers describing its implementation in point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) to date. This article aims to introduce and explain the principles of phase‐rotation, describe the implementations that were carried out so far in the current literature, compare phase‐rotation and phase‐cycling experimentally, and introduce the application of phase‐rotation in double‐quantum filtered (DQF) spectroscopy. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 147–153, 2007

Metabolic Profiling Technologies for Biomarker Discovery in Biomedicine and Drug Development

The state-of-the-art of nuclear magnetic resonance spectroscopy, mass spectrometry and statistical tools for the acquisition and evaluation of complex multidimensional spectroscopic data in metabolic profiling is reviewed in this article. The continuous evolution of the sensitivity, precision and throughput has made these technologies powerful and extremely robust tools for application in systems biology, pharmaceutical and diagnostics research. Particular emphasis is also given to the collection and storage of biological samples that are subjected to metabolite profiling. Selected examples from preclinical and clinical applications are paradigmatically shown. These illustrate the power of the profiling technologies for characterizing the metabolic phenotype of healthy, diseased and treated subjects. The complexity of disease and drug treatment is asking for an adequate response by integrated and comprehensive metabolite profiling approaches that allow the discovery of new combinations of metabolic biomarkers.

Valeurs contrôles obtenues avec une séquence press 135 ms en neurospectroscopie monovoxel du proton

The clinical value of MR spectroscopy is now well established and this technique has been added to the current French classification of medical acts (CCAM). This paper presents a set of normal control values for 3 metabolite ratios obtained using a PRESS sequence with a TE of 135 ms at 1.5T: NAA/Cho, NAA/Cr and Cho/CR. Spectroscopy data acquisition were obtained from the following 12 anatomical regions: parieto-occipital white matter, centrum semiovale, frontal white matter, thalamus, basal ganglia, cerebellum (hemisphere, including dentate nucleus), brain stem (including pons, medulla and midbrain), anterior and posterior temporal lobe, parietal, occipital and pre-frontal cortices. The presented data allow radiologists equipped with a similar MR system to implement a clinical spectroscopy program without undergoing research protocols in order to obtain control values.

Survey for Galaxies Associated withz∼ 3 Damped Lyα Systems. I. Spectroscopic Calibration ofu′BVRIPhotometric Selection

We present a survey of z ~ 3 Lyman break galaxies (LBGs) associated with damped Lyα systems (DLAs) with the primary purpose of determining the DLA-LBG cross-correlation. This paper describes the acquisition and analysis of imaging and spectroscopic data of nine quasar fields having 11 known z ~ 3 DLAs covering an area of 465 arcmin2. Using deep u'BVRI images, 796 LBG candidates up to an apparent RAB magnitude of 25.5 were photometrically selected from 17,343 sources detected in the field. Spectroscopic observations of 529 LBG candidates using the Keck Low Resolution Imaging Spectrometer yielded 339 redshifts. We have conservatively identified 211 z > 2 objects with z = 3.02 ± 0.32. We discuss our method of z ~ 3 LBG identification and present a model of the u'BVRI photometric selection function. We use the 339 spectra to evaluate our u'BVRI z ~ 3 Lyman break photometric selection technique.

Real‐time tissue characterization on the basis of in vivo Raman spectra

AbstractThe application of in vivo Raman spectroscopy for clinical diagnosis demands dedicated software that can perform the necessary signal processing and subsequent (multivariate) data analysis, enabling clinically relevant parameters to be extracted and made available in real time. Here we describe the design and implementation of a software package that allows for real‐time signal processing and data analysis of Raman spectra. The design is based on automatic data exchange between Grams, a spectroscopic data acquisition and analysis program, and Matlab, a program designed for array‐based calculations. The data analysis software has a modular design providing great flexibility in developing custom data analysis routines for different applications. The implementation is illustrated by a computationally demanding application for the classification of skin spectra using principal component analysis and linear discriminant analysis. Copyright © 2002 John Wiley & Sons, Ltd.

Optical Second Harmonic Spectroscopy of Silicon Surfaces, Interfaces and Nanocrystals

We review recent advances in the acquisition and microscopic interpretation of spectroscopic second harmonic data from silicon surfaces, including clean and adsorbate-covered Si(001) in ultrahigh vacuum, and the buried Si/SiO2 interfaces of planar and nanocrystalline structures.

Multichannel photon counting instrument for spatially resolved near infrared spectroscopy

We have developed a multichannel photon counting instrument for near infrared spatially resolved spectroscopy. The instrument uses two laser diodes at 780 and 830 nm. The two wavelengths are time multiplexed at a rate of 5 MHz for virtually simultaneous measurements at the two wavelengths. The photon pulses are then multiplexed with an optical switch so that the incident optical signals are directed to different source positions. Eight time-correlated channels have been employed for simultaneous acquisition of spectroscopic data at multiple locations. Photon detection is performed by multichannel plate photomultiplier tubes. Robust and accurate data analysis tools to perform deconvolution, data fitting, and absorption change quantification are presented. The instrument has been tested with phantoms simulating tissue optical properties. Absolute optical properties, namely absorption and reduced scattering coefficient, have been determined with an accuracy of ±5%. Quantification of absorption changes can be achieved with an accuracy of 10−3 cm−1 and a sensitivity of the order of 10−4 cm−1. Finally spatially resolved measurements of primary motor-cortex activation have been performed and successfully coregistered with functional magnetic resonance imaging data.

EFTEM and STEM EELS Spectrum Imaging

Abstract Electron energy-loss spectroscopy (EELS) in the transmission electron microscope (TEM) is a powerful technique that analyzes the inelastic scattering distribution of the fast TEM electrons after they have lost energy within the sample. The resultant energy-losses are characteristic of elemental, chemical, and dielectric properties and are typically measured in one of two ways. Parallel-detection EELS spectrometers (PEELS) acquire spectral data over a large range of energy-loss simultaneously for rapid acquisition of spectral data at a single point. In contrast, the energy filtering TEM (EFTEM) acquires only a single energy band at once, but does so for thousands or even millions of image pixels simultaneously. Spectrum-imaging concerns the acquisition of spectroscopic data of sufficient detail for rigorous analysis at each pixel in a digital image. (Fig. 1) A STEM EELS spectrum image “data cube” can be acquired by stepping a focused electron probe to each pixel and filling the spectrum image one spectrum at a time.

Photoluminescence studies of quantum-well structures in pulsed magnetic fields

Magneto-photoluminescence spectroscopy at low temperatures has proved to be a powerful technique for investigating the electronic states of quantum well-type semiconductor heterostructures and offers a complimentary tool to electrical transport studies. We have established a magneto-optical facility at NHMFL-LANL and have undertaken a comprehensive investigation of magneto-excitonic and Landau transitions in a large variety of undoped and doped quantum-well structures. Fiber optic probes are used to switch between steady state (to 18 T) and pulsed (to 65 T) magnetic fields applied perpendicular (Faraday geometry) and parallel (Voigt geometry) to the growth axis of the 2D layers. The pulsed field mode requires that the spectroscopic data acquisition to be obtained in 1–2 ms in the `flat-top' region at the peak of the field. A broad range of samples have been investigated in pulsed magnetic fields as a function of temperature, sample geometry, and high pressure. Examples include single and coupled double quantum wells, modulation-doped quantum wells, and single interface heterojunction structures.

Proton Magnetic Resonance Spectroscopy (MRS) in Epilepsy

Summary: For 1H magnetic resonance spectroscopy (MRS) studies in epilepsy in vivo, the main signals of interest have been those from N‐acetyl aspartate (NAA), creatine + phosphocreatine (Cr), choline‐containing compounds (Cho), and lactate (Lac). Several lines of evidence have indicated that NAA is located primarily within neurons. A reduction of the NAA signal is frequently interpreted, therefore, as reflecting loss or dysfunction of neurons. Such a reduction in NAA has been found in practice in many cases where neuronal loss would be expected clinically, and such abnormalities have been shown to be present in patients with intractable focal epilepsy. The acquisition of spectroscopic data in vivo is of limited use unless the spatial origin of the signals obtained is known. It is necessary, therefore, to limit the extent of the volume from which signal is acquired and to relate this volume to the anatomy of the region under investigation. For this reason, a number of common spatial localisation techniques are outlined, and their consequences described. In vivo MRS studies in epilepsy to date have been directed largely at the temporal lobes of patients with intractable epilepsy in whom surgical treatment is under consideration. Results are presented from a number of institutions which demonstrate that 1H MRS can contribute to the lateralization of the epileptic focus and to the identification of bilateral pathology. In providing information both on static metabolic abnormalities, primarily through the NAA signal, and on dynamic changes associated with seizure activity via the lactate signal, MRS offers the possibility of obtaining information on cerebral metabolism that is likely to have significant consequences for the management of patients with epilepsy.

Differential Charging in XPS. Part II: Sample Mounting and X-ray Flux Effects on Heterogeneous Samples

Factors which affect photoelectron peak positions on heterogeneous samples are evaluated using patterned indium tin oxide (ITO) on glass. Local sample environment, sample mounting and spatial variation in x-ray flux are all shown to contribute to differential charging effects if no charge neutralization is used. X-ray photoelectron spectroscopy data acquisition using both Mg Kα and monochromatic Al Kα x-ray sources shows that confusing and potentially misleading results can be obtained if samples are mounted such that only part of the surface is grounded to the spectrometer. In this case, multiple photoelectron peaks were observed for each photoelectron line of each element in the sample. However, more significant differential charging artifacts were observed from the insulating glass than from the ITO. The proximal causes of the photoelectron peak shifts were evaluated using imaging XPS in conjunction with small-area spectroscopy.

NEWDTP 2.2: A versatile system for routine XPS data acquisition and analysis

A system for X-ray photoelectron spectroscopy data acquisition and processing is described, offering a reasonable compromise between flexibility, efficiency and cost. The acquisition program was carefully designed to be user-friendly and to safely guide the operator in obtaining single or repeated multiple-region spectra. The processing program was also designed for fast and reliable operations and, besides all the usual routines, allows for spectral syntheses and differences. In particular, iterative synthesis procedures can be performed in a completely interactive environment: by this approach the chemical sense of the operator drives the iteration strategy throughout the analysis of the spectra. A few selected spectra are processed to describe software operations.

Automatic Spectral Database and Archive System for Optical Spectroscopy

With the advent of computerized data acquisition in spectroscopy, it has become possible to acquire large quantities of data with relative ease. Without a convenient method for archiving and accessing the data at a later date, a number of the capabilities inherent in these systems are unrealized. We have developed a generalized archival system which automatically archives all raw data and generates a rapidly searchable database of text information and spectral data for all spectroscopic results covering the spectral regions from 30 nm to 1000 µun (3.3 × 105 to 10 cm−1). The system executes on a local area network (LAN) of personal computers and consists of a customized file-naming and comment convention that organizes data by research notebooks, an integrated data backup routine, and a spectral database system. The data backup and spectral database consist of two programs: (1) a DOS level copy routine to back up the system and data to an optical write once/read many (WORM) drive, and (2) a spectral database program written in the Lab Calc spectroscopy environment. Stored with each spectral library entry are searchable text fields of character data parsed from a standardized comment line which is entered prior to data acquisition. This system is used consistently with three different spectrophotometers, allowing all results to be treated equivalently for further numerical analysis.

CAMAC-PC analyzer for neutron slowing-down-time spectrometry

A personal computer controlled CAMAC analyzer for time resolved spectroscopy and the design of a specially interfaced CAMAC module for routing data are described. The system is intended for spectroscopic data acquisition of slowing-down-time or time-of-flight neutron spectrometers. Its maximum throughput rate is 140 kHz and can be increased up to 250 kHz.

MICROCOMPUTER CONTROL OF SPECTROSCOPIC INSTRUMENTS

ABSTRACT A small, versatile microcomputer-based data-acquisition system has been developed for astronomical observing in the infrared. The hardware is a 16-bit 8086/8087 based system which has been tailored for use in spectroscopic observing programs. The hardware is operated using interactive software which permits high-speed data acquisition and real-time analysis of spectroscopic data. The combined hardware and software system facilitates flexible, efficient, and uniform operation of a variety of spectroscopic instruments. Key words: microcomputers-spectroscopic instruments

Real-Time Acquisition and Preprocessing of Kinetic and Spectroscopic Data in Laser Flash Photolysis

An automatic flash photolysis system for the measurement of absorption decays and transient difference spectra is described. The apparatus performs a digital measurement of the light transmitted by the sample and a few on-line preprocessing operations on the measured data, such as the digital averaging of the signal and the computation of the change in absorbance. A boxcar averager, used as a gated integrator, constitutes the sampling head of the apparatus. A microprocessor-based acquisition and control unit performs a digital conversion of the value sampled by the boxcar, provides an on-line preprocessing of the data, and supervises every operation required by the measurement process. This unit is interfaced to a personal computer which allows a friendly interaction with the operator as well as the on-line display of the data. The electronic instrumentation features a time resolution of a few nanoseconds, with a boxcar averager as input head, and of a few hundreds of picoseconds, with a sampling oscilloscope as input head.

Study of the Balmer Spectrum of Hydrogen from a High‐Pressure Arc Discharge. I. Spectroscopic Measurements and Plasma Analysis

AbstractThe Balmer spectrum of hydrogen emitted from a wall‐stabilized pulse discharge has been measured covering a pressure range between 0.1 and 1.2 MPa. The temperature achieved in the discharge varied between 13000 and 22000 K corresponding to a variation in the electron concentration between 1023 and 1024 m−3.Special consideration is given to the problems in both diagnostics and spectroscopic data acquisition.