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At least 757 records · Page 42Linked to original sources
PubMed2000

Primordial carbonylated iron-sulfur compounds and the synthesis of pyruvate.

Experiments exploring the potential catalytic role of iron sulfide at 250 degrees C and elevated pressures (50, 100, and 200 megapascals) revealed a facile, pressure-enhanced synthesis of organometallic phases formed through the reaction of alkyl thiols and carbon monoxide with iron sulfide. A suite of organometallic compounds were characterized with ultraviolet-visible and Raman spectroscopy. The natural synthesis of such compounds is anticipated in present-day and ancient environments wherever reduced hydrothermal fluids pass through iron sulfide-containing crust. Here, pyruvic acid was synthesized in the presence of such organometallic phases. These compounds could have provided the prebiotic Earth with critical biochemical functionality.

Carbon Monoxide↗
PubMed2006

In vitro bioactivity of poly(epsilon-caprolactone)-apatite (PCL-AP) scaffolds for bone tissue engineering: the influence of the PCL/AP ratio.

Porous poly(epsilon-caprolactone) (PCL) is used as long-term bioresorbable scaffold for bone tissue engineering. The bone regeneration process can be enhanced by addition of carbonated apatites (AP). This study was aimed at evaluating the influence of the PCL/AP ratio on the in vitro degradation and bioactivity of PCL-AP composites. To this purpose, PCL-AP samples were synthesised with the following PCL/AP weight/weight ratios: 50/50, 60/40 and 75/25. Vibrational IR and Raman spectroscopies coupled to thermogravimetry (TG) and differential scanning calorimetry (DSC) were used to investigate the in vitro degradation mechanism in different media: 0.01 M NaOH solution (pH=12), saline phosphate buffer at pH 7.5 (SPB), esterase in SPB and simulated body fluid (SBF) at pH 7.5. The latter medium was used to evaluate the bioactivity of the composites. A control PCL sample was analysed before the addition of the AP component. As regards the untreated samples, the method of synthesis utilised for preparing the composite was found to enhance the crystallinity degree. The AP component revealed to be constituted of a B-type carbonated hydroxyapatite with a 3% carbonate content. After 28 days of treatment, the samples showed different degradation patterns and extents depending on the degradation medium, the starting PCL crystallinity and composite composition. Weight measurements, Raman and TG analyses revealed deposition of an apatitic phase on all the composites immersed in SBF. Therefore, all the samples displayed a good bioactivity; the sample which showed the most pronounced apatitic deposition was 50/50, i.e. that containing the highest amount of AP.

Apatites↗
PubMed2006

Raman microspectroscopy: a noninvasive tool for studies of individual living cells in vitro.

There is an increasing need for noninvasive methods that are able to monitor individual live cells in vitro, including in vitro testing of chemicals and pharmaceuticals, monitoring the growth of engineered tissues and the development of cell-based biosensors. Raman spectroscopy is a pure optical technique based on inelastic scattering of laser photons by molecular vibrations of biopolymers, which provide a chemical fingerprint of cells or organelles without fixation, lysis or the use of labels and other contrast-enhancing chemicals. Changes in cells during the cell cycle, cell death, differentiation or during the interaction with various chemicals or materials involve biochemical changes that can be measured with high spatial ( approximately 300 nm) and temporal (seconds to minutes) resolution. The latest technological developments, especially high-sensitivity charged coupled detectors and high-power near-infrared lasers, have spurred the growth of Raman microspectroscopy towards being a well established analytical tool. This review covers the recent applications of this technique, including studies of individual cells, both pro- and eukaryotes, and emphasizes the potential impact on modern scientific endeavors, such as tissue engineering and drug discovery.

Animals↗
PubMed2006

Scale-based normalization of spectral data.

Classification of data that arise as signals or images often requires a standardization step so that information extracted from biologically equivalent signals can be quantified for comparison across classes. Differences in global trend, total energy, high-frequency noise and/or local background can arise from variabilities due to instrumentation or conditions during data collection. This article considers some common ways in which such variation is adjusted for and introduces a generalization of the popular "standard normal variate" transformation. Based on a wavelet decomposition this generalization provides increased flexibility for normalizing spectral data affected by local background noise. Examples from three types of spectroscopy data illustrate the method and its properties.

Diagnosis, Computer-Assisted↗
PubMed2001

Radiation effects of carbon ions and gamma ray on UDMA based dental resin.

The radiation effects on the mechanical and physical properties of photo-polymerized UDMA resin without filler was investigated by various mechanical tests and spectroscopic measurements. The radiation sources were carbon ion (12C ion) and gamma ray (gamma-ray). With 640 Gy of 12C ion radiation, Vickers hardness increased by about 40%, the degree of abrasion decreased by 30%, and the flexural strength increased by 20%. With the same dose of gamma-ray radiation, only Vickers hardness increased by 19%. The spectra taken by the Fourier Transform Infrared Spectrometer (FT-IR), Raman spectroscopy, and Fluorescence spectrophotometer showed little change in the peak configuration and background intensities. The relative degree of conversion (DC) of carbon double bonds by radiation to the state of non-radiated samples were estimated by FT-IR. Spectroscopic results were indicative for the formation of cross-linking between carbon chains. Cross-linking of carbon molecules induced by radiation might be one of the reasons for the improved mechanical properties of UDMA resin.

Carbon↗
PubMed1999

Beyond white light endoscopy--the prospect for endoscopic optical biopsy.

The most important factor in the successful treatment of cancer is early detection. This will be more likely to facilitate eradication of abnormal cells prior to systemic invasion. White light endoscopy has been an essential tool in medical diagnosis for a number of years. Direct endoscopic inspection of gastrointestinal organs has revolutionised diagnostic techniques, improving the targeting of biopsies of macroscopic morphological abnormalities. Recent technological developments are threatening a further revolution enabling the instantaneous and non-invasive diagnosis of microscopic tissue abnormalities in vivo. This is made possible by improving the level of information that can be obtained from the tissue. As well as the two-dimensional surface morphology image, which the traditional endoscope can view, new techniques enable structure at depth, i.e., the third-dimension, to be imaged in high resolution. Other advances enable the detection of biochemical changes in tissue that precede any changes in morphology, thus enabling earlier diagnosis of tissue abnormalities. This review details recent advances that have the greatest potential, for use in partnership with endoscopy, for the diagnosis of malignancy and pre-malignancy.

Biopsy↗