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  • Author: E. J. Carpenter x
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Abstract

An experimental method for the determination of Ab-Or exsolution and Al-Si ordering in alkali feldspar is described. Powder infrared spectroscopy was used to measure spectra in the spectral range between 50 and 1500 cm-1 using about 5 mg of sample material. The spectra were analyzed using reference spectra of uniform samples with various Ab-Or compositions and several degrees of Al-Si order. The application of this method is demonstrated for two examples of exsolved feldspar minerals, and it is shown that detailed characterization of alkali feldspars using IR spectroscopy leads to new insight into their structual details.

Abstract

A collection of 42 feldspar mineral samples from a wide geographical range of North America was examined by cold-cathode cathodoluminescence (CL) spectroscopy. Characteristic wavelength peaks, which were determined to be independent of geographic origin, were associated with each feldspar phase. Most of these peaks were attributed to previously assigned Mn2+ and Fe3+ luminescent centers and structural defects. An unattributed set of infrared (IR) peaks was observed in many samples; one uncommon ultraviolet (UV) peak was observed in samples from two locations. The peak centroids associated with the Mn2+ and Fe3+ luminescent centers vary with stoichiometric changes in the K-Na- Ca composition of the feldspars. For both alkali and plagioclase feldspars, shifts in CL peak centroids correlate well with lattice size, as measured by X-ray diffraction (XRD). Additional analyses of the feldspar samples by electron microprobe analysis (EMP), particle-induced X-ray emission spectroscopy (PIXE), energy-dispersive micro-X-ray fluorescence spectroscopy (μXRF), and/or laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were conducted for confirmation of elemental composition. These results demonstrate the potential of CL spectroscopy, a relatively nondestructive analytical technique, to facilitate rapid discrimination between feldspar samples. The addition of CL spectroscopy of feldspars to existing forensic analytical protocols for geologic materials has the potential to provide support for casework, both to discriminate sources in a forensic comparison, as well as to constrain the provenance of an unknown sample.

Abstract

Objective

To determine the frequency of sepsis and other adverse neonatal outcomes in women with a clinical diagnosis of chorioamnionitis.

Methods

We performed a secondary analysis of a multi-center placebo-controlled trial of vitamins C/E to prevent preeclampsia in low risk nulliparous women. Clinical chorioamnionitis was defined as either the “clinical diagnosis” of chorioamnionitis or antibiotic administration during labor because of an elevated temperature or uterine tenderness in the absence of another cause. Early-onset neonatal sepsis was categorized as “suspected” or “confirmed” based on a clinical diagnosis with negative or positive blood, urine or cerebral spinal fluid cultures, respectively, within 72 h of birth. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression.

Results

Data from 9391 mother-infant pairs were analyzed. The frequency of chorioamnionitis was 10.3%. Overall, 6.6% of the neonates were diagnosed with confirmed (0.2%) or suspected (6.4%) early-onset sepsis. Only 0.7% of infants born in the setting of chorioamnionitis had culture-proven early-onset sepsis versus 0.1% if chorioamnionitis was not present. Clinical chorioamnionitis was associated with both suspected [OR 4.01 (3.16–5.08)] and confirmed [OR 4.93 (1.65–14.74)] early-onset neonatal sepsis, a need for resuscitation within the first 30 min after birth [OR 2.10 (1.70–2.61)], respiratory distress [OR 3.14 (2.16–4.56)], 1 min Apgar score of ≤3 [OR 2.69 (2.01–3.60)] and 4–7 [OR 1.71 (1.43–2.04)] and 5 min Apgar score of 4–7 [OR 1.67 (1.17–2.37)] (vs. 8–10).

Conclusion

Clinical chorioamnionitis is common and is associated with neonatal morbidities. However, the vast majority of exposed infants (99.3%) do not have confirmed early-onset sepsis.