Measuring Nd(III) Solution Concentration in the Presence of Interfering Er(III) and Cu(II) Ions: A Partial Least Squares Analysis of Ultraviolet-Visible Spectra

Optical spectroscopy is a powerful characterization tool with applications ranging from fundamental studies to real-time process monitoring. However, it can be difficult to apply to complex samples that contain interfering analytes which are common in processing streams. Multivariate (chemometric) analysis has been examined for providing selectivity and accuracy to the analysis of optical spectra and expanding its potential applications. Here we will discuss chemometric modeling with an in-depth comparison to more simplistic analysis approaches and outline how chemometric modeling works while exploring the limits on modeling accuracy. Understanding the limitations of the chemometric model can provide better analytical assessment regarding the accuracy and precision of the analytical result. This will be explored in the context of UV-Vis absorbance of neodymium (Nd³⁺) in the presence of interferents, erbium (Er³⁺) and copper (Cu²⁺) under conditions simulating the liquid-liquid extraction approach used to recycle plutonium (Pu) and uranium (U) in used nuclear fuel worldwide. The selected chemometric model, partial least squares regression, accurately quantifies Nd³⁺ with a low percentage error in the presence of interfering analytes and even under conditions that the training set does not describe.

Quantification of Raman-Interfering Polyoxoanions for Process Analysis: Comparison of Different Chemometric Models and a Demonstration on Real Hanford Waste

The Hanford site represents a complicated environmental remediation challenge, remaining from the production of nuclear weapons. Over 100 million gallons of liquid radioactive waste of unknown composition will be chemically processed and vitrified, but the varying chemical composition and highly radioactive nature of the waste preclude the implementation of more developed, offline technologies to determine the composition. The only practical approach to waste treatment will require the significant utilization of real-time, chemometric modeling approaches. Although chemometric approaches have been applied to the analysis of Hanford waste, the models developed were highly tank-specialized, and limited discussion was provided on how models fared with interfering signals. As the tank waste is largely composed of oxoanions, which tend to have interfering Raman spectra, the general question was posed as to what chemometric approach is best suited to accurately quantify analytes in the presence of interfering signals. This was carried out by examining the ability of classical least square (CLS), principal component regression (PCR), partial least square (PLS), and locally weighted regression (LWR) to quantify NO₃^- and CO₃^2- using their bands around 1050 cm^-1. For all samples, the PLS-based model was found to be the most efficient approach from a model building and application perspective.

Plasmas: A New Class of Motion-Induced Brightness Illusion

When a white figure is set in smooth continuous motion against a dark background, a ‘shadowy’ region forms around and behind it, somewhat similar to the wake that a boat leaves in water. Conversely, when a dark figure moves against a white background, this ‘wake’ appears lighter than the background. When several such figures move, these ‘wakes’ can link up in surprising ways. For example, if four white circles of radius r are positioned on a dark background at the vertices of an imaginary square whose width is, say, 4 r, and this imaginary square rotates about its centre, bands darker than the background form between the four circles, linking them through the centre. This ‘black cross’ is nonrigid, and is accompanied by dark ‘wakes’ on the outside of the circles. I call these illusory brightness regions ‘plasmas’.

The relation of this effect to other motion-induced brightness illusions is considered. In particular, this effect has different properties than either induced gratings (McCourt, 1982 Vision Research22 119 – 134) or phantom gratings (Tynan and Sekuler, 1975 Science188 951 – 952). Plasmas are not due to retinal afterimages or persistence, since they form in regions never traversed by the moving figure. Nor are they an artifact of the computer screen, since the illusion occurs equally well in displays constructed from paper. Plasmas have the opposite phase relative to the inducing figure, disappear when a figure stops moving, are strongest at high background/inducer contrast, and are most visible when the luminance of the inducers is in the photopic range. Experiments measuring the strength of plasmas as a function of angular velocity and visual angle are described. A model is proposed according to which plasmas are due to a phase lag in luminance-edge induced lateral inhibition.

NOD2/CARD15 gene polymorphisms and Crohn's disease in the Chinese population

BACKGROUND

Crohn's disease affects people world-wide, but the incidence in Asia is lower than in Western countries. This difference may be due to genetic and/or environmental factors. Three single nucleotide polymorphisms (SNPs) of the NOD2/CARD15 gene have been identified to be independently associated with the development of Crohn's disease in Caucasians. Whether these SNPs are involved in the pathogenesis of Crohn's disease in the Chinese population is unknown.

AIM

To determine if NOD2/CARD15 gene polymorphisms are found in Chinese patients with Crohn's disease.

METHODS

Sixty-five consecutive Chinese Crohn's disease patients had genotyping performed using sequence-specific PCR directed against the wild-type and the Arg702Trp, Gly908Arg and 3020insC variants of the NOD2/CARD15 gene. Controls consisted of 63 patients with ulcerative colitis and 70 patients with dyspepsia.

RESULTS

None of the patients with Crohn's disease had heterozygous or homozygous SNP variants. Similarly none of the ulcerative colitis or dyspeptic controls had these SNPs.

CONCLUSION

The three previously described SNPs associated with the development of Crohn's disease in Caucasians are not found in Chinese patients with Crohn's disease.

Helicobacter pylori in an institution for disabled children in Hong Kong

Anti-Helicobacter pylori antibodies were determined in 157 institutionalised Cantonese children, mean age 9.5 +/- 3.9 (SD) years, with profound neurodevelopmental disabilities. Eighty-seven (55.4%) were H. pylori seropositive compared with four of 50 (8%, P > 0.0002) of an age-matched control group, mean age 7.2 +/- 4.3 (SD) years. Eight of 15 seropositive children with a recent history of upper gastrointestinal bleeding underwent endoscopy and in all cases gastric infection with H.pylori was confirmed. Anthropometric data from institutionalised children revealed marked malnutrition but showed no significant difference between seropositive and seronegative children. Disabled children receiving long-term residential care in Hong Kong are confirmed to be at increased risk of H.pylori infection.

Comparison of a single-antigen microimmunofluorescence assay and inclusion fluorescent-antibody assay for detecting chlamydial antibodies and correlation of the results with neutralizing ability

An inclusion fluorescent-antibody assay (IFA) with McCoy cells infected with Chlamydia trachomatis serovar L2 was compared with a single-antigen (L2) microimmunofluorescence (MIF) assay for the detection of antichalmydial antibodies. A total of 562 serum specimens were tested by both assays, and sera representing a range of titers were tested for their ability to neutralize the infectivity of C. trachomatis. Overall, there was poor correlation between the two assays (r2 = 0.62). With most sera the inclusion IFA was more sensitive. There was better correlation between IFA titer and ability to neutralize the five serovars tested (L2, L3, C, E, and F) than between the MIF assay and neutralization. In summary, the IFA appeared to be more sensitive than the MIF assay for detecting antibodies to C. trachomatis.

Detection of herpes simplex virus by 8 h in shell vial cultures with primary rabbit kidney cells

Shell vial (SV) cultures for herpes simplex virus using primary rabbit kidney cells stained at 8 h after inoculation were compared with 20-h SV cultures as well as conventional tissue culture. Of the 326 clinical specimens examined, conventional culture detected 67, and of these, 61 (91%) and 42 (63%) were detected by 20-h SV cultures and 8-h SV cultures, respectively.

Surgery for neglected congenital torticollis

Nineteen patients were operated on for congenital muscular torticollis after the age of 1 year. Tenotomy gave good results below 5 years of age and resection of the sternocleidomastoid muscle was satisfactory in most of the older children.