Extended soft X-ray emission spectroscopy: quantitative assessment of emission intensities.

Soft X-ray emission spectroscopy (SXES) in the energy range between 150 eV and 1500 eV has typical attenuation lengths between tens and a few hundred nanometres. In this work the transmission of soft X-rays in synchrotron-based SXES has been quantitatively analysed using specially prepared layer samples. The possibility of extending the standard qualitative analysis of SXES by exploiting the information underlying the emission intensity was examined for thin layer structures. Three different experiment series were accomplished with model layer systems based on different sulfur-containing substrates: (i) MoS(2), (ii) CuInS(2), (iii) Cu(In,Ga)(S,Se)(2). The absorption of the S L(2,3) emission line by ZnO cover layers of up to 80 nm thickness was monitored and compared with theoretical expectations. By comparison with a reference intensity recorded from a bare substrate, the attenuation of the S L(2,3) emission could be used to accurately determine the ZnO overlayer thickness up to a critical thickness, depending on the set-up and the net S L(2,3) emission intensity. The results from these local energy-resolved spot measurements were compared with spatially resolved scans of the integral S L(2,3) emission intensity over areas of several mm(2). In the scan images the attenuation of the S L(2,3) emission intensity clearly reflects the local ZnO layer thickness. From the attenuation the ZnO layer thicknesses were calculated and compared with ellipsometric measurements and were found to be in excellent agreement. These results demonstrate the benefits of a quantitative analysis of SXES, making it an even more powerful tool for examining buried interfaces and for monitoring lateral inhomogeneities.

Antibodies against N-methyl-D-aspartate receptors in patients with systemic lupus erythematosus without major neuropsychiatric syndromes.

PURPOSE: Approximately 14-54% of patients with systemic lupus erythematosus without a history of major neuropsychiatric syndromes (nonNPSLE) have cognitive deficits. Elevated N-methyl-D-aspartate (NMDA) receptor antibodies (anti-NR2) have been reported in 35% of patients with SLE, but few studies have utilized controls or a composite memory index. We hypothesized that serum anti-NR2 would be elevated in nonNPSLE compared to healthy controls, and that elevated anti-NR2 would be associated with memory dysfunction and depression. METHODS: Subjects included 43 nonNPSLE patients with a mean age of 36.5 (SD=9.0) and mean education level of 14.7 years (SD=2.5). Twenty-seven healthy control subjects with similar demographic characteristics were also enrolled in this study. A global Cognitive Impairment Index (CII) and a Memory Impairment Index (MII) were calculated using impaired test scores from the ACR-SLE neuropsychological battery. Serum samples were analyzed using a standard ELISA for anti-NR2. RESULTS: Elevations of serum anti-NR2 were found in 14.0% of the nonNPSLE and 7.4% of the controls (p=0.47). There was no relationship between elevated anti-NR2 status and higher CII or performance on the MII. No relationship between levels of depressive symptoms and anti-NR2 was found. CONCLUSIONS: The frequency of elevated anti-NR2 was low (14.0%) in this sample of SLE patients and not significantly different from controls. A relationship was not found between the presence of anti-NR2 in serum and global cognitive or memory indices, or with depression. Results suggest that serum anti-NR2 is not likely related to mild cognitive dysfunction in SLE patients without a prior history of NPSLE.

White matter microstructure and cognition in non-neuropsychiatric systemic lupus erythematosus.

OBJECTIVE: This study examined white matter (WM) structural and metabolic alterations in relation to cognition in patients with non-neuropsychiatric systemic lupus erythematosus (non-NPSLE). BACKGROUND: SLE can produce cognitive impairment even without overt neuropsychiatric features, but the pathogenesis of this dysfunction is not well understood. Our preliminary study of non-NPSLE found evidence correlating cognitive impairment with increased choline/creatine (Ch/Cr) in frontal lobe WM. METHODS: Subjects included 60 non-NPSLE patients and 24 controls. Magnetic resonance imaging and magnetic resonance spectroscopy were performed, and a battery of neuropsychologic tests was administered. Structural and metabolic measures were analyzed and correlated with neuropsychologic data. RESULTS: No significant differences were found in total brain, gray matter, and WM volumes, or in frontal WM N-acetylaspartate/Cr, but the non-NPSLE group had significantly increased Ch/Cr in frontal WM. A WM cognitive score (WMCS) that included the Paced Auditory Serial Addition Task, Letter Fluency, and Animal Naming was found to correlate with total WM volume, and lower WMCS correlated with higher left frontal WM Ch/Cr. CONCLUSIONS: Non-NPSLE patients had frontal WM metabolic changes that correlated with cognitive impairment, whereas no cerebral atrophy or WM axonal damage was evident. These data confirm and extend our previous observations supporting the role of microstructural WM changes in the cognitive impairment of non-NPSLE patients. The data also suggest that the WMCS may be sensitive to cognitive dysfunction from myelin damage that develops before axonal injury.

Cognitive and neurologic status in patients with systemic lupus erythematosus without major neuropsychiatric syndromes.

OBJECTIVE: To examine neuropsychological and neurologic functioning in systemic lupus erythematosus (SLE) patients without histories of overt neuropsychiatric disorders (non-NPSLE patients). METHODS: Sixty-seven non-NPSLE patients and 29 healthy controls were administered a standardized neurologic examination and measures of cognition, depression, and self-reported cognitive functioning. RESULTS: Non-NPSLE patients scored lower than controls on the total score of the neurologic examination (P < 0.0001). Item analysis indicated that the physician's description of mentation and mood was the only item that differed significantly between patients with SLE and controls (P = 0.004). Compared with controls, non-NPSLE patients had significantly higher rates of impairment on logical reasoning (P = 0.012) and verbal memory (P = 0.03), and trends toward greater impairment on visual attention (P = 0.06) and working memory (P = 0.098). There were no significant differences between non-NPSLE patients and controls on a cognitive impairment index (CII): 20.9% of non-NPSLE patients and 13.8% of controls were impaired. Patients with SLE scored higher on depressive symptoms (P < 0.0001) and perceived cognitive difficulties (P = 0.001) compared with controls. CONCLUSION: The utility of a standardized neurologic examination in SLE for excluding overt neurologic dysfunction and assuring a non-NPSLE group selection was demonstrated. In contrast to our earlier study, we did not find differences between non-NPSLE patients and controls on the CII. Slightly lower CII scores in non-NPSLE patients and higher CII scores in controls may have reduced cognitive differences between these groups. Non-NPSLE patients demonstrate specific decline in the areas of attention, memory, and reasoning; continued studies of associated brain regions are warranted.