Studying the adsorption of emerging organic contaminants in zeolites with dispersion-corrected density functional theory calculations: From numbers to recommendations

Adsorption energies obtained from dispersion-corrected density functional theory (DFT) calculations show a considerable dependence on the choice of exchange-correlation functional and dispersion correction. A number of investigations have employed different approaches to compute adsorption energies of small molecules in zeolites, using reference values from high-level calculations and/or experiments. Such comparative studies are lacking for larger functional organic molecules such as pharmaceuticals or personal care products, despite their potential relevance for applications, e. g., in contaminant removal or drug delivery. The present study aims to fill this gap by comparing adsorption energies and, for selected cases, equilibrium structures of emerging organic contaminants adsorbed in MOR- and FAU-type all-silica zeolites. A total of 13 dispersion-corrected DFT approaches are compared, including methods using a pairwise dispersion correction as well as non-local van der Waals density functionals. While absolute values of adsorption energies vary widely, qualitative trends across the set of zeolite-guest combinations are not strongly dependent on the choice of functional. For selected cluster models, DFT adsorption energies are compared to reference values from coupled cluster (DLPNO-CCSD(T)) calculations. Although all DFT approaches deliver systematically more negative adsorption energies than the coupled cluster reference, this tendency is least pronounced for the rev-vdW-DF2 functional.

Alpha power during task performance predicts individual language comprehension

Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized these effects in left temporal-parietal brain regions known to be associated with language processing and their right-hemisphere homologues. Our results support the notion that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance.

Genetic risk variants for dyslexia on chromosome 18 in a German cohort

Dyslexia is characterized by impaired reading and spelling. The disorder has a prevalence of about 5% in Germany, and a strong hereditary component. Several loci are thought to be involved in the development of dyslexia. Scerri et al. identified eight potential dyslexia-associated single nucleotide polymorphisms (SNPs) in seven genes on chromosome 18 in an English-speaking population. Here, we present an association analysis that explores the relevance of these SNPs in a German population comprising 388 dyslexia cases and 364 control cases. In case-control analysis, three nominal SNP associations were replicated. The major alleles of NEDD4L-rs12606138 and NEDD4L-rs8094327 were risk associated [odds ratio (OR) = 1.35, 95% confidence interval (CI) = 1.0-1.7, P-value = 0.017 and OR = 1.39, 95% CI = 1.1-1.7, P-value = 0.007, respectively], and both SNPs were in strong linkage disequilibrium (r(2)  = 0.95). For MYO5B-rs555879, the minor allele was risk associated (OR = 1.31, 95% CI = 1.1-1.6, P-value = 0.011). The combined analysis of SNP sets using set enrichment analysis revealed a study-wide significant association for three SNPs with susceptibility for dyslexia. In summary, our results substantiate genetic markers in NEDD4L and MYO5B as risk factors for dyslexia and provide first evidence that the relevance of these markers is not restricted to the English language.

[Why do workers apply for disability pension although their vocational ability is maintained? - a qualitative study of patients after cardiac events]

The central question of this study is why workers in the employable age group apply for disability pension although from a medical point of view their vocational ability is maintained. The aim is to identify factors in the system and of the applicant which may serve as subjective prognostic indicators for maintaining employment and for determining influences which may be of prognostic value for a pension application. Concomitantly, it is aimed to obtain guidelines for practical rehabilitation and to generate impulses for further research in this field. Within a qualitative research project 16 problem-focused interviews with patients insured by "Deutsche Rentenversicherung Nord" and treated in a cardiac rehabilitation centre in Mecklenburg-Vorpommern were undertaken. Patients with either a positive or a negative subjective prognosis concerning employment were interviewed. In addition, the interviews were followed by a questionnaire one year later. The results show differences and similarities in the motivation of patients applying for disability pension. This can be traced back to psychosocial variables, sociodemographic characteristics, moderating factors and the effects of socialisation. Physical impairment was of secondary importance to the patients' motivation to apply for disability pension. The results of the follow-up questionnaire show that an existing job significantly improves the subjective prognosis for maintaining gainful employment. The application for disability pension offers the affected individual a possibility to ensure a basic existence in the case of illness and unemployment. The identified factors may be influenced by modifying the interventions and improving medical counselling during the rehabilitation period.

Which stage of the process of apotransketolase interaction with thiamine diphosphate is affected by the regulatory activity of the donor substrate?

The interaction of thiamine diphosphate (ThDP) with transketolase (TK) involves at least two stages: [formula: see text] During the first stage, an inactive intermediate complex (TK...ThDP) is formed, which is then transformed into a catalytically active holoenzyme (TK* - ThDP). The second stage is related to conformational changes of the protein. In the preceding publication (Esakova, O. A., Meshalkina, L. E., Golbik, R., Hübner, G., and Kochetov, G. A. Eur. J. Biochem. 2004, 271, 4189 - 4194) we reported that the affinity of ThDP for TK considerably increases in the presence of the donor substrate, which may be a mechanism whereby the activity of the enzyme is regulated under the conditions of the coenzyme deficiency. Here, we demonstrate that the substrate affects the stage of the reverse conformational transition, characterized by the constant k(-1): in the presence of the substrate, its value is decreased several fold, whereas K(d) and k(+1) remain unchanged.

The role of a computerised case-based testing procedure in practice performance assessment

INTRODUCTION

For postgraduate training of doctors there is a need for valid and reliable instruments to assess their daily performance. Various instruments have been suggested, some of which use incognito simulated patients (SPs). These methods are resource intensive. Computerised Case-based testing (CCT) is logistically simpler and may still predict performance well. The research question was to evaluate the predictive validity of CCT for performance.

METHODS

Seventeen rheumatologists were each visited by eight incognito SPs presenting various rheumatological complaints, and scoring the performance of the rheumatologists using a predefined checklist. From this checklist a panel of experts identified essential items. In addition the rheumatologists sat a CCT test containing 55 cases with a total of 121 items.

RESULTS

Negative correlations were found between the SP scores and the CCT scores. This was unexpected. Therefore, background variables on experience were used to compare both methods. The correlation between these and CCT were high and positive and with the SP scores high and negative. This pattern did not differ when using the essential items of the checklist. Reliabilities of the SP scores were markedly high.

DISCUSSION

Although CCT was not predictive of SP scores, it was related to working experience. There are good reasons to assume that although SP-scores were more authentic, they were less valid than CCT scores, mainly because they focussed more on thoroughness than on efficiency in data gathering. The results underpin the assumption that for valid performance assessment the most important issue is what information about the candidate is collected and now how authentic the method is.

Rhemulatologists' performance in dailiy practice

OBJECTIVE

To assess rheumatologists' performance for 8 rheumatologic conditions and to explore possible explanatory factors.

METHODS

After written informed consent was obtained, 27 rheumatologists (21% of all Dutch rheumatologists) practicing in 16 outpatient departments were each visited by 8 incognito "standardized patients" (SPs). The diagnoses of these 8 cases account for about 23% of all new referred patients in the Netherlands. Results for ordered lab tests as well as real radiographs with corresponding results from a radiologist were simulated. Information from the visits was obtained from the SPs, who completed predefined case-specific checklists, and by collecting data on resource utilization. Feedback was provided.

RESULTS

Altogether 254 encounters took place, of which 201 were first visits and 53 were followup visits. SPs were unmasked twice during a visit. There was considerable variation in resource utilization (lab tests and imaging) between cases and between rheumatologists. Mean costs per rheumatologist ranged from US $ 4.67 to $ 65.36 per visit for lab tests and from US $ 33.15 to $ 226.84 per visit for imaging tests. No significant correlations were seen between resource utilization costs and number of years of clinical experience or performance on checklist scores. Rheumatologists with longer experience had lower total item checklist scores (r = -0.47; P < 0.05).

CONCLUSION

A considerable variation in resource utilization was found among 27 Dutch rheumatologists. The information obtained is an excellent source for discussion on the appropriateness of care.

Brief communication: Tigaran (Point Hope, Alaska) tooth drilling

In a sample of 48 adult Tigarans (1300-1700 A.D.) from Point Hope, Alaska, 33 exhibited various degrees of periodontal disease, which, in 25, resulted in tooth loss (Schwartz, unpublished data). Although extreme examples of tooth wear were prevalent in the sample, carious infection was noted in only one individual, in whom the lower central incisors (I1S) had been affected. In the left I1, infection had spread through the root's apex into the alveolar bone, causing an abscess. The buccal (labial) side of the root of this tooth, just below the crown, bears a shallow, relatively flat-bottomed depression, with a small perforation into, as well as a second hole that fully penetrates, the root canal. Both of these features appear to have been produced by an implement, and, as they are associated with a diseased tooth, and ritualistic tooth shaping or drilling of any sort was, and is, not practiced among Arctic groups, their purpose was probably therapeutic. As such, this specimen appears to represent a case of precontact New World Arctic dentistry.

Digoxin concentrations in serum and cantharides blister fluid: correlations with cardiac response

The relationship between the pharmacokinetics and dynamics of digoxin was investigated using a skin blistering technique that allows experimental access to tissue fluid concentrations. Eight healthy volunteers received digoxin, 1.0 mg, and placebo intravenously according to a double-blind crossover design. Drug concentrations were determined during a 72-hour period in serum, urine, and cantharides blister fluid (CBF). Digoxin levels in the hypothetic peripheral compartments were calculated from serum concentrations. Digoxin effects (total electromechanical systole [QS2c], left ventricular ejection time [LVETc], preejection period [PEPc], QTc time, heart rate, and T wave amplitude) were measured simultaneously. Peak levels in the shallow and deep compartments occurred at 12 1/2 to 20 minutes and 3 hours and the maximum concentration in CBF (2.75 +/- 0.48 ng/ml) occurred at 1 hour. Digoxin effects on QS2c, PEPc, and the ratio PEP/LVET were not related to serum concentrations but were closely related to CBF concentrations (r = 0.90). CBF concentrations were then within the range of serum digoxin concentrations usually associated with the treatment of heart failure. Thus, CBF allows experimental access to active drug concentrations after a single intravenous dose.