On the role of reachability and observability in NMR experimentation

It is shown that the system theoretic concepts of reachability and observability are relevant to the analysis of NMR experiments. Moreover, the sets of reachable states are examined and Lie theoretic criteria are given for the reachability of the system. The question is investigated how the set of reachable states depends on the class of input functions that are allowed. Both one‐dimensional and multi‐dimensional NMR experiments are considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

HOW DOES THE WAY IN WHICH INDIVIDUAL STUDENTS BEHAVE AFFECT THE SHARED CONSTRUCTION OF MEANING?

Audio taped discussions between three students have been examined to shed light on the way in which the behaviour of individual students may affect the shared construction of meaning with graphical calculators. These discussions revealed a complex pattern of interaction between the students. Each student was responsible for defining his or her own role within the discourse and these roles appeared to change as the discussion progressed. With reference to the framework offered by Winbourne and Watson (1998), it is proposed that local communities of practice have been established and that the individual student's positioning within the community of practice determines their success as a learner and contributes towards the creation of shared knowledge.     

Syntheses of dibenzo[b,e][1,4]dioxin derivatives via iron complexes, and further functionalizations via directed metallation

Double nucleophilic aromatic substitution reactions between (cyclopentadienyl)(η⁶-1,2-dichlorobenzene)iron(1 + ) salts and substituted 1,2benzenediols have been carried out under mild conditions to prepare [η⁶-dibenzo[b,e][1,4]dioxin]iron(1 + ) complexes functionalized in the 1- or 2-position with an alkyl, aldehyde, carboxylic acid, methoxycarbonyl, carboxamide, or hydroxy group. 3-Methyl- and 4-methyl-(η⁶-1,2-dichlorobenzene)iron complexes were treated with substituted 1,2-benzenediols to effect functionalization of both aromatic rings of the heterocycle. The dibenzodioxin ligands were liberated routinely by irradiation with ultraviolet light. Directed deprotonation of the free functionalized dibenzodioxins with an alkyllithium reagent followed by quenching with a variety of electrophiles yielded further derivatives, including two new isoindolone systems.     

Marfan syndrome in Europe

OBJECTIVES: Marfan syndrome (MFS) is a relatively frequent systemic connective tissue disorder with an important physical morbidity and mortality. The influences of MFS on physical problems, perception of severity, and impact on the quality of life and psychosocial well-being have been studied only limitedly. The aim of this study was to assess the association between the severity derived from the reported symptoms and subjectively experienced severity of MFS (expressed as a global judgment), with special emphasis regarding impact on relationships and pregnancies, psychosocial adjustment, and differences between the seven European countries. METHODS: A questionnaire designed specifically for this study and translated in each of the native languages was sent to 2,080 members of one of the patient support groups in Belgium, Denmark, France, Germany, The Netherlands, Switzerland, and the United Kingdom. 857 MFS patients of 13 years and older completed the questionnaire and were included in the data analysis. RESULTS: Physical impairments were scored by perception of severity of physical symptoms by the patients (physical severity perception score) and by their perception of the influence of MFS on their life (subjective severity score). Main discrepancy between physical severity perception and subjective severity score was the higher percentage of patients scoring in physical severity perception as severe (53.5%) compared to subjectively severe (26.5%). 61% of those who scored on the physical severity score as severely affected were designated as being mildly-moderately affected on subjective scoring. Both severity scores increased significantly with age. Two hundred-twenty women have carried 430 pregnancies (1.95 pregnancies/woman), with cardiovascular complications in 1.6%. Prenatal studies for MFS were rejected by 7.6% of MFS patients of 25 years and older, 33.6% were undecided, and 48.5% favored prenatal diagnosis for MFS if available. A positive general self-image was reported by 91.5% of patients. However, more than 90% stated that MFS had a negative influence on their sexual relationships, which they ascribed to negative perception of their body image. CONCLUSIONS: MFS has significant impact on daily life activities, but the majority of patients come to terms with their condition. Acceptance is mainly determined by subjective severity, and less by physical symptoms as reported by the patients themselves. It is important to stimulate a positive attitude towards MFS.     

Determination of dissociation temperature for ArO in inductively coupled plasma-mass spectrometry: Effects of excited electronic states and dissociation pathways

The method of comparing experimental and calculated ion ratios to determine a gas kinetic temperature (T_gas) characteristic of the origin of a polyatomic ion in inductively coupled plasma-mass spectrometry (ICP-MS) is applied to ArO⁺. Repeated measurements of ion ratios involving this species yield erratic T_gas values. Complications arise from the predicted presence of a low-lying excited electronic state (²Π) above the ⁴Σ ground state. Omission of this excited state yields unreasonably high temperatures (> 10,000 K) for nine out of nineteen trials. Inclusion of the excited electronic state in the partition function of ArO⁺ causes temperatures to increase further. The problem appears to be related to the prediction that ArO⁺ in the ²Π excited state dissociates into Ar⁺ and O, different products than ArO^{+ 4}Σ which dissociates into Ar and O⁺. Adjustments to the calculations to account for these different products yield reasonable temperatures (2100 to 3500 K) that are consistent from day-to-day and similar to those seen for other weakly-bound polyatomic ions.     

A quantitative comparison of 5-aminolaevulinic acid- and methyl aminolevulinate-induced fluorescence, photobleaching and pain during photodynamic therapy

The characteristics of protoporphyrin IX (PPIX) fluorescence in superficial basal cell carcinoma (sBCC) and carcinoma in situ (Bowen's Disease, BD) following application of 5-aminolaevulinic acid (5-ALA) and its methyl ester (methyl aminolevulinate [MAL]) before, during and after photodynamic therapy (PDT) were investigated in 40 patients. Photosensitizer prodrug penetration can limit PDT efficacy and understanding the characteristics of PPIX fluorescence through fluorescence spectroscopy, may improve knowledge of photosensitizer delivery. Fluorescence intensity was assessed quantitatively, and the rate of photobleaching was determined by fitting an exponential decay. As a secondary end-point, PDT-induced pain was also measured continuously during treatment using a novel hand-held device, known as a pain logger. In vivo PPIX fluorescence was shown to decrease during irradiation, allowing the in vivo photobleaching of PPIX to be monitored. No significant difference was found between ALA- or MAL-induced PPIX fluorescence in lesions of sBCC and BD (P>0.05), indicating no detectable difference in PPIX kinetics for the two prodrugs as assessed by these measures. Pain, as assessed by the logger device, showed high interindividual variability and pain levels tended to be higher initially, decreasing during treatment. No difference was seen in pain experienced during ALA-or MAL-PDT (P>0.05).