Simplicity of construction and operation are advantages of iTMC (ionic transition metal complex) OLEDs compared with multi-layer OLED devices. Unfortunately, lifetimes do not compare favorably with the best multi-layer devices. We have previously shown for Ru(bpy)3(PF6)2 based iTMC OLEDs that electrical drive produces emission-quenching dimers of the active species. We report evidence here that a chemical process may also be implicated in degradation of devices based on Ir(ppy)2(dtb-bpy)PF6 albeit by a very different mechanism. It appears that degradation of operating devices made with this Ir-based complex is related to current-induced heating of the organic layer, resulting in loss of the dtb-bpy ligand. (The dtb-bpy ligand is labile compared with the cyclometallated ppy ligands.) Morphological changes observed in electrically driven Ir(ppy)2(dtb-bpy)PF6 OLEDs provide evidence of substantial heating during device operation. Evidence from UV-vis spectra in the presence of an electric field as well as MALDI-TOF mass spectra of the OLED materials before and after electrical drive add support for this model of the degradation process.

Although textiles were important commodities in the Aztec political economy, it is widely held that textile production did not involve organized workshops. In the late 1960s, Charlton (1971, 1981) found a concentration of large spindle whorls at the Aztec city-state capital of Otumba that he interpreted as remains of a maguey-fiber workshop. A subsequent survey and surface collections made by the Otumba Project discovered additional concentrations of spindle whorls associated with fiber-processing tools and manufacturing debris that provide substantial evidence for organized maguey-fiber workshops at Otumba. An unusually large sample of more than 1,600 spindle whorls was recovered in surface collections from sites in the Aztec city-state of Otumba where both small cotton whorls and large maguey whorls occurred in low densities associated with concentrations of domestic pottery (and in some cases house-mound remnants). In the Aztec capital town of Otumba, maguey spindle whorls were also present in localized dense concentrations within a restricted area of the site. These concentrations also included molds for making spindle whorls, “wasters,” a high density of heavily worn obsidian blades and basalt scrapers used in fiber production, and obsidian scrapers. Based on the quantities and types of associated artifacts we argue that these concentrations represent remains of Late Aztec maguey-fiber workshops that were household based. The workshops processed maguey fibers and made maguey spindle whorls in a range of sizes for spinning thin and thick threads and cordage. Secondary craft activities in one workshop included making cotton spindle whorls and some lapidary and figurine manufacturing. Maguey-fiber processing, spinning, and, presumably, weaving also took place in rural villages, but evidence of organized workshops has only been found at the urban center. The growth of the maguey-fiber industry at Otumba during the Late Postclassic period was part of a broader economic trend of production intensification in the northeastern Basin of Mexico that included xerophytic plant cultivation and craft specialization.

Objective: To determine the prevalence of dementia in an Irish sample of Down's syndrome (DS) patients and to examine the utility of a number of cognitive and functional scales in the assessment of dementia in this population.

Method: 76 DS patients diagnosed clinically (range 33–72 years; mean age 47.3 ± 8.8 years) were included in the study. The diagnosis of dementia was made on clinical grounds using DSMIIIR criteria. Cognitive and functional impairment were evaluated using the following scales; Test for Severe Impairment (TSI), Down's Syndrome Mental Status Examination (DSMSE), Daily Living Skills Questionnaire (DLSQ), and the Mental State Performance (MSP).

Results: The overall prevalence of dementia was 7.9% (95% C.I = 2.95–16.39). The presence of dementia was associated with late onset epilepsy, anticonvulsant medication and deafness. Standard cognitive tests such as the MSP showed an early ‘floor’ effect in this population. In contrast the TSI and DLSQ showed a satisfactory range of scores in these patients with moderate to severe learning disability.

Conclusions: The low prevalence of dementia in this study may be explained by the strict conservative criteria applied in the clinical diagnosis. Prospective assessment of DS patients on a longitudinal basis using decline on scales such as the TSI and DLSQ may allow more accurate diagnosis of dementia at an earlier stage in this at-risk population.

To introduce the theme of this essay, there are few statements more fitting than the caustic judgment of Albertus Magnus on those whom he considered the enemies of freedom in his day. Reproaching the petty obscurantism of the opponents of Aristotle's philosophy, he described these men, whose sole aim in reading books was to find something to condemn, as stagnant themselves in intellectual inertia, and seeking always to paralyze others into their own state. It was men like these, he said, who killed Socrates, and whose plots forced Aristotle to leave Athens with the words, “I shall not give the Athenians a second chance of sinning against philosophy.” In the world of learning, according to Albertus, such bitter, bilious men are like the liver in the body; “they try to inject their own bitterness into everyone else, and to prevent others from pursuing truth in the sweetness of society.”