Commutation with Ternary Sets of Words

We prove that for any nonperiodic set of words F \subseteq ⁺ with at most three elements, the centralizer of F, i.e., the largest set commuting with F, is F^*. Moreover, any set X commuting with F is of the form X = F^I, for some I \subseteq . A boundary point is thus established, as these results do not hold for all languages with at least four words. This solves a conjecture of Karhumäki and Petre, and provides positive answers to special cases of some intriguing questions on commutation of languages, raised by Ratoandromanana and Conway.     

A 16-year follow-up study of physical capacity in relation to perceived workload among ageing employees

The main purpose of this study was to ascertain musculoskeletal and cardiovascular capacity among ageing employees in relation to workload over a period of 16 years. The data were obtained by physical capacity tests and ratings of perceived exertion (RPE) during working day. The study group consisted of 89 subjects, who were all employed in the municipal branch and were on average 51.9 years old at the beginning of the follow-up period in 1981 and 67.3 years in 1997, when the most of the subjects had retired (with only two subjects still working). During the 16-year follow-up period, age-related decline in physical capacity was observed. Nevertheless the improvement in flexibility of spine and in isometric trunk muscle strength compared with the same age subjects was more common among the subjects with high workload than among the subjects with low workload. However, among the subjects with high workload, physical capacity was poorer than among the subjects with low workload, especially among the women. The results suggest the conclusion that there are differences in workers' physical capacity in relation to their perceived workload during working life. These differences remained when the subjects had retired. Interestingly, those who had high workload had lower muscle strength than those who had low workload. This may indicate that high physical workload does not have any training effect on the muscle strength of ageing workers.     

Microbial diversity in a thermophilic aerobic biofilm process: analysis by length heterogeneity PCR (LH-PCR)

A two-stage pilot-scale thermophilic aerobic suspended carrier biofilm process (SCBP) was set up for the on-site treatment of pulp and paper mill whitewater lining. The microbial diversity in this process was analyzed by length heterogeneity analysis of PCR-amplified 16S ribosomal DNA. The primer pair selected for PCR amplification was first evaluated by a computational analysis of fragment lengths in ten main phylogenetical eubacterial groups. The fragment contained the first third of the 16S rRNA gene, which was shown to vary naturally between 465 and 563 bp in length. The length heterogeneity analysis of polymerase chain reaction (LH-PCR) profile of the biomass attached to carrier elements was found to be diverse in both stages of the SCBP. During normal operating conditions, sequences belonging to beta-Proteobacteria, Cytophaga/Flexibacter/Bacteroides group and gamma-Proteobacteria were assigned to the most prominent LH-PCR peak. Samples from the suspended biomass consisted of completely different bacterial populations, which were, however, similar in the serial reactors. The pilot process experienced alkaline shocks, after which Bacillus-like sequences were detected in both the biofilm and suspended biomass. However, when the conditions were reversed, the normal microbial population in the biofilm recovered rapidly without further biomass inoculations. This study shows that LH-PCR is a valuable method for profiling microbial diversity and dynamics in industrial wastewater processes.     

Determinants of user participation: a Finnish survey

The relationship between user participation and information systems success has intrigued researchers for two decades. Despite this history there is minimal research on the antecedents of user participation. The tenet of the present paper is that the conditions of user participation are essentially changing. Especially, the European tradition of user participation has focused on blue collar workers rather than professionals and managers. Users are normally assumed to be computer illiterate. The North American tradition has almost exclusively focused on the impact of user participation on information systems success. The present paper examined the significance of organizational level of users, their task variety and computer experience as determinants of user participation including age, gender, education, computer training, organizational tenure and job tenure as control variables. The three determinants were found to have a significant positive effect on user participation, computer experience emerging as the most dominant factor. Gender, education and computer training were discovered to have significant effects mediated by organizational level, task variety and computer experience.     

Pareto optima of isostatic trusses

Multicriterion optimization of elastic stress limited isostatic trusses is considered and a numerical method for determining the Pareto optimal set of the problem is developed. The weight of the structure and some chosen nodal displacements are taken as design criteria, and member areas are used as design variables. The corresponding bicriterion problem with weight and one displacement in the objective function is solved exactly, and this result is used as a basis of the proposed method. By introducing certain parameters, each joined with one displacement criterion, the Pareto optimal solutions of the general problem may be obtained with any accuracy. Two examples are given to illustrate the method.     

Why the old world cannot publish? Overcoming challenges in publishing high-impact IS research

We review the status of European publishing in high-impact Information System (IS) journals finding that the European publication record is disappointing. We consider popular explanations to this state of affairs and find them neither credible nor useful for improving the European record. We propose several constructive reasons for this including (1) the lack of appreciation of the article genre, (2) weak publishing cultures, (3) inadequate Ph.D. preparation for article publishing, (4) weak reviewing practices, (5) poorer command of research methods, (6) poorer understanding of the reviewing protocols, and (7) institutional shaping of research funding in Europe. We formulate several recommendations to affect these causes at the individual, institutional, journal, and European community level.     

新辊面包覆降低能耗

正纸与纸板生产属于能耗密集型产业,大部分能量用于流浆箱前的磨木、筛选等备浆工段以及烘干部的蒸发脱水。截至目前,人们研究的重点一直是如何降低这些工艺段的能耗。然而,通过强化压榨脱水,可大幅降低压榨部的传动能耗和烘干部的干燥能耗,由此而产生的成本效益也相当明显。     

The Sixth Sense: The Meaning of Atmosphere and Mood

Through its blinkered emphasis on visual form and function, has modernity divorced us from our sense of belonging to the cosmos? What, then, is the secret of creating architecture that envelops and inspires us? As scientific research increasingly favours the point of view that our unconscious – as opposed to detailed – perception has higher existential value, Helsinki-based architect and professor emeritus Juhani Pallasmaa argues that peripheral vision is key. Only through engagement with this can architects trigger what could be described as our sixth sense – the atmospheric.