An efficient algorithm for positive realizations

We observe that successive applications of known results from the theory of positive systems lead to an efficient general algorithm for positive realizations of transfer functions. We give two examples to illustrate the algorithm, one of which complements an earlier result of [L. Benvenuti, L. Farina, An example of how positivity may force realizations of ‘large’ dimensions, Systems Control Lett. 36 (1999) 261–266]. Finally, we improve a lower-bound of [B. Nagy, M. Matolcsi, A lower-bound on the dimension of positive realizations, IEEE Trans. Circuits Syst. I 50 (2003) 782–784] to indicate that the algorithm is indeed efficient in general.     

Understanding sources of user variability in computer-based data entry performance

The pervasive use of computers in work settings implies that an increased number of workers, with varying levels of skills and abilities, will be performing computerbased tasks. This study investigated the impact of age, cognitive abilities, and computer experience on the performance of a real world data entry task. One hundred and ten subjects, ranging in age from 20 - 75 years, performed the task for nine hours following task training. The results indicated that abilities such as visuo-spatial skills, motor skills and processing speed had a significant impact on performance as did age and prior computer experience. With respect to age, the older participants completed less work than the younger and middle-aged subjects. Age differences in psychomotor skills and processing speed appeared to be important factors underlying age effects. In fact, the data indicated that after controlling for differences in these abilities age was no longer a significant predictor of work output. Further, after controlling for differences in work output the older people made fewer errors than the younger people. Overall the data suggest that older people will be at a disadvantage in the performance of computer-based data entry work to the extent to which speed of responding is emphasized. However, if speed of responding is not a critical element of performance they will be able to achieve comparable levels of performance to that of younger people.     

Levels of polybrominated diphenyl ethers in house dust in Central Poland

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in numerous products, from which they are emitted to the environment, including house dust. House dust is a source of human exposure to these compounds by ingestion. The aim of this article was to determine the levels of selected PBDEs in the house dust and indicate their potential sources of origin. PBDE congeners: BDE‐47, BDE‐99, BDE‐153 and BDE‐209, were analyzed in 129 samples. The geometric mean levels (and 95% CIs) of the aforementioned congeners amounted to 3.8 (3.1–4.7) ng/g, 4.5 (3.5–5.6) ng/g, 2.2 (2.1–2.4) ng/g and 345 (269–442) ng/g respectively. BDE‐209 was the dominant congener in the majority of tested samples. We found a statistically significant correlation between the concentrations of BDE‐47 and the computer operating time per day (r_s – 0.18) and the living area (r_s – 0.20). Statistically significant higher levels of BDE‐99 were found in homes where the floor was not replaced during the last 2 years.     

Allgemeine Untersuchungsverfahren und Laboratoriumstechnik

Ohne Zusammenfassung     

Effects of female hormonal condition on body weight of male partners: Dependence on testicular factors.

Four experiments explored the short-term effects of female estrous condition or gonadal hormones on body weight (BW) of male guinea pigs. The BW of male Ss and their ovulating female partners initialy showed a significant periovular suppression relative to those of female cagemates that were not ovulating at that time. Similar effects in male rats have been hypothesized to result from postcopulatory increases in circulating testosterone (TTT) and the conversion of that TTT to estradiol (ED). To evaluate the role of the guinea pig testes in this phenomenon, intact and castrated males were housed with ovariectomized females. Female estrus, induced by injecting the females with ED and progesterone, resulted in an immediate decline in BW of the intact male partners, but the BW of castrated male partners was unaffected. Additional tests evaluated the direct effects of ED and TTT on BW of males. Injections of up to 1 mg per day of TTT propionate were insufficient to produce short-term suppression of BW in either intact or castrated males. However, treatment of the males with ED readily reduced their BW. Overall, results are not consistent with the hypothesis that short-term reductions in BW of mated males result from immediate postcopulatory increases in circulating TTT. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive and learning difficulties and how they affect access to IT systems

In October 2005, the IBM Human Ability and Accessibility Center and T.J. Watson Research Center hosted a symposium on “cognitive and learning difficulties and how they affect access to IT systems”. The central premise of the symposium was the recognition that cognitive and learning difficulties have a profound impact on a person’s ability to interact with information technology (IT) systems, but that little support is currently being offered by those systems. By bringing together internationally renowned experts from a variety of different, but complementary, research fields, the symposium aimed to provide a complete overview of the issues related to this topic. This paper summarises the discussions and findings of the symposium.     

Using a Square-Wave Signal for Fault Diagnosis of Analog Parts of Mixed-Signal Electronic Embedded Systems

This paper presents a new approach to the detection and localization of single hard and soft faults of analog parts in embedded mixed-signal electronic systems controlled with microcontrollers, DSPs, or Systems-on-a-Chip (SoCs) (generally control units). The approach consists of three stages: a pretesting stage of creation of the fault dictionary using identification curves, a measurement stage based on stimulating the tested circuit by a square-wave signal generated by the control unit, and measurements of voltage samples of the circuit response by the internal ADC of the control unit. In the final stage, fault detection and localization are performed by the control unit. The measurement microsystem [the built-in self test (BIST)] consists only of internal devices of the control unit already existing in the system. Hence, this approach simplifies the structure of BISTs, which allows reduction of test costs. The results of experimental verification of the approach are included in this paper.      

Causes and Effects of Uncontrolled Water Inrush into a Decommissioned Mine Shaft

Central Europe experienced catastrophic rainfalls and flooding in 2010. This paper discusses a decommissioned shaft that was flooded by surface water, which led to displacement of shaft backfill and an inrush of large amounts of water into an underground pumping station. The weather conditions for the period preceding the inrush, the hydrogeological conditions, the quantity of water that entered the mine dewatering systems, and the underground hydraulic connections are all described. Uncontrolled inflow of water as a cause of backfill saturation and the hazard for active underground infrastructure were analysed. A need to rebuild damaged infrastructure was identified. The case study highlights the need to improve underground mine closure requirements to ensure safe conditions above ground, particularly in densely populated areas.