Elevated mortality from nonalcohol-related chronic liver disease among female rubber workers: is it associated with exposure to nitrosamines?

BACKGROUND: Despite several case reports describing liver toxicity of nitrosamines and the fact that some N-nitroso compounds are used to induce cirrhosis of the liver in animal models, this association has not been investigated in epidemiological studies. METHODS: A cohort of 2,875 female rubber workers who were active on January 1, 1976, or hired thereafter, and who had been employed for at least 1 year in one of five plants producing tires or technical rubber goods was followed for mortality from January, 1976, through December, 1991. Work histories were reconstructed using routinely documented "cost center codes" and classified into six work areas. Age and calendar year standardized mortality ratios (SMR) and 95% confidence intervals (95% CI) were calculated and stratified by plant, work area, year of hire, and years of employment in the respective work area. RESULTS: The excess mortality from cirrhosis of the liver was most pronounced for nonalcohol-related cirrhosis of the liver (ICD-9 571.4-571.9: 10 deaths, SMR 202; 95% CI 97-372). Mortality from alcohol-related cirrhosis of the liver (ICD-9 571.0-571.3: 3 deaths, SMR 153; 95% CI 31-446) and from other alcohol-related diseases (organic psychoses, injury, and poisoning) was not statistically significantly elevated. All 10 cases of nonalcohol-related cirrhosis had worked in production of technical rubber goods (SMR 279; 95% CI 134-514) and risks increased with earlier years of hire and with longer duration of employment in this work area. DISCUSSION: Although our results must be interpreted with caution, they suggest that the observed excess deaths from cirrhosis of the liver are associated with occupational risk factors. In light of additional evidence from case reports and animal data, exposure to nitrosamines may be a plausible risk factor for the observed excess mortality.     

Steady state analysis of level dependent quasi-birth-and-death processes with catastrophes

Quasi-birth-and-death processes, that is multi-dimensional Markov chains with block tridiagonal transition probability or generator matrices, are appropriate models for various types of queueing systems, amongst many other population dynamics. We consider continuous-time level dependent quasi-birth-and-death processes (LDQBDs) extended by catastrophes, which means that the transition rates are allowed to depend on the process level and additionally in each state the level component may drop to zero such that the generator matrix deviates from the block tridiagonal form in that the first block column is allowed to be completely occupied. A matrix analytic algorithm (MAA) for computing the stationary distribution of such processes is introduced that extends and generalizes similar algorithms for LDQBDs without catastrophes. The algorithm is applied in order to analyze M/M/c queues in random environment with catastrophes and state dependent rates. We present a detailed steady state analysis by computing the stationary distribution for different parameter sets, thereby focusing on the marginal probabilities of the level component which represents the number of customers. It turns out that the stationary marginal distribution is bimodal in the sense that it has two local modes that significantly depend on the specific parameters and rates. We also study the efficiency of our matrix analytic algorithm (MAA). Comparisons with standard solution algorithms for Markov chains demonstrate its superiority in terms of runtime and memory requirements.     

Tactile feedback enhanced hand gesture interaction at large, high-resolution displays

Human beings perceive their surroundings based on sensory information from diverse channels. However, for human–computer interaction we mostly restrict the user on visual perception. In this paper, we contribute to the investigation of tactile feedback as an additional perception modality. Therefore, we will first discuss existing user studies and provide a classification scheme for tactile feedback techniques. We will then present and discuss a comparative evaluation study based on the ISO 9241-9 [Ergonomic requirements for office work with visual display terminals (VDTs) – Part 9: requirements for non-keyboard input devices, 2000]. The 20 participants performed horizontal and vertical one-directional tapping tasks with hand gesture input with and without tactile feedback in front of a large, high-resolution display. In contrast to previous research, we cannot confirm a benefit of tactile feedback on user performance. Our results show no significant effect in terms of throughput (effective index of performance (IPe)) and even a significant higher error rate for horizontal target alignment when using tactile feedback. Based on these results, we suggest that tactile feedback can interfere with other senses in a negative way, resulting in the observed higher error rate for horizontal targets. Therefore, more systematic research is needed to clarify the influencing factors on the usefulness of tactile feedback. Besides these results, we found a significant difference in favor of the horizontal target alignment compared with the vertical one in terms of the effective index of performance (IPe), confirming the work by Dennerlein et al. [Force feedback improves performance for steering and combined steering–targeting tasks, in: CHI ’00: Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM, New York, NY, USA, 2000, pp. 423–429].     

Nonlinear robust blood–gas control by state linearisation for the cardiopulmonary bypass

A new feedback-control strategy is presented for the control of oxygen and carbon dioxide contents in the arterial blood during cardiopulmonary heart–lung support. In this highly nonlinear system incorporating process dependent time-delays, various uncertainties and time-varying parameters, the adjustment of blood gases has up to now been achieved manually by experienced perfusionist staff. This new control approach uses a state feedback-linearisation method with a Smith-like predictor and two external linear gain scheduled controllers. In a first stage the control was robustly designed and tuned with a complex and validated model of the blood–gas process. In a second stage the control was tested in simulations with the oxygenator model, extended by heart–lung machine dynamics. Both, oxygen and carbon dioxide controllers showed stability over the whole operating range and a good disturbance rejection to extracorporeal blood flow changes. The new control method is suggested to improve the patients’ safety and, as a side effect, to remove workload from the anaesthetist and the perfusion technician, so that they can focus on more critical tasks during the surgery.     

Optimization of process parameters for sputtering of ceramic ZnO:Al2O3 targets for a-Si:H/μc-Si:H solar cells

Aluminum doped ZnO layers with a thickness of 800 nm were deposited dynamically by d.c. magnetron sputtering from a ceramic planar ZnO: Al₂O₃ target (1 wt.%). A wide range of process parameters, namely oxygen partial pressure, total pressure and power, was covered, while temperature was held constant at 300 °C. Visual absorption in the range of 2.3-4.7% and resistivities between 380 and 2150 µΩcm were obtained. In addition static imprints were performed to reveal the dependence of layer properties on target erosion. It was shown, that films deposited from targets with a race track deeper than 1.8 mm had very stable etching morphologies as well as optical and electrical properties in the range of the observed process parameters. In contrast, a new target yields very different etching structures and an increased resistivity.     

The block-transitive,point-imprimitive 2-(729, 8, 1) designs

The block-transitive point-imprimitive 2-(729,8,1) designs are classified. They all have full automorphism group of order 729.13 which is an extension of a groupN of order 729, acting regularly on points, by a group of order 13. There are, up to isomorphism, 27 designs withN elementary abelian, 13 designs withN=Z ₉ ³ and 427 designs withN the relatively free 3-generator, exponent 3, nilpotency class 2 group, a total of 467 designs. This classification completes the classification of block-transitive, point-imprimitive 2-(, k, 1) designs satisfying , which is the Delandtsheer-Doyen upper bound for the number of points of such designs. The only examples of block-transitive, point-imprimitive 2-(, k, 1) designs with are the 2-(729, 8, 1) designs constructed in this paper.The first three authors acknowledge the support of an Australian European Awards Program scholarship, a Deutsche Akademische Austauschdienst scholarship, and an Australian Research Council Research Fellowship, respectivelyThe authors wish to thank Brendan McKay for his independent verification of the non-isomorphism of the classes of designs found, and of their automorphism groups, using different, nauty techniques [6].     

Tailoring nanostructured, graded, and particle-reinforced Al laminates by accumulative roll bonding

Accumulative roll bonding (ARB) is a very attractive process for processing large sheets to achieve ultrafine-grained microstructure and high strength. Commercial purity Al and many Al alloys from the 5xxx and the precipitation strengthened 6xxx alloy series have been successfully processed by the ARB process into an ultrafine-grained state and superior ductility have been achieved for some materials like technical purity Al. It has also been shown that the ARB process can be successfully used to produce multi-component materials with tailored properties by reinforcement or grading, respectively. This allows optimizing the properties based on two or more materials/alloys. For example, to achieve high corrosion resistance and good visual surface properties it is interesting to produce a composite of two different Al alloys, where for example a high strength alloy of the 5xxx series is used as the core material and a 6xxx series alloy as the clad material. It has been shown that such a composite achieves more or less the same strength as the core material although 50% of the composite consists of the significant softer clad alloy. Furthermore, it has been found, that the serrated yielding which typically appears in 5xxx series alloys and limits applications as outer skin materials completely disappears. Moreover, the ARB process allows many other attractive ways to design new composites and graded material structures with unique properties by the introduction of particles, fibres and sheets. Strengthening with nanoparticles for example is a very attractive way to improve the properties and accelerate the grain refining used in the severe plastic deformation process. With an addition of only 0.1 vol.-% Al2O3 nanoparticles a significantly accelerated grain refinement has been found which reduces the number of ARB passes necessary to achieve the maximum in strength. The paper provides a short review on recent developments in the field of ARB processing for producing multicomponent ultrafine-grained sheet materials with tailored properties.