Electric‐Field‐Controlled Dopant Distribution in Organic Semiconductors

Stable electrical doping of organic semiconductors is fundamental for the functionality of high performance devices. It is known that dopants can be subjected to strong diffusion in certain organic semiconductors. This work studies the impact of operating conditions on thin films of the polymer poly(3‐hexylthiophene) (P3HT) and the small molecule Spiro‐MeOTAD, doped with two differently sized p‐type dopants. The negatively charged dopants can drift upon application of an electric field in thin films of doped P3HT over surprisingly large distances. This drift is not observed in the small molecule Spiro‐MeOTAD. Upon the dopants’ directional movement in P3HT, a dedoped region forms at the negatively biased electrode, increasing the overall resistance of the thin film. In addition to electrical measurements, optical microscopy, spatially resolved infrared spectroscopy, and scanning Kelvin probe microscopy are used to investigate the drift of dopants. Dopant mobilities of 10^?9 to 10^?8 cm² V^?1 s^?1 are estimated. This drift over several micrometers is reversible and can be controlled. Furthermore, this study presents a novel memory device to illustrate the applicability of this effect. The results emphasize the importance of dynamic processes under operating conditions that must be considered even for single doped layers.     

Social competence is reduced in socially deprived rhesus monkeys (Macaca mulatta).

Rhesus monkeys deprived for some period from their mother have often served as a model for the effect of adverse rearing conditions on social competence in humans. Social competence is the capacity to react in a species-specific way to social interactions. The current study assesses whether early deprivation from peers also affects the rates of behavior and social competence in rhesus monkeys. This was studied in groups of rhesus monkeys with different rearing conditions: subadult females that were mother-only reared during their first year of life and subsequently housed with peers were compared with subadult females from five naturalistic social groups. Socially deprived monkeys showed higher rates of submission and stereotypic behaviors than socially reared individuals. In addition, they show socially incompetent behavior, since they react with agonistic behavior to nonthreatening social situations. The results suggest that this socially incompetent behavior is rooted in a general feeling of anxiety toward group companions. The authors hypothesize that anxiety negatively affects social information processing, which results in socially incompetent behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Robot control for robust stability with finite reachability time in the whole

A robot model incorporates possible discontinuous nonlinearities with unknown forms and values, unknown payload and unknown predictable external disturbance variations, all in known bounds. A control algorithm is synthesized to guarantee the following: 1.Robust global both stability and attraction with finite reachability time of an appropriately chosen sliding set. 2.The robot motions reach, on the sliding set, a desired motion in a prespecified finite time. 3. Robust both stability and global attraction with finite reachability time of the given robot desired motion. 4. A prespecified convergence quality of real motions to the desired motion, independently of the internal dynamics of the system and without oscillations, hence without chattering in the sliding mode. Robot control robustness means that the controller realizes the control without using information about the real robot internal dynamics. All this is achieved by using the Lyapunov method in a new way combined with a sliding mode approach, but without a variation of the controller structure. The theoretical results are applied to a rotational 3‐degree‐of‐freedom robot. The simulations well verify the robustness of the control algorithm and high quality of robot motions with a prespecified reachability time. ©1999 John Wiley & Sons, Inc.     

A quantitative approach towards a better understanding of the dynamics of Salmonella spp. in a pork slaughter-line

Pork contributes significantly to the public health disease burden caused by Salmonella infections. During the slaughter process pig carcasses can become contaminated with Salmonella. Contamination at the slaughter-line is initiated by pigs carrying Salmonella on their skin or in their faeces. Another contamination route could be resident flora present on the slaughter equipment. To unravel the contribution of these two potential sources of Salmonella a quantitative study was conducted. Process equipment (belly openers and carcass splitters), faeces and carcasses (skin and cutting surfaces) along the slaughter-line were sampled at 11 sampling days spanning a period of 4 months. Most samples taken directly after killing were positive for Salmonella. On 96.6% of the skin samples Salmonella was identified, whereas a lower number of animals tested positive in their rectum (62.5%). The prevalence of Salmonella clearly declined on the carcasses at the re-work station, either on the cut section or on the skin of the carcass or both (35.9%). Throughout the sampling period of the slaughter-line the total number of Salmonella per animal was almost 2 log lower at the re-work station in comparison to directly after slaughter. Seven different serovars were identified during the study with S. Derby (41%) and S. Typhimurium (29%) as the most prominent types. A recurring S. Rissen contamination of one of the carcass splitters indicated the presence of an endemic 'house flora' in the slaughterhouse studied. On many instances several serotypes per individual sample were found. The enumeration of Salmonella and the genotyping data gave unique insight in the dynamics of transmission of this pathogen in a slaughter-line. The data of the presented study support the hypothesis that resident flora on slaughter equipment was a relevant source for contamination of pork.     

Evaluation of the Onset of Flashover in Room Fire Experiments

Two series of full scale room fire tests comprising 16 experiments are used for a study of the onset of flashover. The fire loads were varied and represented seven different commercial applications and two non-combustible linings with significantly different thermal inertia were used. The test results showed that by lowering the thermal inertia and thereby lowering the heat loss from the room and at the same time increasing the thermal feedback, a thermal runaway occurred before significant fire spread; but only for objects composed of a mixture of plastic/rubber/textiles and wood/celluloses. In these cases the onset of thermal runaway was found to occur at room temperatures in the range 300°C to 420°C, supporting that the room temperature at the onset of thermal runaway is strongly dependent on the thermal inertia. It also shows that the onset of thermal runaway cannot in all cases implicitly be predicted by the traditional flashover temperature criterion of 500°C to 600°C. For fire loads composed of pure wood/celluloses the onset of flashover occurred about the same time as fire spread irrespectively of linings and at significantly higher room temperatures (725°C). This can be explained by flammability parameters making wood/celluloses less sensitive to thermal feedback.     

Legislation reduces exposure to second-hand tobacco smoke in New Zealand bars by about 90%

Aim

To measure exposure to second‐hand smoke (SHS) in New Zealand bars before and after comprehensive smoke‐free legislation enacted on 10 December 2004.

Methods

Cotinine is the main specific metabolite of nicotine and a well‐established biomarker for SHS exposure. We measured cotinine levels in saliva of non‐smoking volunteers before and after a 3 h visit to 30 randomly selected bars in 3 cities across the country. Two measures of cotinine before the smoke‐free law change during winter and spring 2004, and two follow‐up measurements in the same volunteers and venues during winter and spring 2005, were included.

Results

Before the smoke‐free law change, in all bars and in all volunteers, exposure to SHS was evident with an average increase in saliva cotinine of 0.66 ng/ml (SE 0.03 ng/ml). Increases in cotinine correlated strongly with the volunteers'' subjective observation of ventilation, air quality and counts of lit cigarettes. However, even venues that were judged to be “seemingly smoke free” with “good ventilation” produced discernable levels of SHS exposure. After the law change, there remained some exposure to SHS, but at much lower levels (mean saliva cotinine increase of 0.08 ng/ml, SE 0.01 ng/ml). Smoking indoors in bars was almost totally eliminated: in 2005 only one lit cigarette was observed in 30 visits.

Conclusions

Comprehensive smoke‐free legislation in New Zealand seems to have reduced exposure of bar patrons to SHS by about 90%. Residual exposures to SHS in bars do not result from illicit smoking indoors.Before December 2004, smoking was prohibited in most, but not all, workplaces in New Zealand. Bars, restaurants and hotels were not required to be smoke free. This changed on 10 December 2004 when the Smokefree Environments Amendment Act 2003 came into force. Since that time, smoking is not permitted in any indoor place of work. After Ireland, which passed its legislation in March 2004, New Zealand was one of the first countries to introduce national, comprehensive smoke‐free legislation.The purpose of this study was to measure the impact of this legislation on personal exposures to second‐hand smoke (SHS) in New Zealand bars. Previous papers^1,2,3 have described exposures of bar workers in Ireland, New York and Scotland before and after legislation. The effects of reduced exposures to SHS on the respiratory health of employees in this industry have also been documented.^3,4 However, we know of no other study that has examined the effects of smoke‐free laws on exposures of the patrons of bars and hotels. In an earlier publication,⁵ we have described in greater detail the analytical methods and findings at baseline.