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This study addressed the prevalence of working overtime in relation to psychosocial work characteristics and need for recovery. More precisely, the aim of this study was to find out (1) whether a relationship exists between working overtime and psychosocial work characteristics (job demands and job control), (2a) whether a relationship exists between working overtime and need for recovery, and finally (2b) whether such a relationship depends on job type (a specific combination of job demands and job control). The study sample (N=1,473) consisted of a national random sample of office-based municipal administration employees who worked full-time. These employees completed a questionnaire on working conditions, overtime and need for recovery, among other things. Overtime was especially common in jobs characterised by high demands. The analyses showed that working overtime is not associated with a higher need for recovery in the total study population. However, there was a positive relationship between overtime hours and need for recovery in high strain jobs (high demands, low control). Furthermore, there was a positive relationship between structural overtime and need for recovery in active jobs (high demands, high control). The relationship between overtime and need for recovery seems to be dependent upon working conditions; indicators of overtime were associated with a higher need for recovery only for employees who experienced high job demands. Longitudinal research within a heterogeneous sample will be necessary to draw firm conclusions about causality with respect to the relationship between overtime, need for recovery and working conditions.

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Due to the unattended nature of WSN (Wireless Sensor Network) deployment, each sensor can be subject to physical capture, cloning and unauthorized device alteration. In this paper, we use the embedded SRAM, often available on a wireless sensor node, for secure data (cryptographic keys, IDs) generation which is more resistant to physical attacks. We evaluate the physical phenomenon that the initial state of a 6T-SRAM cell is highly dependent on the process variations, which enables us to use the standard SRAM circuit, as a Physical Unclonable Function (PUF). Important requirements to serve as a PUF are that the start-up values of an SRAM circuit are uniquely determined, unpredictable and similar each time the circuit is turned on. We present the evaluation results of the internal SRAM memories of low power ICs as PUFs and the statistical analysis of the results. The experimental results prove that the low power 90nm commercial 6T-SRAMs are very useful as a PUF. As far as we know, this is the first work that provides an extensive evaluation of 6T-SRAM-based PUF, at different environmental, electrical, and ageing conditions to representing the typical operating conditions of a WSN.