Direct, solid-state X-ray detectors based on organic single crystals are shown to operate at room temperature, in air, and at voltages as low as a few volts, delivering a stable and reproducible linear response to increasing X-ray dose rates, with notable radiation hardness and resistance to aging. All-organic and optically transparent devices are reported.

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Abstract. The role of firms in commercial Open Source projects (e.g., former MySQL, EnterpriseDB, SugarCRM) is a consolidated and generally accepted fact. On other hand, community Open Source projects, which are built upon communities and not directly associated with firms, are commonly perceived to be based mainly on the work of volunteers. Up to now, firms' role in these projects has been poorly investigated. We conducted a survey on 1,302 SourceForge.net projects to inquire about the level and the typology of involvement of firms. We propose three different models for firm participation and provide empirical evidence on their diffusion in SourceForge.net.

Monitoring the performance of processes is often considered critical in classic engineering fields. However, in the area of software engineering (and especially in the Open Source context) it seems that the literature has not yet taken into consideration the problem of identifying the process characteristics and performance of debugging. The aim of this paper is the identification of the performance characteristics of the bug fixing process of Open Source applications, focusing on continuity and efficiency indicators. The importance of such indicators is even more relevant today, since Open Source software is now adopted also in many business contexts. We have analyzed the debugging process of 9 active and popular Open Source projects, collecting a dataset comprising more than 65,000 closed bugs. Results have highlighted four types of bug fixing processes that can be distinguished by considering temporal continuity and efficiency dimensions.

A quality degradation effect of proprietary code has been observed as a consequence of maintenance. This quality degradation effect, called entropy, is a cause for higher maintenance costs. In the Open Source context, the quality of code is a fundamental tenet of open software developers. As a consequence, the quality degradation principle measured by entropy cannot be assumed to be valid.The goal of the paper is to analyze the entropy of Open Source applications by measuring the evolution of maintenance costs over time. Analyses are based on cost data collected from a sample of 1251 Open Source application versions, compared with the costs estimated with a traditional model for proprietary software. Findings indicate that Open Source applications are less subject to entropy, have lower maintenance costs and also a lower need for maintenance interventions aimed at restoring quality. Finally, results show that a lower entropy is favored by greater functional simplicity.

Previous contributions in the empirical software engineering literature have consistently observed a quality degradation effect of proprietary code as a consequence of maintenance. This degradation effect, referred to as entropy effect, has been recognized to be responsible for significant increases in maintenance effort. In the Open Source context, the quality of code is a fundamental design principle. As a consequence, the maintenance effort of Open Source applications may not show a similar increasing trend over time. The goal of this paper is to empirically verify the entropy effect for a sample of 4,289 community Open Source application versions. Analyses are based on the comparison with an estimate of effort obtained with a traditional effort estimation model. Findings indicate that community Open Source applications show a slower growth of maintenance effort over time, and, therefore, are less subject to the entropy effect.

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