Juan Hernández

Approaching the capacity limit in image watermarking: a perspective on coding techniques for data hiding applications

Abstract An overview of channel coding techniques for data hiding in still images is presented. Use of codes is helpful in reducing the bit error probability of the decoded hidden information, thus increasing the reliability of the system. First, the data hiding problem is statistically modeled for the spatial and DCT domains. Then, the benefits brought about by channel diversity are discussed and quantified. We show that it is possible to improve on this basic scheme by employing block, convolutional and orthogonal codes, again giving analytical results. It is shown that the use of superimposed pulses does not produce any benefit when applying them to data hiding. The possibility of using codes at the ‘sample level’ (that is, without repeating every codeword symbol) is introduced and its potential analyzed for both hard- and soft-decision decoding. Concatenated and turbo coding are also discussed as ways of approaching the hidden channel capacity limit for the sample level case. Finally, experimental results supporting our theoretical approach are presented for some cases of interest.

The response of brain serotonergic and dopaminergic systems to an acute stressor in rainbow trout: a time course study

SUMMARY The brain monoaminergic neurotransmitter systems are known to be involved in the integrated response to stress in vertebrates. However, present knowledge about the timing of their actions as well as their specific roles in the regulation of the endocrine axes that drive the stress response is incomplete. This is partly because of the complexity of the reciprocal interactions among the monoaminergic systems and other biochemical effectors of the stress response such as corticotropin-releasing factor (CRF), arginine vasotocin (AVT), adrenocorticotropic hormone (ACTH) and corticosteroids. In this study, we show for the first time in teleost fish (rainbow trout) the short- and mid-term time course of the response of the forebrain serotonergic and dopaminergic activities after exposure to an acute stressor. Other stress markers like the plasma levels of cortisol, glucose and lactate were also monitored, providing a context in which to precisely locate the monoaminergic activation within the fish acute stress response. Our results show that acute stress induced a rapid increase in forebrain serotonergic activity, which became elevated after only 15 s of chasing. Several hours after stress, serotonergic activity recovered its basal levels, in parallel with the recovery of other stress markers such as plasma catecholamines and cortisol. Dopaminergic activity was also increased after stress, but only in the telencephalon and only after 20 min. The increase in serotonergic activity happened before the elevation of plasma catecholamines, suggesting that this monoamine system could have a key role in triggering the initial steps of the activation of not only the hypothalamus–pituitary–inter-renal axis but also the brain–sympathetic–chromaffin axis in fish.

Improving the performance of spatial watermarking of images using channel coding

Abstract In this paper we present a spatial-domain watermarking scheme for data hiding and copyright protection of still images and analyze the effect that the application of channel coding has on the performance of the watermark detection and decoding tests. Detector structures are derived for both tests and analytical bounds and approximations are obtained for the bit error rate (BER) and the receiver operating characteristic (ROC) associated with the watermark decoding and detection tests when block codes are employed. Finally, the analytical expressions are contrasted with experimental results in several cases of interest.

A Case Study on Integrating Extra-Functional Properties in Web Service Model-Driven Development

Being one of the most promising current technologies, Web services are at the crossing of distributed computing and loosely coupled systems. Although vendors provide multiple platforms for service implementation, service integrators, developers and providers demand approaches for managing service-oriented applications at all stages of development. In this sense, approaches such as model-driven development (MDD) and service component architecture (SCA) can be used jointly for modeling and integrating services regardless of the underlying platform technology. Besides, WS-policy provides a standard description for extra-functional properties, which remains independent of both the final implementation and the binding to the service in question. In this paper we show a case study in which the aforementioned MDD, SCA and WS-policy are assembled in order to develop Web services and their extra-functional properties from a platform independent model, which is later transformed into platform specific ones and then into code.

Gradation of the stress response in rainbow trout exposed to stressors of different severity: the role of brain serotonergic and dopaminergic systems.

After an intense acute stressor, fish develop a metabolic and behavioural response that usually lasts for several hours. Brain monoaminergic systems, particularly the serotonergic system, appear to play a key role in the central regulation of the stress response. However, the influence of stressor severity on brain monoaminergic systems and on the induced stress responses is yet poorly understood. We hypothesise that serotonergic system could have a direct role in the integration of sensory information during stressor exposure and in the organisation of the subsequent integrated stress response. According to our hypothesis, a low stressor intensity would induce a low response of brain serotonergic system and therefore stress responses of low magnitude and duration. To test this hypothesis, we exposed fish to handling disturbance for 5 s, 15 s or 3 min. We sampled fish at 0 (controls), 3, 15, 45 and 240 min after the start of the stress protocol. Brain levels of serotonin, dopamine and their respective main oxidative metabolites were quantified, along with plasma levels of stress markers (catecholamines, cortisol, glucose and lactate). Regarding stress markers, the 5‐s and 15‐s stress protocols induced similar and relatively low elevations in all parameters assessed. As expected, the 3‐min protocol induced responses of a higher intensity and duration in all plasma parameters. Interestingly, the alterations of brain monoaminergic systems did not follow the same trend. The three stress protocols induced increases in the serotonergic activity in all brain regions analysed (hypothalamus, telencephalon and medulla oblongata), independently of the duration of the handling disturbance, whereas the effects on the dopaminergic system were minor and brain region‐dependent. These data suggest that the brain serotonergic system, although likely involved in the recognition of the stressor stimuli, is not the only actor determining the magnitude and duration of the acute stress response in trout.

Shedding More Light on Image Watermarks

In this paper a general model of a watermarking system for copyright protection of outputs from an arbitrary source is presented. This model is proposed as a framework for an information-theoretical analysis of watermarking schemes. The main elements which comprise such schemes are described, performance measures are defined and important issues such as imperceptibility, robustness and cryptographic security are discussed. The application of concepts such as channel capacity, authentication and secrecy in the context of watermarking is also discussed. As a particular case, a spatial-domain image watermarking system based on direct sequence spread spectrum modulation techniques is described. Special enphasis is placed in discussing the analogies and differences between spread spectrum communication systems and watermarking applications.

Is gill cortisol concentration a good acute stress indicator in fish? A study in rainbow trout and zebrafish

Cortisol is the main biomarker of physiological stress in fish. It is usually measured in plasma, which requires blood collection. Though cortisol is produced in the anterior kidney, it can diffuse easily through cell membranes due to its lipophilic nature. Taking advantage of that, some non-invasive techniques have been developed to measure cortisol directly in the water from fish-holding tanks, in skin mucus or in scales. In this study, we explored the possibility to analyze fish cortisol from gill filaments as a reliable acute stress marker. Our results show that gill cortisol levels correlate well with plasma cortisol levels in both rainbow trout and zebrafish exposed or not to an acute stress protocol. Measuring cortisol in gill filaments increases the available possibilities for stress assessment in fish. Although this approach should yet be tested for its use with other stressors, it has several advantages: In relatively large fish (i.e. above 30 g) gill cortisol levels could be measured in vivo. Sampling of gill biopsies is very fast and easy, and the procedure does not induce stress if properly performed, making it an ideal option for in vivo stress assessment. In small fish, the use of gill tissue to measure cortisol has important technical advantages with respect to the current methods using whole-body homogenates. Gill homogenates could be used directly for ELISA cortisol analysis, avoiding the need of tedious and expensive cortisol extraction protocols, and, since no organic solvent is required, contributing for a more environmentally friendly analysis.

Discovering Volatile and Aspectual Requirements Using a Crosscutting Pattern

A modern software development approach needs to cope with the constant requirements changes observed in current business markets. Such volatile requirements are usually tangled with other requirements making systems evolution difficult. In this poster, we propose a conceptual framework to identify volatile requirements as well as requirements that classic approaches are unable to modularize. This framework is based on what we called the crosscutting pattern and uses traceability matrices and matrix operations.

Towards the Use of Unmanned Aerial Systems for Providing Sustainable Services in Smart Cities

Sustainability is at the heart of many application fields where the use of Unmanned Aerial Systems (UAS) is becoming more and more important (e.g., agriculture, fire detection and prediction, environmental surveillance, mapping, etc.). However, their usage and evolution are highly conditioned by the specific application field they are designed for, and thus, they cannot be easily reused among different application fields. From this point of view, being that they are not multipurpose, we can say that they are not fully sustainable. Bearing this in mind, the objective of this paper is two-fold: on the one hand, to identify the whole set of features that must be provided by a UAS to be considered sustainable and to show that there is no UAS satisfying all these features; on the other hand, to present an open and sustainable UAS architecture that may be used to build UAS on demand to provide the features needed in each application field. Since this architecture is mainly based on software and hardware adaptability, it contributes to the technical sustainability of cities.