Luca Ferrari

Disposable fluorescence optical pH sensor for near neutral solutions.

The design, development and performance evaluation of a fluorescence-based pH sensor for on-line measurements is presented. The pKa of the sensing element has been calculated to be 7.9, thus the sensor is suitable for measurement of near neutral solutions. The sensor consists of a low-cost disposable polymer sensing probe, in contact with the solution under test, interrogated by an optoelectronic transduction system. The pH sensitive dye is based on fluorescein O-methacrylate, which has been covalently linked to a hydrogel matrix, realized through the use of HEMA (2-hydroxyethyl methacrylate), HDDA (1,6-hexanediol diacrylate) and PEGDA (polyethylene glycol diacrylate). The optical interrogation setup, together with the electronics, has been developed to acquire and process the fluorescence signal. The sensor works over a pH range between 6.5 and 9.0. In the range between 7.0 and 8.0, the sensor shows a linear behavior with a maximum linearity error of 5%. Thanks to the good performance of the sensing element and transduction system, the short term drift of the reading (measured over 40 min) is lower than 0.15%. The measuring system also exhibits good performance in terms of response time and reproducibility.

Injecting roles in Java agents through runtime bytecode manipulation

Agents are problem-solving entities that can be used to develop complex and distributed systems because they are autonomous, mobile, reactive, social, and proactive. Todays trends in agent technology include the development of applications as multi-agent systems, where several agents interact within the same application. In these systems, the interactions among agents must be carefully considered. Roles constitute a powerful paradigm for modeling interactions, allowing algorithmic issues and interaction-dependent issues to be handled independently. In this paper, we present the RoleX interaction infrastructure, which enables JavaTM agents to dynamically assume and use roles at runtime. Our approach is based on using bytecode manipulation to add (or remove) Java members from agents, changing their capabilities. We detail the main component of RoleX, the Role Loader, which performs the bytecode manipulation that allows agents to dynamically assume and release roles.

Enabling mobile agents to dynamically assume roles

Agent-based application development must face the issues related to the interactions among agents. In fact, their sociality allows decomposing large applications into collaborating agents, while open environments, such as the Internet, require agents belonging to different applications to compete to gain resources. In the BRAIN framework, interactions among agents are fruitfully modeled and implemented on the basis of roles. This approach achieves several advantages, from separation of concerns between the algorithmic issues and the interaction issues, to the reuse of solutions and experiences in different applications. In this paper we propose a mechanism to enable Java agents to dynamically assume roles at runtime. Our approach is based on the modification of the bytecode of Java agents, in order to implement an appropriate interface and to add the related methods. An application example and the comparison with other approaches show the effectiveness of our approach.

Role agent pattern: a developer guideline

Agents are an emerging technology that grants programmers a new way to exploit distributed resources. One of the hardest difficult in the development of this kind of application is the managing of agent interactions, since agents must interact in a collaborative and/or competitive way to achieve their task. Roles are a powerful paradigm that can be used to model agent interactions, both between two (or more) agents and between an agent and the platform/node on which it is running. In this paper we propose a guideline to role developing and use, with regard to the agent technology. In particular we focus on the main problems that a role system and a role developer must take into account.

Construction and evaluation of a disposable pH sensor based on a large core plastic optical fiber

The fabrication and characterization of a disposable optical fiber sensor for the detection of pH in the range 5-8 are described. The sensing element is a drop of sol-gel hybrid material containing phenol red and deposited onto the tip of a large core plastic optical fiber. This fiber is also exploited for the optical interrogation. This probe can be used as a disposable part of a measuring system. The dynamic range and temporal response of the sensor are here investigated.

Development of a Sensor System for the Determination of Sanitary Quality of Grapes

An instrument for the automatic quantification of glycerol in grapes has been developed. We verify here that this analyte can be used as a benchmark of a serious disease affecting the grapevines, namely Botrytis cinerea. The core of the instrument is an amperometric biosensor consisting of a disposable screen printed electrode, generating the analytical signal thanks to a bi-enzymatic process involving glycerol dehydrogenase and diaphorase. The full automation of the analysis is realised by three micropumps and a microprocessor under control of a personal computer. The pumps allow the correct and constant dilution of the grape juice with a buffer solution also containing [Fe(CN)6]3− redox mediator and the injection of NAD+ cofactor when the baseline signal reaches a steady state; the instrument leads to automated reading of the analytical signal and the consequent data treatment. Although the analytical method is based on an amperometric technique that, owing to heavy matrix effects, usually requires an internal calibration, the analyses indicate that a unique external calibration is suitable for giving accurate responses for any grapes, both white and black ones.

Plastic Optical Fiber pH Sensor Using a Sol-Gel Sensing Matrix

Because it is the most ubiquitous species encountered in chemical reactions, hydrogen ion occupies a very special place in chemistry and biology, most of the chemical and biological processes being dependent on its activity. From the analytical point of view, the abundance of hydrogen ions is quantified in terms of pH, the negative logarithm of its activity. Its importance is evident by considering that, if the pH of the human blood changes as little as 0.03 pH units or less, the functioning of the body will be greatly impaired; also, brain pH decreases from normal pH of 7.4 to a pH of 6.75 during the brain insult and a continuous monitoring system would be beneficial in the treatment of comatose neurosurgical patients and those who have suffered traumatic brain injury, ischemic brain insult and so forth (Zauner, 1995). Furthermore, the kind of animals and plants living in lakes, rivers and oceans depends on pH values, as well as pH of soil affects the livability of plants. For this reason, the use of pH sensors is widely diffused in various fields to monitor chemical and biological processes and it is finding an increasing number of applications in medicine, biomedicine, industry and environmental monitoring.

A case study in role-based agent interactions

Mobile agents are an emerging approach to develop distributed and parallel application. They also can be exploited to develop enterprise applications, since they can act as active network components, and can execute on heterogeneous platforms or architectures. In this paper, we analyze the interaction issues of an agent based application for the automatic registration system of e-mail accounts, and we propose a role-based approach to deal with these interactions. Such an approach enables the development of flexible and reusable agent-based applications, which can also be exploited by enterprise systems to perform automatic or administrative tasks.

Photobleaching effects in organic thin film sensing probes

The phenomenon of photobleaching of fluorescence indicators in organic thin films is presented. The study is performed on the fluorescein methacrylate indicator immobilized in an acrylate matrix. A LED based interrogation setup has been realized to evaluate the effects of photobleaching. The experimental results show as stability and drift of the fluorescence signal induced by photobleaching are the most critical aspects in sensing applications.

Continuous haematic pH monitoring in extracorporeal circulation using a disposable florescence sensing element.

Abstract. During extracorporeal circulation (ECC), blood is periodically sampled and analyzed to maintain the blood-gas status of the patient within acceptable limits. This protocol has well-known drawbacks that may be overcome by continuous monitoring. We present the characterization of a new pH sensor for continuous monitoring in ECC. This monitoring device includes a disposable fluorescence-sensing element directly in contact with the blood, whose fluorescence intensity is strictly related to the pH of the blood. In vitro experiments show no significant difference between the blood gas analyzer values and the sensor readings; after proper calibration, it gives a correlation of R>0.9887, and measuring errors were lower than the 3% of the pH range of interest (RoI) with respect to a commercial blood gas analyzer. This performance has been confirmed also by simulating a moderate ipothermia condition, i.e., blood temperature 32°C, frequently used in cardiac surgery. In ex vivo experiments, performed with animal models, the sensor is continuously operated in an extracorporeal undiluted blood stream for a maximum of 11 h. It gives a correlation of R>0.9431, and a measuring error lower than the 3% of the pH RoI with respect to laboratory techniques.