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The ability of semiconductor nanocrystals (NCs) to display multiple (size-specific) colors simultaneously during a single, long term excitation holds great promise for their use in fluorescent bio-imaging. The main challenges of using nanocrystals as biolabels are achieving biocompatibility, low non-specific adsorption, and no aggregation. In addition, functional groups that can be used to further couple and conjugate with biospecies (proteins, DNAs, antibodies, etc.) are required. In this project, we invented a new route to the synthesis of water-soluble and biocompatible NCs. Our approach is to encapsulate as-synthesized, monosized, hydrophobic NCs within the hydrophobic cores of micelles composed of a mixture of surfactants and phospholipids containing head groups functionalized with polyethylene glycol (-PEG), -COOH, and NH{sub 2} groups. PEG provided biocompatibility and the other groups were used for further biofunctionalization. The resulting water-soluble metal and semiconductor NC-micelles preserve the optical properties of the original hydrophobic NCs. Semiconductor NCs emit the same color; they exhibit equal photoluminescence (PL) intensity under long-time laser irradiation (one week) ; and they exhibit the same PL lifetime (30-ns). The results from transmission electron microscopy and confocal fluorescent imaging indicate that water-soluble semiconductor NC-micelles are biocompatible and exhibit no aggregation in cells. We have extended the surfactant/lipidmore » encapsulation techniques to synthesize water-soluble magnetic NC-micelles. Transmission electron microscopy results suggest that water-soluble magnetic NC-micelles exhibit no aggregation. The resulting NC-micelles preserve the magnetic properties of the original hydrophobic magnetic NCs. Viability studies conducted using yeast cells suggest that the magnetic nanocrystal-micelles are biocompatible. We have demonstrated, for the first time, that using external oscillating magnetic fields to manipulate the magnetic micelles, we can kill live cells, presenting a new magnetodynamic therapy without side effects.« less

We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons.

Several sensor network applications based on data diffusion and data management can determine the communication transfer rate between two sensors beforehand. In this framework, we consider the problem of energy efficient communication among nodes of a wireless sensor network and propose an application-driven approach that minimizes radio activity intervals and prolongs network lifetime. On the basis of possible communication delays we estimate packet arrival intervals at any intermediate hop of a fixed-rate data path. We propose two different strategies of radio activity minimization that maintain the radio switched on just in the expected packet arrival intervals and guarantee low communication latency. We define a probabilistic model that allows the evaluation of the packet loss probability that results from the reduced radio activity. The model is used to optimally choose the radio activity intervals that achieve a certain probability of successful packet delivery. Relying on the probabilistic model we also define a cost model that estimates the energy consumption of the proposed strategies, under specific settings. We finally validate our work with a simulation made with Tossim (the Berkeley motes' simulator). The simulation results confirm the validity of the approach and the accuracy of the analytic models.

The problem of medical devices and data integration in health care is discussed and a proposal for the remote monitoring of patients based on recent developments in networking and data management is presented.

This report presents the results of the first three months of activity of the project Management of Data in Wireless Sensor Networks (MaD-WiSe). More specifically, it presents a survey on the state of the art on Wireless Sensor Networks, focusing on the issues related to communication, data centric paradigms and stream processing applied to sensor networks.

Wireless ad hoc networks are generally characterised by random node locations and multi-hop routes. A quantitative knowledge of the relation between hop count and Euclidean distance could provide a better understanding of important network parameters such as end-to-end delay, power consumption along the route, and node localisation. In this paper, we present an analytic approach to capture the statistics on hop count for a given source-to-destination Euclidean distance in a greedy routing approach. We also show that, for a given hop count, the bounds on Euclidean distance can be computed from the distribution characteristics of per-hop progress.

A novel routing protocol for wireless, mobile ad hoc networks is presented. This protocol incorporates features that enhance routing reliability, defined as the ability to provide almost 100% packet delivery rate. The protocol is based on a virtual structure, unrelated to the physical network topology, where mobile nodes are connected by virtual links and are responsible for keeping physical routes to their neighbors in the virtual structure. Routes between pairs of mobiles are set up by using information to translate virtual paths discovered in the virtual structure. Route discovery and maintenance are based on unicast messages travelling across virtual paths, with sporadic use of flooding protocol. Most floodings are executed in background using low priority messages. The routing protocol has been evaluated and compared with the Dynamic Source Routing protocol (DSR) by means of simulation.

An abstract is not available

This report presents the results of Task 1 - Workpackage 5 (Protocolli per rete MANET:Sperimentazione di una MANET single hop IEEE802.11) of the IS-MANET project. More specifically it reports the experimental results of the tests on a single hop wireless network using the DS2 software for file storage in MANETs.

This paper introduces a distributed data storage for mobile, wireless networks based on a peer-to-peer paradigm. The distributed storage provides support to create and share files under a write-once model, and ensures at the same time data confidentiality and dependability by encoding files in a Redundant Residue Number System. More specifically files are partitioned into records and each record in encoded separately as (h+r)-tuples of data residues using h+r moduli. In turn, the residues are distributed among the mobiles in the network. Dependability is ensured since data can be reconstructed in the presence of up to s£r residue erasures, combined with up to corrupted residues, and data confidentiality is ensured since recovering the original information requires knowledge of the entire set of moduli.

A novel approach aimed at evaluating the diagnosability of regular systems under the PMC model is introduced. The diagnosability is defined as the ability to provide a correct diagnosis, although possibly incomplete. This concept is somehow intermediate between one-step diagnosability and sequential diagnosability. A lower bound to diagnosability is determined by lower bounding the minimum of a ''syndrome-dependent'' bound $t_\sigma$ over the set of all the admissible syndromes. In turn, $t_\sigma$ is determined by evaluating the cardinality of the smal\-lest consistent fault set containing an aggregate of maximum cardinality. The new approach, which applies to any regular system, relies on the ''edge-isoperimetric inequalities'' of connected components of units declaring each other non-faulty. This approach has been used to derive tight lower bounds to the diagnosability of toroidal grids and hypercubes, which improve the existing bounds for the same structures.

Wireless ad hoc Sensor networks are gaining increasing attention as they are suitable to monitor a wide variety of environments, where the deployment of classical wired communication infrastructure is neither economical, nor possible. The network collects environmental information which, in turn, is sent to a sink node (accessible to external users) when the connection with the sink node is available. If a sensor fails when the connection with the sink node is unavailable, all data sensed by this sensor are definitively lost. Neither the classical approaches to fault recovery nor the recently proposed approaches for the recovery in mobile computing are appropriate under this scenario, because they would require that the sensors be equipped with stable storage and/or a permanent connection with the sink node. Such requirement can hardly be met in sensor networks. This paper introduces a fault recovery scheme for single hop wireless sensor networks, where the network is able to operate independently of the sink node for long periods of time. The proposed scheme does neither require that the sensors be equipped with stable storage nor that they are permanently connected to the sink node. Rather, the sensors cooperate to maintain redundant information in their memories in order to be able to recover the lost information after a failure, and to distribute the recovered information among the memories of the surviving sensors. The proposed scheme minimizes the memory overhead.

The problem of identifying faulty mobiles in ad-hoc networks is considered. Current diagnostic models were designed for wired networks, thus they do not take advantage of the shared nature of communication typical of ad-hoc networks. In this paper we introduce a new comparison-based diagnostic model based on the one-tomany communication paradigm. Two implementations of the model are presented. In the first implementation, we assume that the network topology does not change during diagnosis, and we show that both hard and soft faults can be easily detected. Based on this implementation, a diagnosis protocol is presented. The evaluation of the communication and time complexity of the protocol indicates that efficient diagnosis protocols for ad-hoc networks based on our model can be designed. In the second implementation we allow the system topology to change during diagnosis. As expected, the ability of diagnosing faults under this scenario is significantly reduced with respect to the stationary case.

The problem of multiple faults diagnosis in safety-critical systems is considered. Error propagation between system components is modeled as a directed graph, where the errors propagate instantaneously along the edges. Some of the system components are equipped with alarms, which ring when abnormal conditions are detected. A diagnosis algorithm identifies the set of potential failure sources based on the set of ringing alarms. This paper introduces the D-FAULTS algorithm, which diagnoses the system when at most two nodes can be failure sources at any time. The concept of equential diagnosis is also introduced, to deal with an unknown number of faults. Sequential diagnosis is aimed at locating the smallest set of nodes containing at least one fault. Using this approach, a faulty system can be restored to normal condition by executing repeatedly the diagnosis and repair phases. To this purpose, we introduce the sequential diagnosis algorithm S-DIAG with optimal time complexity

A new diagnosis algorithm for square grids is introduced. The algorithm always provides correct diagnosis if the number of faulty processors is below T, a bound with T 2 ...n2=3+, which was derived by worst-case analysis. A more effective tool to validate the diagnosis correctness is the syndrome dependent bound T, with T T, asserted by the diagnosis algorithm itself for every given diagnosis experiment. Simulation studies provided evidence that the diagnosis is complete or almost complete if the number of faults is below T. The fraction of units which cannot be identified as either faulty or nonfaulty remains relatively small as long as the number of faults is below n=3 and, as long as the number of faults is below n=2, the diagnosis is correct with high probability.

Three related diagnosis algorithms for systems consisting 01 a large number 01grid-interconnected units (usually, but not necessarily, processors) are presented. The application domain of these algorithms includes selfdiagnosis of massive parallel systems and testing 01 VLSIchips in the manufacturing processo The basic algarithm, called Al, is analyzed in more detail. It is shown that its diagnosis is provably correct, although possibly incomplete, assuming that the number of the actualfaults is not above certain bounds. Two different bounds are presented: a syndrome dependent bound Tdn) which.For any syndrome G'. is asserted by the diagnosis algorithm itself, and a syndrome independent bound T(n). FunctionT(n) is (}(n 213), where n is the number 01 units in the system. From simulation results, it is shown that the diagnosis is also likety to be complete and, if not complete. that the number of units whose state cannot be identified can be expected to be very small. With the application ta the testing 01 VLS/ in the mind, two alternate algorithms (named A2 and A3) are also analyzed. These algorithms, which are correct under the same conditions holding for algorithm Al, provide different trade-offs between the time complexity and the degree of completeness.

We propose a technique for performing the manufacturing test of integrated circuits in a wafer which consists in exercising all the chips with the same test sequence and in comparing the outputs of an appropriate set of chip pairs. The comparison outcomes are collected by a test computer, which uses this information to identify the good chips. Identification is correct under conditions which are very likely to hold and almost all good chips are very likely to be identified. Since the chips can be tested in parallel and the time to perform the identification algorithm is negligible. this approach greatly reduces the time needed to perform the manufacturing test. The role of the test computer is essentially limited to collecting and processing the comparison outcomes and the test can proceed at the maximum allowable speed of the circuits under test.