Optimisation and validation of an HPLC method for determination of polycyclic aromatic hydrocarbons (PAHs) in mussels

A method for determination of 11 polycyclic aromatic hydrocarbons (PAHs) in mussels (Mytilus galloprovincialis), using HPLC coupled to a fluorescence detector, has been optimised and validated, according to European Community rules. Sample preparation involves alkaline digestion of mussel tissue, liquid–liquid extraction of organic compounds and solid phase clean-up. Accuracy and precision of the method were determined by a validation study, carried out to demonstrate that the method is useful for both screening purposes and confirmation. Commission Regulation (EC) No. 2007/333/EC stated the performance criteria for the analysis of the only benzo[a]pyrene (BaP) in food products of animal origin, since BaP is the most studied PAH. We extended the BaP analysis performance criteria to other 10 toxic PAHs (listed in Commission Recommendation (EC) No. 2005/108/EC) and the validation study was performed also in agreement with Commission Decision (EC) No. 2002/657/EC. The method was applied to investigate 27 mussel samples from actively producing shellfish plants located in Campania (Italy) and variable levels of PAHs were detected ranging from <0.2 to 16 μg/kg wet weight.     

Self-assembled diphenylalanine nanowires for cellular studies and sensor applications

In this paper we present a series of experiments showing that vertical self-assembled diphenylalanine peptide nanowires (PNWs) are a suitable candidate material for cellular biosensing. We grew HeLa and PC12 cells onto PNW modified gold surfaces and observed no hindrance of cell growth caused by the peptide nanostructures; furthermore we studied the properties of PNWs by investigating their influence on the electrochemical behavior of gold electrodes. The PNWs were functionalized with polypyrrole (PPy) by chemical polymerization, therefore creating conducting peptide/polymer nanowire structures vertically attached to a metal electrode. The electroactivity of such structures was characterized by cyclic voltammetry. The PNW/PPy modified electrodes were finally used as amperometric dopamine sensors, yielding a detection limit of 3,1 microM.     

A method for the visual analysis of early‐stage Parkinson's disease based on virtual MRI‐derived SPECT images

Objective: Nuclear medicine imaging of dopamine transporter (DAT) binding is used in the differential diagnosis of neurodegenerative Parkinsonism but DAT receptor density in the posterior part of the putamens is of difficult evaluation because it is strongly affected by the partial‐volume effect. Since its quantitative correction is often difficult, we propose here a qualitative method to compare the real study to virtual images of the patient, obtained as if he/she was healthy. Method: The virtual images are obtained coregistering the magnetic resonance images to SPECT's; segmenting magnetic resonance images to obtain the real shape and position of caudates and putamens; digitally filling these volumes with an activity concentration close to normal condition; blurring and convolving images with the measured point‐spread function of the SPECT system. Result: The method was applied to phantom and, retrospectively, to a small cohort of 20 patients, that underwent SPECT examination more than 3 years ago, to prove the feasibility of the method in a clinical environment. Conclusions: This method enhances the accuracy of the nuclear medicine interpretation by the inclusion of the proper morphological information of each patient, helping the physician to differentiate between partial‐volume effects and real hypofixation of the tracer. The method proved to be feasible but is applicability is fostered by the need of a concomitant MR. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 172–176, 2012     

In vivo lamellar bone formation in fibre coated MgCHA–PCL-composite scaffolds

Bio-inspired materials with controlled topography have gained increasing interest in regenerative medicine, because of their ability to reproduce the physical features of natural extracellular matrix, thus amplifying certain biological responses both in vitro and in vivo, such as contact guidance and differentiation. However, information on the ability to adapt this high cell potential to 3D scaffolds, effective to be implanted in clinical bone defect, is still missing. Here, we examine the pattern of bone tissue generated within the implant in an ectopic model, seeding bone marrow progenitor cells onto PCL-MgCHA scaffolds. This composite material presented a porous structure with micro/nanostructured surfaces obtained by combining phase inversion/salt leaching and electrospinning techniques. Histological analysis of grafts harvested after 1-2-6 months from implantation highlights an extent of lamellar bone tissue within interconnected pores of fibre coated PCL-MgCHA composites, whereas uncoated scaffolds displayed sparse deposition of bone. Pure PCL scaffolds did not reveal any trace of bone for the overall 6 months of observation. In conclusion, we show that a structural modification in scaffold design is able to enhance bone regeneration possibly mimicking some physiological cues of the natural tissue.     

Joint Routing and Playout Buffering of IP Telephony Flows in MANETs

The low-cost of packet-based networking technologies with respect to traditional circuit-switched ones and the reliability of the current (wired) IP networks have brought to a considerable employment of the VoIP (Voice over IP) technologies in the voice services market. This success is expected to happen also in mobile ad hoc networks (MANETs), which may offer a good platform for the fast deployment of VoIP mobile networks. However, efforts must be made to improve performance before MANETs can be used for this purpose. One of the main limitations is related to the highly variability of the network topology and channel behavior, which heavily influences the service quality due to route losses and significant delay variations. In this paper, we propose a strategy where these impairments are jointly addressed. The source is responsible for jointly selecting the transmission paths and adjusting the playout delay, with an adaptive inter-talkspurt approach. These tasks are accomplished on the basis of historical data on network connectivity and transmission delays, and are driven by a quality-based approach. The collection of statistics of the network status relies on the QOLSR routing algorithm, whereas the voice quality is measured by means of the ITU-T E-Model.     

Majority Logic Mapping for Soft Error Dependability

This work proposes the use of analog majority gates to implement combinational circuits that are intrinsically tolerant to transient faults. A new type of voter circuit, that uses some knowledge from the analog design arena is proposed, together with a new mapping approach to implement circuits given their input/output table. This new mapping approach is shown to compare favorably against a classic mapping. The implementation and validation of an adder circuit, using conventional triple modular redundancy (TMR), the classic mapping, and the proposed solution are analyzed, in order to confirm that the shown technique is indeed fault tolerant, and has advantages in terms of area and performance when compared to TMR. Finally, implementations of a subset of the ISCAS 85 benchmark circuits using TMR with the analog voter and the proposed approach are compared and the results analyzed.     

Chemistry Constraints on the Origin of Life

This analysis starts from the view that prebiotic chemical evolution, leading to the first forms of life on earth, was based on a series of sequential steps, each determined by its own contingent initial conditions. This view is opposed to the more established one, which sees the origin of life as a series of preordered series of events, where each one is deterministically caused by the previous one and causally determines the next one. Some of the main constraints of chemistry that affect such prebiotic chemical evolution are examined. The notion of contingency is seen as a very important organizing process subjected to chemistry, whereby contingency also responds to a certain degree of determinism. Kinetic control, as another determinant and constraint of the prebiotic evolutionary process, can be critically important and, at a certain point of the chemical evolutionary process, kinetic control in the form of catalysis will become essential. Simple peptides can be considered as the first catalysts, at least for the condensation of peptide bonds. The concentration threshold for prebiotic reactions is often not taken into account in the literature, particularly in the field of the prebiotic RNA world. In addition, this shortcoming can make the entire prebiotic RNA world construction shaky and unreliable, including the “myth” of the perennial self-replication of an RNA macromolecule. The general question of self-replication and the problem of homochirality are also briefly discussed. Although these chemical constraints may hinder the reconstruction of life as it is now in the laboratory, their understanding can be useful and even essential for devising a synthetic alternative route to functional macromolecules and to their metabolic interactions.