Development of a Bacteriophage-based Portable Biosensor for the Detection of Shiga-toxin Producing Escherichia coli (STEC) Strains in Food and Environmental Matrices

A fast and reliable on-site foodborne pathogens screening can reduce the incidence of foodborne illnesses, hospitalizations and economic loss. It can also circumvent conventional laboratory-based tests with minimal sample treatments and shorter turnaround time. Rapid detection of biological hazards has been largely dependent on immunological agents (ie antibodies). Antibodies are expensive to manufacture and experience cross-reactivity, instability with shorter shelf life. Our aim was to improve the screening process of Shiga-toxin producing Escherichia coli (STEC) strains in food and environmental matrices by developing a novel, inexpensive handheld bacteriophage-based amperometric biosensor that can directly detect live STEC cells.This biosensor development began by isolating STEC-specific bacteriophages from natural environmental samples (ie cow manure and surface water) hence, constructing a comprehensive bacteriophage isolates collection targeting an array of significant STEC serogroups. As an alternative to antibodies, purified bacteriophages could be easily and inexpensively propagated in a standard laboratory. Isolated bacteriophages were morphologically characterized while its physiologic behavior and specific host interactions were also investigated. The results indicated that majority of STEC-specific bacteriophages belong to Myoviridae and Siphoviridae families. Suitable bacteriophages for biosensor purposes were selected on the basis of the presence of head and tail and absence of virulence genes (stx1/stx2). Chemical modification via site-specific biotinylation of bacteriophage heads was performed prior to its biosensor incorporation. The results showed that biotinylation of bacteriophages did not reduce biofunctionality. Representative STEC O26, O157, and O179-specific biotinylated bacteriophages were immobilized onto the surface of streptavidin-modified screen-printed carbon electrodes (SPCE) to capture their target STEC cells. After STEC cells were bound to the capture elements, another set of biotinylated bacteriophages labeled with streptavidivin-horseradish peroxidase were added forming stable binding complexes which were then subjected to amperometric detection. The sandwich-type bacteriophage-based detection approach allowed live STEC cells rapid detection in microvolume samples (50 µL) via amperometric readouts (∆ current) between target and non-target bacteria in pure culture setup and complex matrices. With its simplicity and reliability, this technology can immensely assist the food industry and regulatory inspectors to efficiently maintain food safety in a fraction of the cost of traditional method

Biometric authentication using brain responses to visual stimuli

This paper studies the suitability of brain activity, namely electroencephalogram signals, as raw material for conducting biometrie authentication of individuals. Brain responses were extracted with visual stimulation, leading to biological brain responses known as Visual Evoked Potentials. We evaluated a novel method, using only 8 occipital electrodes and the energy of differential EEG signals, to extract information about the subjects for further use as their biometrie features. To classify the features obtained from each individual, we used a one-class classifier per subject and we tested four types of classifiers: K-Nearest Neighbor, Support Vector Data Description and two other classifiers resulting from the combination of the two ones previously mentioned. After testing these four classifiers with features of 70 subjects, the results showed that visual evoked potentials are suitable for an accurate biometrie authentication

Efeito do detergente neutro na mortalidade de ninfas da bemisia tabaci biótipo b no feijoeiro comum.

Tendo em vista os riscos que envolvem o uso de inseticidas convencionais, principalmente aqueles associados à saúde do homem, a organismos benéficos, à poluição do ambiente e a seleção de resistência às formulações sintéticas por parte da mosca-branca, o presente trabalho teve como objetivo avaliar o efeito do detergente neutro na mortalidade de ninfas do 2º ínstar da B. tabaci biótipo B e de ninfas em desenvolvimento até o 4º ínstar no feijoeiro comum.CONAFE

Resposta do feijoeiro a diferentes níveis de desfolha artificial.

Os insetos são os desfolhadores mais importantes do feijoeiro, embora desfolhas possam ser provocadas também por lesmas, doenças e fatores abióticos como as chuvas de granizo. As principais espécies de insetos que causam desfolha no feijoeiro são as vaquinhas, Diabrotica speciosa e Cerotoma spp., as lagartas, Pseudoplusia includens, Hedylepta indicata e Urbanus proteus e o minador, Liriomyza sp.bitstream/item/59063/1/Foco-49.pd

Efeito do Orthene 750 BR em tratamento de sementes no controle da lagarta Elasmopalpus lignosellus no feijoeiro e algodoeiro.

O objetivo deste trabalho foi avaliar a eficiência do inseticida Orthene 750 BR em tratamento de sementes no controle da lagarta Elasmopalpus lignosellus no feijoeiro e algodoeiro.bitstream/CNPAF/26718/1/comt_146.pd

Electrical transport properties of nanostructured ferromagnetic perovskite oxides La_0.67Ca_0.33MnO_3 and La_0.5Sr_0.5CoO_3 at low temperatures (5 K > T >0.3 K) and high magnetic field

We report a comprehensive study of the electrical and magneto-transport properties of nanocrystals of La_0.67Ca_0.33MnO_3 (LCMO) (with size down to 15 nm) and La_0.5Sr_0.5CoO_3 (LSCO) (with size down to 35 nm) in the temperature range 0.3 K to 5 K and magnetic fields upto 14 T. The transport, magnetotransport and non-linear conduction (I-V curves) were analysed using the concept of Spin Polarized Tunnelling in the presence of Coulomb blockade. The activation energy of transport, \Delta, was used to estimate the tunnelling distances and the inverse decay length of the tunnelling wave function (\chi) and the height of the tunnelling barrier (\Phi_B). The magnetotransport data were used to find out the magnetic field dependences of these tunnelling parameters. The data taken over a large magnetic field range allowed us to separate out the MR contributions at low temperatures arising from tunnelling into two distinct contributions. In LCMO, at low magnetic field, the transport and the MR are dominated by the spin polarization, while at higher magnetic field the MR arises from the lowering of the tunnel barrier by the magnetic field leading to an MR that does not saturate even at 14 T. In contrast, in LSCO, which does not have substantial spin polarization, the first contribution at low field is absent, while the second contribution related to the barrier height persists. The idea of inter-grain tunnelling has been validated by direct measurements of the non-linear I-V data in this temperature range and the I-V data was found to be strongly dependent on magnetic field. We made the important observation that a gap like feature (with magnitude ~ E_C, the Coulomb charging energy) shows up in the conductance g(V) at low bias for the systems with smallest nanocrystal size at lowest temperatures (T < 0.7 K). The gap closes as the magnetic field and the temperature are increased.Comment: 13 figure

Roman or gaulic: orientation as a footprint of cultural identity?

The towns of Aventicum (Avenches, Switzerland) and Augusta Raurica (Augst, Switzerland) were the main Roman towns of the Civitas Helvetiorum in the province of Gallia Belgica (and later shifted to Germania Superior). Both were probably founded ex–nihilo, the first at the time of Claudius (mid first century AD), the second by Caius Munatius Plancus around 44 BC and was refounded soon after the 15 BC . The layout of both towns conforms to all Roman standards with an urban grid in orthogonal shape and with several public buildings to hail the splendor of Roman society. Also the orientation of such grid seems to conform to most Roman standards. The archaeoastronomical study of both towns is contextualised following two paths. Firstly, we consider the orientation of the layout of some other regional Roman foundations as Vesontio (Besançon, France), Iulia Equestris (Nyon, Switzerland), Forum Claudii (Martigny, Switzerland), and Vindonissa (Windisch, Switzerland). Secondly, we realize that the sacred areas (including temples, sanctuaries and often theaters) of this two towns seem to break the general layout in both of them: these appear to bear orientations skewed several degrees with respect to the general grid. In both cases a Roman theater seems to feature some kind of relation with the temple as in other areas in the Roman Empire. Notably, the orientation of these temples share similarities to other sacred precincts in the region possibly built prior to the Roman conquest. This duality in orientations, with a grid with an orientation different to that of some of the main public buildings may be a witness to a period when a compromise, negotiation, or resistance either implicit or explicit, took place between conquered and conquerors. Interestingly, similar cases have recently been reported in the Roman towns of Augusta Treverorum (present day Trier, Germany) or Augustodum (modern day Autun, France)S