Search

Antimicrobial drug residues in food are strictly controlled and monitored by national laws in most territories. Tetracyclines are a major broad-spectrum antibiotic class, active against a wide range of Gram-positive and Gram-negative bacteria, and they are the leading choice for the treatment of many conditions in veterinary medicine in recent years. In dairy farms, milk from cows being treated with antibiotic drugs, such as tetracyclines, is considered unfit for human consumption. Contamination of the farm bulk tank with milk containing these residues presents a threat to confidence of supply and results in financial losses to farmers and dairy. Real-time monitoring of milk production for antimicrobial residues could reduce this risk and help to minimise the release of residues into the environment where they can cause reservoirs of antimicrobial resistance. In this article, we review the existing literature for the detection of tetracyclines in cow’s milk. Firstly, the complex nature of the milk matrix is described, and the test strategies in commercial use are outlined. Following this, emerging biosensors in the low-cost biosensors field are contrasted against each other, focusing upon electrochemical biosensors. Existing commercial tests that identify antimicrobial residues within milk are largely limited to beta-lactam detection, or non-specific detection of microbial inhibition, with tests specific to tetracycline residues less prevalent. Herein, we review a number of emerging electrochemical biosensor detection strategies for tetracyclines, which have the potential to close this gap and address the industry challenges associated with existing tests.

Karpathos is one of the biggest Greek islands, located between Crete and Rhodes in Aegean Sea. As the most of the islands in the area Karpathos is prone to earthquakes and tsunamis. The event of 9 February 1948 (M 7.1) near the eastern coast of the island caused local tsunami with damages in the area of Pigadia bay, nevertheless tsunamis also from regional sources are expected. The tsunami hazard for the Karpathos Island, focusing on the city of Karpathos and the Airport area, is modelled merging the data from simulation of tsunamis generated by three seismic sources: Eastern Hellenic Arc (EHA referring the 1303 A.D. event, Mw = 8.0); near Rhodes (hypothetical scenario earthquake, Mw = 7.3); and near the coast of Karpathos, based on the 1948, Mw = 7.3 earthquake. Numerical calculations are made using the code UBO-TSUFD on a set of nested grids. Tsunami observables, such as maximal water column height, maximum velocity flux, inundation, are computed for each individual scenario and merged to individuate the areas most exposed to tsunami. The seismic source EHA dominates in the tsunami hazard maps: moreover, the impact over the southern part of Karpathos has biggest risk since the airport and the main city of the island are located in this part.

Presented is an application of a method for constructing a deep inhomogenity on the base of the relative variation of the amplitudes of Rayleigh waves and relative contrast of seismic velocities. Depth microseismic drilling method uses the ambient microseismic noise, it does not utilise active sources and it has a good resolution. Advantages of the method are the modern environmental requirements for study which does not consist of explosions of deep incision and the low cost of carrying out the measurements, especially for significant depths. Results of data processing, by 6 broadband seismic stations, from the local seismic network in region of town Provadia in the territory of East Bulgaria are presented in this study. Provadia region is one of the most specific and curious seismic regions in Bulgaria. The seismic potential, the location of the zone near the big cities (as Varna for example), makes this zone dangerous and put it at high seismic risk. The most important purpose in this case should be defined as establishing the seismic generation properties of the Provadia region. To do this, it is necessary to study in details the deep interior around the seismogenic source in the region of Provadia trying to establish all peculiarities with high resolution.

Summary We study spatial and temporal properties of the seismic activity in the Shabla-Kavarna-Balchik region over the period 1986–2014. This region is located in the NE part of Bulgaria (longitude range between 27.75E and 30.0E, and latitude range between 43.0N and 44.3N). The seismic activity there is related to a multitude of onshore and offshore faults. We use data from the Bulgarian National Seismic Network to identify 204 earthquakes in the region for the considered period. We find that the seismic activity rate increases abruptly after the August 5th 2009 Md=4.7 offshore earthquake. We identify the most active faults in the region for the considered period: (1) the Kaliakra fault; (2) the Batovo fault; (3) the Shabla fault; (4) the Razelm fault, as well as several near-coastal NNE-SSW faults where the aftershocks of the strong quake of August 2009 concentrated. The spatiotemporal behviour of the earthquake activity in the region suggests possible interaction between adjacent or intersecting regional faults.

Multilayered films of cellulose nanoparticles (NFC’s) and modified multi-walled carbon nanotubes (MWCNT’s) were assembled by means of alternate electrostatic adsorption with positively charged poly(ethyleneimine) (PEI) onto cellulose support. The free carboxylic groups of NFC’s and MWCNT’s were coupled with ethylenediamine. Glucose oxidase and laccase were immobilized by means of Schiff base reaction between aldehyde groups of glutaraldehyde and the free amino sites of the proteins. The immobilized enzymes on the surface of nanoparticles have higher value for the specific activity compared to the enzymes immobilized directly on the cellulose surface indicating the stabilization of the proteins by the nanoparticles. The kinetics of the enzymes, catalyzed reactions and reusability of the enzymes were investigated and were showing better properties for enzymes cross-linked with glutaraldehyde. After 5 days the initial enzyme activity of glucose oxidase was around 85%, but the initial enzyme activity of laccase was 60%. The kinetic investigations of the immobilized enzymes showed no significant difference in Michaelis constant but the maximum reaction rate is decreased.

We define the structure and rheology of the lithosphere in Italy and surrounding, combining the cellular velocity models derived from nonlinear tomographic inversion with the distribution vs. depth of hypocentres to assess the brittle properties of the Earth’s crust. We average, over cells sized 1×1 degree, the mechanical properties of the uppermost 60 km of the Earth, along with seismicity, grouping hypocentral depths in 4-km intervals. For most of the cells, the earthquake energy is concentrated in the upper crust (4–12 km). For some regions, where orogenic processes occur, the release of earthquake energy is shallower and limited to the uppermost 10 km of the crust. Ambiguities in the structural models are minimized considering the hypocentral distribution, mainly to define the location of the Moho boundary, when its identification, based on shear-wave velocities, is not straight- forward.

Velocity structure of the lithosphere-asthenosphere system, to the depth of about 350 km, is obtained for almost 400 cells, sized 1 degree by 1 degree in the Mediterranean region. The models are obtained by the following sequence of methods and tools: surface-wave dispersion measurements and collection; 2D tomography of dispersion relations; non-linear inversion of cellular dispersion relations; smoothing optimization method to select a preferred model for each cell. The 3D velocity model, that satisfies Occam razor principle, is obtained as a juxtaposition of selected cellular models. The reconstructed picture of the lithosphere-asthenosphere system evidences the, globally well known, asymmetry between the W- and E-directed subduction zones, attributed to the westward drift of the lithosphere relative to the mantle. Different relationship between slabs and mantle dynamics cause strong compositional differences in the upper mantle, as shown by large variations of seismic waves velocity, consistent with Polarized Plate Tectonics model., Comment: presented on 8th Congress of the Balkan Geophysical Society, October 4-8 2015, Chania, Crete, Greece

Digital seismograms from 25 earthquakes located in the southeastern part of Europe, recorded by three-component very broadband seismometers at the stations Vitosha (Bulgaria) and Muntele Rosu (Romania), were processed to obtain the dispersion properties of Rayleigh and Love surface waves. Rayleigh and Love group-velocity dispersion curves were obtained by frequency–time analysis (FTAN). The path-averaged shear-wave velocity models were computed from the obtained dispersion curves. The inversion of the dispersion curves was performed using an approach based on the Backus–Gilbert inversion method. Finally, 70 path-averaged velocity models (35 R-models computed from Rayleigh dispersion curves and 35 L-models computed from Love dispersion curves) were obtained for southeastern Europe. For most of the paths, the comparison between each pair of models (R-model and L-models for the same path) shows that for almost all layers the shear-wave velocities in the L-models are higher than in the R-models. The upper sedimentary layers are the only exception. The analysis of both models shows that the depth of the Moho boundary in the L-models is shallower than its depth in the R-models. The existence of an anisotropic layer associated with the Moho boundary at depths of 30–45 km may explain this phenomenon. The anisotropy coefficient was calculated as the relative velocity difference between both R- and L-models at the same depths. The value of this coefficient varies between 0% and 20%. Generally, the anisotropy of the medium caused by the polarization anisotropy is up to 10–12%, so the maximum observed discrepancies between both types of models are also due to the lateral heterogeneity of the shear-wave velocity structure of the crust and the upper mantle in the region. D 2003 Elsevier B.V. All rights reserved.

The western Mediterranean is the backarc basin of the Apennines-Maghrebides subduction, which retreated from west to east since Oligocene to present times. The slab transported into the mantle different segments of the oceanic and transitional continental lithosphere, previously stretched during the Mesozoic Tethys realm. The widest extension in the Mediterranean backarc basin occurred where the thinned, possibly oceanic lithosphere was present in the foreland, i.e., the present Ionian basin. The stretching in the Western Mediterranean backarc generated lithospheric boudins as the Corsica-Sardinia microplate. The stretching was asymmetric, being the roots of the boudins shifted eastward relative to the shallow section of the continental lithosphere. The “eastward” rejuvenation of the Western Mediterranean sub-basins, the eastward migration of the slab retreat, and the related magmatism and foredeep depocenters, they all support an eastward sub-lithospheric relative flow of the mantle. The slab retreat and the related backarc extension moved at a speed of few cm/year, being the fastest speed (2–4 cm/yr?) localized at the crest of the arc, presently positioned in the Ionian Sea. Contemporaneous to this process, the counter-clockwise rotation of Africa relative to Europe, generated a N-S convergence of few (2–5) mm/yr, responsible for the Pliocene to present compression acting along the northern offshore of Africa and Sicily. Being the Africa-Europe convergence much slower than the slab retreat, the origin of this latter process must be independent from the relative motion of the two major plates. This supports the coexistence of different geodynamic processes in the same area.

The S-wave velocity model, to the depth of 300 km for the Iberian area and surroundings, is obtained with the non-linear inversion of Rayleigh wave tomographic data in the period range from 5 to 150 s. The three-dimensional model of the region is assembled from 74 juxtaposed one-dimensional cellular structures, sized 1° 9 1°, by means of a local smoothing optimisation. The S-wave velocity model shows the almost constant velocity (*4.40 km/s) in the upper mantle beneath the Iberian Massif, the well- developed low-velocity zones in the Valencia Trough and under northwest Africa, and specific features of the upper mantle layering in the zone of the Iberian range. The thickness of the crust varies between 25 and 35 km with exceptions in the zones of the Valencia Trough (11–18 km) and Pyrenees (35–45 km). Our Vs models are well correlated with the geological structure along Transmed I and evidence several features of the lith- osphere–asthenosphere system in the Betic–Rif domain: quite distinct Iberian, Alboran and Meseta crustal domains; relatively thin, well-developed lithosphere under the Rif system; and clearly defined boundary between the upper and lower asthenosphere. The cellular velocity model of the Betics, where ultrapotassic lamproitic magmatism is observed, has features similar to those of other three areas in the western Mediterranean where ultra- potassic lamproitic magmatism of different age is observed. The crust and upper mantle models in these four areas can be correlated with the age of the magmatism and the local heat flow, and outline how, starting from a naturally quite undifferentiated mantle where magma genesis is currently in progress, the differentiation in lithosphere and asthenosphere can take place in time.

A set of two hundred shear-wave velocity models of the crust and uppermost mantle in southeast Europe is determined by application of a sequence of methods for surface-waves analysis. Group velocities for about 350 paths have been obtained after analysis of more than 600 broadband waveform records. Two-dimensional surface-wave tomography is applied to the group-velocity measurements at selected periods and after regionalisation, two sets of local dispersion curves (for Rayleigh and Love waves) are constructed in the period range 8–40 s. The shear-wave velocity models are derived by applying non-linear iterative inversion of local dispersion curves for grid cells predetermined by the resolving power of data. The period range of observations limits the velocity models to depths of 70 km in accordance to the penetration of the surface waves with a maximum period of 40 s. Maps of the Moho boundary depth, velocity distribution above and below Moho boundary, as well as velocity distribution at different depths are constructed. Well-known geomorphologic units (e.g. the Pannonian basin, southeastern Carpathians, Dinarides, Hellenides, Rodophean massif, Aegean Sea, western Turkey) are delineated in the obtained models. Specific patterns in the velocity models characterise the southeast Carpathians and adjacent areas, coast of Albania, Adriatic coast of southern Italy and the southern coast of the Black Sea. The models obtained in this study for the western Black Sea basin shows the presence of layers with shear-wave velocities of 3.5 km/s–3.7 km/s in the crust and thus do not support the hypothesis of existence of oceanic structure in this region.

Two cross-sections of the western Mediterranean Neogene-to-present back-arc basin are presented, in which geological and geophysical data of the TRANSMED Project are tied to a new shear-wave tomography. Major results are i) the presence of a well stratified upper mantle beneath the older African continent, with a marked low-velocity layer between 130-200 km of depth; ii) the dilution of this layer within the younger western Mediterranean back-arc basin to the north, and iii) the easterly raising of a shallower low-velocity layer from about 140 km to about 30 km in the Tyrrhenian active part of the back-arc basin. These findings suggest upper mantle circulation in the western Mediterranean back-arc basin, mostly easterly-directed and affecting the boundary between upper asthenosphere (LVZ) and lower asthenosphere, which undulates between about 180 km and 280 km. © 2007 Elsevier B.V. All rights reserved.

The paper presents the assessment of the hardware and software equipment as the initial stage of the implementation of the project DFNI I02/11 “Creating an information base for exploration of seismicity and Earth structure of Livingston Island and surroundings by complex research in the Bulgarian Antarctic Base area”. Broad Band seismometer Guralp CMG40T with flat frequency response from 30s to 50Hz and digitizer Reftek DAS130 were installed in the yard of Vitosha Geophysics Observatory (1400m). The equipment was working in extreme weather conditions during February, 2015. The distribution of Power Spectral Density of the ambient noise was estimated and the performance of the tested equipment and the seismological equipment working in the Observatory was compared. Software developed on the base of Golitzynin method and the receiver function techniques were applied over several earthquakes. The assessment of the efficiency of the hardware equipment and the methods applied proved that they are suitable to explore the seismicity of Livingston Island and surroundings.