Molecular diagnostics with electrochemical biosensors and arrays

Biosensors are self-contained analytical devices in which a bioreceptor is integrated with a transducer. The interaction between the bioreceptor and a target analyte generates a signal suitable for analytical purposes. In electrochemical biosensors, a change in the redox state of the biorecognition/analyte system generates a change in an electrochemical quantity which can be monitored by electroanalytical techniques. Electrochemical sensors can be miniaturized using ultramicroelectrodes and nanoelectrodes and their arrays as transducers. These devices are characterized by high specificity and sensitivity and improved detection limits. Biosensors can be used by non-specialist operators at the point of care. For the above reasons, within the frame of the Trans2care project, the Laboratory of Electrochemical Sensors of the University Ca’ Foscari of Venice will collaborate with the project partners to develop electrochemical sensors suitable for specific clinical needs

Dynamical tidal Love numbers of Kerr-like compact objects

We develop a framework to compute the tidal response of a Kerr-like compact object in terms of its reflectivity, compactness, and spin, both in the static and the frequency-dependent case. Here we focus on the low-frequency regime, which can be solved fully analytically. We highlight some remarkable novel features, in particular: i) Even in the zero-frequency limit, the tidal Love numbers (TLNs) depend on the linear-in-frequency dependence of the object's reflectivity in a nontrivial way. ii) Intriguingly, the static limit of the frequency-dependent TLNs is discontinuous, therefore the static TLNs differ from the static limit of the (phenomenologically more interesting) frequency-dependent TLNs. This shows that earlier findings regarding the static TLNs of ultracompact objects correspond to a measure-zero region in the parameter space, though the logarithmic behavior of the TLNs in the black hole limit is retained. iii) In the non-rotating case, the TLNs generically vanish in the zero-frequency limit (just like for a black hole), except when the reflectivity is ${\cal R}=1+{\cal O}(M\omega)$, in which case they vanish with a model-dependent scaling, which is generically logarithmic, in the black-hole limit. The TLNs initially grow with frequency, for any nonzero reflectivity, and then display oscillations and resonances tied up with the quasi-normal modes of the object. iv) For rotating compact objects, the TLNs decrease when the reflectivity decreases or the rotation parameter increases. Our results lay the theoretical groundwork to develop model-independent tests of the nature of compact objects using tidal effects in gravitational-wave signals.Comment: 15+ 11 pages, 7 figure

Ensembles of nanoelectrodes modified with gold nanoparticles: characterization and application to DNA-hybridization detection

A new method to increase the active area (A (act)) of nanoelectrode ensembles (NEEs) is described. To this aim, gold nanoparticles (AuNPs) are immobilized onto the surface of NEEs using cysteamine as a cross-linker able to bind the AuNPs to the heads of the nanoelectrodes to obtain the so-called AuNPs-NEEs. The analysis of the cyclic voltammograms recorded in pure supporting electrolyte showed that the presence of the nanoparticles reflects in an, approximately, ten-times increase in the electrochemically active area of the ensemble. The measurement of the amount of electroactive polyoxometalates, which can be adsorbed on the gold surface of NEEs vs. AuNPs-NEEs, confirmed a significant increase of active area for the latter. These evidences indicate that there is a good electronic connection between the AuNPs and the underlying nanoelectrodes. The possibility to exploit AuNPs-NEEs for biosensing application was tested for the case of DNA-hybridization detection. After immobilization on the gold surface of AuNPs-NEEs of a thiolated single-stranded DNA, the hybridization with complementary sequences labeled with glucose oxidase (GOx) was performed. The detection of the hybridization was achieved by adding to the electrolyte solution the GOx substrate (i.e., glucose) and a suitable redox mediator, namely the (ferrocenylmethyl) trimethylammonium (FA(+)) cation; when the hybridization occurs, an electrocatalytic increase of the oxidation current of FA(+) is recorded. Comparison of electrocatalytic current recorded at DNA modified NEEs and AuNPs-NEEs indicate, for the latter, a significant increase in sensitivity in the detection of the DNA-hybridization event

Implicit Extended Kalman Filter for Optical Terrain Relative Navigation Using Delayed Measurements

The exploration of celestial bodies such as the Moon, Mars, or even smaller ones such as comets and asteroids, is the next frontier of space exploration. One of the most interesting and attractive purposes from the scientific point of view in this field, is the capability for a spacecraft to land on such bodies. Monocular cameras are widely adopted to perform this task due to their low cost and system complexity. Nevertheless, image-based algorithms for motion estimation range across different scales of complexities and computational loads. In this paper, a method to perform relative (or local) terrain navigation using frame-to-frame features correspondences and altimeter measurements is presented. The proposed image-based approach relies on the implementation of the implicit extended Kalman filter, which works using nonlinear dynamic models and corrections from measurements that are implicit functions of the state variables. In particular, here, the epipolar constraint, which is a geometric relationship between the feature point position vectors and the camera translation vector, is employed as the implicit measurement fused with altimeter updates. In realistic applications, the image processing routines require a certain amount of time to be executed. For this reason, the presented navigation system entails a fast cycle using altimeter measurements and a slow cycle with image-based updates. Moreover, the intrinsic delay of the feature matching execution is taken into account using a modified extrapolation method

Investigation of current noise in underdamped Josephson devices by switching current measurements

AbstractExperimental measurements on critical current noise in underdamped niobium based Josephson devices by a technique based on the switching current measurements is reported. By sweeping the junction with a current ramp we measure the critical current switching as a function of the time using the standard time of flight technique. In such a way it is possible to obtain the critical current fluctuations ΔIc=Ic(t)-<Ic(t)> and the relative standard deviations which corresponds to the root square of the current fluctuation power. Pointing at the white noise fluctuations (above few Hz) and taking into account the physical frequency of the device, it is possible to evaluate the power spectral density of the critical current. The analysis has involved high quality underdamped Josephson junctions having an area ranging from (4x4) μm2 to (40x40) μm2 in the temperature range from 4.2K to few tenth of mK. These measurement provide very useful information about the intrinsic noise of Josephson devices involving SQUIDs and qubits

NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications

Abstract. We report on the design, the fabrication and the performance of an integrated magnetic nano-sensor based on niobium dc-SQUID (Superconducting QUantum Interference Device) for nanoscale applications is presented. The nano-sensors are based on nanometric niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200 nm. Measurements of voltage-flux characteristic, flux to voltage transfer factor and noise performances are reported. In small signal mode, the sensors have shown a magnetic flux noise spectral density of 1.5 µΦ0/Hz1/2 corresponding to a spin sensitivity in unit of Bohr magneton of 60 spin/Hz1/2. Supercurrent decay measurements of these devices are also reported. Such measurements provide useful information for applications which employ the SQUID as a trigger where the sensor works on the zero voltage state. The experimental data, have shown an intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature, corresponding to an intrinsic sensor magnetic flux resolution of a few mΦ0. In view of the nano-SQUID employments in the detection of small spin populations, the authors calculated the spin sensitivity and the magnetic response relative to the single spin, as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position

Xanthinuria secondary to allopurinol treatment in dogs with leishmaniosis: current perspectives of the Iberian veterinary community

Research Areas: Immunology ; Microbiology ; Veterinary SciencesXanthinuria is a significant adverse effect in dogs on long-term allopurinol for treatment of leishmaniosis. The study aims to investigate how the Iberian veterinary community (IVC) identifies, manages, and proactively prevents xanthinuria secondary to allopurinol treatment. A cross-sectional study was conducted using an online survey, translated into two languages, and disseminated to the IVC via social networking forums. Respondents were asked to share their treatment regimens, adverse effects attributed to treatment, as well as preventive and reactive measures against xanthuria. Of two-hundred and thirty respondents, 99.6% prescribe allopurinol for canine leishmaniosis. Xanthinuria was estimated to happen in less than one out of every four dogs by 91.7% of the clinicians. Xanthinuria has been detected by 71.6% of respondents at least once. Three out of every four respondents inform owners about deleterious effects of allopurinol, and 28.4% consider implementing a change in diet in advance of treatment as a proactive measure. To monitor xanthinuria, urinalysis and diagnostic imaging are used by 71.2% and 31% of clinicians respectively. When xanthinuria is detected, 43.2% of the respondents discontinue allopurinol, 24% replace it by nucleotide-analogs, 14.9% reduce its dosage, and 3.1% split its dosage but increase administration frequency. Additional measures are taken by 72.1% of the respondents, 59.4% of whom prescribe a low-purine diet. The IVC recognizes xanthinuria as a fairly common secondary effect of long-term allopurinol treatment in dogs with leishmaniosis and recommends periodically monitoring and preventive measures.info:eu-repo/semantics/publishedVersio

New clinico-pathological findings and prognostic factors of canine leishmaniasis in endemic and nonendemic areas

Canine Leishmaniasis (CanL) is due to Leishmania infantum (syn. Leishmania chagasi) and is endemic in Mediterranean countries, Portugal, Latin America and Southern Asia. In the last few decades, imported and even autochthonous cases have been recorded in traditionally non-endemic areas such as Central and Northen Europe and Northen America. This is possibly due to a wider spread of the vector and especially to a larger numbers of travelling dogs. Many studies about CanL have been published in the last years and have contributed in understanding different aspects of this disease, including the alternative ways of transmission and the pathologic mechanisms underlying the clinical findings. However, CanL still remains a very challenging disease to diagnose, treat and prevent. Moreover, it is still very difficult to predict the outcome given the low numbers of controlled studies evaluating markers of prognosis. So, the main aims of the present thesis were to investigate new clinico-pathological aspects of CanL and to possibly identify useful prognostic factors. The first study demonstrated that a significant proportion of dogs with leishmaniasis have increased serum cTnI concentration, suggesting that CanL can cause cardiac disease, mainly myoand endocarditis. In the second study, the iron status and its relationship with C-reactive protein (CRP) was for the first time investigated in CanL. The results indicated that dogs with leishmaniasis have decreased serum iron, total iron-binding capacity (TIBC), unsaturated iron-binding capacity (UBIC) and percentage of transferrin saturation and increased concentrations of ferritin. Increased CRP and decreased TIBC are also risk factors for moratility. Finally, since the disease is progressively changing its geographical distribution, the last investigation was conducted in the United Kingdom (UK), currently considered a non-endemic country. The majority of dogs that were diagnosed of leishmaniasis have been adopted from an endemic area (especially from the Mediterranean countries) respect a minority that have travelled to those regions. No autochthonous cases were recognised. Purebreed dogs and those that were classified in stage D according to the Canine Leishmaniasis Working Group guidelines were at higher risk of death. Differently to what has been reported in endemic countries, serology titre at diagnosis and IRIS staging for chronic kidney disease did not influence the outcome