1,721,047 research outputs found
Recombinant Probiotics for Allergen Immunotherapy
No full textResearch efforts to improve the efficacy of Allergen Immunotherapy (AIT) involve the discovery of new adjuvant. Some strains of probiotic bacteria are
able to induce up-regulation of co-stimulatory molecules in DCs, promote TH1 cytokine production and trigger Treg differentiation and activity. In mouse models, they have been shown to prevent or suppress the harmful TH2 response and to potentiate allergen- or allergoid-based mmunotherapy of type I allergic diseases. These observations could explain the effectiveness of the prolonged administration of probiotics in the prevention of allergic disorders in infants. Consequently, the probiotics could be used as adjuvant for AIT. However, the simultaneous administration of probiotics and AIT might not come to specific responses because of degradation and not optimal presentation to APC. Moreover, the lack of specificity of the immunological response might be overcome by using probiotic bacteria expressing the sensitizing allergen. This would allow the stimulation of the intestinal immune system by both immunomodulating factors at the same site. Only a few studies noticed the development of AIT strategies
based on recombinant bacteria expressing the allergen. However, most of them reported basic favorable immunomodulatory properties, rather than showing the development of immune tolerance or symptoms reduction. The allergen sequestration inside the bacterial cell may represent limits for these preventive and therapeutic approaches. Recently, our research group developed a novel AIT strategy based on a food-grade bacterium Streptococcus Thermophilus (ST) with TH1 skewing property, able to produce the allergen intracellularly and to release it at the gut-associated lymphoid tissue (GALT) level thanks to its intrinsic autolytic behavior with tolerance induction, and readdressing the pre-existing allergen-elicited TH2 response. Hence, the present knowledge on the subject will be critically considered in this review, underlying the most recent experimental
achievements
Effect of high frequency conducted disturbances on the interturn insulation of an inverter-fed induction motor
No full textAs shown in recent papers, Partial Discharge activity has a fundamental role in the premature failure of electrical insulation of machine stator windings fed by PWM inverters. The existence of Partial Discharges can be easily explained if the presence of micro voids inside a composite insulation is considered to be unavoidable. Since such micro cavities are filled with a gas whose permittivity is generally several times lower than the permittivity of the surrounding dielectric, the electric field in such occlusions can be much higher than the local expected average stress. On the basis of a numerical study carried out by using a multi conductor transmission line model for the evaluation of the potential distribution inside the machine and a PD simulation model for the evaluation of the possible ensuing PD activity, in this paper, a new experimental approach to evaluate the effect of PD generated by inverter distorted voltages is proposed. PD measurements under 50 Hz -10 kHz quasi-square and sine wave voltage waveform are performed by means of an Hv capacitive bridge measurement system in order to reject external disturbances, like voltage overshoots, and they are acquired by ultra-wide band (UWB) acquisition system
DMPPT experimental demonstration unit based on buck converter
Full text linkDistributed Maximum Power Point Tracking (DMPPT) technique represents the most promising solution to enhance the lackluster energetic performance of the mismatched PhotoVoltaic (PV) systems. Despite that, there are several factors which restrict its performance some of which are still to be explored. To fully understand the advantages offered by the DMPPT solution, the implementation of a DMPPT emulator is necessary. Based on the above needs, this paper describes the realization and use of a DMPPT experimental demonstration unit based on the Buck DC/DC converter. The above device is capable to emulate the output current vs. voltage (I-V) characteristics of many commercial PV modules with a dedicated Buck DC/DC converter not only in controlled atmospheric conditions but also with different currents rating of the switching devices. The system implementation is based on a commercial power supply controlled by a low-cost Arduino board. Data acquisition is performed through a low-cost current and voltage sensor by using a multichannel board by National Instruments. Experimental results confirm the validity and potential of the proposed DMPPT emulator
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Lora-based Smart Sensor for PD Detection in Underground Electrical Substations
Full text linkThe paper deals with the development of an IoT smart sensor for the monitoring of Partial Discharges (PD) in underground substations. The sensor consists of (i) an ultrasonic receiver for the detection of discharges, (ii) a programmable conditioning circuit that adapts the output of the ultrasonic receiver to the noise floor of the environment, and (iii) a digital section of processing and transmission of eventual warning message if the presence of discharges is detected. Given the challenge of transmitting messages from underground substations, LoRaWAN has been adopted as transmission technology. In the paper, several tests for the sensor assessment have been reported. In particular, the analog section has been assessed through tests in high voltage laboratory; it was so possible to tailor the conditioning circuit to the ultrasonic signal and to establish the alarm thresholds, comparing the sensor signal with a reference instrument for PD detection based on the electrical method. The performance of the transmission module has been evaluated through on field tests, placing the transmission module in a manhole. Finally the entire smart sensor has been assessed through tests in a real electrical substation. All tests have shown that the developed sensor is capable of detecting discharges with a reliability comparable to reference systems currently used by electrical energy distributors, and that LoRaWAN transmission has remarkable reliability also in underground environments characterized by thick concrete walls and high electromagnetic interference
Steep Fronted Overvoltages in Inverter-Fed Induction Motors: Numerical Identification of Critical Parameters
No full textAnalysis of ultrawide-band detected partial discharges by means of a multiresolution digital signal-processing method
No full textModeling of pv module and dc/dc converter assembly for the analysis of induced transient response due to nearby lightning strike
Full text linkPhotovoltaic (PV) systems are subject to nearby lightning strikes that can contribute to extremely high induced overvoltage transients. Recently, the authors introduced a 3D semi-analytical method to study the electromagnetic transients caused by these strikes in a PV module. In the present paper we develop an improved model of the PV module that: (a) takes into account high-frequency effects by modelling capacitive and inductive couplings; (b) considers the electrical insulation characteristics of the module; (c) includes the connection to a DC/DC converter. The whole process involves three major steps, i.e., the magnetic-field computation, the evaluation of both common-mode-and differential-mode-induced voltages across the PV module, and the use of the calculated voltages as input to a lumped equivalent circuit of the PV module connected to the DC/DC converter. In such a framework, the influence of the PV operating condition on the resulting electrical stresses is assessed; moreover, the relevance or insignificance of some parameters, such as the module insulation or the frame material, is demonstrated. Finally, results show that the induced overvoltage are highly dependent both on the grounding of the conducting parts and on the external conditions such as lightning current waveforms and lightning channel (LC) geometry
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