Rosilene Agra da Silva

High surface area LaNiO3 electrodes for oxygen electrocatalysis in alkaline media

LaNiO3 coatings on nickel-foam supports were prepared by brush painting. The electrochemical properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Comparative studies were performed with LaNiO3-pelleted electrodes. The roughness factors were determined by CV and found to be 5,208xa0±xa0350 and 4,037xa0±xa0250 for the pelleted and coated electrodes, respectively. EIS measurements confirm the results obtained by CV. Values lower than 0.3 were calculated for the morphology factors for both electrodes, indicating low electrochemical porosity. The experimental method used in this work to synthesise the oxide coupled with the use of Ni foam as support has proved to be very effective in producing oxide electrodes with surface areas higher than those referred to in relevant literature.

Stability of LaNiO3 gas diffusion oxygen electrodes

In this work LaNiO3 perovskite-type oxide, prepared by a self-combustion method, was optimized for activity and stability as an anode material for water electrolysis. A full electrochemical study was conducted in order to kinetically characterize electrodes prepared using carbon paper as a base for porous gas-diffusion electrodes in alkaline media, regarding water oxidation and oxygen reduction reactions at room temperature. An electrode stability study was performed by potential cycling and at constant current density, using cyclic voltammetry and electrochemical impedance spectroscopy to check on stability after cycling with complementary scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) analysis of fresh and degraded electrodes. Comparison was made using nickel foam as a support for LaNiO3 deposition. Carbon instability in the potential region of interest contrasted with the lower contact resistance between the oxide and support of the Ni foam. Higher metal oxide loadings and dimensional stability were also possible.

EndoTOFPET-US data acquisition system

The EndoTOFPET-US system is a multi-modal imaging system, combining Time of Flight PET (200 ps time resolution) and Ultra-Sound into an endoscopic probe. The PET component has an asymmetric configuration. The in-probe detector is based on 0.8xa0×xa00.8xa0×xa010xa0mm3 LYSO crystal fibers, read by a Geiger mode SIPM with digital output. The other detector is a 200xa0×xa0200xa0mm external plate, based on 3xa0×xa03×xa015xa0mm3 LYSO crystals, coupled to discrete 3xa0×xa03 SiPMs read by a 64 channel ASIC. A compact data acquisition system based on digital reconfigurable electronics is proposed. FGPAs on the front end concentrate event data and transmit it to an external trigger. The probe electronics also transmit event data to the trigger. The trigger is a single PCIe card which sits directly in the acquisition computer. A preliminary event selection is performed directly in the trigger FPGA, while more sophisticated event processing is handled by software. The system is capable of handling rates up to 40xa0MHz from the external plate and 200 kHz from the probe.

TOFPET2: a high-performance ASIC for time and amplitude measurements of SiPM signals in time-of-flight applications

We present a readout and digitization ASIC featuring low-noise and low-power for time-of flight (TOF) applications using SiPMs. The circuit is designed in standard CMOS 110 nm technology, has 64 independent channels and is optimized for time-of-flight measurement in Positron Emission Tomography (TOF-PET). The input amplifier is a low impedance current conveyor based on a regulated common-gate topology. Each channel has quad-buffered analogue interpolation TDCs (time binning 20 ps) and charge integration ADCs with linear response at full scale (1500 pC). The signal amplitude can also be derived from the measurement of time-over-threshold (ToT). Simulation results show that for a single photo-electron signal with charge 200 (550) fC generated by a SiPM with 320 pF capacitance the circuit has 24 (30) dB SNR, 75(39) ps r.m.s. resolution, and 4(8) mW power consumption. The event rate is 600 kHz per channel, with up to 2 MHz dark counts rejection.

Red Propolis Antifungal Action on Species of Candida of the Oral Cavity

Introduction: propolis is a substance that has aroused the interest of many researchers because of its numerous therapeutic properties, antibacterial and antifungal.

A free-running, time-based readout method for particle detectors

For the EndoTOFPET-US experiment, the TOFPET ASIC has been developed as a front-end chip to read out data from silicon photomultipliers (SiPM) [1]. It introduces a time of flight information into the measurement of a PET scanner and hence reduces radiation exposure of the patient [2]. The chip is designed to work with a high event rate up to 100 kHz and a time resolution of 50 ps LSB. Using two threshold levels, it can measure the leading edge of the event pulse precisely while successfully suppressing dark counts from the SiPM. This also enables a time over threshold determination, leading to a charge measurement of the signals pulse. The same, time-based concept is chosen for the PASTA chip used in the PANDA experiment. This high-energy particle detector contains sub-systems for specific measurement goals. The innermost of these is the Micro Vertex Detector, a silicon-based tracking system. The PASTA chips approach is much like the TOFPET ASIC with some differences. The most significant ones are a changed amplifying part for different input signals as well as protection for radiation effects of the high-radiation environment. Apart from that, the simple and general concept combined with a small area and low power consumption support the choice for using this approach.

Validation of a highly integrated SiPM readout system with a TOF-PET demonstrator

We have developed a highly integrated, fast and compact readout electronics for Silicon Photomultiplier (SiPM) based Time of Flight Positron Emission Tomography (TOF-PET) scanners. The readout is based on the use of TOP-PET Application Specific Integrated Circuit (PETsys TOFPET1 ASIC) with 64 channels, each with its amplifier, discriminator, Time to Digital Converter (TDC) and amplitude determination using Time Over Threshold (TOT). The ASIC has 25 ps r.m.s. intrinsic time resolution and fully digital output. The system is optimised for high rates, good timing, low power consumption and low cost. For validating the readout electronics, we have built a technical PET scanner, hereafter called ``demonstrator, with 2048 SiPM channels. The PET demonstrator has 16 compact Detector Modules (DM). Each DM has two ASICs reading 128 SiPM pixels in one-to-one coupling to 128 Lutetium Yttrium Orthosilicate (LYSO) crystals measuring 3.1 × 3.1 × 15 mm3 each. The data acquisition system for the demonstrator has two Front End Boards type D (FEB/D), each collecting the data of 1024 channels (8 DMs), and transmitting assembled data frames through a serial link (4.8 Gbps), to a single Data Acquisition (DAQ) board plugged into the Peripheral Component Interconnect Express (PCIe) bus of the data acquisition PC. Results obtained with this PET demonstrator are presented.

Action of Propolis on Microorganisms of the Oral Cavity: an Integrative Review

Introduction : In the mouth there are several microorganisms, including bacteria and fungi, which, under favorable conditions, can cause oral health problems. In combating these diseases there are several antibiotics and antifungals, synthetic drugs and also natural. Objective: identifying the action of propolis on microorganisms in the oral cavity. Method: we opted for the integrative literature review, using the descriptors: oral cavity, propolis, anti-inflammatory activity, antimicrobial activity, endodontics, antimicrobial, propolis, saliva, metabolism, microbiology, antimicrobial activity and mouth; the consulted databases were PubMed, LILACS and SciELO, published between 1999 and 2014. The results were obtained through the selection of 09 articles, through close reading, critical and reflective texts, and then the organization of summary frames of data. Results: evidence was gathered and synthesized, pointing to the antibacterial action ( Gram-positive and Gram-negative ) and antifungal ( C. albicans and C. tropicallis ) of propolis. The methodological designs of the studies analyzed were in majority, of weak evidence, for evidence-based practice. Therefore, the findings may be questioned. Conclusion: it needs that are carried out research studies in a systematic review and randomized clinical studies with humans, because they are considered major force evidence and are defined therapeutic parameters and minimum chemical composition, the different types of propolis, so having the appropriate/desired therapeutic properties.

Variações diurna e sazonal da defensividade das abelhas africanizadas (Apis mellifera L.)

A defensividade das abelhas Apis mellifera L. e uma forma de protecao contra os predadores e evitar o roubo na colmeia. Este trabalho teve o objetivo de avaliar a variacao diurna e sazonal na defensividade das abelhas Africanizadas, por meio de testes de comportamento defensivo. A pesquisa foi realizada em tres apiarios no sertao do estado da Paraiba. Cada apiario possuia 30 enxames, alojados em colmeias padrao Langstroth. Destas, foram selecionadas aleatoriamente 10 colonias e identificadas de 01 a 10, com populacao adulta e area de cria semelhante. Os testes de defensividade foram realizados em cada colmeia, uma por vez, escolhida em tres repeticoes, nos horarios de 07:00 as 10:00 horas, de 12:00 as 14:00 horas e das 15:00 as 17:00 horas, e em duas etapas, em um mes da estacao chuvosa (Abril) e outro mes da estacao seca (Agosto), sendo realizado apenas uma vez por mes, devido a grande perda de abelhas por teste. A partir dos resultados obtidos observamos que o horario influenciou positivamente na defensividade das abelhas analisadas, sendo das 15:00h as 17:00h aquele de maior agressividade nos dois periodos do ano. Na estacao da seca as abelhas se apresentaram menos defensivas do que na estacao das chuvas. A analise dos dados caracterizam as abelhas como altamente defensivas, sendo maior ao final da tarde e na epoca das chuvas.

Vaginal Yeasts and the Antifungal Action of Red Propolis Extract

Introduction: Vulvovaginitis is an inflammatory process that affects the vulva, vagina and cervix, most of the times of infectious cause. Vulvovaginal candidiasis is the second most frequent cause in Brazil, in Europe ranks first. Candida spp can be found in the vagina up to 20% of asymptomatic women. Objective: Understanding the occurrence of vaginal yeasts and evaluating the antifungal action of a red propolis extract. Method: This is a clinical study in vitro with vaginal secretion samples collected from 197 patients treated at the Health Center Frei Damiao in Patos-PB, Brazil. The species were identified using a chromogenic medium CHROMagar Candida ®. At the end, the antifungal activity of the red propolis extract in four different concentrations was observed: 25%, 50%, 75% and 100%, by test disc Agar diffusion. The study was approved by the Research Ethics Committee of the Federal University of Campina Grande, CAAE 35203614.8.0000.5575. Results: Of the samples analyzed other species identified by the medium used were the most prevalent corresponding to 59.8%, followed by C. albicans , with 21.7%. The antifungal activity was observed in 81.25% of the tested samples. According to the average and standard deviation of the inhibition zone of the four concentrations, the one that presented the smallest variation was the concentration at 50%, followed by concentration to 75%. Conclusions: The results of this research showed that there was antifungal action of red propolis extract, since occurred inhibition in 81.25% of the analyzed samples. However did not show clearance regarding this action, since positivity tendency was not growing by increasing or decreasing the concentration of propolis extract.