RESUMEN
Temperature plays an important role in promoting the corrosion of metals. The Arrhenius plot can interpret the corrosion rate-temperature dependence, where the Arrhenius behavior gives a geometrical meaning and makes explicit a positive or negative linear dependence of charge transitivity and temperature. In addition, according to the Arrhenius interpretation, it represents the energy that the molecule in the initial state of the process must acquire before it can take part in the reaction, whether it is a physical, or a chemical process. Taking into account the deviation from the linearity, we have extended the Arrhenius-type expression by one term in 1/T2 and we have given some physical meaning to the new related coefficients for which it is found that they depend closely on the number of acid hydrogen atoms in the polyacid for the corrosion and passivation of the Nickel based metallic glass alloy of the composition Ni82.3Cr7Fe3Si4.5B3.2. Moreover, we can consider that the deviation to the Arrhenius linear behavior as a super-Arrhenius behavior In addition, a mathematical analysis of the trend of experimental scatter points of the charge transfer resistance with temperature permits us to reveal an interesting homographic behavior which leads us to suggest an original empirical model with only two optimal adjustable parameters, as well as a new pseudo-power dependence of the number of hydrogen atoms in the polyacid.
RESUMEN
Thin films of Co and Ni electroplated onto a copper electrode from acidic sulfate and Watts baths, respectively, were investigated. The use of an ionic liquid additive in the electrolyte is widespread for producing thin films by electrodeposition. In the present work, the influence of a new ionic liquid, namely, 1-methyl-3-((2-oxo-2-(2,4,5-trifluorophenyl)amino)ethyl)-1H-imidazol-3-ium iodide (Im-IL), in the electrodeposition of two metals was investigated using cathodic polarization (CP), cyclic voltammetry (CV), and anodic linear stripping voltammetry (ALSV) measurements and cathodic current efficiency (CCE%). The surface morphology of the Co- and Ni-coated samples was examined using Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and atomic force microscopy (AFM). The corrosion protection of the Co and Ni samples in a marine environment (3.5% NaCl solution) was studied by the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results show that the addition of Im-IL inhibits Co2+ and Ni2+ deposition, which leads to more fine-grained deposits, especially at low Im-IL concentrations. The inhibition of Co2+ and Ni2+ reduction in the presence of Im-IL ions occurs via adsorption, which obeys the Langmuir adsorption isotherm. The CCE% is higher in the presence of Im-IL. SEM images show smoother deposits of Co and Ni in 1 × 10-5 M and 1 × 10-4 M Im-IL solution respectively. The results prove that Im-IL acts as an efficient additive for electroplating soft Co and Ni films.
RESUMEN
In this paper, we report the use of a nematic liquid crystal material filled cell in transmission mode as a voltage controlled phase modulator for the characterization of microlenses. In one arm of the Mach-Zehnder interferometer, a nematic liquid crystal filled cell with DC voltage connection was placed, and in another arm of the interferometer microlenses with a 4-F imaging system were placed. Interference takes place between the light beams coming from the two arms of the Mach-Zehnder interferometer, one after passing through the nematic liquid crystal cell and another after passing through microlenses. Interference patterns were recorded by a CCD camera. By applying DC voltage to the nematic liquid crystal filled cell, various phase shifted interferograms were recorded, and from phase shifted interferograms, the shape and size of microlenses were determined. The results of the reconstructed profile of the microlenses are compared with white-light profilometry.
RESUMEN
PURPOSE: The goal of this study was to determine the dose contributions from image guided adaptive brachytherapy (IGABT) to individual suspicious pelvic lymph nodes (pLNN) in cervical cancer patients. Data were collected in two cancer centers, University of Pittsburgh Cancer Institute (UPCI) and University Medical Center Utrecht (UMCU). MATERIAL AND METHODS: 27 and 15 patients with node positive cervical cancer treated with HDR (high dose rate) or PDR (pulsed dose rate)-IGABT were analyzed. HDR-IGABT (UPCI) was delivered with CT/MRI compatible tandem-ring applicators with 5.0-6.0 Gy × five fractions. PDR-IGABT (UMCU) dose was delivered with Utrecht tandem-ovoid applicators with 32 × 0.6 Gy × two fractions. Pelvic lymph nodes with short axis diameter of ≥ 5 mm on pre-treatment MRI or PET-CT were contoured for all BT-plans. Dose contributions to individual pLNN expressed as D90 (dose to 90% of the volume) were calculated from dose-volume histograms as absolute and relative physical dose (% of the reference dose) for each fraction. For each node, the total dose from all fractions was calculated, expressed in EQD2 (equivalent total dose in 2 Gy fractions). RESULTS: Fifty-seven (UPCI) and 40 (UMCU) individual pLNN were contoured. The mean D90 pLNN was 10.8% (range 5.7-25.1%) and 20.5% (range 6.8-93.3%), respectively, and therefore different in the two centers. These values translate into 2.7 Gy (1.3-6.6 Gy) EQD2 and 7.1 Gy (2.2-36.7 Gy) EQD2, respectively. Differences are caused by the location of the individual nodes in relation to the spatial dose distribution of IGABT, differences in total dose administered and radiobiology (HDR versus PDR). CONCLUSIONS: The IGABT dose contribution to individual pelvic nodes depends on patient and treatment related factors, and varies considerably.
RESUMEN
We report the measurement of birefringence of nematic liquid crystal (NLC) material using multiple-wavelength interferometry. A nearly common path single-stage Mach-Zehnder interferometer was used for recording interferograms of high stability. The Fourier transform fringe analysis technique was used to reconstruct the two-dimensional phase maps of interferograms consisting of the entire active area of the liquid crystal cell. Change in phase as a function of applied voltage to a liquid-crystal cell was measured for blue, green, and red color laser light, keeping the temperature constant during the experiment. From the change in phase, the birefringence for three colors, i.e., red, green, and blue light, was determined. It is found that the birefringence of NLC material for red, green, and blue colors decreases with the increase in wavelength in the visible range. The present method is noncontact, nonmechanical scanning and highly stable due to a common path interferometer.
RESUMEN
PURPOSE: To evaluate the effect of different α/ß and half-time of repair T(½) on the assessment of clinical treatment plans for patients with cervical cancer. MATERIALS AND METHODS: We used EBRT and BT treatment plans of five patients, planned with MRI guided BT. We computed 3D EQD2 dose distributions of combined EBRT and BT treatments and calculated D90 of high-risk clinical target volume (HR-CTV) and D(2cc) for bladder and rectum, and the ratio D(2cc)(bladder)/D90(HR-CTV). BT was modelled as PDR (two applications of 32×60cGy) and HDR (two applications of 2×7Gy). We assumed a low, standard and high value for the biological parameters: HR-CTV α/ß=5/10/15Gy and T(½)=0.5/1.5/2.5h; OAR α/ß=2/3/4Gy; T(½)=0.5/1.5/4.5h. RESULTS: The chosen variation in modelling parameters had a much larger effect on PDR treatments than on HDR treatments, especially for OAR, thus creating larger uncertainties. The relative mean range of the ratio D(2cc)(bladder)/D90(HR-CTV) is 72% for PDR and 25% for HDR. Out of the 125 modelled combinations 48 PDR plans and 23 HDR plans comply with clinical objectives. CONCLUSION: For HDR brachytherapy, only α/ß has a significant impact on reported EQD2 values, whereas for PDR both α/ß and T(½) are important. Generally, the ratio D(2cc)(bladder)/D90(HR-CTV) is more favourable for PDR, even considering the larger uncertainties in EQD2.