Numerical Simulation of Nano Scanning in Intermittent-Contact Mode AFM under Q control

We investigate nano scanning in tapping mode atomic force microscopy (AFM) under quality (Q) control via numerical simulations performed in SIMULINK. We focus on the simulation of whole scan process rather than the simulation of cantilever dynamics and the force interactions between the probe tip and the surface alone, as in most of the earlier numerical studies. This enables us to quantify the scan performance under Q control for different scan settings. Using the numerical simulations, we first investigate the effect of elastic modulus of sample (relative to the substrate surface) and probe stiffness on the scan results. Our numerical simulations show that scanning in attractive regime using soft cantilevers with high Qeff results in a better image quality. We, then demonstrate the trade-off in setting the effective Q factor (Qeff) of the probe in Q control: low values of Qeff cause an increase in tapping forces while higher ones limit the maximum achievable scan speed due to the slow response of the cantilever to the rapid changes in surface profile. Finally, we show that it is possible to achieve higher scan speeds without causing an increase in the tapping forces using adaptive Q control (AQC), in which the Q factor of the probe is changed instantaneously depending on the magnitude of the error signal in oscillation amplitude. The scan performance of AQC is quantitatively compared to that of standard Q control using iso-error curves obtained from numerical simulations first and then the results are validated through scan experiments performed using a physical set-up

Scan speed control for tapping mode SPM

In order to increase the imaging speed of a scanning probe microscope in tapping mode, we propose to use a dynamic controller on 'parachuting' regions. Furthermore, we propose to use variable scan speed on 'upward step' regions, with the speed determined by the error signal of the closed-loop control. We offer line traces obtained on a calibration grating with 25-nm step height, using both standard scanning and our scanning method, as experimental evidence

Aplicação do movimento kepleriano na orientação de imagens HRC - CBERS 2b

Nos últimos 20 anos, pesquisas voltadas ao desenvolvimento de modelos rigorosos para a orientação de sensores orbitais puhbroom lineares vêm sendo desenvolvidas e apresentadas. Na maioria destas pesquisas, a trajetória e a orientação do satélite durante a formação das cenas são obtidas a partir de polinômios de 1º, 2º e até 3º grau. Porém, a atribuição de significado físico aos coeficientes polinomiais indica que o primeiro e o segundo termo se referem à velocidade e a aceleração da plataforma no instante referente à aquisição da primeira linha da cena. Estas quantidades podem ser associadas ao Problema dos Dois Corpos, sendo desenvolvido de acordo com a equação do Movimento Uniformemente Variado. O modelo resultante deste desenvolvimento foi denominado por Michalis e Dowman como Modelo de Kepler. Nesta pesquisa, o Modelo de Kepler é aplicado na orientação de imagens HRC/CBERS 2B e comparado com os modelos que utilizam polinômios para a propagação dos Parâmetros de orientação exterior (POE), amplamente utilizados atualmente. Os resultados obtidos ao comparar o Modelo de Kepler e os modelos polinomiais indicaram que o uso do primeiro modelo permitiu a obtenção de melhores resultados em relação ao segundo

Do toxic metals and trace elements have a role in the pathogenesis of conotruncal heart malformations?

Objective: The aim of the present study was to determine the role of toxic elements and trace elements in the pathogenesis of conotruncal heart defects by measuring their concentrations in the first meconium specimens of the affected newborns. Methods: Concentrations of lead, cadmium, iron, zinc, and copper were measured in 1st-day meconium specimens that were collected from 60 newborns with conotruncal heart defects (Group I) and 72 healthy newborns (Group II). Results: The newborns with conotruncal defects and the healthy newborns had statistically similar demographic and clinical characteristics. When compared with healthy newborns, mean concentrations of lead, cadmium, iron, zinc, and copper were significantly higher in newborns with conotruncal heart defects (p = 0.001 for each). In total, 51 newborns with conotruncal heart defects had normal karyotype. These newborns had significantly higher concentrations of lead, cadmium, iron, zinc, and copper when compared with healthy newborns. There were significant and positive correlations between the concentrations of lead and cadmium (r = 0.618, p= 0.001), lead and iron (r= 0.368, p= 0.001), lead and zinc (r = 0.245, p= 0.005), lead and copper (r = 0.291, p= 0.001), cadmium and iron (r = 0.485, p= 0.001), cadmium and zinc (r = 0.386, p= 0.001), and cadmium and copper (r = 0.329, p= 0.001). Conclusion: Toxic metals and trace elements may disturb DNA repair mechanisms by impairing DNA methylation profiles, and thus have a role in the pathogenesis of conotruncal heart defects