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The NASA Kepler mission yields an unprecedented amount of data in the form of photometric light curves. Apart from valuable information on exoplanets and stellar pulsations, the light curves contain rotation signals from starspots crossing the stellar disk. These modulations of the light curves are modeled and 105 simulations are carried out to analyze and understand a similar analysis of the Kepler light curves. The periodogram is calculated for each light curve. Under the assumption that the main source of variability at periods >1 day is due to spots, the simulations show that the rotation period can be easily determined for spot lifetimes of 30-60 days, but becomes more unreliable for spots lifetimes of 10-20 days. The amplitude of the periodogram peaks appear to be only weakly dependent on changes in the size of the spots, while the width of the peaks shows no clear change with increasing spot lifetimes (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Reports on the development of a caesium ion sputter source for the production of small mass-selected atomic clusters. Schematic of the cluster source; Sputter ion source; Mass selection and ion optics; Beam characterization.

Abstract: The electrification of wind-blown dust grains was studied in a series of laboratory experiments to examine how grain electrification depends on grain size, grain mineralogy, atmospheric composition, atmospheric pressure, and the method of dust dispersal. This work is intended to contribute to a deeper physical understanding of particle electrification on both Mars and Earth. Findings indicate that the amount of electrification per suspended particle generally is independent of dust entrainment process and atmospheric composition. As expected, the electrification process is grain size-dependent, with smaller grains predominantly electrifying negatively. Although there appears to be a weak dependence upon dust mineralogy, this work supports the expectation that dust suspended in the Martian atmosphere will be significantly electrified. [Copyright &y& Elsevier]

Abstract: Spectrograms in medical ultrasound are usually estimated with Welch’s method (WM). WM is dependent on an observation window (OW) of up to 256 emissions per estimate to achieve sufficient spectral resolution and contrast. Two adaptive filterbank methods have been suggested to reduce the OW: Blood spectral Power Capon (BPC) and the Blood Amplitude and Phase EStimation method (BAPES). Ten volunteers were scanned over the carotid artery. From each data set, 28 spectrograms were produced by combining four approaches (WM with a Hanning window (W.HAN), WM with a boxcar window (W.BOX), BPC and BAPES) and seven OWs (128, 64, 32, 16, 8, 4, 2). The full-width-at-half-maximum (FWHM) and the ratio between main and side-lobe levels were calculated at end-diastole for each spectrogram. Furthermore, all 280 spectrograms were randomized and presented to nine radiologists for visual evaluation: useful/not useful. BAPES and BPC compared to WM had better resolution (lower FWHM) for all OW<128 while only BAPES compared to WM had improved contrast (higher ratio). According to the scores given by the radiologists, BAPES, BPC and W.HAN performed equally well (p >0.05) at OW 128 and 64, while W.BOX scored less (p <0.05). At OW 32, BAPES and BPC performed better than WM (p <0.0001) and BAPES was significantly superior to BPC at OW 16 (p =0.0002) and 8 (p <0.0001). BPC at OW 32 performed as well as BPC at OW 128 (p =0.29) and BAPES at OW 16 as BAPES at OW 128 (p =0.55). WM at OW 16 and 8 failed as all four methods at OW 4 and 2. The intra-observer variability tested for three radiologist showed on average good agreement (90%, κ =0.79) and inter-observer variability showed moderate agreement (78%, κ =0.56). The results indicated that BPC and BAPES had better resolution and BAPES better contrast than WM, and that OW can be reduced to 32 using BPC and 16 using BAPES without reducing the usefulness of the spectrogram. This could potentially increase the temporal resolution of the spectrogram or the frame-rate of the interleaved B-mode images. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to validate angle independent vector velocity methods for blood velocity estimation. Conventional Doppler ultrasound (US) only estimates the blood velocity along the US beam direction where the estimate is angle corrected assuming laminar flow parallel to vessel boundaries. This results in incorrect blood velocity estimates, when angle of insonation approaches 90° or when blood flow is non-laminar. Three angle independent vector velocity methods are evaluated in this paper: directional beamforming (DB), synthetic aperture flow imaging (STA) and transverse oscillation (TO). The performances of the three methods were investigated by measuring the stroke volume in the right common carotid artery of 11 healthy volunteers with magnetic resonance phase contrast angiography (MRA) as reference. The correlation with confidence intervals (CI) between the three vector velocity methods and MRA were: DB vs. MRA: R =0.84 (p <0.01, 95% CI: 0.49–0.96); STA vs. MRA: R =0.71 (p <0.05, 95% CI: 0.19–0.92) and TO vs. MRA: R =0.91 (p <0.01, 95% CI: 0.69–0.98). No significant differences were observed for any of the three comparisons (DB vs. MRA: p =0.65; STA vs. MRA: p =0.24; TO vs. MRA: p =0.36). Bland–Altman plots were additionally constructed, and mean differences with limits of agreements (LoA) for the three comparisons were: DB vs. MRA=0.17ml (95% CI: −0.61–0.95) with LoA=−2.11–2.44ml; STA vs. MRA=−0.55ml (95% CI: −1.54–0.43) with LoA=−3.42–2.32ml; TO vs. MRA=0.24ml (95% CI: −0.32–0.81) with LoA=−1.41–1.90ml. According to the results, reliable volume flow estimates can be obtained with all three methods. The three US vector velocity techniques can yield quantitative insight into flow dynamics and visualize complex flow patterns, which potentially can give the clinician a novel tool for cardiovascular disease assessment. [Copyright &y& Elsevier]

Examines the sonography assessment of the thymic size in infants at an age of 24 months for creation of longitudinal prediction model. Lack of correlation between thymic index and clinical variables, breastfeeding and illness; Significance of test for the effect of breast feeding status; Prediction of thymic size from birth to 24 months of age.

Purpose: To sonographically evaluate the thymic size in preterm infants.Material and Methods: In 6 healthy infants, born in gestational weeks 34-37, and 6 infants born in weeks 24-32, the thymic volume estimate (the thymic index) was assessed. The measurements were compared to the estimates calculated from the prediction model for neonates.Results: The slightly preterm infants fit the prediction model. In cases where the results failed to fit into the model, it was adjusted in order to cover lower birth rates. The extremely preterm infants initially had a very low thymic index but, when healthy, they reached the normal range.Conclusion: With the knowledge of the birth weight it is now possible to predict the thymic size in healthy infants weighing 2,070 g or more. [ABSTRACT FROM AUTHOR]