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[1] Atmospheric dust samples were collected at monthly or seasonal time intervals at six sites on the Chinese Loess Plateau during 1995-1996 and 2000. The dusts are mainly composed of mineral grains in addition to a considerable amount of organic material, especially in the case of the dusts deposited in summer. The magnetic susceptibility of these modern dusts is generally higher than that of glacial loess, and in addition they show clear seasonal variations with maximum values in the summer dust and minimum values in the winter dust. Assuming that pollution effects on modern dust can be excluded, this implies that the high susceptibility values of Quaternary paleosols may arise either from the direct effect of climate on the baseline susceptibility of the raw dust or from further enhancement by post-depositional pedogenesis. The pattern of seasonal dust flux shows that most of the total annual dust deposition is generated by continuous deposition throughout the year rather than by dust storms in specific seasons; however, the flux does exhibit seasonal variability with highest flux occurring in spring or early summer, especially in the northern Loess Plateau. The grain-size distribution of modern dust shows a positive-skewed asymmetrical pattern that is analogous to Quaternary loess. Seasonal variations in dust grain size are characterized by coarsening in spring and summer and by fining in autumn and winter. At a specific site the dust grain-size strongly depends on height above the local ground surface and decreases nonlinearly with increasing height. On the basis of vertical profiles, spatial trends and the seasonal variability of dust flux and grain size, we infer that modern dust, and thus Quaternary loess, is mostly transported at a low level of the atmosphere throughout the year with intensified dust deposition in spring and early summer.

Optical coherence tomography (OCT) is a promising tool for detecting micro channels, metal prints, defects and delaminations embedded in alumina and zirconia ceramic layers at hundreds of micrometers beneath surfaces. The effect of surface roughness and scattering of probing radiation within sample on OCT inspection is analyzed from the experimental and simulated OCT images of the ceramic samples with varying surface roughnesses and operating wavelengths. By Monte Carlo simulations of the OCT images in the mid-IR the optimal operating wavelength is found to be 4 µm for the alumina samples and 2 µm for the zirconia samples for achieving sufficient probing depth of about 1 mm. The effects of rough surfaces and dispersion on the detection of the embedded boundaries are discussed. Two types of image artefacts are found in OCT images due to multiple reflections between neighboring boundaries and inhomogeneity of refractive index.

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Although coherence scanning interferometry (CSI) is capable of measuring surface topography with sub-nanometre precision, it is well known that the performance of measuring instruments depends strongly on the local tilt and curvature of the sample surface. Based on 3D linear systems theory, however, a recent analysis of fringe generation in CSI provides a method to characterize the performance of surface measuring instruments and offers considerable insight into the origins of these errors. Furthermore, from the measurement of a precision sphere, a process to calibrate and partially correct instruments has been proposed. This paper presents, for the first time, a critical look at the calibration and correction process. Computational techniques are used to investigate the effects of radius error and measurement noise introduced during the calibration process for the measurement of spherical and sinusoidal profiles. Care is taken to illustrate the residual tilt and curvature dependent errors in a manner that will allow users to estimate measurement uncertainty. It is shown that by calibrating the instrument correctly and using appropriate methods to extract phase from the resulting fringes (such as frequency domain analysis), CSI is capable of measuring the topography of surfaces with varying tilt with sub-nanometre accuracy.