Orientation angle preserving a posteriori polarimetric SAR calibration

Fully polarimetric synthetic aperture radar (SAR) data analysis has found wide application for terrain classification, land-use, soil moisture, and ground cover classification. Critical to all analyses and applications is accurate calibration of the relative amplitudes of and phases between the various polarimetric channels. Here we propose an a posteriori method imposing only the weakest of constraints, scattering reciprocity, on the polarimetric data. Calibration parameters are self-consistently estimated from full 4/spl times/4 polarimetric covariance matrices. Whilst the complete set of calibration parameters is underdetermined, we give several reasonable heuristic methods to provide a complete calibration. Stronger constraints reduce the number of independent parameters and provide an overdetermined set of equations but at a cost - the loss of polarimetric fidelity when the underlying assumptions are violated. Without recourse to in situ calibration targets, the extent of the polarimetric distortion that results from polarimetric calibration remains unknown. We apply our new method to simulated data, anechoic chamber data and polarimetric SAR imagery. We also present comparisons with alternate calibration methods and different approximate solutions of the new technique.     

Innovation or Notoriety?

The purpose of this column is to give some perspective and words of advice to new inventors. When you choose to be an innovator, you will have lots of fun intellectually, but the road can be pretty bumpy when it comes to the politics of receiving proper credit for your ideas, and when it comes to "selling" your ideas and seeing them through to implementation. This column documents some of the possible bumps in the road, including the three stages toward acceptance of a new idea: ridicule, opposition, and obviousness.     

Defect assessment procedures at high temperature

Within Nuclear Electric PLC, a comprehensive assessment procedure for the high-temperature response of structures is being produced. The procedure is referred to as R5 and is written as a series of step-by-step instructions in a number of volumes. This paper considers in detail those parts of R5 which address the behaviour of defects. The defect assessment procedures may be applied to defects found in service, postulated defects, or defects formed during operation as a result of creep-fatigue loading. In the last case, a method is described for deducing from endurance data the number of cycles to initiate a crack of a specified size. Under steady loading, the creep crack tip parameter C* is used to assess crack growth. Under cyclic loading, the creep crack growth during dwell periods is still governed by C* but crack growth due to cyclic excursions must also be included. This cyclic crack growth is described by an effective stress intensity factor range. A feature of the R5 defect assessment procedures is that they are based on simplified methods and approximate reference stress methods are described which enable C* in a component to be evaluated. It is shown by comparison with theoretical calculations and experimental data that reliable estimates of C* and the associated crack growth are obtained provided realistic creep strain rate data are used in the reference stress approximation.     

Constitutively methylated CpG dinucleotides as mutation hot spots in the retinoblastoma gene (RB1)

Adrenomedullin is a potent vasodilator peptide that exerts major effects on cardiovascular function. Adrenomedullin is biosynthesized in a wide variety of organs and cells, although it was initially isolated from human pheochromocytoma tissue. In addition to adrenomedullin, proadrenomedullin N-terminal 20 peptide was found to be processed from adrenomedullin precursor. Both adrenomedullin and proadrenomedullin N-terminal 20 peptide show hypotensive effects in anesthetized rats, but exhibit different hypotensive mechanisms. Further, adrenomedullin possesses multiple biological effects involved in cardiovascular homeostasis. Plasma adrenomedullin concentration is increased in patients with cardiovascular diseases such as hypertension, congestive heart failure, renal failure and septic shock. The present review summarizes the recent advancement of adrenomedullin research and demonstrates that adrenomedullin is one of the important vasoactive peptides involved in the physiology and pathophysiology of circulatory control and control of body fluid.     

Fast and accurate NURBS fitting for reverse engineering

Fast and accurate fitting of non-uniform rational B-spline (NURBS) curves and surfaces through large sets of measured data is an important problem in applications such as reverse engineering and geometric modelling. This paper presents a method for realising significant improvements in the computational efficiency of this task. The basic idea is that the sparsity structures of the relevant matrices that are specific to the problem of NURBS fitting can be precisely defined and that full exploitation of these structures leads to significant savings in both computational and storage requirements. These savings allow for a large number of control points to be used in order to define the surface and consequently to improve the accuracy of shape representation. The achieved computational complexity is linear in both the number of measured points and the number of control points while the storage requirements of the algorithm are linear with the number of control points only. The complexity analysis, as well as the analysis of actual running times is presented. The results demonstrate that, using this approach, highly complex shapes may be modelled accurately with a single NURBS surface.     

Automated strategies to identify compounds on the basis of GC/EI-MS and calculated properties

The identification of unknown compounds based on GC/EI-MS spectrum and structure generation techniques has been improved by combining a number of strategies into a programmed sequence. The program MOLGEN-MS is used to determine the molecular formula and incorporate substructural information to generate all structures matching the mass spectral information. Mass spectral fragments are then predicted for each structure and compared with the experimental spectrum using a match value. Additional data are then calculated automatically for each candidate to allow exclusion of candidates that did not match other analytical information. The effectiveness of these "exclusion criteria", as well as the programming sequence, was tested using a case study of 29 isomers of formula C(12)H(10)O(2). The default classifier precision resulted in the generation of too many structures in some cases, which was improved by up to several orders of magnitude by including additional classifiers or restrictions. Combining this with the exclusion of candidates based on a Lee retention index/boiling point correlation, octanol-water partitioning coefficients, steric energies, and finally spectral match values limited the number of candidate structures further from over 1 billion without any restrictions down to less than 6 structures in 10 cases and below 35 in all but 3 cases. This method can be used in the absence of matching database spectra and brings unknown identification based on MS interpretation and structure generation techniques a step closer to practical reality.     

Stray light correction for diode-array-based spectrometers using a monochromator

Photodiode-array-based spectrometers are increasingly being used in a wide variety of applications. However, the signal measured by this type of instrument often is not what is anticipated by the user and is often subject to contamination from stray light. This paper describes an efficient and low-cost stray light correction approach based on a relatively simple system using a monochromator-based source. The paper further discusses the limitations of using a monochromator instead of a laser, as used by previous researchers, and its impact on the quality of the stray light correction. The reliability and robustness of the stray light correction matrix generated have been studied and are also reported.     

Differentiation of two strains of Mycoplasma gallisepticum with monoclonal antibodies and flow cytometry

Identification of infecting Mycoplasma spp. is difficult and not routine for strain. This paper describes a procedure for the rapid identification of the strain of M. gallisepticum. Monoclonal antibodies were prepared against M. gallisepticum F and M. gallisepticum S6. Aliquots of 24-hour broth cultures of these organisms were incubated briefly with either of the monoclonal antibodies. A second incubation was made with anti-mouse immunoglobulin conjugated to fluorescein isothiocyanate. Fluorescent intensity associated with the organisms was measured with a flow cytometer. The criterion for identification was a comparative increase in fluorescent intensity when the strain and monoclonal antibody were homologous. The procedure correctly differentiated the F and S6 strains of M. gallisepticum in a blind study.