Estimation of soil moisture with radar remote sensing

The radar response to soil moisture content was investigated using a truck-mounted 1-18 GHz (30-1.67 cm wavelength, respectively) active microwave spectrometer (MAS) system. The sensitivity to soil moisture content and the accuracy with which it could be estimated were evaluated for both bare and vegetation-covered fields. Bare field experiments were conducted to determine the optimum radar parameters (frequency, angle of incidence range, and polarization configuration) for minimizing the response to surface roughness while retaining strong sensitivity to moisture content. In the vegetation-covered case, the effects of crop type, crop height and row direction relative to the radar look direct were evaluated

Effects of roughness on the radar response to soil moisture of bare ground

The radar response to soil moisture content was experimentally determined for three different bare fields with considerably different surface roughnesses at eight frequencies in the 2 to 8 GHz band and for Horizontal transmit-Horizontal receive (HH) and Vertical transmit-Vertical receive (VV) polarizations. Analysis of the data indicated that the effect of roughness on the radar backscattering coefficient can be minimized by proper choice of the radar parameters. If, in addition, sensitivity to soil moisture variations and system design constraints are considered, the following radar parameters for an operational soil moisture mapper are recommended: frequency= 4 GHz, angle of incidence range= 7 deg to 15 deg and either HH or VV polarization. The corresponding sensitivity is about 0.25 db/ 0.01 gram/cubic cm

The effects of soil moisture and plant morphology on the radar backscatter from vegetation

The results of experimental studies on the backscattering properties of corn, milo, soybeans and alfalfa are presented. The measurements were made during the summer of 1973 over the 8 to 18 GHz frequency band. The data indicate that soil moisture estimation is best accomplished at incidence angles near nadir with lower frequencies, while crop discrimination is best accomplished using two frequencies at incidence angles ranging from 30 deg to 65 deg. It is also shown that temporal plant morphology variations can cause extreme variations in the values of the scattering coefficients. These morphological changes can be caused by growth, heavy rain and in the case of alfalfa, harvesting

Paediatrician\u27s guide to post-operative care for functionally univentricular CHD: A review

IMPORTANCE: Single ventricle CHD affects about 5 out of 100,000 newborns, resulting in complex anatomy often requiring multiple, staged palliative surgeries. Paediatricians are an essential part of the team that cares for children with single ventricle CHD. These patients often encounter their paediatrician first when a complication arises, so it is critical to ensure the paediatrician is knowledgeable of these issues to provide optimal care. OBSERVATIONS: We reviewed the subtypes of single ventricle heart disease and the various palliative surgeries these patients undergo. We then searched the literature to detail the general paediatrician\u27s approach to single ventricle patients at different stages of surgical palliation. CONCLUSIONS AND RELEVANCE: Single ventricle patients undergo staged palliation that drastically changes physiology after each intervention. Coordinated care between their paediatrician and cardiologist is requisite to provide excellent care. This review highlights what to expect when these patients are seen by their paediatrician for either well child visits or additional visits for parental or patient concern

Particle embolization of systemic-to-pulmonary collateral artery networks in congenital heart disease: Technique and special considerations

Systemic-to-pulmonary artery collateral networks commonly develop in patients with single-ventricle physiology and chronic hypoxemia. Although these networks augment pulmonary blood flow, much of the flow is ineffective and contributes to cardiac volume loading. This volume loading can have detrimental effects, especially for single-ventricle patients. Some data suggest that occluding collaterals may improve outcomes after subsequent operations, especially when the volume of collateral flow is significant. Traditional practice has been to coil occlude the feeding vessel. We perform particle embolization of these collateral networks for two primary reasons. First, access to the feeding vessel is not blocked as collaterals may redevelop. Second, particles occlude the most distal connections. Thus, embolization with particles should be considered as an alternative to coil occluding the proximal feeding vessel