A new method for the precise multiband microwave dielectric measurement using stepped impedance stub

This article presents a new method of wideband dielectric measurement at microwave frequencies. This method can be used to determine the complex dielectric properties of solid and semisolid materials from 0.9GHz to 4.5GHz, including the ISM bands of 915 MHz and 2450MHz. The new method is based on the scattering parameter measurement of a stepped impedance open circuited micro-strip stub, partly loaded with dielectric test material. Current microwave wideband spectroscopy techniques generally measure dielectric materials over a wide range of frequencies but their accuracy is limited. In contrast, narrowband techniques generally measure dielectric properties to a high accuracy but only at a single frequency. This new technique is capable of measuring dielectric properties over a wide range of frequencies to a high accuracy. The technique has been verified by the empirical characterisation of the dielectric properties of Teflon and Duroid 5880 materials. Empirical results were in good agreement with values in the manufacturer’s data sheets. The complex permittivity data will be useful for further microwave processing of the materials

Bovine Practitioner 40 2 86 94 Stillwater, USA: American Association of Bovine Practitioners.

A clinical trial was conducted to determine the perceived and actual utility of milk urea nitrogen (MUN) notification and interpretation as a tool for monitoring protein and energy imbalances in dairy cows. Based on MUN results during the summer of 2001, 50 farms with high MUN values and 30 with low values were randomly allocated to become either intervention or control farms. From January to November 2002 (the trial period), intervention included monthly notification of individual cow MUN results, interpretation of abnormal average MUN values in subgroups of cows based on parity and days-in-milk, and suggestion of possible nutritional reasons for the abnormal MUNs. Intervention farms responded to a survey regarding report utilization, subsequent feed changes and perceptions of MUN testing. Control farms received the individual cow MUN results, but no additional interpretation. No significant differences in average MUN or standardized milk production between intervention and control farms were seen during the last three months of the trial (the outcome period). However, in herds making a feed change in response to MUN notification and interpretation (71% of intervention herds), milk production increased 2.4 lb (1.1 kg)/cow per day in the month after the feed change when compared to randomly selected herds not making a feed change during the same time period. Most dairy producers receiving the MUN notification and interpretation reports felt they knew how to use MUN reports after the trial, and felt that MUN testing was at least somewhat useful as a nutritional tool.

Relationships among milk urea-nitrogen, dietary parameters, and fecal nitrogen in commercial dairy herds

Our study objective was to determine the ability of milk urea-nitrogen concentrations ([MUN]) to predict fecal nitrogen concentrations ([Fecal N]) in commercial dairy herds. A total of 83 dairy herds were each visited 3 times within 48 h after a monthly herd milk test. For each farm visit, forages were sampled for nutrient analyses, which were entered into a computerized ration evaluator, and fecal samples were taken per rectum from each of 6 cows (2 early-, 2 mid-, and 2 late-lactation). Fecal samples were pooled, mixed, and analyzed for nitrogen content. Fecal nitrogen concentrations were compared with the routinely measured nutritional parameters from the ration evaluation, and the herd average [MUN] for the previous milk test date using mixed linear regression analyses. Total protein supplied in the ration was significantly positively associated with [Fecal N], but herd average [MUN] was not associated (P > 0.10) with [Fecal N]