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The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to +97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.

This prospective, randomized study of 142 women with mild or moderate dysplasia of the uterine ectocervix shows that the double-freeze technique is significantly more effective than the single-freeze technique, the recurrence rates being, respectively, 6.2% and 16.3%. The highest recurrence rate was found in the group treated with a single freeze and having the most extensive portio involvement. All patients were examined colposcopically before cryosurgery in order to exclude patients with lesions extending into the cervical canal and in order to evaluate the size of the lesion. Recurrent lesions were usually diagnosed within the first year (75%) and in only one patient more than 2 years after treatment. None of the patients developed invasive cancer. The mean follow-up period was 27 months (24-42 months). We consider cryosurgery to be an acceptable treatment for selected patients. Our criteria for entry were mild or moderate dysplasia of the uterine ectocervix, and colposcopic visualization of the entire transformation zone to ensure that the lesion does not extend into the cervical canal. Our experience from the present study is that the following criteria should be added: the portio involvement must not be too extensive and the patient must agree to follow-up examination. When these conditions are fulfilled, future treatment in our department will consist of a double freeze extending 3 mm beyond the lesion, with a thaw interval of 4 min.