Determination of the dynamics of the odour release from a pig house, using an electronic odour sensor.

The widely fluctuating operating conditions in pig husbandry, due to climatic and biological changes (changes in temperature and air flowrate between day and night, as well as between summer and winter, increasing animal mass during the fattening process, etc.) exert a significant influence on the amount of actual odour emission. The project presented here comprised the measurement of seasonal (fattening course), daytime-related, and short-term (feeding) dynamic effects of odour release, as well as the identification of potential factors which influence the amount of odour emitted. In parallel with "classic" olfactometry, an electronic odour sensor with a chemosensor array of ten metal oxide sensors was employed. The highest odour emissions are measured on hot summer days, while the lowest emissions were determined on cold winter days. On the one hand, the sensor signals of the electronic odour sensor exhibited considerable differences on days with large volume flow alterations. On the other hand, continuous measurement with the electronic odour sensor allowed changes in the gas- and odorant composition of the exhaust air during feeding times to be shown. From the measurement results, recommendations for odour sampling, the consideration of seasonal odour emission fluctuations, and the use of electronic odour sensors for the evaluation of odour emissions have been derived.

Influence of different pig housing systems on odor emissions.

The odor emissions from two different housing systems were determined during three fattening periods from October 1999 to November 2000 by analyzing weekly samples by means of dynamic olfactometry. The objects of the investigations were a standard housing system with fully slatted floor and forced ventilation (FF) compared with a kennel housing system with natural shaft ventilation (KN) in parallel operation. Only little data but with a wide range of odor emission values are available from the literature and these are difficult to compare and interpret, because of missing standards in presenting the results and experimental conditions. Therefore minimum requirements for measuring odor emissions from livestock buildings have been derived. In the scope of the measurements during the first two fattening periods (October 1999 to June 2000), no differences in odor emissions could be determined with mean values related to the livestock units (1 LU = 500 kg life weight) of 85 (FF) /87 (KN) in period A and 60 (FF) / 61 (KN) (OU/s)LU(-1) in period B. The overall range of the results of all measurements in periods A and B was 4 to 355 (OU/s)LU(-1). In period C (August-November 2000), the system FF showed higher odor emissions with 193 (28-550) compared to system KN with 105 (25-218) (OU/s)LU(-1). The air flow rates and odor concentrations at the three different naturally ventilated exhaust shafts of system KN differed considerably from each other. Odor measurement techniques with a higher temporal resolution than olfactometry are necessary to give evidence for the main factors influencing the odor formation and release.

Detection of the dynamics of odour emissions from pig farms using dynamic olfactometry and an electronic odour sensor.

The dynamics of odour emissions from a pig house was investigated by olfactometry and using an electronic odour sensor. In addition, several suggested influencing factors on the odour emission were measured to get insight into the reasons for the fluctuation of the odour emission. Odour emission tended to increase over the fattening period f rom August to November 2000 by a factor of two to three, although temperature and air-flow rate decreased according to the seasons. Feeding caused a significant temporary rise in animal activity, dust and odour concentration resulting in an increase of odour emission. The sensor signals of an electronic odour sensor increased simultaneously and showed a good relation to the odour concentration. There is a promising potential of electronic odour sensors to detect the dynamic and the level of odour concentrations. Further investigation will be done, to ensure a standardised measuring protocol and to obtain a calibration of electronic odour sensor signals direct to odour concentrations.

Effect of Magnesium Ions on the Properties of Foam Films Stabilized with Sodium Dodecyl Sulfate

Unstable and equilibrium foam films and foams formed from solutions of sodium dodecyl sulfate and bivalent electrolyte, MgCl2 or MgSO4, are experimentally investigated. It was found that at low ionic strength and low surfactant concentration the films with magnesium ions are more stable than films with sodium ions. At higher surfactant concentration the films containing MgCl2 become stable while the films with MgSO4 remain unstable. The unstable films exhibit at least five types of rupture which are documented by photographs and frequency distribution curves of the film lifetimes. In the case when magnesium ions are present the formation of lenses inside the film was observed; the lenses contribute to a longer lifetime of the films. With the stable films the transition from common to Newton black film occurs at magnesium concentrations between 0.01 and 0.015 M. The results for the stability of single microscopic films are found to correlate with the results for the foam drainage. Copyright 1997 Academic Press. Copyright 1997Academic Press

Isokinetic contractile properties of the quadriceps with relation to fiber type.

Fifteen subjects were assigned to three groups on the basis of the proportion of fast-twitch fibers (% FT) in their vastus lateralis muscles. Torque production per unit of fat free thigh volume was then determined during knee extension on an isokinetic dynamometer at 60, 120, 180, 240, and 300 degrees . s-1. Maximal isometric force was also obtained at 65 degrees from horizontal. Subjects with predominantly fast twitch muscle fibers demonstrated significantly greater peak power, rate of power production and work than subjects with predominantly slow twitch fibers at all but the lowest velocity of 60 degrees . s-1. Mean peak power for all subjects occurred at approximately 30% of maximal knee extension velocity (210 degrees x s-1) and 34% of maximal voluntary isometric contraction. When work, peak power and rate of power production were correlated with % FT fibers, then the highest correlations of 0.69, 0.57, and 0.73 respectively, all occurred at 180 degrees . s-1. These observations suggest that: 1) the torque-velocity, power-velocity relationship of the quadriceps is similar to the force-velocity, power-velocity relation found for excised muscle, 2) when using the knee extension exercise for the prediction of muscle fiber composition of the quadriceps the most appropriate speed for testing appears to be 80 degrees . s-1.