Power frequency (60 Hz and harmonics) AC currents were measured on four Wisconsin dairy farms using resistivity and potential gradient measurements by techniques adapted from magnetotelluric (MT) geophysical exploration. Several measurement sites were located on each farm in addition to a remote site as far away from the nearest power line as could reasonably be achieved. Electric field intensity and earth resistivity measurements were used to calculate the near-surface current density for 60 Hz and the 12 next order harmonics. Earth currents and the corresponding electrical voltages at 60 Hz and higher harmonics were inconsistent from farm to farm. Electric fields at the farms ranged from roughly 1 to 10 mV/m RMS at 60 Hz, and the current densities ranged from about 5 to 50 microampere/m2, roughly 10 to 1000 times stronger than at the corresponding remote sites. As expected, the presence of 60-Hz power frequency current and its harmonics was stronger near points of electrical use and distribution. The resulting step potentials, measured with high impedance equipment, were 26 to 8300 times lower than the maximum cow contact voltages prescribed by the Public Service Commission of Wisconsin (PSCW). Assuming a typical reduction of half in the contact voltage with a 500-ohm body impedance the resulting current flow through a cow attributable to earth currents in this study was 50 to 16,000 times below the PSCW action level. Considering the substantial body of literature supporting the PSCW level of concern, the extremely low exposure levels resulting from earth currents would not be expected to cause harm to dairy cows.

Two different types of orange juice, ultrafrozen (UFOJ) and from concentrate (OJFC), were analysed to evaluate the applicability of a chromatographic method for analysing organic acids to quantify vitamin C. The 2,6-dichlorophenolindophenol titration method was used as reference. Detection at 214 nm allowed vitamin C to be quantified accurately in OJFC. For UFOJ, the levels of vitamin C obtained by means of the selected wavelengths were significantly different than those obtained using the reference method, indicating that the HPLC method is not suitable for the determination of vitamin C in this juice | Sono stati analizzati due tipi di succhi d'arancia (da prodotto surgelato o da concentrato) con l'obiettivo di valutare la validità di un metodo cromatografico per la determinazione di acidi organici per la quantificazione della vitamina C. Prendendo come riferimento il metodo di valutazione con 2,6-diclorofenolindofenolo, il monitoraggio degli acidi organici a 214 nm permette di quantificare in modo esatto la vitamina C in esame. Nel caso dei succhi surgelati, le lunghezze d'onda di monitoraggio selezionate portano all'ottenimento di livelli di acido ascorbico significativamente differenti da quelli ottenuti con il metodo di riferimento, indicando che il metodo per HPLC non è adatto alla determinazione della vitamina C in questo tipo di succo

The distribution of horn flies, Haematobia irritans (L.) (Diptera: Muscidae), in herds of Danish Holstein-Friesian cattle was investigated in two studies conducted during two field seasons. In the first study, highly significant differences in fly distribution between the most and the least fly-susceptible heifers were observed. In one herd, the mean difference between the most fly-susceptible and the most fly-resistant heifers was 268 Ha. irritans specimens. The highest ratio between upper and lower mean fly number was 64.1:1, whereas the lowest was 3.1:1. In the second year, it was demonstrated that the heifers kept their rank in fly attraction over time. The trial clearly demonstrated that some heifers were attracting flies, whereas others, even in the same herd, only carried a few. In the second study, heifers were moved in and out of herds in an attempt to manipulate fly loads in the herds. In year 1, one herd (herd A) received four fly-resistant heifers from another herd (herd B), resulting in a drop in the mean number of flies, whereas herd B received four fly-susceptible heifers from herd A, resulting in an elevation of the mean number of flies. In year 2, a similar pattern emerged using herds C and D, and when the cattle were later returned to their original herds, the fly loads returned to their original distribution. The data presented here show unequivocally that, for horn flies, there can be considerable differences in fly loads for individual heifers within the Holstein-Friesian breed. Furthermore, the overall fly load within herds can be manipulated, and can be reversed. Thus, the distribution in the number of flies within a herd appears to depend on the number of fly-resistant or fly-susceptible heifers. The possible role of chemical factors emitted by heifers, i.e. volatile semiochemicals, in determining differences in fly loads is discussed, whereby attractants are emitted by fly-susceptible heifers and enable flies to locate their host, and repellents are emitted by fly-resistant heifers such that the flies are actively repelled from the herd.

An aerosol time-of-flight mass spectrometer (ATOFMS) was used to determine, in real time, the size and chemical composition of individual particles in the atmosphere at the remote inland site of Eskdalemuir, Scotland. A total of 51 980 particles, in the size range 0.3–7.4 µm, were detected between the 25th and 30th June 2001. Rapid changes in the number density, size and chemical composition of the atmospheric aerosol were observed. These changes are attributed to two distinct types of air mass; a polluted air mass that had passed over the British mainland before reaching Eskdalemuir, interposed between two cleaner air masses that had arrived directly from the sea. Such changes in the background aerosol could clearly be very important to studies of urban aerosols and attempts at source apportionment. The results of an objective method of data analysis are presented. Correlations were sought between the occurrence of: lithium, potassium, rubidium, caesium, beryllium, strontium, barium, ammonium, amines, nitrate, nitrite, boron, mercury, sulfate, phosphate, fluorine, chlorine, bromine, iodine and carbon (both elemental and organic hydrocarbon) in both fine (d < 2.5 µm) and coarse (d > 2.5 µm) particle fractions. Several previously unreported correlations were observed, for instance between the elements lithium, beryllium and boron. The results suggest that about 2 in 3 of all fine particles (by number rather than by mass), and 1 in 2 of all coarse particles containing carbon, consisted of elemental carbon rather than organic hydrocarbon (although a bias in the sensitivity of the ATOFMS could have affected these numbers). The ratio of the number of coarse particles containing nitrate anions to the number of particles containing chloride anions exceeded unity when the air mass had travelled over the British mainland. The analysis also illustrates that an air mass of marine origin that had travelled slowly over agricultural land can accumulate amines and ammonium.

The effect of single actinobacterial endophyte seed inoculants and a mixed microbial soil inoculant on the indigenous endophytic actinobacterial population in wheat roots was investigated by using the molecular technique terminal restriction fragment length polymorphism (T-RFLP). Wheat was cultivated either from seeds coated with the spores of single pure actinobacterial endophytes of Microbispora sp. strain EN2, Streptomyces sp. strain EN27, and Nocardioides albus EN46 or from untreated seeds sown in soil with and without a commercial mixed microbial soil inoculant. The endophytic actinobacterial population within the roots of 6-week-old wheat plants was assessed by T-RFLP. Colonization of the wheat roots by the inoculated actinobacterial endophytes was detected by T-RFLP, as were 28 to 42 indigenous actinobacterial genera present in the inoculated and uninoculated plants. The presence of the commercial mixed inoculant in the soil reduced the endophytic actinobacterial diversity from 40 genera to 21 genera and reduced the detectable root colonization by approximately half. The results indicate that the addition of a nonadapted microbial inoculum to the soil disrupted the natural actinobacterial endophyte population, reducing diversity and colonization levels. This was in contrast to the addition of a single actinobacterial endophyte to the wheat plant, where the increase in colonization level could be confirmed even though the indigenous endophyte population was not adversely affected.

The purpose of this paper was to determine the content of selenium in 50 samples of Sicilian virgin olive oils produced in six olive-growing zones from 10 different varieties of olives, and to investigate the possible connection between the olives varieties (cultivar), the zone of provenience and the selenium content in the oils. Cathodic stripping potentiometric analysis was used as a rapid, sensitive and reproducible method to determine selenium levels in acid extracts of olive oils. A precision of 2.8%, expressed as relative standard deviation of the measurements, and a detection limit of 0.6 microgram kg(-1) were obtained. The content of selenium found in the studied Sicilian virgin olive oils, ranged from 3.0 to 122.9 microgram kg(-1). The obtained results evidenced that olive oil samples from the same cultivar had a similar content of selenium, whereas some differences among the cultivars from the six studied zones were observed. These data provided evidence that both genetic factors (cultivar) and geographic factors (olive-growing zone), may influence the content of selenium in the studied Sicilian olive oils.

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