Field cages

Mclnnes, D.O. and T.T.Y. Wong. 1990. Mediterranean fruitfly interference of oviposition by radiation-sterilized females in field cages. Entomol. Exper. Appl. 56 125-130. 

The use of field cages or semifield tunnel tests was originally devised by Gerig [71] and has constituted a useful and cost-effective part of the hazard evaluation... 

The pheromone chemistry of A. hilare has been studied in detail, using both laboratory (vertical Y-tube) and field bioassays [75]. In Y-tube bioassays, mature females were attracted by male odors, but males were not attractive to other males, and females were not attractive to either sex. Males produced (-)-cis-Z-BAE and (-)-frazzs-Z-BAE in a -19 1 ratio, and other compounds in the extracts were not active. The 19 1 blend was more attractive to females than other ratios, and the individual components were not attractive, indicating that both compounds were required. Females were attracted to the synthetic blend in field cage trials [75],but as with most other phytophagous pentatomids,few bugs were caught in pheromone-baited traps (J.G. Millar and H.M. McBrien, unpublished data). 

Mating disruption experiments with spruce budworm in laboratory, small-scale field tests and "semi-operational" field trials have recently been reviewed (27). Work to date, on the disruption of spruce budworm mating behavior has concentrated on the use of the primary components /Zll-14 Ald s (95-97% E), and the results indicate that some mating disruption does occur. There appears to be a positive correlation between the applied pheromone concentration and the percent disruption, and based on field cage studies, percent disruption is inversely related to insect density (27) as would be predicted (32). 

Keywords Three dimensional microstructures, electric field, field cage, cell adhesion, cell... 

Field cages can also be used to create layered particle aggregates of defined shape which can then be made permanent by e.g. photopolymerisation (Fig. 6) [44]. Possible applications of this technique range from the encapsulation of drugs in micron scale structures with controlled release pores to the creation of ordered aggregates of living cells. 

Fig. 6. This particle aggregate was formed in an octopole field cage. It has six tails of which four are visible here. The cage was 200 pm in diameter and energised by 25 V at 1 MHz. The aggregate is formed of 3.9 pm diameter latex beads levitated and held by the forces in the cage. By alterations of driving regime, different shapes are possible and suitably prepared particles can be crosslinked to form a permanent structure by photo-polymerisation or by chemical means. The bar is 200 pm...

The first practical applications are likely to include field cages for cell positioning, inexpensive cell sorters and single cell cultivation depots. But once the basic elements for cell handling have been developed, very many kinds of device will become easy to produce. We can expect to see new systems for use in medical diagnosis and pharmaceutical testing within the next decade and a range of cell based biosensors. 

The pheromone of the rice stem borer, Chilo suppressalis, is a mixture of two aldehydes, (Z)-ll-hexadecenal and (Z)-13-octa-decenal. Field-cage trials carried out in the Philippines at the International Rice Research Institute showed that the fully stabilised microencapsulated formulations of these aldehydes persisted for over 30 days and virtually eliminated the laying of fertile eggs during this period (6). 

Figure 12 Combination of dielectrophoretic field cage (DFC) and optical tweezers (OT) for the measurement of bead-cell adhesion (A) 4.1-(xm polystyrene particle trapped with laser tweezers (right) in contact with T-lymphoma cell ( — 1 5 pm in diameter). Cell and bead were brought into contact. The time for stable adhesion was measured. (B) Schematic representation of the experimental system used to measure the adhesion forces between bead and cell with the cell trapped in a DFC and the bead trapped in the laser focus of the OT. (C) Probing different surface regions of the cell for bead-cell adhesion (five beads are attached to a single cell). (Reprinted from Ref. 91 with permission.)...

T. Schnelle, T. Muller and G. Fuhr, The influence of higher moments on particle behaviour in dielectrophoretic field cages, J. Electrostal, 46, 13-28 (1999). 

All these tests were conducted in field or greenhouse cages and also in greenhouse compartments, i.e. under nearly natural climatic conditions and permanent exposure. Sometimes, parallel experiments were conducted in greenhouse and in field cages to determine whether both situations gave similar results. 

In field cage studies in which zea larvae on several plant lines were exposed to adult parasitoids (one plant line per cage), percent paras itization by both species was significantly lower on BC2, (a backcross ((L, esculentum x PI 134417) x PI 134417) line with intermediate levels of 2-tridecanone and glandular trichome density), and PI 134417 than on L. esculentum and the Fi hybrid (L. esculentum X PI 134417) (Table ViTT. This pattern reflects levels of 2-tridecanone-mediated resistance to sexta. These data indicate that fewer zea larvae are parasitized on the more resistant plant lines but do not indicate whether this is due to elevated densities of glandular trichomes or methyl ketones, or both. 

Table VII. Percent parasitization of zea larvae by sonorensis and A. marmoratus in nonchoice field cage studies...

Zimmermann, U., 1996. Trapping of viruses in high-frequency electric field cages. Naturwissenschaften 83, 172-176. 

Schnelle T, Muller T, Fuhr G (2000) Trapping in AC octode field cage. J Electrostal 50 17-29... 

Often, a simplified SRLS model is sufficient to describe experimental data. Most commonly, only one additional dynamical parameter, Rj, is needed to describe the cage diffusion. Also, the mean-field cage potential can often be approximated with cylindrical symmetry, so that only the L = 2 parameters need be retained in the cage orienting potential. 

To measure characteristic parameters of single cells requires exact positioning (pm-range) However, most cells show physiological reactions after mechanical contact with artificial surfaces The occurrence of negative dielectrophoresis allows the development of field cages since cells are focused toward the central part of three-dimensional octupole-electrode configurations (for more details see [2, 7])... 

In such cages individual cells can be levitated in physiological solutions and held in a stable position or rotated by applying travelling electric fields [2] The field cage can be opened and closed by changing the amplitude, frequency of phase of the electrode signals [8] By this procedure cells can be released or trapped... 

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