Samplers for evaluation and quantification of ultra-low volume space sprays

A field study was conducted to explore the suitability of 5 pesticide deposition samplers for airborne spray and ground deposits from ultra-low-volume (ULV) space sprays. Samplers included horizontally stretched stationary cotton ribbons at 2 heights, rotating ribbon, rotating Teflon slides, and filter paper. Slides were also used for droplet-size analysis. A set of 7 samplers of each type was placed at 1, 7, 15, 25, 40, 65, and 90 m from the spray line along the spray swath. Water and BVA13 oil with fluorescent dyes as tracers were sprayed with the use of a truck-mounted ULV sprayer at dusk and dawn. Results suggest that the horizontal and rotating cotton ribbons are best for quantification of airborne spray and filter paper is best for ground deposition collection. The rotating slide samplers only detected the BVA13 oil-based sprays.

Canopy penetration and deposition of barrier sprays from electrostatic and conventional sprayers

An experimental study was conducted to investigate the usefulness of electrostatic and conventional sprayers for barrier applications. Two conventional and three electrostatic sprayers were used in the study. Usefulness of the sprayers was rated based on penetration of spray into and deposition onto 2 sides of leaves on natural vegetation. Bifenthrin (Talstar adulticide) was applied at labeled rate, fluorescent dye was added to the tank mix as tracer, and all sprayers applied the dye and insecticide at the same rate. The results indicated that sprayers producing larger droplets produced significantly higher deposition on vegetation in barrier applications than the sprayers producing smaller droplets. Sprayers with higher air velocity at the nozzle discharge proved significantly better for barrier sprays than the sprayers with lower air velocity. Electrostatic sprayers did not show any improvement in deposition on vegetation or in penetration into vegetation over the conventional sprayers. There was no difference in deposition between truck-mounted and backpack sprayers.

Spray characterization of thermal fogging equipment typically used in vector control

Droplet size spectra from different sprayers used to generate insecticide-laden fogs for controlling flying insects were measured by a laser diffraction instrument and Teflon-coated slides. The objectives of this work were to present not only information on spray-system droplet size generated by different sprayers, but to compare methodologies by which other similar systems can be evaluated and give applicators sprayer-system performance data. Data from 45 replicated spray tests, comprising 11 sprayers and 5 pesticides, showed a wide range in the droplet size spectra produced. The volume median diameter measurements ranged from 2.6 to 75.5 microm for diesel-diluted sprays and from 27.9 to 59.9 microm for water-diluted sprays. Similarly, the percent volume <20 microm ranged between 12.0-100% and 8.5-30.7%, for diesel- and water-diluted sprays, respectively. The droplet sizes measured by the swinging slide and laser diffraction methods were not consistent. The information presented aids users in sprayer selection and operation to produce the specific droplet size spectra required for a particular application.

Characterization of truck-mounted atomization equipment typically used in vector control

The control of medically important arthropod vectors of human and animal disease is a high priority for both public health and military officials. Because droplet size of pesticide spray material is a critical factor affecting vector control applications, the droplet-size spectra produced by 11 sprayers and 3 spray formulations were evaluated. Droplet-size spectra were measured by a laser diffraction instrument, a hot-wire system, and rotating slides. There were considerable differences in the droplet-size spectra produced by the different sprayers tested. The volume median diameter (Dv0.5) for the water-based sprays ranged from 4.7 to 211 microm, depending on the sprayer, and the percent of spray volume contained in droplets less than 20 microm (%vol <20 microm) ranged between 0.5% and 98.9%. The Dv0.5 measurements for the oil-based sprays ranged from 9.4 to 125.3 microm and the %vol <20 microm ranged between 2.4% and 97.9%. The correlations between the Dv0.5 measured by the laser system (Dv0.5-laser) and the mass median diameter, Sauter diameter, and Dv0.5 measured by the AIMS probe were all significant. Generally, the slide Dv0.5s were numerically similar to the Dv0.5 from the laser system and the Sauter diameter from the Army Insecticide Measuring System probe. There was less consistent agreement between the % <32 microm values obtained from the slides and those from the other 2 samplers. The information presented can be used by applicators to select the sprayer that produces the droplet-size spectra needed for their particular application situation.

The transition to high school for academically promising, urban, low-income African American youth

In nine urban Ohio school systems, low-income minority students identified as academically promising in sixth grade are eligible to participate in an intervention program. In the present study, twenty-two African American students in the program were asked to provide their perceptions of the transition to ninth grade. Specifically, the role of motivating factors, peers, school, teachers, parents, and neighborhood were examined. These students faced similar stressors, yet some were more able to achieve academic success. Results highlight the salience of mothers, the challenges of the ninth-grade curriculum, and adjustment to a bigger, more complex school environment for high and low performers. The implications for improving cooperation between school and family are discussed.

Intentionality detection and "mindreading": why does game form matter?

By around the age of 4 years, children "can work out what people might know, think or believe" based on what they say or do. This is called "mindreading," which builds upon the human ability to infer the intentions of others. Game theory makes a strong assumption about what individual A can expect about B's intentions and vice versa, viz. that each is a self-interested opponent of the other and will reliably analyze games by using such basic principles as dominance and backward induction, and behave as if the normal form of an extensive form game is equivalent to the latter. But the extensive form allows intentions to be detected from actual sequential play and is therefore not necessarily equivalent psychologically to the normal form. We discuss Baron-Cohen's theory of the mindreading system [Baron-Cohen, S. (1995) Mindblindness: An Essay on Autism and Theory of Mind (MIT Press, Cambridge, MA)] to motivate the comparison of behavior in an extensive form game with its corresponding normal form. As in the work of Rapoport [Rapoport, A. (1997) Int. J. Game Theory 26, 113-136] and Schotter et al. [Schotter, A., Wiegelt, K. & Wilson, C. (1994) Games Econ. Behav. 6, 445-468], we find consistent differences in behavior between the normal and extensive forms. In particular, we observe attempts to cooperate, and in some treatments we observe the achievement of cooperation, occurring more frequently in the extensive form. Cooperation in this context requires reciprocity, which is more difficult to achieve by means of intentionality detection in the normal as opposed to the extensive form games we study.

A comparison of naive and sophisticated subject behavior with game theoretic predictions

We use an extensive form two-person game as the basis for two experiments designed to compare the behavior of two groups of subjects with each other and with the subgame perfect theoretical prediction in an anonymous interaction protocol. The two subject groups are undergraduates and advanced graduate students, the latter having studied economics and game theory. There is no difference in their choice behavior, and both groups depart substantially from game theoretic predictions. We also compare a subsample of the same graduate students with a typical undergraduate sample in an asset trading environment in which inexperienced undergraduates invariably produce substantial departures from the rational expectations prediction. In this way, we examine how robust are the results across two distinct anonymous interactive environments. In the constant sum trading game, the graduate students closely track the predictions of rational theory. Our interpretation is that the graduate student subjects' departure from subgame perfection to achieve cooperative outcomes in the two-person bargaining game is a consequence of a deliberate strategy and is not the result of error or inadequate learning.

First Report of Powdery Mildew on Cornus florida in Connecticut Caused by Microsphaera pulchra

Powdery mildew of dogwood (Cornus florida L.) has been observed on landscape trees since 1992, and has been increasing in severity recently. In 1998, mildewed leaves (n = 100) were collected from each of four locations in Connecticut. White mildew colonies first appeared in the early summer, 4 to 6 weeks after leaf emergence, and the initial colonies rapidly coalesced to cover the entire adaxial leaf surface. Incidence on observed trees reached nearly 100%. Premature autumn coloration and defoliation occurred on those trees where incidence was highest; tree mortality due solely to powdery mildew was not observed. Cleistothecia were apparent on both adaxial and abaxial leaf surfaces within 4 to 6 weeks of initial infection. Mycelium was white in color, and conidiophores were three-celled with a slightly bent foot cell. Fibrosin bodies were not present in conidia (n = 400), which measured 14.1 m ± 0.80 × 28.1 m ± 1.60 (mean + standard error of the mean). Cleistothecia measured 114.7 m ± 1.77 in diameter, and had 4 to 10 dichotomously branched appendages, which measured 140.7 m ± 3.95 in length (1.23× cleistothecial diameter). The fungus was identified as Microsphaera pulchra based on mycelial, conidial, and cleistothecial characteristics (1). In addition, cleistothecia were found on twigs and on fallen leaves of dogwood; these overwintering cleistothecia contained mature asci and mature ascospores in March 1999. Microsphaera penicillata recently was redescribed to include only that species causing powdery mildew on Alnus spp., and having appendages 1.5× cleistothecial diameter (2). The fungus causing powdery mildew in Connecticut previously had been reported to be M. penicillata, which was not found in the present study. References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer, New York, 1995.

First Report of Powdery Mildew of Tomato Caused by an Erysiphe sp. in Connecticut

In 1995 and 1996, powdery mildew was observed on several samples of field-grown tomato foliage (Lycopersicon esculentum Mill.; various cultivars) submitted to the CAES Plant Disease and Information Office. Symptoms included gray superficial mycelium with abundant sporulation on adaxial and abaxial leaf surfaces, followed in the field by dessication of the foliage and rapid defoliation. No cleistothecia were observed, and single-celled, hyaline, ellipsoidal conidia occurred, usually singly, on unbranched conidiophores. Pyriform conidia occurred at a frequency of less than 1%. Conidia ranged in length from 25.6 to 43.2 μm (mean = 33.6, SE = 0.4) and in width from 13.1 to 23.1 μm (mean = 18.2, SE = 0.2; n = 500). Fibrosin bodies were not observed, and vacuoles were present. Based on conidial characteristics, the fungus was identified as an unknown Erysiphe sp. To confirm pathogenicity, 2-week-old tomato seedlings (cv. Rutgers) were inoculated by shaking dry conidia onto the leaves and placed within plastic tents on a greenhouse bench. Control plants were treated identically but not inoculated. The inoculated plants developed foliar powdery mildew symptoms, and sporulation was observed. Susceptible cultivars that were naturally infected included Better Boy, Better Beef, Celebrity, Rutgers, Ultra Magnum, Ultra Sweet, Whopper, Yellow Brandywine; cherry type tomatoes Matts Wild Cherry and Sweet Chelsea; and plum type tomatoes Roma and Super San Marzano. Eastern black nightshade (Solanum ptycanthum Dunal), eggplant (S. melongena L. 'Black Pride'), and tobacco (Nicotiana tabacum L. 'C9') were also naturally infected under greenhouse conditions. However, conidia size and number of conidia per conidiophore differed between hosts. Conidia from tobacco, eggplant, and nightshade averaged 37.8 × 19.1 μm (SE = 0.5 and 0.2, respectively) with a 95% CI of 35.5 to 40.0 × 18.1 to 20.3 μm (n = 300). Conidia from tomato were smaller, averaging 33.6 × 18.2 μm (SE = 0.3 and 0.2, respectively) with a 95% CI of 32.7 to 34.4 × 17.5 to 18.9 μm (n = 300). Factorial inoculation experiments between tomato and other hosts demonstrated cross-infectivity, but isolates originally from tobacco had significantly larger conidia when infecting tomato than isolates originally from tomato infecting tobacco. Powdery mildew isolates on tomato had fewer (P = 0.001) conidia per conidiophore (mean = 1.39, range = 1 to 4) than isolates infecting tobacco inoculated at the same time and held under the same conditions (mean = 2.54, range = 1 to 6). These results demonstrate considerable morphological variation in the powdery mildew fungus, perhaps associated with hosts such as tomato or other solanaceous plants. This is the first report of powdery mildew of tomato and tobacco in Connecticut. Powdery mildew of tomato has been reported to occur in the field in California, and in greenhouse tomatoes in New York (2). Powdery mildew of tobacco has only been reported on artificially inoculated plants in California (1). References: (1) C. R. Arredondo et al. Plant Dis. 80:1303, 1996. (2) D. M. Karasevicz and T. A. Zitter. Plant Dis. 80:709, 1996.

Game theory and reciprocity in some extensive form experimental games

We examine decision making in two-person extensive form game trees using nine treatments that vary matching protocol, payoffs, and payoff information. Our objective is to establish replicable principles of cooperative versus noncooperative behavior that involve the use of signaling, reciprocity, and backward induction strategies, depending on the availability of dominated direct punishing strategies and the probability of repeated interaction with the same partner. Contrary to the predictions of game theory, we find substantial support for cooperation under complete information even in various single-play treatments.

Infant feeding and phonologic development

The relationship between breastfeeding and speech development was examined to determine what duration (if any) of breastfeeding is associated with better performance on a measure of phonologic development. Twenty-nine children aged 36-48 months and their parents were recruited from preschools to serve as subjects. The children's durations of exclusive breastfeeding ranged from 0 (always bottle fed) to 6 months. Phonologic development was assessed using an instrument known as the Percentage of Consonants Correct (PCC) [12]. Feeding histories were obtained by retrospective interviews with parents. Parents and teachers also made ratings of children's speech and total communication on a 5-point scale. This study fails to replicate earlier researchers' findings of an association between breastfeeding and phonologic development. No evidence was found of an association between any duration of either exclusive or partial breastfeeding and PCC scores. Pearson r correlations between parents' and teachers' ratings and PCC scores were weak. Results are discussed in comparison with previous reports of a correlation between breastfeeding and phonologic development.

Comparison of Telazol, Telazol-ketamine, Telazol-xylazine, and Telazol-ketamine-xylazine as chemical restraint and anesthetic induction combination in swine

The use of Telazol (T, tiletamine and zolazepam, 4.4 mg T/kg) alone, Telazol-ketamine (TK, 4.4 mg T/kg and 2.2 mg K/kg), Telazol-xylazine (TX, 4.4 mg T/kg, 2.2 mg X/kg), and Telazol-ketamine-xylazine (TKX, 4.4 mg T/kg, 2.2 mg K/kg, and 2.2 mg X/kg) as chemical restraint and anesthetic induction combination was compared in pigs. Forty mixed-breed healthy pigs (24.4 +/- 5.6 kg, mean +/- SD) were randomly assigned to the four treatment groups (T, TK, TX, TKX) with 10 pigs in each group. All the anesthetics were premixed by adding sterile water, ketamine, xylazine, or xylazine and ketamine directly into the Telazol vial and given as a single intramuscular injection. All four anesthetic combinations induced a rapid onset of sternal recumbency within 1.76 +/- 1.0 minutes and lateral recumbency within 3.02 +/- 2.2 minutes in pigs after intramuscular injection; there was no significant difference among treatments. The combinations TX and TKX induced analgesia (as evident by a lack of response to needle prick in the middle portion of the pinna and flank regions) duration of 29.0 +/- 11.0 and 36.0 +/- 12.2 minutes, respectively, and ability to tolerate tracheal intubation (as evident by lack of coughing and chewing response to a laryngoscope) for a period of 34.0 +/- 8.4 and 39.0 +/- 9.9 minutes, respectively. The combinations T and TK did not induce analgesia nor conditions suitable for intubation. Duration of lateral recumbency was 29.9 +/- 10, 33.1 +/- 6.9, 52.2 +/- 6.9, and 61.5 +/- 10.7 minutes in T-, TK-, TX-, and TKX-treated pigs, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Smart Computer-Assisted Markets

The deregulation movement has motivated the experimental study of auction markets designed for interdependent network industries such as natural gas pipelines or electric power systems. Decentralized agents submit bids to buy commodity and offers to sell transportation and commodity to a computerized dispatch center. Computer algorithms determine prices and allocations that maximize the gains from exchange in the system relative to the submitted bids and offers. The problem is important, because traditionally the scale and coordination economies in such industries were thought to require regulation. Laboratory experiments are used to study feasibility, limitations, incentives, and performance of proposed market designs for deregulation, providing motivation for new theory.

Gustatory neural coding in the monkey cortex: stimulus intensity

1. We analyzed the activity of single neurons in gustatory cortex of alert cynomolgus monkeys in response to a range of stimulus intensities. Chemicals were deionized water, fruit juice, and several concentrations of the four prototypical taste stimuli: 10(-3)-1.0 M glucose, 10(-3)-1.0 M NaCl, 10(-4)-3 x 10(-2) M HCl, and 10(-5)-3 x 10(-3) M quinine HCl. 2. Taste-evoked responses could be recorded from a cortical gustatory area that measured 2.5 mm in its anteroposterior extent, 6.0 mm dorsoventrally, and 3.0 mm mediolaterally. Taste-responsive cells constituted 62 (3.7%) of the 1,661 neurons tested. Nongustatory cells gave responses associated with mouth movement (10.1%), somatosensory stimulation (2.2%), and approach or anticipation (0.9%). 3. Intensity-response functions were determined across 62 gustatory neurons. Neural thresholds for each stimulus quality conformed well to human psychophysical thresholds. Mean discharge rate was a direct function of stimulus concentration for glucose, NaCl, and quinine HCl. The most effective of the basic stimuli was glucose. 4. Power function exponents were calculated from the responses of neural subgroups most responsive to each basic stimulus. Those for glucose, NaCl, and quinine were within the range of psychophysically derived values. Thus the perceived intensity of each basic quality is presumably based on the activity of the appropriate neural subgroup rather than on the mean activity of all taste cells. 5. The mean breadth-of-tuning (entropy) coefficient for 62 gustatory neurons was 0.65 (range, 0.00-0.98). 6. There was no clear evidence of chemotopic organization in the gustatory cortex. 7. An analysis of taste quality indicated that sweet stimuli evoked patterns of activity that were clearly distinct from those of the nonsweet chemicals. Among the latter group, NaCl was differentiable from HCl and quinine HCl, whose patterns were closely related. 8. The response characteristics of cortical taste cells imply gustatory thresholds and intensity-response functions for the nonhuman primate that conform well to those reported in psychophysical studies of humans, reinforcing the value of this neural model for human taste intensity perception.

Effect of ozone on growth of mosses on disturbed forest soil

Mixed forest floor organic matter and upper mineral soil from a 1580 m elevation conifer-hardwood stand in the Pisgah National Forest, NC, was placed in 4-cm diameter x 21-cm deep tubes and exposed to 0.00, 0.08, 0.16, 0.24 or 0.32 microl O3/liter air (ppm). Twelve tubes in each of three replications/treatment were fumigated in continuously-stirred tank reactors in a greenhouse for 6 h/day on 4 consecutive days/week. Soil was watered 3 days/week with deionized water amended with ions and adjusted to pH 4.3 with H2SO4 + HNO3 (70 meq SO4(2-): 30 meq NO3(-)). After 10 weeks the amount of soil surface covered by moss (predominantly Ditrichum pusillum, but also D. lineare, and Pohlia nutans) was estimated visually and assigned a rating on a scale of: 1 = 0-25%; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%. Linear regression analysis revealed a significant (p < 0.001) negative relationship between coverage ratings and O3 concentration. Surface coverage in tubes exposed to 0.32 or 0.24 ppm was about half of that for 0.00 ppm (mean ratings of 1.1, 1.4 and 2.6, respectively). Coverage differences appeared to be due in part to O3 suppression of plant numbers. Linear regression analysis also revealed a significant (p < 0.001) negative relationship between heights of D. pusillum plants (measured after 12 weeks treatment) and O3 concentration.

Eyewitness accuracy and confidence: within- versus between-subjects correlations

Previous researchers using between-subjects comparisons have found eyewitness confidence and accuracy to be only negligibly correlated. In this study, we examined the predictive power of confidence in within-subject terms. Ninety-six subjects answered, and made confidence ratings for, a series of questions about a crime they witnessed. The average between-subjects and within-subject accuracy-confidence correlations were comparably low: r = .14 (p less than .001) and r = .17 (p less than .001), respectively. Confidence is neither a useful predictor of the accuracy of a particular witness nor of the accuracy of particular statements made by the same witness. Another possible predictor of accuracy, response latency, correlated only negligibly with accuracy (r = -.09 within subjects), but more strongly with confidence (r = -.27 within subjects). This pattern was obtained for both between-subjects and within-subject comparisons. The theoretical and practical implications of these results are discussed.

Rapid purification of the 30 kDa calcimedin using DNase I affinity chromatography

The 30 kDa calcimedin was found to bind directly to phenyl-Sepharose in a calcium dependent manner similar to calmodulin. The 30 kDa calcimedin was also found to bind to and inhibit DNase I. This calcium-dependent binding was exploited to develop a two-step purification scheme for this calcimedin. In addition, affinity-purified antibodies to the 30 kDa calcimedin were used to examine its tissue distribution. The highest levels were found in lung, trachea and diaphragm while the lowest levels of the 30 kDa calcimedin were found in brain and skeletal muscle.

The expression of the 35- and 67-kDa calcimedins is dependent on thyroid hormone

We have investigated the expression of the 35- and 67-kDa calcimedins and calmodulin during fetal and neonatal periods and in adulthood in rat liver, muscle, and brain. The 35- and 67-kDa calcimedin expression in liver and muscle increased during the perinatal period and correlated with the thyroid status of the developing rat. In fact, animals treated with thyroxine demonstrated a precocious appearance of the 35- and 67-kDa calcimedin in liver and muscle. Animals treated with methylthiouracil, an inhibitor of T4 and T3 synthesis, strongly suppressed the synthesis of the calcimedins in these tissues. Neither treatment influenced the levels of either the 35- and 67-kDa calcimedins in brain. In contrast, each tissue examined produced a unique pattern of calmodulin expression during development. None of the tissue calmodulin concentrations changed during hyper- or hypothyroid states. Collectively, these data support the concept that the intracellular calcium signal possesses multiple, independent molecular pathways of mediation. In addition, the variety of these pathways is influenced by hormonal preconditioning in that the cellular response to elevated cytosolic calcium is dependent upon the thyroid status of a tissue.

Structure and sequence of the Drosophila melanogaster calmodulin gene

A series of phage clones overlapping the single calmodulin gene locus of Drosophila melanogaster has been isolated and the exons of the gene positioned and sequenced within these clones. A calmodulin cDNA clone of the electric eel was used to identify these clones and to position the two major protein-coding exons of the gene. cDNA clones for D. melanogaster calmodulin were then isolated, characterized and used to identify the remaining exons. The gene consists of four exons separated by three introns of 3400 to 4300 bases in length. Exon 1 consists of the 5' untranslated region and the initiator ATG; exon 2 encodes amino acid residues 1 to 58.3; exon 3 encodes residues 58.3 to 139.3; and exon 4 encodes residues 139.3 to 148 and the 3' untranslated region. From the sequence of the 3' untranslated region and the lengths of the cDNA clones, two or three polyadenylation sites are indicated. Sequences potentially involved in the control of transcription of the gene and splicing of the mRNA product have been identified. Comparison of the intron-exon structures of the D. melanogaster calmodulin gene, the chick calmodulin gene, and other genes of the troponin C superfamily reinforces previous hypotheses that these genes arose from a common progenitor and permits identification of four introns that were probably present in the progenitor gene structure. The D. melanogaster calmodulin gene contains three of these introns, and the chick gene contains all four. These gene comparisons also indicate that the region of these genes encoding Ca2+-binding loop 3 is highly variable in structure. The chick and D. melanogaster calmodulin genes differ in this region, the chick gene containing a fifth intron here that is absent from the D. melanogaster gene.

An immunological comparison of several novel calcium-binding proteins

Polyclonal antibodies prepared against each of the calcimedins were utilized to determine their tissue distribution. The immunological survey of rat tissues revealed that the levels of the 35-kDa calcimedin varied, while the amount of the 67-kDa calcimedin was relatively constant in the tissues examined. A new immunoreactive species, 52 kDa, was detected with the antibody to the 35-kDa calcimedin; this protein appears to be the predominant immunoreactive species in the tissues examined. Antibodies to the 35-kDa calcimedin were also used to compare many other calcium-binding proteins in order to determine immunological relationships. These comparisons demonstrate that the epidermal growth factor receptor/kinase substrate (p35), the src kinase substrate (pp36), and calregulin are immunologically unrelated to the calcimedins. However, it was found that the 67-kDa calcimedin and the p70 calelectrin are identical, as are the 35-kDa calcimedin and the p32.5 calelectrin. The calimedins are a subset of the chromobindins. In addition, the antibody to the 35-kDa calcimedin also cross-reacts with synexin, which may be related to the new 52-kDa immunoreactive protein identified.

Experimental Methods in the Political Economy of Exchange

Traditionally, economics has been considered a nonexperimental science. In the last quarter century experimental methods have become a growing part of the economist's effort to more fully understand how individual motivation, individual information, and exchange rules relate to market outcomes in different institutions. Empirical support has been found in a wide variety of different experiments for the theoretical proposition that markets serve to aggregate the dispersed information of individuals to produce wealth-creating outcomes for society. A number of different experiments are presented to illustrate the type of questions addressed, including some in which the process is governed by political institutions such as majority rule.

The intron boundaries and flanking rRNA coding sequences of Calliphora erythrocephala rDNA

We have sequenced the available cloned examples of the intron-coding sequence junctions for the rDNA of the higher Dipteran, Calliphora erythrocephala. The introns interrupt the rDNA at the same position as the type 1 intron family detected in Drosophila melanogaster and D. virilis (10,11). A duplication of 14 base pairs of the 28S rRNA coding sequence surrounds a short version of the major genomic length class of introns. This same duplication is associated with boundaries of the type 1 introns in D. virilis and D. melanogaster (10, 13,14). We have detected considerable homology between the 3' intron sequences of C. erythrocephala and D. virilis. The rRNA coding sequences flanking the introns are extremely homologous in C. erythrocephala, D. melanogaster and D. virilis, with only one small region of significant divergence. This corresponds to a variable stem region previously identified in eukaryotic 28S rRNA at a site analogous to the L1 ribosomal protein binding site of prokaryotic 23S rRNA (27).