Showing papers by "Hofstra University published in 1979"

Length and evolutionary stability of food chains

Abstract: Grazing food chains in natural ecosystems tend to be relatively short, usually involving no more than four or five trophic levels 1–3. Cohen4 describes 19 food webs with a total of 102 top predators. Recent independent analyses of these data by Cohen4 and Pimm (see ref. 5) show that most top predators occupy the third trophic level. However, as Slobodkin3 has observed, “It is possible to conceive of predators that are small enough and ferocious enough to attempt to live off the top of a trophic pyramid, and thereby become a seventh, or even an eighth, trophic level. It is by no means clear why this situation has not occurred.” Our answer, which we discuss here, incorporates energy transfer calculations introduced by Hutchinson1 and Odum and Odum2 within the framework of the evolutionarily stable strategy (ESS) developed by Maynard-Smith and Price 6,7. We argue that food chains should collapse to the shortest possible length compatible with biochemical and physiological constraints. This minimal length is frequently three, and is largely independent of primary productivity.

Tip Transformation in Tetrahymena: A Morphogenetic Response to Interactions Between Mating Types*

Abstract: SYNOPSIS. In Tetrahymena thermophila subline B, a morphogenic alteration of the anterior end of cells of mating types III and VII results from a cellular interaction which precedes and is a prerequisite for pairing. Cell pairing begins 1 h after starved cells of complementary mating type are mixed. The 1 h-long lag period is characterized by an actinomycin D-sensitive inductive interaction in the first 30 min, followed by a maturation period. Tip transformation begins during the maturation period and continues after pairing. Scanning electron microscopy of deciliated cells reveals ridges which form a chevron meeting in a midline seam between the oral apparatus and the anterior tip. During transformation, the seam broadens until the ridged surface is completely smooth. Melding of the ridges also occurs at the tip of the cell resulting in its blunted appearance. Cells of complementary mating types join in the region of this modified surface, which eventually becomes a specialized cell junction perforated by cytoplasmic bridges. Thus, pursuant to an inductive interaction the structure of the tip of cells is modified in anticipation of the pairing event. Rate of cell pairing might be limited by rate of tip transformation.

Relationship between Hurricane Surface Winds and L-Band Radar Backscatter from the Sea Surface

Abstract: High-altitude, airborne, L-band synthetic aperture radar (SAR) data were collected in Hurricane Gloria on 28 and 30 September 1976. The backscattered power levels (proportional to the surface scattering coefficient) averaged over a few square kilometers of surface area were found to vary with surface wind speed and the angle of the wind relative to the radar. Comparisons between the backscatter from the eye and eye-wall regions of the hurricane were made with low-level aircraft wind measurements that were nearly coincident in space and time. The SAR has the potential advantage over other radar types because of its higher spatial resolution. It also appears to have the ability to penetrate rainfall, with a reduction in the echo from the surface. One difference when compared with higher frequency microwave radars is a decrease in the sensitivity of the backscatter to changes in wind speed. This dependence of L-band radar backscatter on surface winds suggests that the winds associated with hurricanes can be measured with airborne or spaceborne radars.

Can you standardize international marketing strategy

Abstract: The intent of this paper is to examine the possibilities for standardization of marketing elements within a multinational marketing strategy. A majority view among international marketers is that each national is unique, and thus each must be treated as a separate and independent operation. This “localized” strategy view is examined first. A growing number of international marketers however, are finding that by standardizing various elements oftheir marketing strategy across national borders, cost savings and/or increased revenues to be realized can yield greater profits. The second, and major, part of the paper examines the opportunities for and potential benefits of standardization of product, packaging, advertisting, and pricing.

Rough surface wavelength measurement through self mixing of Doppler microwave backscatter

Abstract: A microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering "patches" stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.

Effects of behavior rehearsal, audiotaped observation, and intelligence on assertiveness and adjustment in third-grade children

Abstract: The effects of behavior rehearsal and audiotaped vignettes as added components to a 12-session assertion training lecture series were studied. Subjects were 96 third-grade children of average or above average IQ. Results showed that on both measures of assertion, behavior rehearsal was a significant adjunct to the assertion lecture, which was also given to the attention control children. On one measure of assertion an effect was also noted for the audiotaped observation condition. There was no effect of IQ. While clear increases in assertion were found, no effect on neuroticism or trait anxiety was noted. It was recommended that school mental health programs include an assertiveness segment in their curriculum.

Factors related to the efficacy of treatment of enuresis.

Abstract: Summary.-The variables of sex, frequency of wetting, a family history of enuresis, and use of positive reinforcement were examined to determine if they were significantly related to response to the bell-and-pad procedure. Dependent measures were number of days required to achieve dryness and frequency of werting in a l-yr. follow-up. Among the findings was that girls achieved the dryness criterion more quickly than boys. Frequency of enuresis was inversely related to number of days required to achieve dryness. Evidence was obtained suggesting a generic basis for resistance to reduction in enuretic behavior. Children who were tangibly reinforced for dryness did not wet less frequently in the follow-up nor did they achieve the dryness criterion more quickly. Nocturnal enuresis, the persistent nighttime wetting of the bed, is exhibited by more than 15% of all 5-yr.-olds and by about twice as many boys as girls (Lovibond & Coote, 1970; Yates, 1970). Treatment of enuresis by behaviorally oriented methods has generally been shown to be more effective than the use of psychodynamic or medical procedures (Jones, 1960; Lovibond, 1964; Yates, 1970). The typical behavioral treatment involves the use of an alarm box which is connected to two wire mesh pads. This device is frequently referred to as the bell-and-pad. The pads are placed in the bed with the child and urine passing through the pads creates a circuit which sets off the alarm. The child is conditioned to retain urine and to awaken in response to bladder distension by continued pairing of wetting with the sounding of the alarm. A recent review of enuresis studies (Doleys, 1977) included a survey of 12 investigations in which the age range of the children was between 4 and 15 yr. Following a treatment duration which ranged from a mean of five to 12 weeks, bedwetting was arrested in 75% of the children. The criterion for arrest was generally 14 consecutive dry nlghcs but ranged from seven to 28 dry nights. Of those enuretic children for whom adequate follow-up data were presented, 41% relapsed within 6 mo. of treatment. It should be pointed out that there is no over-all consensus regarding what constitutes a relapse. Owing to variation in the definition of relapse, rates have been reported to be as low as 6% (Forsythe & Redmond, 1974) to as high as 75% (Turner, Young, & Rachrnan, 1970). Generally, reported relapse rates of 40% are common and in most cases a relapse does not mean that the child is wetting at the same frequency as before treatment but simply that occasional wets are occurring. In devising a program called dry-bed training, Azrin, Sneed, and Foxx

Univariate and Multivariate Analysis of Categorial Variables

Abstract: Recent trends in the analysis of categorical or nominal variables were discussed for univariate, multivariate, and psychometric problems. It was shown that several statistical procedures commonly u...

Cursive Writing An aid to Reading and Spelling

Abstract: A widespread belief among teachers is that manuscript writing is easier for young children to learn than cursive writing. Many experts in the field of special education, such as William Cruickshank and Alex Bannatyne, have come to realize that, in practice, the reverse is true. Our personal experiences in the classroom have also shown us that exceptional children can learn cursive writing at an early age. We developed a structured, logical, and sequential method of teaching cursive writing. The long-term goal, however, is to teach writing in conjunction with reading and spelling. Since it is necessary to spell as you write, and then to read what you have written, it is natural and meaningful to teach writing, spelling, and reading together. A separation of these three subject areas is artificial and eliminates the help and reinforcement each area gives to the others. A study undertaken at Indiana State University by George Early and his coworkers, in which an experimental group of children were taught cursive writing exclusively in first grade, appears to support our position. Achievement in spelling and word reading was higher in the experimental group, while

Question form analysis in discourse agreement between a mother and a language-learning child

Abstract: This study analyzed the question form used in discourse between a mother and her language-learning child. Spontaneous taped data of mother-child interactions were collected at three different time periods. Initially the child was 2;3 and data collection stopped at 2;5. Analysis of dialogue units based on protocols of discourse proposed by Mishler (1974) was conducted. Results indicated that question chaining occurred most frequently in discourse, followed by arching, then embedding. All question forms except one were initiated by the mother. Evidence also indicated that the subject did not have the linguistic competence of allwh-question forms by 2;5. This study indicated that question chaining was the most frequent type of discourse analysis with this dyad.