Acoustic Signals of \u3ci\u3eGraminella Nigrifrons\u3c/i\u3e (Homoptera: Cicadellidae)

The deltocephaline leafhopper, Graminella nigrifrons, produces low intensity sub- strate transmitted vibrations (signals) to facilitate location of virgin females by males during courtship. In the laboratory, signals produced on maize leaves were received by a phonographic cartridge, amplified, and analyzed on an oscillograph and sonograph. Male calls, that are produced spontaneously, are complex, consisting of three consecutive sections. Section 1 consists of ca. 3 sec of irregular clicks. Section 2 has ca. 4 sec of repeated phrases consisting of a continuous series of 0.4 sec chirps and a roll. Section 3 consists of ca. 5 sec of an intermittent series of 0.2 sec chirps and a roll. Female calls are produced in response to male calls. Female calls are simple compared to male calls and consist of ca. 4-5 sec of low frequency clicking. Signal patterns of G. nigrifrons are compared to those of other leafhoppers and evolutionary scenarios are presented to account for the observed gender differ­ences in signals

Economic optima in soil conservation farming and fertilizer use for farms in the Ida-Monona soil area of western Iowa

Soil erosion is a major agricultural problem in western Iowa. While farmers in the area generally are aware of the erosion problem, relatively few use farm plans which result in the level of conservation needed to stabilize soil loss. Previous studies indicate that economic considerations, particularly, retard adoption of soil-conserving systems of farming. One problem evidently is that insufficient attention has been devoted to determining erosion-control programs for farmers with different amounts of capital, labor and other resources. The purpose of this study is to determine profitable erosion-control systems of farming for operators with different amounts of capital and for two different sizes of farms. Emphasis is on profit maximization for the farm as a whole. Since Ida-Monona soils respond readily to fertilization, the plans considered allow an integration of investment in crops, fertilizer and livestock. Specifically, the study is designed to determine the optimum combination of crop rotations, fertilization levels, erosion-control practices and livestock systems. Conservation systems which primarily control erosion either through land cover or mechanical practices are compared by the linear programming technique

Critical Casimir effect and wetting by helium mixtures

We have measured the contact angle of the interface of phase-separated $^{3}$He-$^{4}$He mixtures against a sapphire window. We have found that this angle is finite and does not tend to zero when the temperature approaches $T_t$, the temperature of the tri-critical point. On the contrary, it increases with temperature. This behavior is a remarkable exception to what is generally observed near critical points, i.e. "critical point wetting''. We propose that it is a consequence of the "critical Casimir effect'' which leads to an effective attraction of the $^{3}$He-$^{4}$He interface by the sapphire near $T_{t}$.Comment: submitted july 13 (2002), published march 20 (2003

Economics of some soil conservation practices

In applying conservation and fertility improvement plans, farmers have a choice between alternative combinations of land use, fertilizer applications and erosion control practices. Within limits, they may choose between different rotations and different fertilizer applications combined with different erosion control practices and still farm the land in accordance with the soil capabilities. While land use in accordance with soil capabilities and appropriate fertilization is basic to soil conservation, these measures need to be supplemented by supporting conservation practices such as contouring, sod waterways, mulching, drainage, flumes, etc., if soil is to be conserved and improved most efficiently. Successful conservation farming (that system which will increase total farm production, build up soil fertility, control erosion and maximize earnings) cannot be tailor-made to fit all farms but involves consideration of each individual\u27s situation. The farmer (and those working with him) must analyze his problem to determine his costs and returns for the farm as a whole under alternative combinations of crops, fertilization and supporting conservation measures to determine which system will best fit his capital position and abilities and still do the conservation job

Taxing the Informal Economy: The Current State of Knowledge and Agendas for Future Research

This paper reviews the literature on taxation of the informal economy, taking stock of key debates and drawing attention to recent innovations. Conventionally, the debate on whether to tax has frequently focused on the limited revenue potential, high cost of collection, and potentially adverse impact on small firms. Recent arguments have increasingly emphasised the more indirect benefits of informal taxation in relation to economic growth, broader tax compliance, and governance. More research is needed, we argue, into the relevant costs and benefits for all, including quasi-voluntary compliance, political and administrative incentives for reform, and citizen-state bargaining over taxation

Price and income policies

Discussion and objective debate is an important and necessary ingredient of social decision-making in a democracy. Only thus can the public, legislators, administrators and special interest groups inventory and understand the complete range of phenomena relevant for public decision. Discussion and analysis is a method of measurement, for a more complete inventory of goals and sub-goals of public policy and for expression of hypotheses and predictions in respect to outcomes of various policy means. Discussion is the most ancient and universal process for reasoned calculation in social policy, whether this be at the program committee of the 4-H Club or in presidential elections.https://lib.dr.iastate.edu/card_reports/1006/thumbnail.jp

On becoming (un)committed: A taxonomy and test of newcomer on-boarding scenarios

How does the bond between the newcomer and the organization develop over time? Process research on temporal patterns of newcomer's early commitment formation has been very scarce because theory and appropriate longitudinal research designs in this area are lacking. From extant research we extract three process-theoretical accounts regarding how the newcomer adjustment process evolves over time: (1) Learning to Love; (2) Honeymoon Hangover; and (3) High Match, Moderate Match, or Low Match. From these scenarios we develop a taxonomy of newcomer adjustment scenarios. Further, we empirically verify these different scenarios by examining naturally occurring "trajectory classes," which are found to display strengthening, weakening, or stabilizing of the employee-organization linkage. For this, we use a sample of 72 Ph. D. graduates whose organizational commitment history was recorded in their first 25 consecutive weeks of new employment. In closing, we discuss the theoretical and practical implications of the scenario-based approach