Scattering Amplitudes and the CPT theorem in String Theory

We discuss the role of the CPT transformation in first quantized string theories, both on the world-sheet and in the space-time. We explicitly show that the space-time CPT theorem holds for all first-quantized (perturbative) string theories in a Minkowski background of even dimension $D>2$.Comment: LaTeX2e, 8 pages, talk given at the Conference "Gauge Theories, Applied Supersymmetry and Quantum Gravity", London, July 199

Compact hyperbolic tetrahedra with non-obtuse dihedral angles

Given a combinatorial description $C$ of a polyhedron having $E$ edges, the space of dihedral angles of all compact hyperbolic polyhedra that realize $C$ is generally not a convex subset of $\mathbb{R}^E$ \cite{DIAZ}. If $C$ has five or more faces, Andreev's Theorem states that the corresponding space of dihedral angles $A_C$ obtained by restricting to {\em non-obtuse} angles is a convex polytope. In this paper we explain why Andreev did not consider tetrahedra, the only polyhedra having fewer than five faces, by demonstrating that the space of dihedral angles of compact hyperbolic tetrahedra, after restricting to non-obtuse angles, is non-convex. Our proof provides a simple example of the ``method of continuity'', the technique used in classification theorems on polyhedra by Alexandrow \cite{ALEX}, Andreev \cite{AND}, and Rivin-Hodgson \cite{RH}.Comment: 19 page

TRANSPORTATION COSTS IN ECONOMETRIC MODELS OF STATE AGRICULTURAL SECTORS: THE CASE OF BEEF IN HAWAII

Econometric models designed to show how national policies affect state agricultural sectors often use national prices as proxies for state prices. Consequently, they ignore the influence of freight rates on state production. An application to the Hawaii beef industry demonstrates that both freight rates and national beef prices have important impacts on Hawaii beef prices and production. By using state prices rather than national prices, error from changes in freight rates might be reduced, and the model's capacity for policy analysis might be broadened.Livestock Production/Industries,

The ER-2 meteorological measurement system

The objectives of ER-2 Meteorological Measurement System (MMS) are: (1) to measure the meteorological parameters (pressure, temperature, and the three dimensional wind vector) accurately; (2) to provide high resolution data on atmospheric state variables and aircraft flight track to ER-2 investigators on a timely basis; and (3) to conduct collaborative research in atmospheric dynamics and chemistry. A summary of progress and results are presented

PLANT NUTRIENT DEMAND FUNCTIONS FOR TENNESSEE WITH PRICES OF JOINTLY APPLIED NUTRIENTS

Several studies have estimated plant nutrient demand functions for nitrogen, phosphate, and potash. All included own-price effects but excluded prices of jointly applied nutrients. In this study, nutrient demand functions, which include prices of all three nutrients, are estimated for Tennessee by seemingly unrelated regression. Results suggest that cross-price effects are important in determining plant nutrient demand, at least in the case of Tennessee, and that multicollinearity need not be a hindrance in all cases to including cross-price effects in plant nutrient demand models.Crop Production/Industries,

Problem-based leadership: nurturing managers during turbulent times

Purpose – The paper explores problem-based learning (PBL) as a useful methodology in leadership development during turbulent times. It identifies several pertinent action points for managers to lead through problems while understanding their capacity to empower themselves and others to face challenges at work. Design/methodology/approach – Broad concepts of PBL are used to distil the characteristics of this methodology and how they might be applicable to leadership development. An actual case of PBL in leadership education and training is employed to illustrate the processes of problem solving and reflective action-taking. Findings – When confronted by problems, managers should adopt a learning-oriented mindset and draw on the strengths of others to generate immediate solutions for experimentation. In doing so, they need to accept failure as a prerequisite for creative tensions to be generated and applied in messy circumstances. Until they think out of the box, they will continue to solve problems in tried-and-tested ways obstructing the emergence of revolutionary solutions. Practical implications – In order for managers to make an impact on organizational process and improvement, they need to focus on the action and learn components of PBL. They should be given the space to listen to their own “voice” and internalize the “voice” of others through reflection and dialogue. They should also be recognized for their courage and boldness in confronting problems even if more problems are generated in the process. It is facing the goliath that managers truly grow to become real leaders. Originality/value – Although the concept of PBL has been around for a long while, its applicability to leadership development has not been sufficiently explored in both theory and practice. This paper brings another dimension to the common idea of problem solving where solution seeking is not an end it itself. At best, it is a means to discovering the potential of true leadership in those whose mindset is focused on learning and reflective decision-making