Allgemeine Methoden

Ohne Zusammenfassung     

Magnetoelastic effects in terbium

The variation of the elastic modulus C₃₃ of terbium has been investigated as a function of temperature in the range 200–230 K, which includes the whole of the antiferromagnetic phase, and as a function of magnetic field applied along the easy magnetic direction, the b axis. Hysteresis in C₃₃ in the antiferromagnetic phase is interpreted in terms of spiral spin domains. The magnetic phase changes are reflected in anomalies in the elastic constant and these are used to produce a magnetic phase diagram of terbium. The final phase diagram has been compared with earlier measurements of magnetisation and magnetostriction.     

A Planning and control system for the small firm: A development of operations research application in agriculture

Summary This article reviews the use of operations research techniques in agriculture and suggests the methods available have not been fully exploited due to both the strong influences of biological factors on the farm business and the variety of tasks that the manager has to perform. There would appear to be a requirement for a simple system of business control which provides a rapid analysis of farm data without involving the manager in excessive time-consuming recording. A pig enterprise simulation model has been developed which can be combined with data from pig herds to provide a forecast of individual herd performance. This model could be used as the basis of a national or regional budgetary control scheme to provide farm managers with regular and current budgetary control information at relatively low cost.

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Zusammenfassung Der Artikel gibt einen Überblick über OR-Techniken in der Landwirtschaft. Es wird angedeutet, daß die vorhandenen Methoden nicht voll genutzt werden, wegen des großen Einflusses biologischer Faktoren und der Aufgabenvielfalt, die der anwendende Landwirt zu erfüllen hat. Nützlich wäre ein einfaches System der Geschäftsführung, das eine schnelle Analyse landwirtschaftlicher Daten erlaubt, ohne den Manager durch aufwendige Aufzeichnungen zu beanspruchen. Es ist das Simulationsmodell eines Schweinezuchtbetriebes entwickelt worden, das in Verbindung mit den Zuchtdaten benutzt werden kann, um individuelle Vorhersagen zu liefern. Das Modell könnte als Basis einer nationalen oder regionalen Bestandssteuerung eingesetzt werden, um den Farmer bei relativ geringen Kosten mit regelmäßigen und zeitnahen Steuerungsinformationen zu versorgen.

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The Authors are indebted toFrank M. Anderson for critical comments on an earlier draft of this paper.     

Advanced aspects of electromagnetic SERS enhancement factors at a hot spot

In this paper, we discuss some advanced theoretical aspects of electromagnetic enhancement factors (EFs) in surface‐enhanced Raman scattering (SERS). We focus in particular on the influence of surface selection rules (SSRs) on SERS EFs at hot spots, and the determination of SERS depolarization ratios. Both aspects could be viewed as secondary (compared to the overall magnitude of the SERS EF), but are nevertheless observable experimentally and crucial for a fundamental understanding of SERS. They also share the property that they cannot be studied within the commonly used |E | ⁴ approximation to the SERS EFs, and appropriate tools are developed here to make predictions beyond this approximation in the case of a SERS hot spot. In addition, theoretical estimates of different types of (previously defined) EFs are provided, and their origins discussed for the typical example of a SERS substrate dominated by SERS hot spots. Finally, experimental measurements of SERS depolarization ratios are presented to support the theoretical predictions. Copyright © 2008 John Wiley & Sons, Ltd.     

Bi-analyte SERS with isotopically edited dyes

Isotopically substituted rhodamine dyes provide ideal probes for the study of single-molecule surface enhanced Raman scattering (SM-SERS) events through multiple-analyte techniques. Isotopic editing should, in principle, provide probes that have identical chemical properties (and surface chemistries); while exhibiting at the same time distinct Raman features which enable us to identify single-molecule SERS events. We present here a specific example of two-analyte SM-SERS based on the isotopic substitution of a methyl ester rhodamine dye. The dyes are carefully characterized (in both standard and SERS conditions) to confirm experimentally their similar chemical properties. We then demonstrate their utility for bi-analyte SERS (BiASERS) experiments and, as an example, highlight the transition from a single, to a few, to many molecules in the statistics of SM-SERS signals.