<Emphasis Type="BoldItalic">In Situ</Emphasis> Experiments with X ray Tomography: an Attractive Tool for Experimental Mechanics

This paper aims at illustrating the potential of X-ray tomography for studying the mechanical behaviour of materials through in situ experiments. Typical experimental tomography set ups which use laboratory and synchrotron X ray sources are described; advantages and limitations of both types of sources are presented. Dedicated experimental devices which allow deformation and/or temperature changes to be applied to various types of materials are described. Examples of results of in situ mechanical experiments are presented and discussed; they include monotonic tensile testing of steel fiber entanglements, high temperature compression and room temperature fatigue of Al alloys. Examples of quantitative assessment of localisation of deformation in the interior of optically opaque samples under mechanical loading are also described.     

Die Kristallstruktur von Bi2O2Se

Bi₂O₂Se crystallizes in the (Na_0.25Bi_0.75)₂O₂Cl type structure (space group I4mmm–D _4h ¹⁷ ;a=3.891 Å,c=12.21₃ Å). The crystal chemical properties of the bismuth oxiselenide are discussed in connection with the other compounds having this structure type.

---

---

Herrn Prof. Dr.F. Hecht zum 70. Geburtstag gewidmet.     

Einige Komplexcarbide und-nitride in den Systemen Ti-{Zn,Cd, Hg}-{C,N} und Cr-Ga-N

Zusammenfassung Die Phasen Ti₃(Ti, Zn)C, Ti₃(Ti, Zn)N, Ti₃(Ti, Cd)C, Ti₃(Ti, Cd)N, Ti₃(Ti, Hg)C, Ti₃(Ti, Hg)N besitzen Perowskitstruktur. Cr₂GaN ist eine H-Phase (Ti₂SC-Typ).

---

Some complex carbides and nitrides in the systems Ti-{Zn, Cd, Hg}-{C, N} and Cr-Ga-N

The phases Ti₃(Ti, Zn)C, Ti₃(Ti, Zn)N, Ti₃(Ti, Cd)C, Ti₃(Ti, Cd)N, Ti₃(Ti, Hg)C, Ti₃(Ti, Hg)N have the perowskite structure. Cr₂GaN is a H-phase (Ti₂SC-type).

---

---

Mit 1 Abbildung     

2.5-GHz repetition-rate singly resonant optical parametric oscillator synchronously pumped by a mode-locked diode oscillator amplifier system

We report on an optical parametric oscillator (OPO) that is synchronously pumped directly by a diode laser. This laser is an actively mode-locked master-oscillator power-amplifier system that produces 20-ps pulses at 927 nm with a repetition rate of 2.5 GHz and an average power of 0.9 W. The OPO, which is a singly resonant device based on periodically poled lithium niobate, generates 7.8-ps pulses. The OPO threshold is 300 mW of average pump power, and the maximum average idler output power is 78 mW at a wavelength of 2100 nm. By changing the crystal temperature we can wavelength tune the output in the ranges 1530-1737 nm (signal) and 1986-2348 nm (idler). Rapid wavelength tuning of the OPO over 46 nm (signal) and 74 nm (idler) is achieved through tuning the cavity length over 28 microm by use of a piezoelectric transducer.