Knicken von schlanken Pfählen in weichen Böden

Buckling of slender piles in soft soils. Buckling of piles is resisted by the surrounding soil. Therefore, in sufficiently stiff soils there is no risk of buckling of piles with conventional geometry (L/D ratio). National and international design codes require checks of the safety against buckling for slender piles in soils with an undrained shear strength of c_u < 15 kPa or c_u < 10 kPa, respectively. In practice, the codes are taken to imply that buckling failure does not occur at higher undrained shear strengths. However, using simple calculations this assumption has been proven to be invalid for slender piles in very soft soils. Therefore, buckling tests on piles up to 4 m long were carried out at the Zentrum Geotechnik of the Technical University of Munich. Based on these results a concept for calculating buckling loads was derived, which covers all essential aspects observed in the tests. The proposed model accounts for material non‐linearity as well as second order effects.     

Externally modulated mode-locked laser diodes for microwave transmission links

An externally modulated mode-locked laser diode is proposed to transmit high centre frequency, fractional bandwidth microwave signals over optical fibres. The authors demonstrate the feasibility of this scheme using an external Bragg cell to modulate (at 68.7 MHz) an actively mode-locked laser diode (mode-locked at 2.05 GHz).<>     

Electroconvulsive therapy for treatment of intractable seizures. Initial findings in two children

We treated two children with intractable epilepsy with electroconvulsive therapy (ECT) for seizure control. One child showed a change in seizure pattern with treatment, which at greater intensity was also effective in stopping nonconvulsive status epilepticus. The other child showed a decrease in spontaneous seizure frequency during short-term treatment. These findings suggest a possible role for ECT in the management of intractable epilepsy in children who are not candidates for epileptic surgery.     

Process Modelling and Empirical Studies of Software Evolution (PMESSE'97) Workshop Report

Much progress is being made in both the areas of process modelling and software metrics. However, neither of these concepts is complete without the other: processes cannot be improved if no assessment of quality is available, and metrics are useless if they cannot be applied in order to assess the evolution of systems. The PMESSE (Process Modelling and Empirical Studies of Software Evolution) Workshop, held in Boston MA, on May 18, 1997, brought together researchers and practitioners from both of these fields, and stimulated some very lively debate on these issues. This collection of reports reflects the work done by the Workshops five Working Groups.Dialogue between the software metrics and process modelling communities is essential. This workshop succeeded in bringing together researchers with a wide range of research interests, and the resulting discussions were very animated. Perhaps the most contentious point of discussion lay in the 'level of granularity' question; some suggested that only high-level measurements were sensible, whereas others preferred to 'divide and conquer' the system, providing detailed process measurement schemas. No doubt this debate will continue.     

Heat-transfer coefficients within the cavity formed by the tip of cryosurgical probes

The heat-transfer coefficients between a jet of liquid nitrogen and the inside surface of the tip of three different cryoprobes were measured by a transient method. Forced-convection nucleate boiling and unstable film boiling of liquid nitrogen in the cavity of the tip were investigated. The heat-transfer data was correlated in terms of dimensionless groups: Nusselt, Prandtl and Reynolds numbers, temperature difference and geometrical parameters.