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11:37 IWF (Göttingen) English 1987

Amorphous Metals - Preparation by a Melt-Spinning Method

The structure of amorphic metals is explained using models. The melt-spinning method for making flash-cooled metallic glass is shown. Time-distorted sequences clarify the melt-spinning method, especially the fusion of several melt-jets.
  • Published: 1987
  • Publisher: IWF (Göttingen)
  • Language: English
2:36:48, Foundation for Fundamental Research on Matter (FOM) English 2012

Master class with John Turner

This lecture will introduce the components of photoelectrochemical hydrogen production devices as well as a discussion of the economics of hydrogen production and how that determines the necessary fundamental material properties of the semiconductor in addition to the other components of the system.
  • Published: 2012
  • Publisher:, Foundation for Fundamental Research on Matter (FOM)
  • Language: English
02:52 IWF (Göttingen) German 2004

Bestimmung von Cp/Cv nach Rüchardt

The ratio cp/cv is determined by means of a small object swinging on a gas column. After introducing the experimental setup air and argon are measured three times each. There is no interpretation but all relevant data are given in order to calculate the adiabatic index of both gases.
  • Published: 2004
  • Publisher: IWF (Göttingen)
  • Language: German
04:56 Copernicus Publications English 2017

System for δ13C-CO2 and xCO2 analysis of discrete gas samples by cavity ring-down spectroscopy

A method was devised for analysing small discrete gas samples (50 ml syringe) by cavity ring-down spectroscopy (CRDS). Measurements were accomplished by inletting 50 ml syringed samples into an isotopic-CO2 CRDS analyser (Picarro G2131-i) between baseline readings of a standard reference air, which produced sharp peaks in the CRDS data feed. A custom software script was developed to manage the measurement process and aggregate sample data in real-time. The method was successfully tested with CO2 mole fractions (xCO2) ranging from <0.1 to >20000 ppm and δ13C-CO2 values from -100 up to +30000 ‰ vs VPDB. Throughput was typically 10 samples h-1, with 13 h-1 possible under ideal conditions. The measurement failure rate in routine use was ca. 1 %. Calibration to correct for memory effects was performed with gravimetric gas standards ranging from 0.05 to 2109 ppm xCO2 and δ13C-CO2 levels varying from -27.3 to +21740 ‰. Repeatability tests demonstrated that method precision for 50 ml samples was ca. 0.05 % in xCO2 and 0.15 ‰ in δ13C-CO2 for CO2 compositions from 300 to 2000 ppm with natural abundance 13C. Long-term method consistency was tested over a 9-month period, with results showing no systematic measurement drift over time. Standardised analysis of discrete gas samples expands the scope of applications for isotopic-CO2 CRDS and enhances its potential for replacing conventional isotope ratio measurement techniques. Our method involves minimal set-up costs and can be readily implemented in Picarro G2131-i and G2201-i analysers or tailored for use with other CRDS instruments and trace gases.
  • Published: 2017
  • Publisher: Copernicus Publications
  • Language: English
03:27 Institute of Physics (IOP) English 2012

Transformational capacity and the influence of place and identity

Climate change is altering the productivity of natural resources with far-reaching implications for those who depend on them. Resource-dependent industries and communities need the capacity to adapt to a range of climate risks if they are to remain viable. In some instances, the scale and nature of the likely impacts means that transformations of function or structure will be required. Transformations represent a switch to a distinct new system where a different suite of factors become important in the design and implementation of response strategies. There is a critical gap in knowledge on understanding transformational capacity and its influences. On the basis of current knowledge on adaptive capacity we propose four foundations for measuring transformational capacity: (1) how risks and uncertainty are managed, (2) the extent of skills in planning, learning and reorganizing, (3) the level of financial and psychological flexibility to undertake change and (4) the willingness to undertake change. We test the influence of place attachment and occupational identity on transformational capacity using the Australian peanut industry, which is presently assessing significant structural change in response to predicted climatic changes. Survey data from 88% of peanut farmers in Queensland show a strong negative correlation between transformational capacity and both place attachment and occupational attachment, suggesting that whilst these factors may be important positive influences on the capacity to adapt to incremental change, they act as barriers to transformational change.
  • Published: 2012
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:33 Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG) English 2013

Mapping gigahertz vibrations in a plasmonic–phononic crystal

We image the gigahertz vibrational modes of a plasmonic–phononic crystal at sub-micron resolution by means of an ultrafast optical technique, using a triangular array of spherical gold nanovoids as a sample. Light is strongly coupled to the plasmonic modes, which interact with the gigahertz phonons by a process akin to surface-enhanced stimulated Brillouin scattering. A marked enhancement in the observed optical reflectivity change at the centre of a void on phononic resonance is likely to be caused by this mechanism. By comparison with numerical simulations of the vibrational field, we identify resonant breathing deformations of the voids and elucidate the corresponding mode shapes. We thus establish scanned optomechanical probing of periodic plasmonic–phononic structures as a new means of investigating their coupled excitations on the nanoscale.
  • Published: 2013
  • Publisher: Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG)
  • Language: English
04:03 Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG) English 2017

Cooperative Lamb shift and superradiance in an optoelectronic device

When a single excitation is shared between a large number of two-level systems, a strong enhancement of the spontaneous emission appears. This phenomenon is known as superradiance. This enhanced rate can be accompanied by a shift of the emission frequency, the cooperative Lamb shift, issued from the exchange of virtual photons between the emitters. In this work we present a semiconductor optoelectronic device allowing the observation of these two phenomena at room temperature. We demonstrate experimentally and theoretically that plasma oscillations in spatially separated quantum wells interact through real and virtual photon exchange. This gives rise to a superradiant mode displaying a large cooperative Lamb shift.
  • Published: 2017
  • Publisher: Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG)
  • Language: English
03:53 Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG) English 2013

Collective cell streams in epithelial monolayers depend on cell adhesion

We report spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell–cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns.
  • Published: 2013
  • Publisher: Institute of Physics (IOP), Deutsche Physikalische Gesellschaft (DPG)
  • Language: English
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