Do higher standards of detention promote well-being?

Sweden is generally considered to have high standards of immigrant detention. However, a recent study conducted in Swedish detention centres suggests that irrespective of the high standards life in detention still poses a huge threat to the health and wellbeing of detained irregular migrants

Slow fluctuations in enhanced Raman scattering and surface roughness relaxation

We propose an explanation for the recently measured slow fluctuations and ``blinking'' in the surface enhanced Raman scattering (SERS) spectrum of single molecules adsorbed on a silver colloidal particle. We suggest that these fluctuations may be related to the dynamic relaxation of the surface roughness on the nanometer scale and show that there are two classes of roughness with qualitatively different dynamics. The predictions agree with measurements of surface roughness relaxation. Using a theoretical model for the kinetics of surface roughness relaxation in the presence of charges and optical electrical fields, we predict that the high-frequency electromagnetic field increases both the effective surface tension and the surface diffusion constant and thus accelerates the surface smoothing kinetics and time scale of the Raman fluctuations in manner that is linear with the laser power intensity, while the addition of salt retards the surface relaxation kinetics and increases the time scale of the fluctuations. These predictions are in qualitative agreement with the Raman experiments

Plasmonic band gap structures for surface-enhanced Raman scattering

Cataloged from PDF version of article.Surface-enhanced Raman Scattering (SERS) of rhodamine 6G (R6G) adsorbed on biharmonic metallic grating structures was studied. Biharmonic metallic gratings include two different grating components, one acting as a coupler to excite surface plasmon polaritons (SPP), and the other forming a plasmonic band gap for the propagating SPPs. In the vicinity of the band edges, localized surface plasmons are formed. These localized plasmons strongly enhance the scattering efficiency of the Raman signal emitted on the metallic grating surfaces. It was shown that reproducible Raman scattering enhancement factors of over 105 can be achieved by fabricating biharmonic SERS templates using soft nano-imprint technique. We have shown that the SERS activities from these templates are tunable as a function of plasmonic resonance conditions. Similar enhancement factors were also measured for directional emission of photoluminescence. At the wavelengths of the plasmonic absorption peak, directional enhancement by a factor of 30 was deduced for photoluminescence measurements. (c) 2008 Optical Society of America

The past and future of enzyme measurements using surface enhanced Raman spectroscopy

The ability to accurately and sensitively measure the activity of specific enzymes is central to many aspects of modern chemistry and when combined with new nanoscience based approaches, offers significant opportunities for advancing other scientific disciplines. We review the development of surface enhanced resonance Raman scattering (SERRS) for the detection of enzymes, from the initial direct spectroscopy of enzymes, substrate/product and inhibitors adsorbed onto metallic colloids, to the current approach of measuring enzymatic activity by recording the SERRS spectra of a product which is only 'switched on' after enzyme activity. Developments focussed on improvements to modular masked SERRS substrates, which are unmasked by specific enzymes, are also reviewed. Finally, we set out the remaining grand challenges within the area of enzymatic analysis by SERRS which include single molecule detection, in vivo studies and increased multiplexing for screening of evolved enzyme libraries

Raman and Fluorescence Spectroscopy of Single Molecules and Metal Particles

Technological and conceptual advances have led to the realization of single-molecule spectroscopy. This permit detailed investigations of heterogeneous systems in fields ranging from condensed matter physics to biochemistry. It was recently discovered that surface-enhanced Raman scattering (SERS) can be used to study single molecules. A part of this thesis deals with single-molecule SERS measurements of heme-proteins adsorbed on small Ag-particle aggregates. The SERS signal exhibits temporal and spectral fluctuations, a phenomenon that appears to be characteristic of single-molecule optical spectroscopy at room temperature. The enormous SERS sensitivity can be understood in the framework of electromagnetic interparticle coupling. Various metal particles were explored as SERS substrates. Electron beam lithography was used to make substrates consisting of particles with different shapes, sizes, and inter-particle distances. Given the precise control of fabrication, these substrates are suitable for quantitative analysis. For many sensor applications, however, cheap and fast metal deposition in an aqueous environment is desirable. A simple and robust synthesis route of noble metal nanoparticles for optical sensing based on laser-controlled growth and deposition is demonstrated. We further examined the irreversible and highly heterogeneous photochemical transformation of aromatic precursors to amorphous carbon that occurs on aggregated and immobilized Ag nanocrystals, using SERS. The results highlight the importance of surface-enhanced photochemistry in experiments which rely on high electromagnetic fields near metal nanoparticles. We also observed photo-induced effects on hemoglobin in red blood cells. The implementation of a through-the-objective total internal reflection (TIR) microscope is described. This type of microscopy permits single-molecule fluorescence imaging because of the low fluorescence background and the high detection efficiency inherent to the technique. The fluorescence emission from single dye-molecules, immobilized in polymer films, was measured and the sensitivity of the TIR set-up was compared to the epi-illumination geometry

Raman and Fluorescence Spectroscopy of Single Molecules and Metal Particles

Technological and conceptual advances have led to the realization of single-molecule spectroscopy. This permit detailed investigations of heterogeneous systems in fields ranging from condensed matter physics to biochemistry. It was recently discovered that surface-enhanced Raman scattering (SERS) can be used to study single molecules. A part of this thesis deals with single-molecule SERS measurements of heme-proteins adsorbed on small Ag-particle aggregates. The SERS signal exhibits temporal and spectral fluctuations, a phenomenon that appears to be characteristic of single-molecule optical spectroscopy at room temperature. The enormous SERS sensitivity can be understood in the framework of electromagnetic interparticle coupling. Various metal particles were explored as SERS substrates. Electron beam lithography was used to make substrates consisting of particles with different shapes, sizes, and inter-particle distances. Given the precise control of fabrication, these substrates are suitable for quantitative analysis. For many sensor applications, however, cheap and fast metal deposition in an aqueous environment is desirable. A simple and robust synthesis route of noble metal nanoparticles for optical sensing based on laser-controlled growth and deposition is demonstrated. We further examined the irreversible and highly heterogeneous photochemical transformation of aromatic precursors to amorphous carbon that occurs on aggregated and immobilized Ag nanocrystals, using SERS. The results highlight the importance of surface-enhanced photochemistry in experiments which rely on high electromagnetic fields near metal nanoparticles. We also observed photo-induced effects on hemoglobin in red blood cells. The implementation of a through-the-objective total internal reflection (TIR) microscope is described. This type of microscopy permits single-molecule fluorescence imaging because of the low fluorescence background and the high detection efficiency inherent to the technique. The fluorescence emission from single dye-molecules, immobilized in polymer films, was measured and the sensitivity of the TIR set-up was compared to the epi-illumination geometry

Images, Motives, and Challenges for Western Health Workers in Humanitarian Aid

This thesis presents how humanitarian aid workers were attracted, motivated, recruited, and prepared for fieldwork, and how they reported their work experience directly from the field and when they returned home. Data were derived from interviews with experienced aid workers, focus group discussions with presumptive aid workers, analysis of letters from aid workers in the field on MSFs homepages in Europe, and from interviews with recruitment officers at some of the main humanitarian organisations. Health professionals were attracted by the positive images of humanitarian action. They wished to work in teams with like-minded people, and to make a difference in the world. However, this image was not supported by the recruitment officers, or experienced aid workers, who described a complex reality in humanitarian action. The experienced aid workers instead had realised they learned more than they contributed. The recruitment system for relief workers would benefit from a more holistic approach, where personalities of the aid workers are more in focus. More time must be spent with the applicants, both recruited and returning aid workers, in order to improve the system. A socialisation approach could help identify the right personnel and to motivate current personnel to continue