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As outlined in the previous chapters, optical antennas concentrate incident light within a small spatial volume. As shown throughout this book, these nanostructures may lead to strong local field enhancements depending on their size and shape. Because of that connection, one often encounters figures plotting the near-field as if it were a purely intrinsic property of an optical antenna. However, this viewpoint does not provide a complete description, because the incident radiation must also have an influence. In this chapter, we deal with the question of how one can make use of the degrees of freedom present in the external field in order to manipulate the spatial and temporal properties of the excited near-field. Specifically, we will discuss the usage of shaped femtosecond laser pulses as they contain a broad bandwidth of different frequencies that can be modulated. It will turn out that amplitude, phase and polarization properties are relevant for controlling nano-optical excitations coherently.
It is intuitively clear that the external field must be relevant for the properties of antenna fields. For example, using monochromatic incident light, the local oscillation frequency is the same as that of the external field in the limit of linear response. Upon changing the frequency, however, the amplitude of the local field changes even when the external spectral field amplitude is kept constant, because the field enhancement factor in general varies while moving into or out of material resonances. Furthermore, a phase difference can exist between the external and local field, i.e. their oscillation maxima need not occur at the same time.
Nano-optical devices have a great potential for technological applications [201, 597, 598]. Consequently, the investigation of plasmonic excitations in nanostructures and on surfaces has evolved into a tremendous research field, made possible only by the progress in nanotechnology. Nowadays, nanoantennas with highly complex shapes are fabricated with an extremely high accuracy by standardized procedures . The spectral features and near-field properties of such optical antennas are determined on a length scale that is intrinsically smaller than the diffraction limit of electromagnetic waves. However, experimental access to the spatial properties of these antennas on the nanoscale is essential for an understanding of the underlying mechanisms that lead to strong near-field enhancements, interferences and mode hybridization. Thus, there is a particular need for a real-space microscopy technique that delivers information about near-field distribution within and in the vicinity of nanostructures, with a resolution below the diffraction limit. In addition to pure imaging of static field distributions, knowledge of the dynamical properties of electronic excitations is relevant for encoding and manipulation of information on the nanoscale. The microscopic understanding of the associated dynamics is crucial for many other research fields, such as molecular biology or catalytic chemistry. Considering technological applications, well-tuned spectral properties and high reproducibility of the nanostructures is most important. Smallest differences on the nanoscale of individual structures (e.g. induced by the fabrication process) lead to strong variations of their optical response.
The author describes the history and the premises and characteristics of the action of the ICRC in favour of persons deprived of liberty. He believes that the efficiency of its approach, in particular the visits to detainees, is closely linked to the respect of a constant and rigorous working method including the modalities of the visits and the confidentiality of the interventions to the authorities. Finally, the implication of the ICRC is to be inscribed in a large process and is complementary to the efforts of the authorities, other organizations and mechanisms as well as of the international community at large. Its approach however remains unique in several aspects.
Le projet de diffusion mis en discussion dans cet article a pris naissance fin 1993, lorsque des violences dites interethniques ont éclaté au Burundi, suite à la tentative de putsch d'octobre 1993 et à l'assassinat du président Ndadaye et de plusieurs hautes personnalités de l'Etat. Devant l'ampleur des destructions matérielles et humaines (il est couramment admis qu'il y eut plusieurs dizaines de milliers de morts durant les premieères semaines) et face à la cruauté des actes commis, les délégués du CICR se sont montres d'abord réticents à entreprendre une action spécifique de diffusion.
Borrelia burgdorferi isolates were obtained from Ixodes ricinus from three sites in Switzerland. They were examined by SDS-PAGE and immunoblotting. The phenotypes, in respect of three outer surface proteins (Osp), differed between the sites of collection. In site 1, most isolates had an OspA of 31 kDa and an OspB of 34 kDa: in site 2, isolates presenting an OspA of 33 kDa dominated and in site 3, the isolates with an OspA of 32 kDa and an OspB of 35 kDa were most frequent. This distribution differed significantly. About half of the isolates from sites 1 and 3 reacted with anti-OspA monoclonal antibody H5332 compared to 29% from site 2. Site 1 isolates reacted significantly more frequently (81 %) with another anti-OspA monoclonal antibody LA-31 than isolates from site 3 (P < 0·0001). These findings have implications for the epidemiology of Lyme borreliosis, for the further development of serodiagnostic reagents and for the development of a vaccine.
Spin injection from GaAs(100) to organic semiconductor copper phthalocyanine (CuPc) has been investigated experimentally with spin-resolved two-photon photoemission (SR-2PPE) spectroscopy. With SR-2PPE, the dynamics of both electron and spin relaxation have been studied with femtosecond time resolution. The spin-polarized electrons are originally generated in GaAs through optical pumping and injected into CuPc. We observed an enhancement in spin polarization at the interface after initial CuPc deposition. This demonstrates that interface spin scattering is insignificant, which is similar to our previous result of spin injection at CuPc/Co interface. The spin polarization dropped when the CuPc film became thick, an effect attributed to bulk attenuation in CuPc. The lifetime of the unoccupied orbits in CuPC was also studied with red-blue excitation of photon energy 1.56 eV and 3.12 eV, respectively. There was a strong asymmetry in the time-resolved spectra, and an unexpected long lifetime when the lower unoccupied orbital was excited. A simple explanation of this phenomenon will be discussed.
El proyecto de difusión que se propone para examen en este artículo se inició a finales de 1993, cuando se desencadenaron en Burundi las llamadas violencias interétnicas, tras la tentativa de golpe de Estado de octubre de 1993 y el asesinato del presidente Ndadaye y de varias altas personalidades del país. Ante la gravedad de las destrucciones materiales y humanas (generalmente se reconoce que hubo varias decenas de miles de muertos durante las primeras semanas) y ante la crueldad de los actos perpetrados, los delegados del CICR se mostraron primeramente reticentes a la idea de emprender una acción específica de difusión. Así pues, en un primer momento, se limitaron a una «demostración concreta»del gesto humanitario y a la utilización de mensajes radiodifundidos cuya prioridad era informar para facilitar el trabajo operacional.
The idea of the dissemination project described in the present article first came up at the end of 1993, when what is known as interethnic violence broke out in Burundi following the attempted coup of October 1993 and the assassination of President Ndadaye together with a number of other leading figures. Given the scale of destruction and the heavy loss of life (it is now generally acknowledged that tens of thousands of people were killed during the first few weeks), and in view of the cruelty of the acts committed, ICRC delegates were at first hesitant to embark on any specific operation to promote humanitarian principles. Initially, they confined themselves to a practical demonstration of humanitarian conduct and to the use of radio broadcasts to supply information designed to facilitate operational work.
Among 89 episodes of Staphylococcus aureus bacteremia, factors identified as independent predictors of hospital mortality were Acute Physiology and Chronic Health Evaluation III score >60 (odds ratio [OR], 3.2; 95% confidence inter val [CI95], 1.7 to 5.9) and Lifestyle score >1 (OR, 2.1; CI95, 1.2 to 3.6). Future studies of S aureus bacteremia should take into consideration acute severity of illness (as well as treatment and source of infection) when evaluating outcome.
Species of the genus Sitona Germar (Col., Curculionidae) have been recorded on all continents and all develop at the expense of a number of Leguminosae. In their larval stages, they attack the root system and may be especially injurious to the nodules (Aeschlimann, 1986), whereas the longlived adults consume the stems and foliage of their host plants. The four palaearctic representatives which comprise the S. humeralis group of species all depend upon Medicago spp. as host plants (Aeschlimann, 1984). One of these, S. discoideus Gyllenhal, was accidentally introduced into the southern hemisphere, where it has become a pest of economic importance to both perennial cultivated lucerne and volunteer annual Medicago species used for pasture throughout southeastern Australia and subsequently in the south island of New Zealand.
As a consequence of the importance of S. discoideus, surveys were carried out from 1973 to 1985 over most of the Mediterranean basin (Aeschlimann, 1980) with the aim of identifying efficient natural enemies of the various stages of S. discoideus that would be suitable for deliberate introduction into Australia. These investigations demonstrated that the parasitoid Microctonus aethiopoides Loan (Hym., Euphorinae) was the most promising biological control agent for use against adult Sitona weevils. Based on these findings, several biotypes of this natural enemy were imported between 1975 and 1979 from various parts of the western Mediterranean region to Australia for mass-rearing in quarantine and subsequent field release against S. discoideus (Aeschlimann, 1983a). Initial establishment followed by spreading was recorded in Australia 2 years after the start of the release programme (Aeschlimann, 1983a).
The optically induced spin polarization P of the photoelectrons emitted from tin and germanium during ps and ns laser pulses is measured as a function of the pulse energy. P is defined by the lattice symmetry of the sample. It vanishes for amorphous or molten surfaces. The melting of the metal and the semiconductor is found to occur on a time scale which is short compared to the duration of a 70 ps laser pulse. The emission of positive ions starts at the laser intensity for which the drop of the polarization is observed. If Ge is heated with ns laser pulses a temperature dependent shift of the work function causes a decrease of the spin polarization for laser energies far below the energy necessary for melting. With ps laser pulses the polarization only vanishes for pulse energies exceeding Eion- The difference between the ps and ns measurements on Ge points to an unexpected dynamical behavior of the work function shift in semiconductors.
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