Using Wave-Packet Interferometry to Monitor the External Vibrational Control of Electronic Excitation Transfer

We investigate the control of electronic energy transfer in molecular dimers through the preparation of specific vibrational coherences prior to electronic excitation, and its observation by nonlinear wave-packet interferometry. Laser-driven coherent nuclear motion can affect the instantaneous resonance between site-excited electronic states and thereby influence short-time electronic excitation transfer (EET). We first illustrate this control mechanism with calculations on a dimer whose constituent monomers undergo harmonic vibrations. We then consider the use of nonlinear wave-packet interferometry (nl-WPI) experiments to monitor the nuclear dynamics accompanying EET in general dimer complexes following impulsive vibrational excitation by a sub-resonant control pulse (or control pulse sequence). In measurements of this kind, two pairs of polarized phase-related femtosecond pulses following the control pulse generate superpositions of coherent nuclear wave packets in optically accessible electronic states. Interference contributions to the time- and frequency-integrated fluorescence signal due to overlaps among the superposed wave packets provide amplitude-level information on the nuclear and electronic dynamics. We derive the basic expression for a control-pulse-dependent nl-WPI signal. The electronic transition moments of the constituent monomers are assumed to have a fixed relative orientation, while the overall orientation of the complex is distributed isotropically. We include the limiting case of coincident arrival by pulses within each phase-related pair in which control-influenced nl-WPI reduces to a fluorescence-detected pump-probe difference experiment. Numerical calculations of pump-probe signals based on these theoretical expressions are presented in the following paper

The role of the Fulbe in the urban life and economy of Lunsar, Sierra Leone: being a study of the adaptation of an immigrant group

In 1954 Dr. J. Littlejohn conducted a pilot survey of the town of Lunsar in Sierra Leone on behalf of the Department of Social Anthropology in the University of Edinburgh. Five years later, in May 1959 under the direction of Dr. K. L. Little, Dr. Littlejohn returned to Sierra Leone as leader of the University of Edinburgh, Lunsar Research Team. The other two team members at that time were Dr. D. Gamble (anthropologist) and Dr. R. Mills (physician). This team, generous- ly financed by the Nuffield Foundation, had the aim of studying the process of urbanisation in a town which had grown solely as a result of open cast iron mining activities taking place less than a mile away. During the course of his investi- gations Dr. Littlejohn reported that one tribal group, the Fula or Fulbe, were different from the other immigrants in that they kept separate from the other tribes, appeared to be strongly Muslim, and had defeated the Temne on a number of occasions in Historical times. It was recommended that I go to Lunsar and study the Fulbe to find out how they adapted themselves to living in Lunsar so that the Fulbe might be compared with the other tribal groups. An outline of techniques used in the study of the Fulbe is given below. Participant observation. This in itself is more of a way of life than a special technique, a kind of omnidirectional departure point from which the field worker gathers information by a number of means, viz: - a. observation and noting of the physical distribution and movement of the subjects of study. b. the interception by ear and eye of distribution and content of communications between subjects. c. the asking of direct and indirect questions to elucidate what has been seen or heard, or read as being the behaviour of the subjects. The taking up of a special identity, the effort of learning the language, the assumption of a local name, the sharing of food when offered and the other deli- berate acts of behaviour already mentioned are in fact 'participant observations' which are unstructured and can themselves only lead to impressions based on chance contacts. The study period in Lunsar was originally to be six months, although this was later extended to ten months. Clearly, to collect enough data within this time a very intensive study had to be conducted. Selection of informants. Since there were so few Fulbe in Lunsar it was important to obtain certain basic data on all the residents and as many Fulbe passing through Lunsar as possible. To assist in this an interview guide was drawn up which appears as an Appendix. From information gained in this way the demography and statistical structure of Lunsar and itinerant Fulbe was calculated. In analysis, all Fulbe who had stayed in Lunsar longer than nine months were treated as residents, and those staying for a shorter period were regarded as itinerants. This is a purely arbitrary division but no other could be adopted because of the unpredictability and high mobility of the Fulbe. Additional specialist information, for example on occupations, ritual and vi. family was obtained directly from the persons best able to provide the informa- tion. An attempt was made to avoid using one informant more than others. Pachometric Tests. The psychometric tests used were not intended to be anything more than a more exact way of verifying or refuting hypothesesmade on the basis of data obtained by observation and interview. Where the data from such tests appears in the text only a minimum of arithmetic appears, and the main calcula- tions appear separately in an appendix. Samples. The informants subjected to tests of one kind or another were not all selected at random. Although random samples may be ideal, especially when the distribution of variations in the population is known, they were found to be un- satisfactory because of the informant's' continuous coming and going as they went about their business, trailing, etc. Also, even if the population in Lunsar had been correctly represented, the total statistical universe of Fulbe all over Africa could not be. To get round this difficulty large samples were used (3 plus) stratified by age and occupation in as similar manner as possible as the total Lunsar Fulbe population. Also appearing as an appendix is a list of Fulbe informants in Lunsar and the tests set them. It will be noted that few women have been used in these special studies. This is because the Fulbe women although very independent are not considered by their menfolk as repositories of knowledge and wisdom. The women themselves act according to their society's expectations of them and consider intensive question- ing on topics other than domestic issues embarrassing and answer such questions by "mi anda" - I do not know. Documentary material. Although there is an enormous literature on the Fulbe, most of it takes its subject matter from areas dominated by Fulbe. Little has been written about the behaviour of Fulbe on the peripheries of these concentra- reemburs oÇ tions, where they are faced with the problem of interacting with ,(other cultures ulture, while maintaining their own c vii. A few articles on Fulbe in Sierra Leone have been written and where possible the relevant material has been incorporated in this study. Native Authority court records were consulted, although they reported few cases involving Fulbe. A far richer source of information way, the District Commissioner's files at Port Lokko, from which the history of political conflict since the war between Fulbe and the Temnes and Lokkos was in part obtained. Mechanical E uioment, a. A camera was used to obtain pictorial illustrations, some it of which appear in the text. However, it was found that /was very difficult to com- bine note taking and picture taking, so most photographs were taken on outings specifically assigned for this purpose. It was found that the best technique was to write down a list of the photographs required and systematically tick off each subject as it was photographed. when the social situation to be studied is out- side the control of the field worker, e.g. rituals, a decision has to be made at the time on whether notes or photographs will be of most use. When long sequen- ces of photographs can be taken and the films processed locally it is fairly easy to ask informants to explain them afterwards. b. A tape recorder was used to collect material at cere- monies, although for various reasons it did not work on some important occasions. The tape recorder was sometimes used during interviews when more than one informant was being used. This enabled me to find out afterwards what was discussed by people not actually talking to me at the time. c. General information on each informant was transferred on to 'Cope. Chat Paramount Punch Cards' to assist in the processing of statistical data. Each informant was given a code number on being first interviewed. This helped me to differentiate between a number of people with the same names. Each individuals card could also be sorted out by the code number. A complete descrip- tion of the card system and codes appearsin appendix D. This was written in the field so that in the event of an accident to myself, the material would be understandable to anyone else

Behaviour of Bridge Abutment on Fractured Chalk

Loading tests on 865 mm diameter plates showed that the fractured chalk was much more compressible than at other sites on the same deposit but it was still considered that slab foundations would be adequate for the bridges at most locations. Detailed measurements have been made on one of the bridge abutment foundations both during and following construction. Measurements were made of vertical pressures applied to the ground, lateral earth pressures acting on the abutment wall, settlements of the foundation slab, tilt of the wall, and vertical displacements in the ground below the foundations. These observations confirmed the adequacy of slab type foundations for simple single span highway bridges founded on highly fractured chalk. Values of deformation moduli back analysed from the measurements on the bridge foundation were in reasonable agreement with the values obtained from loading tests on 865 mm diameter plates at the bridge site and the low values obtained at another local site. The values back analysed from the bridge measurements were however much lower than those determined from a large tank loading test and 865 mm diameter plate tests on the same grade of chalk in another part of the deposit

Hierarchy of integrable Hamiltonians describing of nonlinear n-wave interaction

In the paper we construct an hierarchy of integrable Hamiltonian systems which describe the variation of n-wave envelopes in nonlinear dielectric medium. The exact solutions for some special Hamiltonians are given in terms of elliptic functions of the first kind.Comment: 17 page

Highly erosive glaciers on Mars - the role of water

International audiencePolewards of 30 • in each hemisphere, the surface of Mars hosts a suite of landforms reminiscent of glacial landscapes on Earth. Amongst these landforms are: 1) Viscous Flow Features (VFF), which resemble glaciers on Earth and are thought to contain large volumes of water ice, 2) martian gullies which are km-scale features resembling water-eroded gullies on Earth and 3) arcuate ridges thought to be moraines from previous glaciations. Gullies have been long-associated with a surface unit originally called "pasted-on terrain" and now often called the "latitude dependant mantle". Arcuate ridges are often found at the base of hillslopes with gullies, but are also found on hillslopes with pasted-on terrain and no gullies. We have found a systematic lowering of the slope of the bedrock exposure located topographically above the pasted-on terrain whether that same slope hosts gullies or not. The lowered bedrock exposures display a different surface texture from bedrock exposed on other parts of the crater wall and from fresh crater walls-it appears fragmented and has reduced relief. Using 1-m-digital elevation models from the High Resolution Imaging Science Experiment (HiRISE) we compared the slopes of eight "eroded" craters and seven unmodified craters. We estimated their age using the crater size-frequency distribution of small craters on their ejecta blankets. From this information we calculated bedrock retreat rates for the eroded craters and found they were up to ∼103 m Myr-1-equivalent to erosion rates of wet-based glaciers on Earth. This is several orders of magnitude higher than previous estimates of erosion by VFF (10-2-101 m Myr-1), which themselves are roughly equivalent to cold-based glaciers on Earth. Such erosion rates are sufficient to erase previously existing landforms, such as martian gullies. We hypothesise, therefore, that the pasted-on terrain is a glacial deposit, overturning its previous interpretation as an airfall deposit of ice nucleated on dust. We maintain the interpretation of the arcuate ridges as moraines, but further conclude that they are likely the result of glaciotectonic deformation of sub-marginal and proglacial sediment in the presence of sediment pore-water. We do not support the generation of large quantities of glacial meltwater because it would have broken-up and degraded the arcuate ridges and pasted-on terrain an produced a suite of landforms (e.g., hummocky moraine, lacustrine forms, outwash plains, eskers) which are not observed

PCR for the detection of pathogens in neonatal early onset sepsis.

BACKGROUND: A large proportion of neonates are treated for presumed bacterial sepsis with broad spectrum antibiotics even though their blood cultures subsequently show no growth. This study aimed to investigate PCR-based methods to identify pathogens not detected by conventional culture. METHODS: Whole blood samples of 208 neonates with suspected early onset sepsis were tested using a panel of multiplexed bacterial PCRs targeting Streptococcus pneumoniae, Streptococcus agalactiae (GBS), Staphylococcus aureus, Streptococcus pyogenes (GAS), Enterobacteriaceae, Enterococcus faecalis, Enterococcus faecium, Ureaplasma parvum, Ureaplasma urealyticum, Mycoplasma hominis and Mycoplasma genitalium, a 16S rRNA gene broad-range PCR and a multiplexed PCR for Candida spp. RESULTS: Two-hundred and eight samples were processed. In five of those samples, organisms were detected by conventional culture; all of those were also identified by PCR. PCR detected bacteria in 91 (45%) of the 203 samples that did not show bacterial growth in culture. S. aureus, Enterobacteriaceae and S. pneumoniae were the most frequently detected pathogens. A higher bacterial load detected by PCR was correlated positively with the number of clinical signs at presentation. CONCLUSION: Real-time PCR has the potential to be a valuable additional tool for the diagnosis of neonatal sepsis

Confined magnetic guiding orbit states

We show how snake-orbit states which run along a magnetic edge can be confined electrically. We consider a two-dimensional electron gas (2DEG) confined into a quantum wire, subjected to a strong perpendicular and steplike magnetic field $B/-B$. Close to this magnetic step new, spatially confined bound states arise as a result of the lateral confinement and the magnetic field step. The number of states, with energy below the first Landau level, increases as $B$ becomes stronger or as the wire width becomes larger. These bound states can be understood as an interference between two counter-propagating one-dimensional snake-orbit states.Comment: 4 pages, 4 figure