5,415 research outputs found
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
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
Unsupervised machine learning of integrated health and social care data from the Macmillan Improving the Cancer Journey service in Glasgow
Background: Improving the Cancer Journey (ICJ) was launched in 2014 by Glasgow City Council and Macmillan Cancer Support. As part of routine service, data is collected on ICJ users including demographic and health information, results from holistic needs assessments and quality of life scores as measured by EQ-5D health status. There is also data on the number and type of referrals made and feedback from users on the overall service. By applying artificial intelligence and interactive visualization technologies to this data, we seek to improve service provision and optimize resource allocation.Method: An unsupervised machine-learning algorithm was deployed to cluster the data. The classical k-means algorithm was extended with the k-modes technique for categorical data, and the gap heuristic automatically identified the number of clusters. The resulting clusters are used to summarize complex data sets and produce three-dimensional visualizations of the data landscape. Furthermore, the traits of new ICJ clients are predicted by approximately matching their details to the nearest existing cluster center.Results: Cross-validation showed the model’s effectiveness over a wide range of traits. For example, the model can predict marital status, employment status and housing type with an accuracy between 2.4 to 4.8 times greater than random selection. One of the most interesting preliminary findings is that area deprivation (measured through Scottish Index of Multiple Deprivation-SIMD) is a better predictor of an ICJ client’s needs than primary diagnosis (cancer type).Conclusion: A key strength of this system is its ability to rapidly ingest new data on its own and derive new predictions from those data. This means the model can guide service provision by forecasting demand based on actual or hypothesized data. The aim is to provide intelligent person-centered recommendations. The machine-learning model described here is part of a prototype software tool currently under development for use by the cancer support community.Disclosure: Funded by Macmillan Cancer Support</p
Factors Affecting Shark Detection from Drone Patrols in Southeast Queensland, Eastern Australia
Drones enable the monitoring for sharks in real-time, enhancing the safety of ocean users with minimal impact on marine life. Yet, the effectiveness of drones for detecting sharks (especially potentially dangerous sharks; i.e., white shark, tiger shark, bull shark) has not yet been tested at Queensland beaches. To determine effectiveness, it is necessary to understand how environmental and operational factors affect the ability of drones to detect sharks. To assess this, we utilised data from the Queensland SharkSmart drone trial, which operated at five southeast Queensland beaches for 12 months in 2020–2021. The trial conducted 3369 flights, covering 1348 km and sighting 174 sharks (48 of which were >2 m in length). Of these, eight bull sharks and one white shark were detected, leading to four beach evacuations. The shark sighting rate was 3% when averaged across all beaches, with North Stradbroke Island (NSI) having the highest sighting rate (17.9%) and Coolum North the lowest (0%). Drone pilots were able to differentiate between key shark species, including white, bull and whaler sharks, and estimate total length of the sharks. Statistical analysis indicated that location, the sighting of other fauna, season and flight number (proxy for time of day) influenced the probability of sighting shark
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Evidence for Recent Wet-Based Crater Glaciation in Tempe Terra, Mars.
[Introduction]
Mars’ mid-latitudes host abundant putative debris-covered water-ice glaciers (viscous flow features; VFF). Eskers emerging from 110-150 Myr-old VFF in Phlegra Montes and Tempe Terra provide evidence for rare occurences of past, localized basal melting of their parent VFF, despite the cold climates of the late Amazonian (see this conf.). Eskers are sinuous ridges comprising glaciofluvial sediment deposited by meltwater flowing through tunnels within glacial ice.
Here, we describe a population of sinuous ridges emerging from VFF in an unnamed ~45 km-diameter crater (38.47 N, 72.43 W) in Tempe Terra, ~600 km from the VFF-linked esker identified by Butcher et al. We consider two working hypotheses for the formation of the sinuous ridges; that they are either (1) eskers formed by melting of the glaciers from which they emerge, or (2) topographically inverted fluvial channels which formed prior to glaciation of the crater. We present observations from preliminary geomorphic mapping of the crater to start to test those hypotheses
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