Alopecia areata: a multifactorial autoimmune condition

Alopecia areata is an autoimmune disease that results in non-scarring hair loss, and it is clinically characterised by small patches of baldness on the scalp and/or around the body. It can later progress to total loss of scalp hair (Alopecia totalis) and/or total loss of all body hair (Alopecia universalis). The rapid rate of hair loss and disfiguration caused by the condition causes anxiety on patients and increases the risks of developing psychological and psychiatric complications. Hair loss in alopecia areata is caused by lymphocytic infiltrations around the hair follicles and IFN-γ. IgG antibodies against the hair follicle cells are also found in alopecia areata sufferers. In addition, the disease coexists with other autoimmune disorders and can come secondary to infections or inflammation. However, despite the growing knowledge about alopecia areata, the aetiology and pathophysiology of disease are not well defined. In this review we discuss various genetic and environmental factors that cause autoimmunity and describe the immune mechanisms that lead to hair loss in alopecia areata patients

Nonequilibrium Steady State of Photoexcited Correlated Electrons in the Presence of Dissipation

We present a framework to determine nonequilibrium steady states in strongly correlated electron systems in the presence of dissipation. This is demonstrated for a correlated electron (Falicov-Kimball) model attached to a heat bath and irradiated by an intense pump light, for which an exact solution is obtained with the Floquet method combined with the nonequilibrium dynamical mean-field theory. On top of a Drude-like peak indicative of photometallization as observed in recent pump-probe experiments, new nonequilibrium phenomena are predicted to emerge, where the optical conductivity exhibits dip and kink structures around the frequency of the pump light, a midgap absorption arising from photoinduced Floquet subbands, and a negative attenuation (gain) due to a population inversion.Comment: 5 pages, 3 figures, published versio

Breaking of the overall permutation symmetry in nonlinear optical susceptibilities of one-dimensional periodic dimerized Huckel model

Based on infinite one-dimensional single-electron periodic models of trans-polyacetylene, we show analytically that the overall permutation symmetry of nonlinear optical susceptibilities is, albeit preserved in the molecular systems with only bound states, no longer generally held for the periodic systems. The overall permutation symmetry breakdown provides a fairly natural explanation to the widely observed large deviations of Kleinman symmetry for periodic systems in off-resonant regions. Physical conditions to experimentally test the overall permutation symmetry break are discussed.Comment: 7 pages, 1 figur

Experimental demonstration of a high-flux capillary based XUV source in the high ionisation regime

High harmonic generation (HHG) has proven to be a fascinating and incredibly useful nonlinear optical phenomenon and has led to the realisation of tabletop sources of coherent extreme ultraviolet (XUV) radiation. Capillary based geometries in particular have attracted a great deal of attention due to their lengthy interaction regions and the potential to phase-match the HHG process leading to a large increase in XUV flux. Unfortunately due to plasma induced nonlinear and dispersive effects the simple phase-matching mechanism detailed in [1] cannot be scaled to high energy pump pulses and high gas pressures. In this work we have used a computational model [2] to design a capillary that can support a broad interaction region well-suited to quasi-phase-matching (QPM) while simultaneously reducing the effect that XUV reabsorption has on the output flux of the source. This modelling work has involved adjusting both the capillary length and gas density profile (figure 1a) in order to produce rapid oscillations in the radially integrated ionization fraction (figure 1b) coupled with a rapid decrease in gas pressure at the capillary exit. Our theory suggests that these oscillations are driven by a nonlinear self-compression process modulating the intensity of the pump pulse as it propagates through the plasma-filled waveguide [3]. Subsequent experimental work has shown an increase in XUV flux of almost 50 times over our previous capillary-based source (see figure 1c), and preliminary estimates suggest a photon flux of 1012 photons s-1 harmonic-1 in the 45 eV spectral region

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

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

N 1,N 2-Bis[(2-chloro-6-methyl­quinolin-3-yl)methyl­idene]ethane-1,2-diamine

The title mol­ecule, C24H20Cl2N4, lies on an inversion center in an extended trans conformation. In the crystal, weak C—H⋯Cl inter­actions connect the mol­ecules into chains along [010]

Comparative Analysis of the Saccharomyces cerevisiae and Caenorhabditis elegans Protein Interaction Network

Protein interaction networks aim to summarize the complex interplay of proteins in an organism. Early studies suggested that the position of a protein in the network determines its evolutionary rate but there has been considerable disagreement as to what extent other factors, such as protein abundance, modify this reported dependence. We compare the genomes of Saccharomyces cerevisiae and Caenorhabditis elegans with those of closely related species to elucidate the recent evolutionary history of their respective protein interaction networks. Interaction and expression data are studied in the light of a detailed phylogenetic analysis. The underlying network structure is incorporated explicitly into the statistical analysis. The increased phylogenetic resolution, paired with high-quality interaction data, allows us to resolve the way in which protein interaction network structure and abundance of proteins affect the evolutionary rate. We find that expression levels are better predictors of the evolutionary rate than a protein's connectivity. Detailed analysis of the two organisms also shows that the evolutionary rates of interacting proteins are not sufficiently similar to be mutually predictive. It appears that meaningful inferences about the evolution of protein interaction networks require comparative analysis of reasonably closely related species. The signature of protein evolution is shaped by a protein's abundance in the organism and its function and the biological process it is involved in. Its position in the interaction networks and its connectivity may modulate this but they appear to have only minor influence on a protein's evolutionary rate.Comment: Accepted for publication in BMC Evolutionary Biolog