Integral representations combining ladders and crossed-ladders

We use the worldline formalism to derive integral representations for three classes of amplitudes in scalar field theory: (i) the scalar propagator exchanging N momenta with a scalar background field (ii) the "half-ladder" with N rungs in x - space (iii) the four-point ladder with N rungs in x - space as well as in (off-shell) momentum space. In each case we give a compact expression combining the N! Feynman diagrams contributing to the amplitude. As our main application, we reconsider the well-known case of two massive scalars interacting through the exchange of a massless scalar. Applying asymptotic estimates and a saddle-point approximation to the N-rung ladder plus crossed ladder diagrams, we derive a semi-analytic approximation formula for the lowest bound state mass in this model.Comment: 39 pages, 10 pdf figure

Cannabinoid signalling in TNF-alpha induced IL-8 release

Original article can be found at: http://www.sciencedirect.com/science/journal/00142999 Copyright Elsevier B.V. DOI : 10.1016/j.ejphar.2006.04.015Peer reviewe

Algebraic independence of arithmetic gamma values and Carlitz zeta values

We consider the values at proper fractions of the arithmetic gamma function and the values at positive integers of the zeta function for F_q[theta] and provide complete algebraic independence results for them.Comment: 15 page

Electrospun Piezoelectric Polymer Nanofiber Layers for Enabling in Situ Measurement in High-Performance Composite Laminates

This article highlights the effects from composite manufacturing parameters on fiber-reinforced composite laminates modified with layers of piezoelectric thermoplastic nanofibers and a conductive electrode layer. Such modifications have been used for enabling in situ deformation measurement in high-performance aerospace and renewable energy composites. Procedures for manufacturing high-performance composites are well-known and standardized. However, this does not imply that modifications via addition of functional layers (e.g., piezoelectric nanofibers) while following the same manufacturing procedures can lead to a successful multifunctional composite structure (e.g., for enabling in situ measurement). This article challenges success of internal embedment of piezoelectric nanofibers in standard manufacturing of high-performance composites via relying on composite process specifications and parameters only. It highlights that the process parameters must be revised for manufacturing of multifunctional composites. Several methods have been used to lay up and manufacture composites such as electrospinning the thermoplastic nanofibers, processing an inter digital electrode (IDE) made by conductive epoxy-graphene resin, and prepreg autoclave manufacturing aerospace grade laminates. The purpose of fabrication of IDE was to use a resin type (HexFlow RTM6) for the conductive layer similar to that used for the composite. Thereby, material mismatch is avoided and the structural integrity is sustained via mitigation of downgrading effects on the interlaminar properties. X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and scanning electron microscopy analyses have been carried out in the material characterization phase. Pulsed thermography and ultrasonic C-scanning were used for the localization of conductive resin embedded within the composite laminates. This study also provides recommendations for enabling internally embedded piezoelectricity (and thus health-monitoring capabilities) in high-performance composite laminates

A history of education in the Gambia from 1901 to the present day: a study of the western contribution to education in the Gambia during the present century.

Part I of the thesis provides the background necessary for a study of the development of education in The Gambia during the present century. The country's peculiar geographical position, the importance of the River Gambia, the main tribes and their history are clearly subjects of importance. Educational developments prior to I903 are also examined. The efforts of the missions, determined as they were in spite of many difficulties to provide education, were to bear fruit. Then in 1882 the Government moved towards the control and direction of education, when the first Education Ordinance was passed. This provided for a Board of Education, a part-time Inspector of Schools and grants-in-aid, determined mainly by results. Part II is concerned with educational policy and control since 1903. Developments based on the Education Ordinances of I903, 1935 and I946 and the Education Act of 1963 clearly show how the Government gradually exercised more and more control. Generous grants, a full-time officer to administer the Department and extension in the provision led to an intensified control over education. In 1963 the Board of Education was replaced by an Advisory Council on Education. The pattern which had evolved by 1968 makes it clear that intensification of control will go on, though there is no immediate possibility of complete control by the Government. Part III is devoted to the development of education - primary, secondary, teacher training, technical and vocational, adult education, and the welfare of pupils - during the period since I903.Primary education has maintained its continuity since the 1820's, although individual schools have had their vicissitudes. Bathurst and its environs are now reasonably well provided with primary schools; the Provinces, although they are being given priorities, still need a major thrust forward to catch up with the capital. Secondary education has remained very selective; even so it has not been able to acquire as high a prestige as that in other West African countries. Moreover, until recently, its development has been haphazard. Teacher training has a chequered history, and its position even today is not very encouraging. Technical and vocational education has suffered from prejudice against manual labour, from non-availability of teaching staff, and above all from the limitations imposed by the non-industrial bias of the country. Very little has been done in adult education: literacy classes on a small scale have been conducted in Bathurst and the Provinces, mostly by voluntary bodies. The welfare of pupils is a joint responsibility of the family and tribe on the one hand and schools on the other - the moral and physical aspects of welfare are generally looked after satisfactorily. Part IV is simply entitled "Context". Chapter XIII seeks to place the development of Western-type education in The Gambia in a social and economic setting and Chapter XIV briefly reviews the development of education in The Gambia alongside that in other English-speaking West African countries

Role of scavenger receptor MARCO in particle uptake and lung inflammation

Alveolar macrophages (AM) form the first line of defense against chronic inflammation caused by occupational exposure to environmental particulates such as crystalline silica (CSiO2). The chronic inflammatory process triggered by CSiO2 is known to culminate into a fibrotic response called silicosis in the human lungs. Previous studies have indicated the role of membrane glycoproteins called scavenger receptors in binding of environmental particles. The scavenger receptors are classified into different classes (A-H) based on their structure and function. Class A scavenger receptors are critical in uptake of variety of ligands such as bacteria, acetylated lipoproteins and are typically found on macrophages, dendritic and epithelial cells. One of the members of this family is Macrophage receptor with collagenous structure (MARCO). Recent studies have focused on analyzing the interaction between MARCO and inorganic particles such as CSiO2 and titanium dioxide (TiO2). Both in vivo and in vitro binding studies have identified MARCO as a key receptor in CSiO2 uptake and subsequent cytotoxicity in AM from C57Bl/6 mice. Further in vitro studies using a transfected cell line revealed that the 100 amino acid residues long cysteine-rich (SRCR) domain at the C-terminal end of MARCO is required for binding of inorganic particles such as CSiO2, TiO2 and amorphous silica (ASiO2). Moreover, individual particles bind to SRCR domain of MARCO with unique differences and have varying requirements with respect to need for divalent cations. Our studies demonstrate that physiological absence of MARCO in C57Bl/6 mice leads to a more robust inflammatory response following CSiO2 exposure as compared to wild-type mice. The results suggest that diminished clearance of CSiO2 particles from the MARCO-/- lungs exacerbates the lung inflammation. These findings demonstrate that the involvement of different regions of SRCR domain may distinguish downstream events following particle binding. Taken together, these data establish the role of MARCO in uptake of various inorganic particles and elucidate the protective role of MARCO in CSiO2-induced lung inflammation