From Defects to Boundaries

In this paper we describe how relativistic field theories containing defects are equivalent to a class of boundary field theories. As a consequence previously derived results for boundaries can be directly applied to defects, these results include reduction formulas, the Coleman-Thun mechanism and Cutcosky rules. For integrable theories the defect crossing unitarity equation can be derived and defect operator found. For a generic purely transmitting impurity we use the boundary bootstrap method to obtain solutions of the defect Yang-Baxter equation. The groundstate energy on the strip with defects is also calculated.Comment: 14 pages, 10 figures. V2 Removed comparison to RT algebras and added paragraph on the usefulness of transmitting defects in the study of boundary systems. References added. V3 Extended to include application to defect TB

Photostress Recovery Time Among Nigerians

Visual impairment may result from a deficiency of the retinal pigment epithelium or macula. Macula photostress test (MPST) is a quantitative estimation of the functional capability and performance reserve of the photoreceptive elements of the macula/retina. The purpose of this study was to determine the Photostress Recovery Time (PSRT) of different age groups in a sample of healthy subjects. Two hundred subjectswithanage range of 11years to70years (meanage of 33.30±12.74years)were usedfor this study. All the subjects had clear ocularmedia, normal appearance of the fundus, and visual acuityof 6/6 or better inthe testedeye. Prior toexperimentationeachsubjectwas adaptedtothe ambient roomlightingfor about 5mins. The upperlid of the eye to be tested was held firmly while a penlight was shone into the eye for about 10 seconds, PRSTwas assessed immediately after 10 seconds by asking the subjects to read at least three letters on the V.Aline immediately above the subject's best acuity line. The testing order of subjects in different age groups was randomized. Results indicated that the PSRT distribution in the sample population was found to be positively skewed with a mean of PSRTranging from10.34seconds to 46.98 seconds for an age range of 11 years to 70 years. Clinically males had slightly higher PSRT when compared to females. There was a positive relationship between age and PSRT which was highly significant (r =0.96) with a linear regression equation of PSRT=0.785+ 0.60xage. Themean increase in PSRT across consecutive age groups investigated was 27.46%. Males demonstrated a much sharper and larger increase in PSRT across consecutive age groups when compared to the females at all ages investigated except in the presbyopic age group. This study attempts to establish age related PSRTscores among healthy Nigerians in order to provide a quick reference in comparing normal physiological PSRT values and PSRTvalues arising from impending retinal/macular lesions. Keywords: Macular photostress test, Retinal photoreceptors, Retinal pigment epitheliu

Comparative Analysis Of The Effects Of Topical Anaesthetic Agents On Tear Quantity And Tear Quality

This studycompared the effects of different topical anaesthetic agents on tear quantity andtear quality. To establishthis, 30 subjects agedbetween18-35yearswithmeanage 23±2.60years andfree fromocular and systemic diseaseswere used.The study population consisted of 15males and15females.The quantity and quality of tears were measured for each subject before and after instillation of topical anaesthetic agents. The anaesthetic agents used were 2% xylocaine hydrochloride, 0.5% proparacaine hydrochloride and 0.5% tetracaine hydrochloride. Schirmer's tear test was used to assess the quantity of tears while tear qualitywas assessedwithNon-InvasiveTear Break-Up-Time (NITBUT).The result obtained showed that 0.5%proparacaine hydrochloride had a statistically significant decrease in tear quantity produced after instillation, using the one way analysis of variance, ANOVA (F = 4.43, P< 0.005). 0.5% tetracaine hydrochloride had a statistically significant effect on tear filmstability time (F = 16.78, P < 0.005) while 2% xylocaine hydrochloride had the least effect on tear quantity and tear quality. Thus, of these three topical anaesthetic agents, 0.5% tetracaine hydrochloride may be the preferred choice in optometric practice particularly in patients with Keratoconjunctivitis Sicca (KCS) in order to facilitate their tear film stability;while the use of proparacaine should be discouraged in patients with dry eye syndrome. Keywords: 2% Xylocaine hydrochloride, 0.5% Proparacaine hydrochloride, 0.5% Tetracaine hydrochloride,Tear quality,Tear quantity

Massive Star Formation in Luminous Infrared Galaxies: Giant HII Regions and their relation to Super Star Clusters

We have used HST/NICMOS H-band narrow-band Pa-alpha (at rest 1.87micron) images to identify star clusters and HII regions respectively in a sample of 8 luminous infrared galaxies (LIRGs). These observations have revealed the presence of a large population of super star clusters (SSC) and bright HII regions. A significant fraction of the HII regions shows H-alpha luminosities above that of 30 Doradus, the prototypical giant HII region. The excess of extremely luminous HII regions in LIRGs has been confirmed by comparison with normal galaxies observed at similar spatial resolutions. Despite the large numbers of identified star clusters and HII regions in LIRGs, we only find a small fraction of coincidences, between 4% and 30%. Using synthesis models we have reproduced the relative fractions of young HII regions, intermediate and old star clusters observed in Arp299 and the central region NGC3256 using a Salpeter IMF and instantaneous star formation. HII regions with no detected near-infrared cluster counterpart (25-39%) represent the youngest sites of star formation, with ages of up to approximately 5Myr and mostly intermediate mass (~10^5Msun) ionizing clusters. For these two galaxies, and within the present detection threshold we can only detect coincidences (4-10%) between an HII region and a near-infrared star cluster for the most massive star clusters (~10^6Msun) during the first 7Myr of their evolution. The identified near-infrared SSCs with no detectable Pa-alpha emission represent the ``old'' population (53-66% of the detected sources), with ages of between 7 and 20-40Myr. Older clusters possibly created in this or previous episodes of star formation are likely to exist in these systems but cannot be identified with the present detection threshold. (Abridged)Comment: Accepted for publication in AJ (July issue). Figure 2 not included. Go to: http://nicmos2.as.arizona.edu/~aalonso/work/papers/lirghii_v2.ps for a complete version of pape

A Cross-Sectional Survey on Parasites of Chickens in Selected Villages in the Subhumid Zones of South-Eastern Nigeria

A study was carried out to identify and estimate the prevalence of ecto- and endoparasites of village chicken between April and July 2008 in three local councils of Enugu state, Nigeria. A total of 1038 chickens comprising of 468 chicks, 207 growers and 363 adults were examined during the house to house survey for ectoparasites, gastrointestinal helminths and coccidia infections. Our finding showed that 41% were infected with ectoparasites with lice, fleas, and mites having prevalence rates of 62.2%, 35.7% and 2.1%, respectively. Helminths and coccidia had prevalence of 35.5% each. Among the helminths Ascaridia, galli was the most dominant species (17.2%). Generally, there was a significantly higher helminth infestation relative to the ectoparasites (P < .05), high prevalence of mixed infections and absence of tick infestation. Parasitism could be big constraint to production in the study area and we recommend a sustainable control strategy