Comment on "Wave Refraction in Negative-Index Media: Always Positive and Very Inhomogeneous"

In a recent Physical Review Letter [1] Valanju Walser and Valanju (VWV) called into question the basis of work on the so called negative index media (NIM). See for example [2,3]. The key point at issue is, `what is the group velocity of a wave in NIM?'Comment: Comment on Phys. Rev. Lett., v. 88, 187401 (2002

Absorption tails and extinction in luminescent solar concentrators

Non-ultraviolet (UV) photoexposure of luminescent solar concentrators (LSCs) can produce photoproducts that cause additional extinction at wavelengths somewhat longer than the main dye absorption peak. This photo-induced 'tails' extinction is deleterious to luminous output in collectors of useful lengths. An experimental method that enables the subdivision of tails extinction in an LSC into absorbed and scattered components is described. The relevant theory is outlined, and experimental results are presented for a polymethyl methacrylate (PMMA) LSC containing Lumogen F083 dye. For this sample, tails absorption increased significantly with outdoor exposure, while tails scattering remained constant. Further measurements indicate that LSC luminous output is around five times more sensitive to tails absorption than to fluorescence quenching. This work also indicates that merely checking for dye quenching, as is often done, can be a misleading indicator of long-term LSC output. © 2010 Elsevier B.V. All rights reserved

Uniform white light distribution with low loss from coloured LEDs using polymer doped polymer mixing rods

Colour mixing of red, green and blue (RGB) LEDs is demonstrated for a 6 cm long PMMA cylindrical rod with a transparent refractive index matched micro particle (TRIMM) diffuser sheet at the output end. Ray tracing simulations have been performed, and the output light distributions, transmittances and losses modelled and compared with experiment. Photographed and modelled colour mixing results are presented for rods with and without TRIMM sheet mixers. The TRIMM particles homogenize the light output of plain PMMA rods to form white light, with negligible backscattering. A simple method for measuring the concentration of the particles in the diffuser sheet is described, and computer modeling and analysis of TRIMM particle systems is discussed

Evaluation of the efficacy and safety of high dose short duration enrofloxacin treatment regimen for uncomplicated urinary tract infections in dogs.

BackgroundUncomplicated urinary tract infections (UTI) in dogs usually are treated with antimicrobial drugs for 10-14 days. Shorter duration antimicrobial regimens have been evaluated in human patients.HypothesisA high dose short duration (HDSD) enrofloxacin protocol administered to dogs with uncomplicated UTI will not be inferior to a 14-day treatment regimen with amoxicillin-clavulanic acid.AnimalsClient-owned adult, otherwise healthy dogs with aerobic bacterial urine culture yielding ≥ 10(3) CFU/mL of bacteria after cystocentesis.MethodsProspective, multicenter, controlled, randomized blinded clinical trial. Enrolled dogs were randomized to group 1 (enrofloxacin 18-20 mg/kg PO q24h for 3 days) or group 2 (amoxicillin-clavulanic acid 13.75-25 mg/kg PO q12h for 14 days). Urine cultures were obtained at days 0, 10, and 21. Microbiologic and clinical cure rates were evaluated 7 days after antimicrobial treatment was discontinued. Lower urinary tract signs and adverse events also were recorded.ResultsThere were 35 dogs in group 1 and 33 in group 2. The microbiologic cure rate was 77.1 and 81.2% for groups 1 and 2, respectively. The clinical cure rate was 88.6 and 87.9% for groups 1 and 2, respectively. Cure rates between groups did not differ according to the selected margin of noninferiority.Conclusions and clinical importanceHDSD enrofloxacin treatment was not inferior to a conventional amoxicillin-clavulanic acid protocol for the treatment of uncomplicated bacterial UTI in dogs. Further research is warranted to determine if this protocol will positively impact owner compliance and decrease the emergence of antimicrobial resistance

Found: High Surface Brightness Compact Galaxies

We are using the 2dF spectrograph to make a survey of all objects (`stars' and `galaxies') in a 12 sq.deg region towards the Fornax cluster. We have discovered a population of compact emission-line galaxies unresolved on photographic sky survey plates and therefore missing in most galaxy surveys based on such material. These galaxies are as luminous as normal field galaxies. Using H-alpha to estimate star formation they contribute at least an additional 5 per cent to the local star formation rate.Comment: To appear in "The Low Surface Brightness Universe", IAU Coll 171, eds. J.I. Davies et al., A.S.P. Conference Series. 3 pages, LaTex, 1 encapsulated ps-figure, requires paspconf.st

The Management and Use of Social Network Sites in a Government Department

In this paper we report findings from a study of social network site use in a UK Government department. We have investigated this from a managerial, organisational perspective. We found at the study site that there are already several social network technologies in use, and that these: misalign with and problematize organisational boundaries; blur boundaries between working and social lives; present differing opportunities for control; have different visibilities; have overlapping functionality with each other and with other information technologies; that they evolve and change over time; and that their uptake is conditioned by existing infrastructure and availability. We find the organisational complexity that social technologies are often hoped to cut across is, in reality, something that shapes their uptake and use. We argue the idea of a single, central social network site for supporting cooperative work within an organisation will hit the same problems as any effort of centralisation in organisations. We argue that while there is still plenty of scope for design and innovation in this area, an important challenge now is in supporting organisations in managing what can best be referred to as a social network site 'ecosystem'.Comment: Accepted for publication in JCSCW (The Journal of Computer Supported Cooperative Work

The planning and control of multiple task work: a study of secretarial office administration

This paper reports an attempt to construct a design-oriented model of the planning and control of multiple task work (PCMT) based on observations of secretarial office administration (SOA). The model is design-oriented in that it is intended to assist a designer to reason about the behaviours of an interactive human-computer worksystem; in this case, the planning and control behaviours of worksystems which carry out multiple task work. Design-oriented models of engineering contrast with the understanding-oriented models of science, which offer an understanding of phenomena in the form of their explanation and prediction

Screencasts: how effective are they and how do students engage with them?

The use of screencasts as an instructional technology is increasing rapidly in higher education. While there appears to be a consensus around students’ satisfaction with the provision of technology enhanced tools, there is limited evidence revolving around their impact in terms of knowledge acquisition. Moreover, the reasons why students choose to engage (or not) with these resources remain largely unreported. The study assessed the effect of using screencasts on undergraduate students’ understanding and engagement with learning material in one of their modules. Customised screencasts were used as optional additional learning and teaching resources. Grades obtained in a test module (with screencasts) and a control module (without screencasts) were compared to gauge the impact of screencasts on knowledge acquisition. Furthermore, the reasons for students’ engagement (or lack thereof) with the screencasts were explored using questionnaires. A modest but significant impact of screencasts on knowledge acquisition was found and students’ perception of the screencasts was overwhelmingly positive. Students suggested that screencasts should be kept short to summarise lectures or delve in-depth into complex concepts but should not replace whole lectures. Reasons for not using screencasts revolved around a lack of understanding of what the resources were but also a reported lack of fit between the nature of the tool and self-assessed learning style

Consistent quantum mechanics admits no mereotopology

It is standardly assumed in discussions of quantum theory that physical systems can be regarded as having well-defined Hilbert spaces. It is shown here that a Hilbert space can be consistently partitioned only if its components are assumed not to interact. The assumption that physical systems have well-defined Hilbert spaces is, therefore, physically unwarranted.Comment: 10 pages; to appear in Axiomathe

Screencasts: how effective are they and how do students engage with them?

The use of screencasts as an instructional technology is increasing rapidly in higher education. While there appears to be a consensus around students’ satisfaction with the provision of technology enhanced tools, there is limited evidence revolving around their impact in terms of knowledge acquisition. Moreover, the reasons why students choose to engage (or not) with these resources remain largely unreported. The study assessed the effect of using screencasts on undergraduate students’ understanding and engagement with learning material in one of their modules. Customised screencasts were used as optional additional learning and teaching resources. Grades obtained in a test module (with screencasts) and a control module (without screencasts) were compared to gauge the impact of screencasts on knowledge acquisition. Furthermore, the reasons for students’ engagement (or lack thereof) with the screencasts were explored using questionnaires. A modest but significant impact of screencasts on knowledge acquisition was found and students’ perception of the screencasts was overwhelmingly positive. Students suggested that screencasts should be kept short to summarise lectures or delve in-depth into complex concepts but should not replace whole lectures. Reasons for not using screencasts revolved around a lack of understanding of what the resources were but also a reported lack of fit between the nature of the tool and self-assessed learning style