Time for pulse traversal through slabs of dispersive and negative (ϵ\epsilon, μ\mu) materials

The traversal times for an electromagnetic pulse traversing a slab of dispersive and dissipative material with negative dielectric permittivity ($\epsilon$) and magnetic permeability ($\mu$) have been calculated by using the average flow of electromagnetic energy in the medium. The effects of bandwidth of the pulse and dissipation in the medium have been investigated. While both large bandwidth and large dissipation have similar effects in smoothening out the resonant features that appear due to Fabry-P\'{e}rot resonances, large dissipation can result in very small or even negative traversal times near the resonant frequencies. We have also investigated the traversal times and Wigner delay times for obliquely incident pulses and evanescent pulses. The coupling to slab plasmon polariton modes in frequency ranges with negative $\epsilon$ or $\mu$ is shown to result in large traversal times at the resonant conditions. We also find that the group velocity mainly contributes to the delay times for pulse propagating across a slab with n=-1. We have checked that the traversal times are positive and subluminal for pulses with sufficiently large bandwidths.Comment: 9 pages, 9 figures, Submitted to Phys. Rev.

Alternative institutional arrangements for contract farming in poultry production in Bangladesh and their impacts on equity

Also available in the ILRI Repository on Livestock Research at http://hdl.handle.net/10568/217Livestock Production/Industries,

Cavity-induced slow gain recovery in pump-probe experiments of quantum cascade lasers

We show that the Fabry-P´erot cavity dynamics of quantum cascade lasers (QCLs) play an important role in the gain recovery observed in a pump-probe experiment. Due to the residual pump power in the cavity after the pump pulse is reflected from the facet, the probed gain recovers at a slower rate

Isolation, characterization and comparative genomics of bacteriophage SfIV: a novel serotype converting phage from Shigella flexneri

BACKGROUND Shigella flexneri is the major cause of shigellosis in the developing countries. The O-antigen component of the lipopolysaccharide is one of the key virulence determinants required for the pathogenesis of S. flexneri. The glucosyltransferase and/or acetyltransferase genes responsible for the modification of the O-antigen are encoded by temperate serotype converting bacteriophage present in the S. flexneri genome. Several serotype converting phages have previously been isolated and characterized, however, attempts to isolate a serotype converting phage which encodes the modification genes of serotypes 4a strain have not been successful. RESULTS In this study, a novel temperate serotype converting bacteriophage SfIV was isolated. Lysogenisation of phage SfIV converted serotype Y strain to serotype 4a. Electron microscopy indicated that SfIV belongs to Myoviridae family. The 39,758 bp genome of phage SfIV encompasses 54 open reading frames (orfs). Protein level comparison of SfIV with other serotype converting phages of S. flexneri revealed that SfIV is similar to phage SfII and SfV. The comparative analysis also revealed that SfIV phage contained five proteins which were not found in any other phages of S. flexneri. These proteins were: a tail fiber assembly protein, two hypothetical proteins with no clear function, and two other unknown proteins which were encoded by orfs present on a moron, that presumably got introduced in SfIV genome from another species via a transposon. These unique proteins of SfIV may play a role in the pathogenesis of the host. CONCLUSIONS This study reports the isolation and complete genome sequence analysis of bacteriophage SfIV. The SfIV phage has a host range significantly different from the other phages of Shigella. Comparative genome analysis identified several proteins unique to SfIV, which may potentially be involved in the survival and pathogenesis of its host. These findings will further our understanding on the evolution of these phages, and will also facilitate studies on development of new phage vectors and therapeutic agents to control infections caused by S. flexneri

Role of Mothers\u27 Nutritional Knowledge, Nutritional Factors on the School Performance

A cross sectional study was carried out to investigate the effects of mothers\u27 nutritional knowledge, health and nutritional factors and socio-economic parameters on school performance among class five students of University Laboratory School, Dhaka. All of the eighty students were selected for this study. This study found there is a strong relationship between mother\u27s knowledge score and school performance. It was found that mothers\u27 knowledge score was responsible for 91.1 percent change in school performance. The mean BMI of the mothers was 20.44. We found that the school performance measured by class roll number of the students is significantly related with mothers BMI. There was an imperfect negative association between socio-economic parameters and school performance. But the relationship between the school performances with socio-economic parameters was strongly significant. This study also observed the relationship between Individual Dietary Diversity Score (IDDS) of respondent and marks achieved in class 4 final exam. It is alarming that consumption percentage were low for eggs (30) and milk and milk products (37.5), but majority of the students who consumed milk and milk products (63.3%) and eggs (66.7%) got the highest marks

Safe water for urban Bangladesh

Safe water for urban Banglades

An efficient plasmonic photovoltaic structure using silicon strip-loaded geometry

We show that a silicon thin-film photovoltaic structure with silicon strips on the top and grooves on the silver back contact layer can absorb incident solar energy over a broad spectral range. The silicon strips on the top scatter the incident light and significantly help couple to the photonic modes in the smaller wavelength range. The grooves on the silver back contact layer both scatter the incident light and help couple to the photonic modes and resonant surface plasmon polaritons. We find an increase of ∼46% in total integrated solar absorption in the proposed strip-loaded structure compared to that in a planar thin film structure of same dimensions. The proposed structure offers simpler fabrication compared to similar plasmonic-inspired designs

Drug resistance in Plasmodium falciparum from the Chittagong Hill Tracts, Bangladesh.

OBJECTIVE: To assess the efficacy of antimalarial treatment and molecular markers of Plasmodium falciparum resistance in the Chittagong Hill Tracts of Bangladesh. METHODS: A total of 203 patients infected with P. falciparum were treated with quinine 3 days plus sulphadoxine/pyrimethamine (SP) combination therapy, and followed up during a 4-week period. Blood samples collected before treatment were genotyped for parasite mutations related to chloroquine (pfcrt and pfmdr1 genes) or SP resistance (dhfr and dhps). RESULTS: Of 186 patients who completed follow-up, 32 patients (17.2%) failed to clear parasitaemia or became positive again within 28 days after treatment. Recurring parasitaemia was related to age (chi(2) = 4.8, P < 0.05) and parasite rates on admission (t = 3.1, P < 0.01). PCR analysis showed that some of these cases were novel infections. The adjusted recrudescence rate was 12.9% (95% CI 8.1-17.7) overall, and 16.6% (95% CI 3.5-29.7), 15.5% (95% CI 8.3-22.7) and 6.9% (95% CI 0.4-13.4) in three age groups (<5 years, 5-14, > or =15). The majority of infections carried mutations associated with chloroquine resistance: 94% at pfcrt and 70% at pfmdr. Sp-resistant genotypes were also frequent: 99% and 73% of parasites carried two or more mutations at dhfr and dhps, respectively. The frequency of alleles at dhfr, dhps and pfmdr was similar in cases that were successfully treated and those that recrudesced. CONCLUSIONS: The clinical trial showed that quinine 3-days combined to SP is still relatively effective in the Chittagong Hill Tracts. However, if this regimen is continued to be widely used, further development of SP resistance and reduced quinine sensitivity are to be expected. The genotyping results suggest that neither chloroquine nor SP can be considered a reliable treatment for P. falciparum malaria any longer in this area of Bangladesh

Misuse of Antibiotics and Potential Economic Loss in Bangladesh

Misuse of antibiotics is a global phenomenon. It is an increasingly serious threat to global public health that requires action across all government sectors and society. This study is an attempt to determine the rate of inappropriate use or misuse of antibiotics and understand potential economic loss in Bangladesh. This study uses simulated patients and they behaved like ordinary patients when they visited the doctors and collected prescriptions from them. The study finds that of total, 71.2% prescriptions contained antibiotic drug. The more the male doctors the higher the prescription of antibiotics. Doctors in sub-district level prescribe more antibiotics than the doctors in Dhaka urban periphery and public hospitals. This misuse of antibiotics has serious potential economic loss as it will lead to the development of antibacterial resistance coinciding with the increase in drug-resistant organisms which may result in the use of more toxic drugs. It will impose unnecessary costs on the patients and obviously reduce productivity of labor which is a very important factor of economic growth thus economic development. Keywords: Misuse, Antibiotics, Side effects, Economic growth.