Transparent planar solar absorber for winter thermal management.

Indoor heating during winters accounts for a significant portion of energy consumed by buildings in regions of cold climate. Development of transparent coatings for windows that efficiently harvest solar energy can play a major role in reducing energy consumption and fuel costs incurred for winter heating. In recent years, there has been a great research effort towards designing transparent solar absorber coatings using nanophotonic structures. The potential of coatings based on planar multilayer structures, however, has received very little attention. In this work we investigate the performance of planar multilayer thin films using low-cost materials for design of transparent solar absorber window coatings. Our study led to the proposal of two planar multilayer designs. Simulation results predict that an increase in surface temperature by 27 K and 25 K, while maintaining mean visible transmittance of over 50% is possible using these designs. These results illustrate the great promise planar multilayer structures hold for winter thermal management of buildings.

Directional excitation of surface plasmon using multi-mode interference in an aperture.

Plasmonics is a promising technology that can find many applications in nanophotonics and biosensing. Local excitation of surface plasmons with high directionality is required for many of these applications. We demonstrate that by controlling the interference of light in a metal slot with the adjustment of the angle of incidence, it is possible to achieve highly directional surface plasmon excitation. Our numerical analysis of the structure showing a strong directionality of excited surface plasmon is confirmed by near field scanning measurements. The proposed structure can be useful for many applications including excitation of plasmonic waveguides, nanolithography, and optical sensing. To illustrate its usefulness, we experimentally demonstrate that it can be used for highly directional excitation of a dielectric loaded plasmonic waveguide. We also propose a simple structure for surface plasmon interference lithography capable of providing high image contrast using this scheme.

Vertically integrated spot-size converter in AlGaAs-GaAs.

We report on the demonstration of a spot size converter (SSC) for monolithic photonic integration at a wavelength of 850 nm on a GaAs substrate. We designed and fabricated a dual-waveguide AlGaAs chip. The design consists of a lower waveguide layer for efficient end-fire coupling to a single-mode fiber, an upper waveguide layer for high refractive index contrast waveguides, and a vertical SSC to connect the two waveguide layers. We measured a SSC conversion efficiency of 91% (or -0.4 dB) between the upper and lower waveguide layers for the TE mode at a wavelength of 850 nm.

Polarization rotator based on augmented low-index-guiding waveguide on silicon nitride/silicon-on-insulator platform.

Using a newly proposed augmented low-index-guiding scheme with silicon nitride/silicon dual-core waveguide, we have designed, fabricated, and characterized a transverse electric (TE) to transverse magnetic (TM) and TM-to-TE compact polarization rotator. The polarization rotation is realized in an asymmetric directional coupler. The measured peak conversion efficiencies for the TE-to-TM and TM-to-TE rotations are approximately 97%. The measured polarization extinction ratio for the TE-to-TM rotation is greater than 20 dB over 50-nm bandwidth, while for the TM-to-TE rotation it is greater than 15 dB over the C-band.

Compact and broadband polarization beam splitter based on a silicon nitride augmented low-index guiding structure.

We propose a compact polarization beam splitter (PBS) based on a silicon nitride enhanced silicon-on-insulator platform using an augmented low-index guiding (ALIG) waveguide structure. In the ALIG structure, the TM mode is mostly confined in the low-index silicon nitride, while the TE mode is confined in the high-index silicon. Since the two modes are confined in two separate layers, their properties can be controlled independently. The PBS is formed using an asymmetric multimode interference (MMI) section. The TM mode is directed to an output port by the ALIG waveguide, while the TE mode is coupled to the other output port via the multimode interferometer. Such a PBS has a very small footprint, low insertion loss, high polarization extinction ratio, and broadband response.

Effects of salinity and salinity-induced augmented bioactive compounds in purslane (Portulaca oleracea L.) for possible economical use.

Dry matter (DM), total phenolics, flavonoids, carotenoid contents, and antioxidant activity of 12 purslane accessions were investigated against five levels of salinity (0, 8, 16, 24 and 32dSm(-1)). In untreated plants, the DM contents ranged between 8.0-23.4g/pot; total phenolics contents (TPC) between 0.96-9.12mgGAEg(-1)DW; total flavonoid contents (TFC) between 0.15-1.44mgREg(-1)DW; and total carotenoid contents (TCC) between 0.52BCEg(-1)DW. While FRAP activity ranged from 8.64-104.21mgTEg(-1)DW (about 12-fold) and DPPH activity between 2.50-3.30mgmL(-1) IC50 value. Different levels of salinity treatment resulted in 8-35% increases in TPC; about 35% increase in TFC; and 18-35% increases in FRAP activity. Purslane accessions Ac4, Ac5, Ac6 and Ac8 possessed potentials for salinity-induced augmented production of bioactive compounds which in turn can be harnessed for possible human health benefits.

Genetic improvement of purslane (Portulaca oleracea L.) and its future prospects.

Common purslane (Portulaca oleracea), also known as pigweed, fatweed, pusle, and little hogweed, is an annual succulent herb in the family Portulacaceae that is found in most corners of the globe. From the ancient ages purslane has been treated as a major weed of vegetables as well as other crops. However, worldwide researchers and nutritionists have studied this plant as a potential vegetable crop for humans as well as animals. Purslane is a nutritious vegetable with high antioxidant properties and recently has been recognized as the richest source of α-linolenic acid, essential omega-3 and 6 fatty acids, ascorbic acid, glutathione, α-tocopherol and ß-carotene. The lack of vegetable sources of ω-3 fatty acids has resulted in a growing level of attention to introduce purslane as a new cultivated vegetable. In the rapid-revolutionizing worldwide atmosphere, the ability to produce improved planting material appropriate to diverse and varying rising conditions is a supreme precedence. Though various published reports on morphological, physiological, nutritional and medicinal aspects of purslane are available, research on the genetic improvement of this promising vegetable crop are scant. Now it is necessary to conduct research for the genetic improvement of this plant. Genetic improvement of purslane is also a real scientific challenge. Scientific modernization of conventional breeding with the advent of advance biotechnological and molecular approaches such as tissue culture, protoplast fusion, genetic transformation, somatic hybridization, marker-assisted selection, qualitative trait locus mapping, genomics, informatics and various statistical representation have opened up new opportunities of revising the relationship between genetic diversity, agronomic performance and response to breeding for varietal improvement. This review is an attempt to amalgamate the assorted scientific information on purslane propagation, cultivation, varietal improvement, nutrient analyses, medicinal uses and to describe prospective research especially for genetic improvement of this crop.

Regional metastasis in supraglottic and glottic carcinoma of larynx.

This cross sectional study was conducted in Sir Salimullah Medical College Hospital, Mitford and Dhaka Medical College Hospital, Dhaka, Bangladesh from January 2009 to December 2009 by purposive sampling method. Among the 50 cases, involvement of supraglottic (72%) region is significantly higher than glottic (28%) region. Affected peoples are mainly male and mean age was 58.1±10.4 years. Frequency of regional metastasis of supraglottic carcinoma (47.22%) was higher than glottic carcinoma (7.14%). Most of the lymphnode involvement was at level-II to IV. Most of the patients presented at stage-I & stage-II.

Laparoscopic assisted appendicectomy in District Hospital, Joypurhat, Bangladesh.

"Laparoscopic assisted appendicectomy" refers to visualization of abdominal cavity, identification of appendix, drawing the appendix out through the port wound and appendicectomy. The objective of this study is to evaluate the outcome of the procedure of laparoscopic assisted appendicectomy. In this prospective study patients with appendicitis were randomly selected for laparoscopic assisted appendicectomy from August 2007 to February 2009 in the Department of Surgery, Modernized District Hospital, Joypurhat, Bangladesh. Out of 73 patients Laparoscopic assisted appendicectomy was performed successfully in 95.89% cases and conversion rate was 4.11%. Male to female ratio was almost 1:2 with mean±SD age 18.62±9.16 years. The wound infection rate was 8.2% and urinary retention 2.7%. Early postoperative feeding was started within 24 hours in 86.3% cases and mean duration of hospital stay was 2 days in 76.71% patients. More than 82% returned to their home and started social activities within 5 days. Duration of surgery was almost similar in emergency and interval appendicectomy group (19.35±10.13 vs. 23.66±9.43) minutes. Postoperative morbidity in emergency appendicectomy group showed significantly higher morbidity than interval appendicectomy group (p=0.003). This study indicates that the laparoscopic assisted appendicectomy is feasible for the majority of the patients with appendicitis in both emergency and interval settings. It reduces the operative time, shortens hospital stay and helps in early resumption of normal activities with good cosmetic outcome and patients' satisfaction.

Prospects for flavonoid and related phytochemicals as nature-inspired treatments for Clostridium difficile infection.

AIMS: There is a need for novel treatments for Clostridium difficile infection(CDI). Antibacterial flavonoids are part of a large family of polyphenol phytochemicals with a long history of use in ethnomedicine, but are unexamined against Cl. difficile. We explored their anti-difficile properties. METHODS AND RESULTS: Anti-difficile activities were determined for several naturally occurring flavonoids, olympicin A and synthetic 4-chromanone and chalcone analogues. With the exception of olympicin A, most naturally occurring phytochemicals tested were poorly active. Diversified synthetic flavonoids resembling olympicin A retained anti-difficile activity, suggesting olympicin A could act as a pharmacophore to obtain novel agents. They also demonstrated concentration-dependent killing of logarithmic and stationary phase cultures and reduced sporulation and toxin production. Olympicin A and some synthetic flavonoids dissipated the bacterial transmembrane potential. Interestingly, mutants could only be selected with the analogue 207 at a frequency of 10(-9). CONCLUSIONS: Based on the potent anti-difficile properties of olympicin A and modified flavonoids, further exploration of this class of phytochemicals is warranted. SIGNIFICANCE AND IMPACT OF THE STUDY: Clostridium difficile infection is a major problem in developed countries. These studies point to there being an avenue for optimizing plant-derived flavonoids, and related antibacterial phytochemicals, as nature-inspired approaches to treat CDI.

Compact low loss and broadband hybrid plasmonic directional coupler.

We propose a novel broadband coupler for silicon photonics using a hybrid plasmonic waveguide section. The hybrid plasmonic waveguide is used to create an asymmetric section in the middle of a silicon nanowire waveguide coupler to introduce a phase delay to allow for a 3-dB power coupling ratio over a 150 nm bandwidth around 1.55 µm. The device is very compact (<8.5 µm) and has a low insertion loss (<0.15 dB).

Pd-based integrated optical hydrogen sensor on a silicon-on-insulator platform.

We have experimentally demonstrated a compact, integrated optical hydrogen sensor on a silicon-on-insulator platform. The sensor consists of silicon waveguide coated with a thin palladium film. The sensitivity and response time of the sensor was tested for volumetric hydrogen concentrations ranging from 0% to 4%. The proposed hydrogen sensor shows great potential as a building block for an optical nose capable of simultaneous detection of multiple gases as well as environmental effects such as temperature and humidity.

Effect of seasonal variations on jackfruit trunk borer (Batocera rufomaculata De Geer) infestation.

The study of seasonal influence on incidence of trunk borer infestation was undertaken during 2010 at Kapasia upazila under district of Gazipur, Bangladesh. The borer was found in orchard from June to September with a peak emergence in mid July. The larval population of Jackfruit trunk borer is the destructive pest stage, which evokes concern in jackfruit growing areas of Bangladesh. The highest percentage of infestation was in July (7.33%) followed by June and August (6.00%). The cumulative infestation over the year in the study area was 35.33% in October. The lowest infestation was observed in February (0.67%) whereas no activity was found during November to January. The incidence of infestation of trunk borer was influenced by temperature, rainfall and relative humidity due to seasonal variations and their contribution of the regression (R2) were 63, 65 and 31%, respectively. Five independent weather factors in stepwise regression equation pooled responsible for 67.4% of the total variance. Stepwise regression showed that maximum temperature was the most important to influence 35.3% and the influence was lowest (2.1%) in case of average rainfall.

Experimental demonstration of a hybrid plasmonic transverse electric pass polarizer for a silicon-on-insulator platform.

We experimentally demonstrate a transverse electric (TE)-pass polarizer using the recently proposed hybrid plasmonic waveguide. The device consists of a silicon film separated from a chromium layer by a silica spacer. The device was characterized using a tunable laser in the 1.52-1.58 µm wavelength range. For a 30 µm long polarizer, the extinction ratio in this wavelength range varies from 23 to 28 dB and the insertion loss for the TE mode is 2-3 dB. The device is compact; its fabrication is completely compatible with silicon-on-insulator technology, and its performance compares favorably against previously reported silicon-based integrated optic TE-pass polarizers.

Compact hybrid plasmonic polarization rotator.

We propose a novel ultracompact (5 µm) hybrid plasmonic polarization rotator operating at telecommunication wavelength for integrated silicon photonic circuits. The polarization mode of a silicon waveguide is rotated with >14 dB polarization extinction ratio and low total insertion losses of 2.1 dB.

Identification of the causative agent of cutaneous leishmaniasis in Chichaoua province, Morocco.

Cutaneous leishmaniasis (CL) in Morocco is caused by three species, Leishmania major, L. tropica and L. infantum. CL has been known in Chichaoua province since 2000. Using DNA extracted from microscopic slides and parasite cultures, collected in the years 2006 and 2009, we identified for the first time L. tropica as the causative agent of CL in this region. Species identification was achieved by performing the ITS1-PCR-RFLP approach. By using this method it was possible to identify parasites in Giemsa stained slides containing less than five parasites per oil-immersion field even they were conserved for up to four months.

Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer.

Hybrid plasmonic waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted much interest. Here we show that, by suitably choosing the dimensions and material properties of the hybrid waveguide, a very compact and broadband TE-pass polarizer can be implemented. Finite-difference time-domain simulation indicates that the proposed device can provide large extinction ratio with low insertion loss for the TE mode.

Polarization-independent hybrid plasmonic coupler for a silicon on insulator platform.

Hybrid plasmonic waveguides consisting of a high-index slab separated from a metal plane by a low-index spacer provide an optimal compromise between the loss and confinement for surface plasmon waves in passive medium. In such hybrid structures, because power for the TE and TM modes are concentrated in two different regions of the guide, the characteristics of the two modes can be controlled independently by changing the waveguide dimensions. We propose to use this property to implement a hybrid plasmonic polarization-independent directional coupler for a silicon on insulator platform. We also investigate the effects of variations of wavelength and device dimensions on the performance of the proposed device.

Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends.

Hybrid-mode waveguides consisting of a metal surface separated from a high index medium by a low index spacer have attracted much interest recently. Power is concentrated in the low index spacer region for this waveguide. Here we investigate the properties of the hybrid mode in detail and numerically demonstrate the possibility of realizing compact waveguide bends using this wave guiding scheme.

Identification of the agent causing visceral leishmaniasis in Uzbeki and Tajiki foci by analysing parasite DNA extracted from patients' Giemsa-stained tissue preparations.

Our present study is the first attempt to characterize Leishmania parasites from foci in Uzbekistan and Tajikistan endemic for visceral leishmaniasis (VL). PCR-sequencing of the ribosomal internal transcribed spacer 1 and multilocus microsatellite typing (MLMT) were applied to DNA extracted from preparations of Giemsa-stained bone marrow aspirates from 13 cases of VL. L. infantum was shown to cause VL currently occurring in this area. MLMT applying 14 microsatellite markers, previously shown to be polymorphic for strains of the L. donovani complex, revealed that microsatellite profiles of parasites causing human VL in the Namangan and Jizzakh regions in Uzbekistan, and Penjikent region in Tajikistan, basically coincide with those of strains of L. infantum MON-1. Furthermore, these parasites were assigned to a distinct cluster genetically clearly separated from the populations of L. infantum MON-1 from Europe, the Middle East and North Africa. The existence of a genetically homogeneous but distinct group of L. infantum MON-1 indicates that the parasites circulating in the Uzbeki and Tajiki foci studied have been restricted there for a long time rather than having been recently introduced from elsewhere by human or animal reservoir migration.