Scattering characteristics of a metasurface covered chiral sphere.

An analysis of the scattering characteristics of a chiral sphere covered with a metasurface is presented. The electromagnetic fields inside and outside of a metasurface covered chiral sphere are expanded in terms of spherical vector wave functions. The influences of chirality and surface impedance of a metasurface upon the scattering cross section are investigated. It is seen that a specific type of metasurface can be used to significantly enhance and diminish the back scattering cross section from a chiral sphere having a fixed value of chirality but different radii. It is also observed that a chiral sphere having chirality close to unity apparently cannot be cloaked using a lossless metasurface as compared to a dielectric sphere, both having the same electromagnetic and geometrical parameters. A comparative study of the scattering characteristics of metasurface covered realistic chiral and low-loss Teflon dielectric spheres is developed. It is found that a metasurface covered realistic chiral sphere can be used to significantly reduce the scattering as compared to scattering from a metasurface covered Teflon sphere at a specific angle, provided that both spheres have the same radii and surface reactance.

Reflection characteristics of a parallel wire grid embedded in a general bi-isotropic medium.

A periodic wire grid composed of infinitely long thin parallel conducting wires with a bi-isotropic background is considered. The reflection properties of this wire grid have been investigated using numerical calculations. The analytic expressions for the surface impedance and reflection coefficient have been derived using the wave field decomposition approach and with the application of impedance boundary conditions for a wire grid. The influences of various background media upon the reflection magnitude and phase have been studied. The considered background media are taken to be bi-isotropic, Tellegen, and chiral. It is investigated if the zero reflection for a wire grid with a free space background under normal illumination vanishes for bi-isotropic, Tellegen, and chiral background media. It is found that, for a specific type of realistic bi-isotropic background medium, an equivalent wire grid of ideally conducting wires becomes nearly a perfect reflector. It is also studied if this type of perfect reflector is almost independent of incident angles.

Gain manipulation of a slotted sphere using general bi-isotropic coating.

The gain characteristics of a general bi-isotropic (BI) coated slotted sphere have been studied using numerical calculations. An eigenfunction expansion method has been used to derive analytical expressions for the radiated electric and magnetic fields. The effects of various BI and Tellegen coatings upon the gain pattern are investigated. It is proven that the chirality and Tellegen parameters of the coating can significantly modify the gain. It is found that a lossless BI coating has the highest gain in the forward direction as compared to lossless dielectric, Tellegen, and chiral coatings. Such type of enhanced gains in the forward direction are desirable for point-to-point communication. It is further shown that the Tellegen coating guides most of the radiated field from the slot toward polar directions and reduces the gain in the forward direction provided that the Tellegen parameter is not close to unity. For a Tellegen coating whose Tellegen parameter is close to unity, the maximum gain in the forward direction is found. The proposed theory is also extended to realistic BI and low-loss dielectric coatings. It is investigated that by using a proper selection of coating thickness, the forward direction gain of a realistic BI coating can be enhanced or diminished as compared to a low-loss dielectric coating.

Scattering characteristics of a cylindrical reflector covered with a general bi-isotropic layer.

The scattering characteristics of an electric line source radiating in the presence of a bi-isotropic coated circular cylindrical reflector have been investigated using numerical calculations. The analytic expressions of the electric and magnetic fields in the bi-isotropic coating and the background medium have been found using the wave-field decomposition approach. It is studied that a bi-isotropic coating enhances the gain in the forward direction as compared to chiral, Tellegen, and dielectric coatings. It is found that for a thin coating layer, the scattering gains in the forward direction for chiral and bi-isotropic coatings are almost the same. It is investigated that a specific type of bi-isotropic coating can be used to significantly enhance the scattering gain in the forward direction. This type of enhanced forward direction scattering gain is preferred in point to point communications. On the other hand, it is found that a specific type of Tellegen coating significantly reduces the scattering gain in the backward direction. This phenomenon of reduced gain can be used to hide a cylindrical reflector in the backward direction. A comparative study of the scattering gains for realistic bi-isotropic and low-loss dielectric coatings has also been discussed.

Scattering of cylindrical waves by a chiral-coated cylindrical reflector placed in chiral background.

The scattering of cylindrical waves by a chiral-coated cylindrical reflector placed in chiral background has been investigated using numerical simulations. The expressions for electric and magnetic fields inside the chiral coating and in the chiral background have been derived using the wavefield decomposition approach. It is postulated that the scattering gain can be controlled by varying the cylindrical wave source location, thickness of coating, chirality of coating, and chirality of background medium. It is shown that by increasing the chirality of coating for a chiral-coated cylindrical reflector placed in free space, the scattering gain in the forward direction increases, whereas the scattering gain in the backward direction decreases. It is further asserted that a strong chiral-coated cylindrical reflector placed in a certain chiral background guides most of the scattered field toward the rear side of the reflector. It is also observed that the scattering gain pattern becomes isotropic provided the chiral, strong chiral, and chiral nihility coated cylindrical reflectors are placed in a chiral nihility background. A cloaking phenomenon associated with a chiral-coated reflector placed in a chiral background at a specific observation angle is also discussed.

Gain properties of an uncoated and chiral coated slotted sphere embedded in a chiral background.

The gain properties of an uncoated and a chiral coated slotted sphere embedded in a chiral background have been investigated using numerical simulations. In this paper, it is found that a chiral background medium enhances the gain of an uncoated slotted sphere in the forward direction as compared to the free space background. It is shown that the forward direction gain of a chiral coated slotted sphere embedded in a chiral background increases with the increase in the background chirality. It is further determined that the maximum gain moves away from the polar direction toward the forward direction as the chirality of the coating increases for a fixed background chirality. Also, this maximum gain gradually decreases as the chirality of the coating increases. An interesting feature of an angular window is introduced for a chiral coated slotted sphere embedded in a chiral background where the gain is nearly constant for a specific range of angles.

Reflection and transmission properties of a metasurface composed of resonant loaded wire dipoles.

A considered metasurface is assumed to consist of a two-dimensional periodic arrangement of inductively loaded wires. The effects of incident angles and inductive loads upon equivalent surface impedance, reflection, and transmission properties of this metasurface have been investigated using numerical simulations. It is shown that at a particular frequency and angle, a metasurface can be cloaked for the incoming incident wave with nearly zero reflection. It is further studied that this approximate zero reflection is independent of the inductances of the inductively loaded wire dipoles.

Gain of an axially slotted cylinder covered with a chiral coating and embedded in a chiral medium.

The gain characteristics of an axially slotted cylinder coated with a chiral layer and placed in another chiral background have been investigated using numerical simulations. The effects of various types of chiral coatings and chiral backgrounds upon the gain pattern have been studied. It is shown that an increase in the chirality of the coating enhances the gain in the forward direction and reduces the gain in the backward direction for the fixed chirality of the background. It is also studied that, by increasing the chirality of the background medium, the gain in the backward direction also increases. It is further found that the chiral nihility coating makes the gain pattern nearly isotropic, and this gain is almost independent of the chirality of the background chiral medium.

Effects of material parameters upon the dipolar scattering characteristics of uncoated or coated sphere.

An analytical theory for the dipolar scattering characteristics of uncoated or coated sphere with different materials is presented. These materials are magnetodielectric, single negative, single near zero, and double near zero (DNZ) materials. It is shown that an uncoated magnetodielectric sphere has nearly identical E- and H-plane scattered intensities. It is further observed that for an epsilon near zero (ENZ) sphere, the intensity of scattered field in the E plane is nearly isotropic. For a coated sphere, it is shown that a magnetodielectric sphere coated with ENZ and mu near zero materials have nearly identical E-plane scattered intensities in the forward and backward scattering (BS) directions. Likewise, it is also shown that a finite sized magnetodielectric sphere coated with a DNZ layer can be made hidden to the incoming wave in the BS direction.

First Report of Rice Leaf Spot by Alternaria gaisen from Pakistan.

A rice field owned by an individual grower in Lahore, Pakistan, was surveyed in July 2013. Plants with symptoms of black, circular, necrotic spots 3 to 4 mm in diameter and an average of 8 to 10 spots per leaf were observed. Diseased plants were present in the field either singly or in groups of three to five. Ten symptomatic plants were selected randomly, and one infected leaf per plant and one necrotic spot per leaf was selected for the isolation of the pathogen. Necrotic areas were cut into small pieces, surface sterilized with 1% sodium hypochlorite solution, and plated on 2% malt extract agar (MEA) (Sigma, Dorset, UK). After incubation at 25 ± 2°C for 4 to 5 days, fungal mycelium was transferred aseptically to fresh MEA for pure culture. Three different isolates grown for 7 days on MEA were selected for detailed morphological studies. The fungal colony was dark greenish-black, reaching 7 to 8 cm in diameter, with 2 to 3 poorly defined growth rings. Conidiophores were geniculate and 50 to 140 × 3 to 4.5 µm in size. Conidia were in chains of 4 to 10, ovoid, ranging in size from 35 to 50 × 8 to 10 µm, with 12 to 15 transversal and 0 to 2 longitudinal septa. Conidia darkened from dull tan yellow to brown as the culture aged. Based on morphological characteristics, the pathogen was identified as Alternaria gaisen (2). A pure culture of the pathogen was deposited in First Fungal Culture Bank of Pakistan (FCBP1354). Due to the complexity of morphology-based identification of the genus Alternaria, sequencing of the internal transcribed spacer (ITS) region was carried out using the ITS1/ITS4 primer pair (1,3). The nucleotide sequence (KJ806190) of an amplified DNA fragment was compared with those already submitted to GenBank. The BLAST results revealed 99% identity of our A. gaisen isolate to strains NW680 (EU520123.1), FC3s (JX391937.1), and CBS 632.93 (KC584197.1), as well as some other A. gaisen strains. Pathogenicity testing of the fungus was performed on Basmati-198, a common cultivar of rice in Pakistan, by either spraying leaves of 1-month-old plants with 10 ml of spore suspension (2 × 105 spores/ml) or mixing this spore suspension in soil at the time of sowing. Control plants were sprayed with sterilized water. Plants were kept in a glasshouse at 30 ± 2°C and monitored for disease development. After 15 days of incubation, similar leaf necrotic spots to those observed in the field, developed on all inoculated plants, whereas all control plants remained healthy and asympomatic. The experiment was repeated three times and similar results were obtained. Re-isolation of A. gaisen from the symptomatic leaves fulfilled Koch's pathogenicity postulate. Although limited to the field where it was observed, to our best of knowledge, this is the first report of rice leaf spot by A. gaisen from Pakistan. Also, rice has not been reported as the host of A. gaisen from any part of the world. This study indicates that A. gaisen is potentially an important pathogen of rice plants. Further investigations into epidemiology and disease management strategies for this new disease are warranted especially where rice crop is grown extensively. References: (1) G. S. de Hoog and R. Horre. Mycoses 45:259, 2002. (2) E. G. Simmons. Alternaria: An identification manual. CBS, Fungal Biodiversity Center Utrecht, The Netherlands, 2007. (3) T. J. White et al. Page 315 in: PCR Protocols, A Guide to Methods and Applications, Academic Press, San Diego, 1990.

First Report of New Postharvest Rot in Ginger Rhizome by Aspergillus parvisclerotigenus in Pakistan.

Ginger (Zingiber officinale) rhizome is widely used in Pakistan as a spice. During the summer of 2013, several ginger sellers in a local vegetable market of Lahore, Pakistan, reported a green powdery mass of an unidentified pathogen that rotted a considerable quantity of ginger in its packaging. As far as we know, this disease was limited to stored rhizomes and not reported in fields. A survey was conducted in August to September of 2013 in three different vegetable markets in Lahore to collect infected samples. From each of three survey points from individual markets, 20 bags (10 kg each) were selected randomly. Average incidence of decay (by weight) was found to be 45%. Initial symptoms appeared as discoloration, soft and slippery skin with abundant green sporulation. Ten samples (rhizomes) from each market were brought to the laboratory for further studies. Isolation of the causal agent was carried out on two growth media: malt extract agar (MEA) and Czapek Dox agar (CZA). Inoculation was carried out by direct transfer of visible green spores as well as transferring a small fragment of surface sterilized infected rhizome to the media. Inoculated media plates were incubated at 25°C for 3 to 4 days. Emerging fungal colonies were sub-cultured to get pure cultures. The fungal colony was powdery, green, 3.5 to 4 cm in diameter, and without zonation after 7 days of incubation. Sclerotia were brown to black and globose. Conidial heads were columnar and biseriate, occasionally unseriate. Conidiophores were 1 to 2.5 mm long. Vesicles were sub-globose to globose and 25 to 30 µm wide. Metulae were 12 to 18 µm high and phialides were 6 to 12 µm. Conidia were globose to sub-globose, green, and 4 to 5 µm in diameter. Based on morphology, the fungus was identified as Aspergillus parvisclerotigenus (1). The identity of the pathogen was confirmed by ITS sequence analysis of two different isolates. For this, ITS1-5.8S-ITS2 nucleotide sequence of ~560 bp was amplified using total fungal genomic DNA as a template and ITS1 forward (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 reverse primer (5'-TCCTCCGCTTATTGATATGC-3') (2). Sequences from both isolates were 100% similar with each other. A BLAST search showed that this sequence had 99% homology with that A. parvisclerotigenus CBS 121.62 (EF409240.1). A culture of the fungus was deposited in First Fungal Culture Bank of Pakistan (FCBP1352) and the nucleotide sequence of ITS region to GenBank (KJ445022). For completion of Koch's postulates, a spore suspension (105 spores/ml) from a 1-week-old culture was prepared. Ten surface-disinfested, air-dried ginger rhizomes were placed on sterilized wet blotting papers in a glass beaker and inoculated by spore suspension using a hand sprayer. Similarly, 10 control rhizomes were sprayed with sterile distilled water. Rhizomes were incubated at 25°C for 7 days. The experiment was replicated three times. The same symptoms noticed in the vegetable markets were observed in 80% of the inoculated rhizomes while control rhizomes remained healthy. Re-isolation of the pathogen from symptomatic rhizomes fulfilled Koch's postulates. Poor hygiene is thought to be the main cause of rotting; therefore, this disease is not a threat to ginger if stored properly. To our knowledge, this is the first report of postharvest ginger rhizome rot from Pakistan caused by A. parvisclerotigenus. References: (1) J. Varga et al. Stud. Mycol. 69:57, 2011. (2) T. J. White et al. In: PCR Protocols: A Guide to Methods and Applications, page 315. Academic Press, San Diego, CA, 1990.

Diffuse reflectance spectroscopy: Systemic and microvascular oxygen saturation is linearly correlated and hypoxia leads to increased spatial heterogeneity of microvascular saturation.

The microvascular oxygen saturation (SmvO(2)) in the skin and tongue (sublingual mucosa) in pigs (n=6) was characterised using diffuse reflectance spectroscopy (DRS). The correlation between arterial oxygen saturation (SaO(2)) and SmvO(2) as well as the spatial heterogeneity of SmvO(2) was examined during hypoxia. DRS uses shallow-penetrating visible light to assess microvascular oxygen saturation (SmvO(2)) in superficial tissue. Hypoxia was induced by gradual reduction in ventilation or reduction of the inspiratory oxygen fraction. The spatial heterogeneity of SmvO(2) was expressed as the coefficient of variation (CV) of repeated SmvO(2) measurements. Baseline SmvO(2) before interventions was 20.2% (10.3%-38.1%, median with range) in groin skin, 32.9% (13.0%-49.3%) in the ear and 42.2% (32.1%-51.5%) in the tongue. SmvO(2) in the groin was significantly lower than venous oxygen saturation (SvO(2)) (p<0.05) and SmvO(2) in the tongue (p=0.03). There was a significant linear correlation between SaO(2) and SmvO(2) in all measuring sites for both interventions (p<0.05). Similarly there was a significant correlation between CV of repeated SmvO(2) measurements and SmvO(2) in all measuring sites for both interventions (p<0.01). The results from baseline measurements indicate a surprisingly high oxygen extraction in the measurement volume of DRS, especially in the groin skin. A reduction of SmvO(2) with decreasing SaO(2) was found and additionally the results suggest that spatial heterogeneity of microvascular oxygen saturation increases during hypoxia. Microvascular disturbances have been demonstrated in both local vascular diseases and systemic conditions such as shock and sepsis, an assessment of microvascular oxygen saturation using DRS may be useful in the monitoring of the microcirculation in such patients. This study is a part of an ongoing characterization of the DRS technique.

Assessments of skin and tongue microcirculation reveals major changes in porcine sepsis.

AIM: To examine the relation between central hemodynamics, clinical severity and microvascular findings in tongue and skin during sepsis. MATERIALS AND METHODS: Skin and tongue microcirculation was examined using laser Doppler and video microscopy techniques before and 200 min after inducing sepsis in pigs (n=6) by inactivated Neisseria meningitides and in two control animals. RESULTS: All infected pigs developed clinical signs of sepsis. Pericapillary bleedings developed in the tongue in the two pigs with the most severe disease. Capillary density increased in the groin skin in infected pigs after 200 min as compared to baseline (P<0·02). In the same period, mean capillary flow velocity was reduced in groin skin and tongue in septic pigs (P<0·02). At 200 min a fraction of capillaries had developed 'no flow' or 'brisk flow', patterns hardly seen at baseline. Laser Doppler perfusion was reduced in ear and tongue after 200 min (P<0·02 for both). The described pathology was more pronounced in the pigs with the most severe sepsis. CONCLUSION: Capillary bleedings may be used as an early indication of severe sepsis. Examination of skin and tongue microcirculations may be used to characterize severity of sepsis and possibly to assess effect of treatment.

Human microvascular imaging: a review of skin and tongue videomicroscopy techniques and analysing variables.

Imaging techniques are increasingly important in clinical diagnostic work. Microcirculation is essential for function and survival of all tissues, but imaging techniques for microvascular monitoring of patients have only been used to a limited extent in clinical practice. The microcirculation is complex with its static and dynamic feature, and only skin and oral mucosa are readily accessible for microscopic examination. In addition, there is a no general agreement on which microvascular parameters and analysing techniques that could be useful. The aim of this article is to give an overview of techniques for human intra-vital microscopy and to describe software and variables used to analyse pictures and film sequences of human microcirculation. We also present clinical examples where microvascular examinations have been shown to be of diagnostic value. Improved techniques for assessing microvascular morphology and physiology will probably become important tools in clinical work in many disciplines in the near future.

A study on serum triglyceride and lipoproteins cholesterol in coronary heart disease patients.

Sera obtained from 42 patients of myocardial infarction, 28 of unstable angina and 25 healthy control subjects was assayed for total triglycerides, cholesterol, LDL cholesterol (LDL-C), HDL Cholesterol (HDL-C) and VLDL Cholesterol (VLDL-C). The level of cholesterol was also determined among the sub-fractions of HDL. The levels of total triglycerides, cholesterol, LDL-C and VLDL-C were significantly raised in both groups of patients. Total high density lipoprotein cholesterol was low in patients, which was highly significant in HDL2-C and not in HDL3-C. These results suggest that serum lipids are directly correlated with the severity of coronary heart disease (CHD). Total cholesterol when measured in major lipoprotein classes and further partitioned into subfractions, increase their sensitivity, specificity and hence their predictive value as sensitive markers for the assessment of CHD risk.