bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation of the specific surface area and porosity of zinc oxide prepared in various atmospheres
Authors: Mikhail Raouf Sh. , Guindy Nabila M. , Ali Ismail T.
Published: March 2011

Specific surface area and pore structure studies were carried out on zinc oxide samples prepared from zinc oxalate dihydrate by heating at 330 and 370°C and in various atmospheres of water vapour, oxygen and hydrogen. The variation of SBET with water vapour pressure for the samples heated at 330°C was found to show a behaviour which can be compared with the Smith‐Topley effect. For the samples prepared at 370°C, rapid sintering occurred, and the Smith‐Topley effect was not followed in this case. Zinc oxide prepared in an oxygen atmosphere gave higher surface area values than that prepared in a hydrogen atmosphere, which is thought to be due to the oxidation of the carbon impurities on the surface. Analysis of nitrogen adsorption isotherms by the t‐method revealed the existence of micropores in the sample prepared at 330°C in vacuo. The rest of the samples have wide pores.
Kinetics of the catalytic oxidation of carbon monoxide over oxide catalysts
Authors: Sharma Chandra S. , Ramachandran Palghat A. , Hughes Ronald
Published: March 2011

The kinetics of the oxidation of carbon monoxide over five commercially available oxide catalysts have been determined at CO concentrations of 4–15 mol% and initial temperatures up to 170°C. The reaction showed a fractional dependence on the concentration of CO and was inhibited by CO2. From an analysis of the data a Langmuir‐Hinshelwood reaction scheme is proposed.
Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter: I. Influence of viscosity
Authors: Páca Jan , Ettler Petr , Grégr Vratislav
Published: March 2011

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min−1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m3) and sufficient coefficient KLa (160–200 h−1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min−1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m3 and the coefficient KLa ∼ 50 h−1.
Influence of some compounds on gentamicin formation by Micromonospora purpurea
Authors: Abou‐Zeid Abou‐Zeid A. , Eissa Abd El‐Wahab I. , Salem Hassan M.
Published: March 2011

Production of gentamicin antibiotics by Micromonospora purpurea was carried out successfully on a synthetic medium which contained the following ingredients (g/litre): glucose 10.0, NaNO3 2.0, KH2PO4 1.0, and CaCO3 1.0. The initial pH value of the fermentation medium was adjusted to 7.2. Effects of certain amino acids, organic acids, vitamins, purine and pyrimidine bases on the fermentative production of gentamicins were revealed. The ingredients which increased the antibiotic yields were phenylalanine, isoleucine, lysine, methionine, leucine, arginine, glycine, β′‐alanine, cystine, tryptophan, malic acid, maleic acid, cobalamin, folic acid, riboflavin, vitamin B1, vitamin B6, biotin, nicotinamide, uracil, adenine, guanine and adenosine. Trace elements (Co, Mo, Fe, Cu, Zn and Mn) exhibited their important role on the biosynthesis and formation of gentamicins by Micromonospora purpurea.
Multivariate analysis of soils: microbial biomass, metabolic activity, and bacterial‐community structure and their relationships with soil depth and type
Authors: Gelsomino Antonio , Azzellino Arianna
Published: March 2011

A multivariate statistical approach based on a large data set of abiotic and biotic variables was used to classify four contrasting‐land‐use soils. Soil samples were collected at increasing depth from a calcareous agricultural soil, a temperate upland grassland soil, a moderately acidic agricultural soil, and an acidic pine forest soil. Analytical investigations were carried out by using a combination of conventional physical, chemical, and biochemical methods coupled with denaturing gradient gel electrophoresis (DGGE) community fingerprinting of PCR‐amplified 16S rRNA gene‐coding fragments from soil‐extracted total‐community DNA. The data set of soil physical, chemical, and biochemical variables was reduced in dimensionality by means of a principal‐component‐analysis (PCA) procedure. Compositional shifts in soil bacterial‐community structure were analyzed through a clustering algorithm that allowed identifying six main bacterial‐community clusters. DGGE fingerprinting clusters were further analyzed by discriminant analysis (DA) using extracted PCA components as explanatory variables. Soil organic matter–related pools (TOC, TN) and functionally related active pools (microbial biomass C and N, K2SO4‐extractable C) significantly decreased with soil depth, and resulted statistically linked to one other and positively related to enzymatic activities (acid phosphatase, arylsulfatase, β‐glucosidase, dehydrogenase, hydrolysis of fluorescein diacetate) and silt content. Besides organic‐C gradients, pedogenetic‐driven physico‐chemical properties, and possibly soil thermal and moisture regimes seemed to play a key role in regulating size and energetic ecophysiological status of soil microbial communities. DGGE analysis showed that contrasting horizons were conducive to the dominance of particular bacterial ribotypes. DA revealed that the bacterial‐community structure was mainly influenced by organic matter–related variables (TOC, TN, CEC, Cflush, Nflush, Extr‐C), chemical properties such as pH, CaCO3, and EC, together with textural properties. Results indicate that, beyond land use or plant cover, pedogenetic‐driven physico‐chemical conditions changing with soil type and depth are the key factors regulating microbial size and activity, and determining the genetic structure of bacterial community.
Sterols in soil organic matter in relation to nitrogen mineralization in sandy arable soils
Authors: Heumann Sabine , Schlichting André , Böttcher Jürgen , Leinweber Peter
Published: March 2011

Unusually low net N mineralization in soils relatively rich in total organic C and N was repeatedly reported for sandy arable soils in NW Europe. In order to adequately account for it in simulation models, it is necessary to know the involved substances and processes. Therefore, 9 arable top soils (< 6% clay) with a wide range of total organic C (1.1%–5.2%) and C : N ratios (12–35) were studied. The soils varied strongly in the mineralizability of soil organic N which was determined via long‐term laboratory incubations (> 200 d). It was hypothesized that mineralization was controlled by antioxidants, and the Trolox equivalent antioxidant capacity (TEAC) of the soils was measured. In addition, pyrolysis–field ionization mass spectrometry (Py‐FIMS) was applied to investigate the influence of the molecular‐chemical composition of soil organic matter. In these soils, the compound class of sterols from Py‐FIMS analysis was most closely, negatively correlated with the mineralizability of soil organic N (r2 = 0.75, p = 0.003). This was probably not an antioxidative effect, because the TEAC values did not correlate sufficiently with the mineralizability and the sterol intensities. However, the negative relation with sterols could be causal, since the correlation was about as close with other components of the compound class of sterols and even closer with the main plant sterol beta‐sitosterol (r2 = 0.84, p = 0.001). In addition, the variability among samples was strongly governed by the proportions of sterols, and sterols also had a high discriminating power in discriminant analysis. Furthermore, the proportions of sterols were extraordinary in those arable podzol soils that developed under previous heath‐ or woodland (up to 10.2% of total ion intensity from Py‐FIMS). In conclusion, the inhibitory effect of these compounds needs to be investigated in more detail in order to optimize parameterization of N as well as C simulation models especially for podzolized, sandy arable soils with former heath‐ or woodland vegetation.
Phosphorus partitioning in grassland and forest soils of Germany as related to land‐use type, management intensity, and land use–related pH
Authors: Alt Fabian , Oelmann Yvonne , Herold Nadine , Schrumpf Marion , Wilcke Wolfgang
Published: March 2011

Recent literature confirmed that P fractions in soil are controlled by land use. However, differences in intensity of the same type of land use have received less attention although management intensity plays a crucial role in determining nutrient supply in soil. The objective of our work was to assess the influence of land‐use intensity (LUI) on P fractions in soil. In the “Biodiversity Exploratories”, grassland and forest sites in Germany were selected in three regions (Schorfheide‐Chorin, Hainich‐Dün, Schwäbische Alb). In spring 2008, we sampled topsoil of 241 experimental plots. The plots included unfertilized and fertilized meadows, pastures, and mown pastures and near‐natural to intensively used forests. Land‐use intensity was classified according to the extent of annual biomass removal. We used the sequential extraction method of Hedley et al. (1982) to characterize P partitioning in soil. In summary, total P (TP) concentrations in soil were lowest at Schorfheide‐Chorin (62–952 mg kg–1) followed by the Hainich‐Dün (230–1631 mg kg–1) and the Schwäbische Alb (205–1838 mg kg–1). Differences between grassland and forest sites were mainly attributable to pH. The pH value was the most important factor among several soil properties explaining P partitioning in soil. For grassland, at pH values ≈ 6.5, the application of lime‐containing fertilizer increased P availability in soil while effects of organic or mineral P fertilizers were negligible and related to the low application rates (< 12 kg ha–1). Land‐use intensity contributed up to 10% of the variation in the contribution of NaOH‐Pi to TP concentrations (ANOVA, Type I). In the Schwäbische Alb grassland soils, elevated LUI resulted in low NaOH‐Pi concentrations in soil which was probably caused by reduced sorption. Our findings highlight the importance of LUI as a control of P fractions in soil.
Influence of earthworm culture on fertilization potential and biological activities of vermicomposts prepared from different plant wastes
Authors: Kumar Srivastava Pankaj , Singh Poonam C. , Gupta Manjul , Sinha Arpita , Vaish Aradhana , Shukla Ashish , Singh Nandita , Krishna Tewari Sri
Published: March 2011

The present investigation was aimed to analyze influence of earthworm culture on nutritive status, microbial population, and enzymatic activities of composts prepared by utilizing different plant wastes. Vermicomposts were prepared from different types of leaves litter of horticulture and forest plant species by modified vermicomposting process at a farm unit. Initial thermophilic decomposition of waste load using cow‐dung slurry was done in the separate beds. The culture of Eisenia fetida was used for vermicomposting in specially designed vermibeds at the farm unit. The physico‐chemical characteristics, enzyme activities (oxido‐reductases and hydrolases), and microbial population (bacteria, fungi, free‐living nitrogen‐fixing bacteria, actinomycetes, Bacillus, Pseudomonas, phosphate‐solubilizing bacteria and fungi) of vermicomposts were found significantly higher (p < 0.05) than those of control (without earthworm inoculum). The study quantified significant contributions of earthworm culture to physico‐chemical, enzymatic, and microbiological properties of vermicompost and confirmed superior fertilization potential of vermicompost for organic farming. The agronomic utility of vermicompost was assessed on yellow mustard plant in a pot experiment. Pot soil was amended with different ratios (5%, 10%, 20%) of vermicompost and normal compost (without earthworm inoculum). Effects of these amendments on the growth of Brassica comprestis L. were studied. The significant differences (p < 0.05) in the growth of plant were observed among vermicompost‐, compost‐amended soil, and control. Vermicompost increased the root and shoot lengths, numbers of branches and leaves per plant, fresh and dry weights per plant, numbers of pods and flowers, and biochemical properties of plant leaf significantly, especially in 20% amendment. These results proved better fertilization potential of vermicompost over non‐earthworm‐inoculated compost.
Comparing concurrent in situ and batch‐extracted trace element concentrations
Authors: Godbersen Levke , Utermann Jens , Duijnisveld Wilhelmus H. M. , Altfelder Sven , Kuhnt Gerald , Böttcher Jürgen
Published: March 2011

Different procedures to investigate dissolved trace element concentration at the transition from unsaturated to saturated zone in soils were compared by concurrent sampling of soil solution and solid soil material in this zone. The in situ sampled soil solution from the percolated water was used to measure in situ concentrations, while solid soil material was used to measure concentrations at two liquid–solid ratios using batch experiments on 250 sample pairs. The liquid–solid ratios were 2 L kg–1 and 5 L kg–1. At 5 L kg–1, the ionic strength was adjusted with Ca(NO3)2 to a sample‐specific value similar to in situ, while at 2 L kg–1, the ionic strength was not adjusted. The extracted concentrations of most trace elements exhibited a statistically significant but weak correlation (p value < 0.01) to the corresponding in situ concentrations. In the liquid–solid ratio of 2 L kg–1 extracts, Pb and Cr showed very poor comparability with the in situ equivalent. A likely cause was the enhanced dissolved‐organic‐C release in the extract due to the lower ionic strength compared to in situ conditions in combination with effects from drying and moistening soil samples. For the other elements, correlation increased in the order As < Cu, Zn, Sb, Mo, V < Cd, Ni, Co where adjustment of the ionic strength led to slightly better results. In addition to the element‐specific shortcomings, it appeared that low concentration levels of in situ concentrations were generally underestimated by batch extraction methods. The liquid–solid ratio of 2 L kg–1 extracts could only be used as a method to predict exceedance of thresholds if a safety margin of approximately one order of magnitude higher than the thresholds was adopted. The ability of the batch‐extraction methods to estimate in situ concentrations was equally limited.
Feasibility and Safety of Percutaneous Coronary Intervention in Patients with End-Stage Liver Disease Referred for Liver Transplantation
Authors: Azarbal Babak , Poommipanit Paul , Arbit Boris , Hage Antoine , Patel Jignesh , Kittleson Michelle , Kar Saibal , Kaldas Fady M. , Busuttil Ronald W.
Published: March 2011

Percutaneous coronary intervention (PCI) has traditionally not been an option for patients with end-stage liver disease (ESLD) and coronary artery disease (CAD). This retrospective study was designed to demonstrate the feasibility and safety of PCI in liver transplant candidates. Patients with ESLD and hemodynamically significant CAD who were otherwise deemed to be acceptable candidates for liver transplantation underwent PCI. The procedural success rates, mortality and myocardial infarction rates, and bleeding outcomes were examined. Sixteen patients with ESLD underwent PCI: 15 with bare-metal stents (1.3 stents per patient on average) and 1 with balloon angioplasty alone. The median diameter stenosis per lesion was 80%, the median platelet count was 68 × 109/L, the median international normalized ratio was 1.3, and the median Model for End-Stage Liver Disease score was 13. PCI was successful in 94% of the patients. One patient had a suboptimal residual stenosis of 50% after stenting. There were no in-hospital or 30-day deaths or myocardial infarctions, and no patients developed hematomas. One patient required a 1-U platelet transfusion, and another required 1 U of packed red blood cells. All patients remained clinically stable 1 month after PCI. Nine of the 16 patients were listed for liver transplantation, and 3 patients underwent liver transplantation. In conclusion, we have demonstrated the safety and feasibility of PCI in a small cohort of patients with ESLD and hemodynamically significant CAD, the majority of whom had significant thrombocytopenia. Larger studies are required to determine whether PCI is an effective treatment strategy for patients with ESLD and hemodynamically significant CAD who otherwise would not be candidates for liver transplantation. Liver Transpl 17:809-813, 2011. © 2011 AASLD.
Degenerate elliptic operators, Feller semigroups and modified Bernstein‐Schnabl operators
Authors: Altomare Francesco , Montano Mirella Cappelletti , Diomede Sabrina
Published: March 2011

In this paper we study a class of elliptic second‐order differential operators on finite dimensional convex compact sets whose principal part degenerates on a subset of the boundary of the domain. We show that the closures of these operators generate Feller semigroups.

Moreover, we approximate these semigroups by iterates of suitable positive linear operators which we also introduce and study in this paper for the first time, and which we refer to as modified Bernstein‐Schnabl operators. As a consequence of this approximation we investigate some regularity properties preserved by the semigroup.

Finally, we consider the special case of the finite dimensional simplex and the well‐known Wright‐Fisher diffusion model of gene frequency used in population genetics. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Homozygous THAP1 mutations as cause of early‐onset generalized dystonia
Authors: Schneider Susanne A. , Ramirez Alfredo , Shafiee Kaveh , Kaiser Frank J. , Erogullari Alev , Brüggemann Norbert , Winkler Susen , Bahman Ideh , Osmanovic Alma , Shafa Mohammad A. , Bhatia Kailish P. , Najmabadi Hossein , Klein Christine , Lohmann Katja
Published: March 2011

To identify the underlying genetic cause in a consanguineous family with apparently recessively inherited dystonia, we performed genome‐wide homozygosity mapping. This revealed 2 candidate regions including the THAP1 gene, where heterozygous mutations cause dystonia 6. A homozygous missense mutation in THAP1 (c.95T>A; p.Leu32His) was found in all 3 affected siblings. Symptoms started in childhood in the legs and became generalized within a few years. Three heterozygous mutation carriers were unaffected. Because THAP1 regulates the expression of the DYT1 gene, we used reporter gene assays to show that DYT1 expression was significantly increased for Leu32His. However, this increase was less pronounced than for other THAP1 mutations that cause dystonia in the heterozygous state. Our data suggest that homozygous THAP1 mutations cause dystonia and may be associated with a less severe dysfunction of the encoded protein compared with heterozygous disease‐causing mutations. © 2011 Movement Disorder Society
Replication of MAPT and SNCA, but not PARK16‐18, as susceptibility genes for Parkinson's disease
Authors: Mata Ignacio F. , Yearout Dora , Alvarez Victoria , Coto Eliecer , de Mena Lorena , Ribacoba Renee , Lorenzo‐Betancor Oswaldo , Samaranch Lluis , Pastor Pau , Cervantes Sebastian , Infante Jon , Garcia‐Gorostiaga Ines , Sierra Maria , Combarros Onofre , Snapinn Katherine W. , Edwards Karen L. , Zabetian Cyrus P.
Published: March 2011

Recent genome‐wide association studies of Parkinson's disease have nominated 3 new susceptibility loci (PARK16‐18) and confirmed 2 known risk genes (MAPT and SNCA) in populations of European ancestry. We sought to replicate these findings. We genotyped single‐nucleotide polymorphisms in each of these genes/loci in 1445 Parkinson's disease patients and 1161 controls from northern Spain. Logistic regression was used to test for association between genotype and Parkinson's disease under an additive model, adjusting for sex, age, and site. We also performed analyses stratified by age at onset. Single‐nucleotide polymorphisms in MAPT (rs1800547; P = 3.1 × 10−4) and SNCA (rs356219; P = 5.5 × 10−4) were significantly associated with Parkinson's disease. However, none of the markers in PARK16‐18 associated with Parkinson's disease in the overall sample, or in any age stratum, with P values ranging from .09 to .88. Although our data further validate MAPT and SNCA as Parkinson's disease susceptibility genes, we failed to replicate PARK16, PARK17, and PARK18. Potential reasons for the discordance between our study and previous genome‐wide association studies include effects of population structure, power, and population‐specific environmental interactions. Our findings suggest that additional studies of PARK16‐18 are necessary to establish the role of these loci in modifying risk for Parkinson's disease in European‐derived populations. © 2011 Movement Disorder Society
Identifying extreme event climate thresholds for greater Manchester, UK: examining the past to prepare for the future
Authors: Smith Claire , Lawson Nigel
Published: March 2011

Extreme weather events can have severe consequences for the local environment and population. Projected future changes in climate (e.g. UKCP09) indicate that North West England is likely to experience an increasing frequency and intensity of meteorological extremes, leading to flooding, heat waves and storms. Consequently, it is important that the region enhances its preparedness for such events. This paper explores the possibility of developing quantifiable climate risk indices for the case study area of Greater Manchester, using a combination of archival research and statistical analysis of past climate data. For extremes which are the function of a single meteorological variable (e.g. heat waves, pluvial flooding and heavy snowfall) the thresholds proved to be reliable and skillful. Days with maximum daily temperature greater than or equal to 29.2 °C, daily snowfall amount greater than or equal to 6 cm or maximum gust speed greater than or equal to 60 knots are found to be indicative of weather‐related impacts which have in the past affected human health/well‐being, have caused damage to the urban infrastructure or have severely disrupted services. Extreme events which are the result of a more complex interaction between variables (e.g. drought, freezing conditions) were less well captured by applying the thresholds associated with a single variable in isolation. Such critical threshold indices can be used in conjunction with future projections of climate change to establish weather‐related risk for the future. This risk‐based approach can subsequently be integrated to climate change adaptation strategies and development planning to ensure future preparedness. Copyright © 2011 Royal Meteorological Society
Multi‐model ensemble (MME) prediction of rainfall using neural networks during monsoon season in India
Authors: Kumar Ashok , Mitra A. K. , Bohra A. K. , Iyengar G. R. , Durai V. R.
Published: March 2011

The prediction of Asian summer monsoon rainfall on various space and time scales is still a difficult task. Compared to the mid‐latitudes, proportional improvement in the skill in prediction of monsoon rainfall in medium range has been less in recent years. Global models and data assimilation techniques are being further improved for monsoons and the tropics. However, multi‐model ensemble (MME) forecasting is gaining popularity, as it has the potential to provide more information for practical forecasting in terms of making a consensus forecast and reducing the model uncertainties. As major centres are exchanging the model output in near real time, MME is a viable, inexpensive, way for enhancing the forecast skill. Apart from a simple ensemble mean, the MME predictions of large‐scale monsoon precipitation in the medium range was carried out during the 2009 monsoon at NCMRWF/MoES, India. The neural network weights were obtained and a neural network was trained based upon forecast data from four global models for the 2007 and 2008 monsoons in order to develop the multi‐model ensemble system. The skill score for country and sub‐regions, indicates that a multi‐model ensemble forecast has a higher skill than individual model forecasts and also higher skill than the simple ensemble mean in general. Although the skill of the global models falls beyond day 3, a significant improvement could be seen by employing the MME technique up to day 5. Copyright © 2011 Royal Meteorological Society
Rapid merger and recyclogenesis of twin extratropical cyclones leading to heavy precipitation around Japan on 9–10 October 2001
Authors: Yamamoto Masaru
Published: March 2011

The significance of twin extratropical cyclones (in contrast to twin tropical cyclones) has not yet been fully recognized in weather forecasting and analysis of heavy precipitation. This study investigated successive sets of twin extratropical cyclones over the Yellow and East China Seas (YECS) and over the Japan Sea and South Coast areas of the Japanese Islands (JSSC) on 9–10 October 2001. Although these twin cyclones were not strong, they led to heavy precipitation in Japan. The southern low of the YECS twin cyclones, which accompanied a moist tongue, rapidly merged with the northern cold low, resulting in the formation of a moist tongue across the Japanese Islands, causing heavy precipitation. This rapid merger is explained by a coupling of cold upper‐ and warm lower‐level lows in a contact binary rotation system. Subsequently, the JSSC twin cyclones became newly organized. The northern deep low of the JSSC twin cyclones formed north of an upper‐level jet by the merger of the YECS cyclones, while the southern shallow low newly formed around the occlusion point south of the upper‐level jet. The sensitivity experiments of successive sets of the twin cyclones show that condensational heating and topographic effects contribute to the formation of the twin structures. The northern low of the JSSC twin cyclones is amplified by latent heating, while the southern low is hardly amplified. The topography of the Japanese Islands results in intensification of the upward flow and cyclonical flow via topographic convergence and blocking of horizontal flow. Copyright © 2011 Royal Meteorological Society
Printed L‐band monopole antenna with a bionical structure
Authors: Jiang Wen , Gong Shu‐xi , Hong Tao , Mu Xin
Published: March 2011

A bionical structure is applied to antenna design in this letter. An L‐band printed monopole antenna using the shape of the octopus is proposed for 1.6 GHz based on the concept of bionics. Its radiation characteristics including impedance bandwidth, radiation patterns, and gain are simulated and measured. The proposed antenna has attractively good performances that the radiation patterns are unipolar. Method of applying bionics to antenna design will serve as a good candidate for the future antenna design. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1004–1006, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25891
An improvement for the acceleration technique based on monostatic bistatic equivalence for shooting and bouncing ray method
Authors: Ding Jianjun , Chen Ru‐shan , Zhou Huan , Fan Z. H.
Published: March 2011

An efficient algorithm is present for improving the acceleration technique of the monostatic radar cross section (RCS) prediction based on monostatic bistatic equivalence principle for the shooting and bouncing ray (SBR) method. Using the monostatic bistatic principle, the time consumed by the monostatic RCS simulation can be greatly reduced since the ray tracing procedure of the SBR method is avoided for a lot of incident angles. However, the result of the monostatic RCS using the monostatic bistatic equivalence get worse in the case of multiple bounces in ray tracing. To remedy this disadvantage, parts of rays are chosen with a sophisticated algorithm to be traced in order to correct the phase and location of the ray tubes. Numerical results demonstrate that the present algorithm is efficient for the SBR method in analysis of electrical large objects. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1178–1183, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25892
A broadband Fabry–Pérot cavity antenna designed using an improved resonance prediction method
Authors: Kim Dongho , Ju Jeongho , Choi Jaeick
Published: March 2011

We have proposed a wideband Fabry–Pérot cavity (FPC) base station antenna for wireless broadband Internet (WiBro) service in Korea. To widen the radiation bandwidth of our antenna, unit cells printed on a superstrate have been gradually tapered according to a proposed linear tapering equation. Also, all openings in the lateral directions have been enclosed using four metallic sidewalls to enhance the overall performance of the antenna by reducing unnecessary wave leakage. Furthermore, the radiation aperture has been designed in a rectangular shape to create sharp and sectoral beam shapes in the elevational and azimuthal directions, respectively. For a more accurate determination of the FPC resonance, an improved prediction formula has been used. We have demonstrated the basic principle of bandwidth widening using higher mode behavior, which appears at a higher frequency region by means of tapered cells on the superstrate. In addition, to show the effectiveness of simple tapering of unit cells, we have compared the performance of two antennas covered with the tapered and uniform (nontapered) superstrate. Tapering the unit cells has expanded the fractional radiation bandwidth about four times wider than that of the antenna using uniform unit cells. The measured behaviors of our antenna are in good agreement with the simulated data, which confirms the validity of our design and analysis approach. The measured behaviors of our antenna are in good agreement with the simulated data, which confirms the validity of our design and analysis approach. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1065–1069, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25898
Bandpass filter using short stubs and step impedances lines for ultra‐wideband applications
Authors: Ryu Keun‐Kwan
Published: March 2011

A bandpass filter is designed for the applications of ultra‐wideband (UWB) wireless communication.The designed bandpass filter covers the whole UWB passband of 3.1–10.6 GHz, and its construction is achieved by using a distributed high‐pass filter with frequent short‐circuited stubs and a low‐pass filter with step impedance lines. Within the whole UWB passband, the insertion loss lower than 1.65 dB and the group delay variation less than 0.27 ns are measured. This bandpass filter for UWB applications has the miniature size of 9.5 × 5.0 mm2, and the measured electrical performances have good agreement with simulation results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1062–1065, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25899
Fluorescence spectroscopy characterization of cadmium sulfide quantum dots on metal, insulator, and semiconductor substrates
Authors: Daniels‐Race Theda , Thiruvengadam Sathish
Published: March 2011

Colliodal cadmium sulfide quantum dots (Q‐CdS), ranging in size from 1 to 5 nm and capped with dioctyl sulfosuccinate (AOT), were synthesized and deposited upon substrates of gold (Au), mica, and gallium arsenide (GaAs). Fluorescence spectroscopy is used to identify the range and maxima of excitation and emission spectra of each structure. A red shift in emission spectra from the Au to mica to GaAs substrate based samples is observed for the smallest‐sized quantum dots. The midrange and largest‐sized dots display the longest emission wavelengths when physisorbed to the Au substrates with a shift to shorter and then longer emission wavelengths for the mica and GaAs‐based samples, respectively. The display of emission spectra throughout the visible range for the Q‐CdS deposited on all three types of substrates bodes well for future optical device applications using hybrid (organic–inorganic) electronic materials. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1018–1021, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25904
Polymer‐coated fiber Bragg Grating Sensor for cryogenic temperature measurements
Authors: Parne Saidi , Sai Prasad R. L. N. , Dipankar Sen Gupta , Sai Shankar M. , Kamineni Srimannarayana
Published: March 2011

Cryogenic temperature sensing has been demonstrated using Polymer coated Fiber Bragg Grating Sensor, and the experimental results are presented in this article. Teflon coating thicknesses of 20 and 40 μ applied on Fiber Bragg Gratings, inscribed in silica fiber (TFBG) are used for these studies. It was observed that the sensitivity of Teflon‐coated FBG has been enhanced three times compared to uncoated regular FBGs. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1154–1157, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25914
Compact size planar folded pifa design for mobile handset
Authors: Sim Chow‐Yen‐Desmond , Cheng Po‐Chun , Lee Ching‐Her
Published: March 2011

A printed compact size folded inverted‐F antenna with simple configuration for mobile handset operating within the global system for mobile communication/personal communication system/digital communication system bands is initially proposed.To additionally cover the wireless local‐area network frequency spectrum at 2.4 GHz, a narrow stub is protruded from the printed shorting wall. The excitation of these operating bands with desirable bandwidth is achieved by feeding a 50‐Ω microstrip line to the folded radiating element through a via hole. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1045–1050, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25919
Quadrature phase‐shifted white‐light interferometry for the measurement of short‐cavity extrinsic fabry–perot interferometric sensors
Authors: Wang Gao
Published: March 2011

A quadrature phase‐shifted white‐light interferometry is demonstrated to interrogate short‐cavity extrinsic Fabry–Perot interferometric (EFPI) sensors. The absolute cavity length of an EFPI can be recovered by constructing two quadrature signals using the white‐light spectrum of the EFPI. Experimental results show that the measurement resolution can be improved, and a linear output is obtained when interrogating an EFPI temperature sensor. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1011–1015, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25920
A simple stepped‐impedance transmission line load network for inverse Class F power amplifiers
Authors: Grebennikov Andrei
Published: March 2011

In this article, a novel simple load network with harmonic tuning, which is based on a stepped‐impedance transmission line is presented.Based on effect of a spectrum narrowing when poles of the reactance function are approaching adjacent zeros with higher transmission line impedance ratio, an open circuit at the second harmonic and a short circuit at the third harmonic are achieved, thus satisfying inverse Class F conditions. Design example of the load network with second and third harmonic tuning and effect of the device output shunt capacitance Cout and series inductance Lout with design equations are described and analyzed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1157–1160, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25923
Vivaldi with tunable narrow band rejection
Authors: Hamid M. R. , Gardner P. , Hall P. S. , Ghanem F.
Published: March 2011

A novel Vivaldi antenna is presented with tunable narrow band rejection characteristics within the overall operating bandwidth. A microstrip line resonator is incorporated within the Vivaldi antenna to give a narrow stop band action. Three varactors are loaded into the resonator and are used for tuning. The stop band can be activated in the frequency range between 2 and 7 GHz to give a very wide tuning ratio of 3.5:1. Good agreements between simulated and measured results are observed, which verify the design concepts. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1125–1128, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25924
Design of high‐permittivity rectangular dielectric resonator antenna
Authors: Madhuri R. G. , Hadalgi P.M. , Hunagund P. V.
Published: March 2011

In this article, a high‐permittivity rectangular dielectric resonator antenna is proposed. In this configuration, wideband operation is achieved by loading a rectangular dielectric resonator on the center of the rectangular ring slot. Dielectric resonators of three different thicknesses have been studied. In this configuration, slot acts as an effective radiator and the feeding structure of the dielectric resonator. The dual‐band resonances of the two radiators, i.e., slot and dielectric resonator are combined to extend the antenna bandwidth. The measured impedance bandwidth obtained is about 81.7%. The return loss, radiation pattern, and half power beam widths are measured and presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1077–1079, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25927
Switchable dual‐wavelength passively Q‐switched erbium‐doped fiber ring laser using nonlinear polarization rotation technique
Authors: Liu Jia‐Rui , Luo Zhi‐Chao , Luo Ai‐Ping , Yin Hai‐Sen , Xu Wen‐Cheng
Published: March 2011

We experimentally demonstrate a switchable dual‐wavelength passively Q‐switched pulsed operation in an Erbium‐doped all‐fiber ring laser utilizing the nonlinear polarization rotation technique.At a low pump power of 25 mW, Q‐switched pulse train possessing a temporal repetition rate of 12.7 kHz as well as a pulse width of 8.4 μs is generated stably with dual wavelengths centered at 1569.92 nm and 1587.28 nm. In addition, the switching operation between the two wavelengths can be facilely implemented by carefully adjusting the polarization controllers. Self‐mode‐locking effect is also observed and discussed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1000–1003, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25930
Quasi optical phase shifter using cascaded split slot ring frequency selective surfaces
Authors: Euler M. , Fusco V. F.
Published: March 2011

In this article, a prototype X band scale model of a quasi‐optical phase shifter is characterized to demonstrate the utility of the architecture proposed. The prototype arrangement utilizes three double layer split slot ring frequency selective surfaces. It is shown experimentally that the transmission phase of an incident linearly polarized signal can be varied from 0 to 2 π radians over the frequency range of 9.5–10.3 GHz in a linear manner. Over this frequency range, the insertion loss of the assembly varies between 2.5 dB, at 10 GHz, to 6 dB at 9.6 GHz, while axial ratio varies between 25 dB to a worst case value of 5 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:972–974, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25931
A compact CPW‐FED circular patch antenna with pattern and polarization diversities
Authors: Wei Kunpeng , Zhang Zhijun , Chen Wenhua , Feng Zhenghe
Published: March 2011

A compact coplanar waveguide (CPW)‐fed microstrip antenna with pattern and polarization diversities is proposed in this article.By making use of even and odd modes of a CPW feed network, a circular patch antenna operating at TM11 and TM01 modes can be excited, which results in broadside and conical monopole‐like radiation patterns being achieved at an overlapping frequency range for 2.4GHz WLAN applications. The impedance bandwidth (VSWR ≤ 2) are 520 MHz (2.18–2.70 GHz, 21%) and 480 MHz (2.26–2.74 GHz, 20%) for broadside TM11 mode and conical TM01 mode, respectively. The measured isolation is better than 22 dB across the working bandwidth. The measured radiation pattern and gain of the proposed antenna are compared with simulation results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:968–972, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25932
A planar aperture‐coupled patch antenna implemented on dashboard foams for intra‐vehicle communication
Authors: Boeykens Freek , Doolaege Quinten , Declercq Frederick , Rogier Hendrik
Published: March 2011

A robust low‐profile aperture‐coupled quasi‐circularly polarized patch antenna was designed for intra‐vehicle communication in the unlicensed 2.45‐GHz ISM band (2.4–2.485 GHz). As dashboards offer a large platform for invisible integration, the antenna is implemented using materials compatible with the production process of dashboards. This also allows easy, invisible, and low‐cost integration inside a car's dashboard. A measured gain of 6.437 dBi and nearly circular polarization were obtained with the antenna covered by the different dashboard layers. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1186–1189, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25933
Clonal selection algorithm application to simple microwave matching network
Authors: Deniz Ezgi , Ülker Sadik
Published: March 2011

Artificial immune systems are classified as computational systems inspired by theoretical immunology and are mechanisms that can solve complex problems. Clonal selection algorithm is a selection algorithm, which is derived as a special selection algorithm to this artificial intelligence concept. In this work, Clonal selection algorithm is applied to design a simple microwave matching network for a load with arbirtary impedance. The results obtained were tested in a microwave simulator and indicated that clonal selection algorithm can be very effectively applied for microwave design problems. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:991–993, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25935
Compact dual‐band bandpass filter using octagonal split‐ring resonators with side‐coupled stubs
Authors: Liu H. W. , Shen L. , Guan X.H. , Huang D. C. , Lim J. S. , Ahn D.
Published: March 2011

A compact dual‐band bandpass filter using side‐coupled octagonal split‐ring resonators (SRR) is introduced in this letter. The proposed filter employs two sets of SRRs operating at different frequencies to generate two passbands. Besides, the side‐coupled stubs provide sufficient degrees of freedom to control the bandwidth of the two passbands. Four transmission zeros can be created close to passband edges which leads to high skirt selectivity. Measured results are in good agreement with the EM simulation results. The circuit size of the proposed filter occupies only 22.4 × 12.6 mm2 (≈0.25 × 0.14 λg). © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1169–1171, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25938
Measurement and modeling of multiuser multiantenna system in aircraft in the presence of electromagnetic noise and interference
Authors: R. Sai Ananthanarayanan P. , Richards Alyssa Magleby , Furse Cynthia
Published: March 2011

This article evaluates the accuracy with which the performance of a multiuser multiantenna system can be predicted with and without considering cochannel interference and noise (Gaussian, α‐stable, and Cauchy) using a site‐specific three‐dimensional (3D) ray tracing algorithm as well as with statistical models with Gaussian and Nakagami‐m channel models in small to medium sized aircraft. These models expand on previous statistical channel models such as the hyper‐Rayleigh model by including the simultaneous effects of cochannel and adjacent channel interference, antenna matching, efficiency, directivity and polarization as well as (for the 3D model) site‐specific multipath effects. Measurements and comparisons are made in a metallic‐bodied Beech Baron BE 58P and a composite structure Rockwell T‐39 Sabreliner. It was found that the 3D ray tracing model provides a mean capacity within 1% of those measured in the two aircraft in the presence of interference and noise. This was closely followed by the Nakagami‐m distribution (m = 1.4), which was within 1–3% of measured capacity in the presence of interference and within 6% for a combination of interference and noise and the Gaussian model which was within 6% of measured capacity in the presence of interference and within 11% for a combination of interference and noise. The Cauchy noise degraded the capacity more than the other types of noise in the aircraft, providing a lower bound for capacity in an aircraft system. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1137–1144, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25939
Interferometry technique for refractive index measurements at subcentimeter wavelengths
Authors: Andrushchak N. A. , Syrotynsky O. I. , Karbovnyk I. D. , Bobitskii Ya. V. , Andrushchak A. S. , Kityk A. V.
Published: March 2011

We demonstrate the interferometry technique for the refractive index measurements at subcentimeter wavelengths. The method is based on a path length sweeping being introduced into one of the interferometer arms, while the sample is tilted out of its normal position with respect to the incident electromagnetic radiation. The determination of the refractive index is realized through the recording of the interference patterns at several tilt angles. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1193–1196, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25944
Efficient characterization of multilayered microwave wireless circuits on gyrotropic dielectric media including magnetized ferrites
Authors: Tounsi Mohamed Lamine , Yagoub Mustapha C. E.
Published: March 2011

The ever‐growing use of anisotropic ferrite devices in modern wireless communication systems highlighted the need for robust design tools to reliably characterize the dispersion behavior of such devices in radio frequency (RF)/microwave bands, especially for multilayered configurations. Indeed, as ferrites present a biaxial anisotropy, spectral analysis of multilayered configurations with such substrates is not generalized, however, restricted to some particular cases of tensors. Therefore, this article deals with the characterization of anisotropy effects on the dispersion parameters of multilayered wireless circuits with ferrite substrates, particular case of gyrotropic medias. In the proposed approach, a rigorous analysis was carried out by taking into account, for the first time, the electrical aspect of anisotropy. The computed results are in good agreement with those available in the literature. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:978–982, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25951
Multiple Sclerosis: Where Will We Be in 2020?
Authors: Miller Aaron E.
Published: March 2011

The past decade has seen a surge of research interest in multiple sclerosis and an accelerated expansion of investigative efforts into multiple sclerosis therapeutics. Investigators have continued dissecting the complex immunological perturbations that may contribute to the disease and made major advances in understanding the genetics of multiple sclerosis. This article addresses current investigative issues and offers predictions about where the understanding and treatment of multiple sclerosis may stand at the end of the 21st century's second decade. Mt Sinai J Med 78:268–279, 2011. © 2011 Mount Sinai School of Medicine