bluuebunny/crossref_metadata_2025 huggingface dataset:
3,5‐Bis(trifluoromethyl)phenyl Sulfones for the Highly Stereoselective Julia–Kocienski Synthesis of α,β‐Unsaturated Esters and Weinreb Amides
Authors: Alonso Diego A. , Fuensanta Mónica , Gómez‐Bengoa Enrique , Nájera Carmen
Published: April 2008

The 3,5‐bis(trifluoromethyl)phenyl (BTFP) sulfones tert‐butyl α‐(BTFPsulfonyl)acetate (4) and Weinreb α‐(BTFPsulfonyl)acetamide (5) have successfully been employed in the Julia–Kocienski olefination of aldehydes with K2CO3 as the base at 120 °C in DMF under solid/liquid phase‐transfer catalysis conditions to afford α,β‐unsaturated esters and Weinreb amides, respectively. The corresponding products were obtained in good yields and with high E stereoselectivities (E/Z up to >99:1), especially in the case of the amides. A detailed computational study of the Julia–Kocienski olefination with BTFP sulfone 4 was carried out and confirmed the existence of an equilibrium in the initial addition of the sulfone enolate to the aldehyde and, in contrast to other proposed mechanisms, a non‐concerted final elimination of SO2 and 3,5‐bis(trifluoromethyl)phenoxide. A plausible explanation for the high E diastereoselectivity observed in the reaction has been suggested based on kinetic considerations at spirocyclic TS2 and thermodynamic factors during the elimination after TS2. ESI‐MS studies carried out during the olefination reaction of benzaldehyde with BTFP sulfone 4 were used to characterize the sulfone enolate and the intermediate assumed for the reaction mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Annulation of Seven‐Membered Rings to [2.2]Paracyclophane
Authors: Ramm Sonja Margaretha , Hopf Henning , Jones Peter G. , Bubenitschek Peter , Ahrens Birte , Ernst Ludger
Published: April 2008

Tropylidenes 16 and 17 were prepared from [2.2]paracyclophane (10). On treatment with the corresponding trityl salts they were converted into tropyliophanes 26a (tetrafluoroborate) and 26b (perchlorate). With acetone, 26a furnished trapping product 27, which underwent a homo‐Diels–Alder addition with tetracyanoethylene to afford adduct 29. All new compounds were characterized by their spectroscopic and analytical data and for most – including 17 and 26b – the structures were also determined by X‐ray diffraction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Bismuth Film Microelectrode Modified with Overoxidized Poly‐1‐Naphtylamine Protective Membrane for Enhanced Stripping Voltammetric Detection
Authors: Slavec Marija , Hočevar Samo B. , Ogorevc Božidar
Published: April 2008

The application of protective overoxidized poly‐1‐naphtylamine membrane (ONAP) is demonstrated in combination with bismuth film microelectrode (ONAP‐BiFME) for anodic stripping voltammetric measurement of trace heavy metals in the presence of some selected surfactants. The ONAP membrane was electrochemically deposited on the surface of bare single carbon fiber microelectrode followed by the in situ or ex situ preparation of the bismuth film. The key operational parameters influencing the stripping performance of the ONAP‐BiFME were optimized and its electroanalytical performance was examined in the model solution containing Cd(II) and Pb(II) as test metal ions. The ONAP‐BiFME exhibited significantly enhanced stripping voltammetric response (approximately 70% for Cd(II) and 45% for Pb(II)) in comparison with unmodified BiFME in the absence of surfactants. In the presence of high concentrations, e.g., 20 mg L−1, of anionic or cationic surfactants, the stripping signal for, e.g., Cd(II) decreased for less than 6% at the ONAP‐BiFME, whereas at the unmodified BiFME the signal attenuated considerably (approximately 38%). Moreover, in the presence of 10 mg L−1 of nonionic surfactant Triton X‐100, the stripping signals at the bare BiFME were almost completely suppressed, whereas at the ONAP‐BiFME exhibited linear concentration behavior in the examined concentration range from 10 to 120 μg L−1, with the calculated limit of detection of 5.0 μg L−1 and 3.4 μg L−1 for Cd(II) and Pb(II), respectively in connection with 60 s accumulation time. The attractive behavior of ONAP‐modified BiFME expands the applicability of bismuth‐based electrodes for measurement of trace heavy metals in real environments, where the presence of more complex matrix can be expected.
Adenine Determination in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode
Authors: Farias Percio Augusto Mardini , Aguiar Castro Arnaldo , de Luca Rebello Wagener Angela , Monsores Miguel Eliane
Published: April 2008

Highly sensitive, simple and inexpensive techniques of adenine determination are particularly interesting in relation to the present development of ATP and DNA sensors. A nanomolar concentration of adenine can be determined in the presence of copper. For an accumulation time of 30 minutes, the detection limit found was 0.22 ppb (1.63×10−9 M). The method is based on controlled adsorptive accumulation of adenine‐copper at thin‐film mercury electrode followed by linear scan voltammetric measurement of the surface species. By applying a condition time of 60 s at −0.9 V, the same thin‐film can be used over several measurements. Optimum experimental conditions were found to be the use of a 5.0×10−3 M NaOH solution, an accumulation potential over the −0.20 to −0.40 V range, and a scan rate of 100 mV s−1. The response of adenine‐copper is linear over the concentration range 20–100 ppb. The more convenient ways to measuring adenine in the presence of metals and other nitrogenated bases were also investigated. The adenosine triphosphate (ATP) or deoxyribonucleic acid (DNA) are first treated with acid (e.g., 0.1 M perchloric acid), and the acid‐released adenine (without separation from others products of the degradation) is directly determined by adsorptive stripping voltammetry.
Constant Current Chronopotentiometry and Voltammetry of Native and Denatured Serum Albumin at Mercury and Carbon Electrodes
Authors: Ostatná Veronika , Kuralay Filiz , Trnková Libuše , Paleček Emil
Published: April 2008

Constant current chronopotentiometric peak H at mercury electrodes was recently shown as a sensitive tool for global and local changes in protein conformation [1]. Large differences between the heights of peak H of native (hBSAnat) and denatured BSA (hBSAden) were observed. The ratio hBSAden/hBSAnat increased with more negative stripping current suggesting that the rate of potential change is important for discrimination between native and denatured BSA. Voltammetric peaks of BSA were less well developed and BSAden/BSAnat was much smaller. It was not possible to discriminate BSAden and BSAnat using carbon electrodes.
Particle holdup in a liquid–solid circulating fluidized bed
Authors: Hashizume Kenichi , Morita Shinichi
Published: April 2008

An experiment was conducted to acquire a set of systematic data of particle holdup in risers of a liquid–solid circulating fluidized bed. In the experiment, two kinds of riser were provided, their inner diameter being 24 mm and 36 mm, respectively. Tested particles were of glass and ceramics, having a diameter range from 2.10 to 4.95 mm. Water at ambient conditions was used as the fluidizing liquid. Particle holdup was measured using a shut‐off method. Based on the experimental data, a correlation for predicting the particle holdup was derived, which could reproduce almost all experimental data with an accuracy of ±15%. The effect of the wall was not recognized within the experimental range, i.e., the diameter ratio of particle to riser is less than 0.2. The independent parameters affecting the flow characteristics of liquid–solid circulating fluidized beds were identified. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 184–196, 2008; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/htj.20194
Enhancement of heat transfer in hydrogen storage tank with hydrogen absorbing alloy (optimum fin layout)
Authors: Mitsutake Yuichi , Monde Masanori , Shigetaka Kengo , Tsunokake Shigeru , Fuura Tatsuya
Published: April 2008

Optimization of the fin layout in a metal hydride (MH) bed has been sought to enhance poor heat transmission in a hydrogen storage tank, and to obtain a maximum hydrogen absorption rate with a smaller volume of fins. Two different fin configurations, radial and circular fins, in a vertical cylindrical reactor vessel were tested with a La‐Ni‐based AB5 type hydrogen storage alloy. A two‐dimensional transient heat conduction analysis, coupled with predicted temperature and concentration of absorbed hydrogen in the bed for the exothermic hydride reaction, was used to evaluate enhancement of the hydrogen absorption time. The estimated temperature and concentration agreed within 6 K and 8.5%, respectively, with our experimental results. The effect of thickness and the spacing and shape of fins on the hydrogen absorption time were analytically evaluated, so that the optimum range of the each fin layout was obtained by the trade off between absorption time and reduction in the MH volume due to the volume occupied by fins. The hydrogen absorption time for the recommended layout of circular fins was reduced to approximately one‐third of that without fins. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 165–183, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20195
Heat transfer characteristics of liquid–solid circulating fluidized beds
Authors: Hashizume Kenichi , Kimura Yoichi
Published: April 2008

An experiment was conducted to obtain heat transfer data in liquid–solid circulating fluidized beds. In the experiment, two kinds of risers were provided, their inner diameter being 24 mm and 12 mm, respectively. Tested particles were of glass and ceramics, having a diameter range from 2.10 to 4.95 mm. Water at ambient conditions was used as the fluidizing liquid. The experimental data showed a trend where the heat transfer coefficient increases gradually with increasing liquid velocity approaching that for a liquid single‐phase flow (“heat transfer enhanced region”), and finally coincides with that for a liquid single‐phase flow (“liquid single‐phase heat transfer region”). The heat transfer coefficient in the heat transfer enhanced region was found to be a function of the slip velocity between liquid and particles. Based on the experimental data, a correlation was proposed for predicting the heat transfer coefficient in the entire region from the heat transfer enhanced region to the liquid single‐phase heat transfer region, which could reproduce the experimental data with an accuracy of ±15%. The proposed correlation agreed well with existing data. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 127–137, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20200
The interaction of human neuroglobin with hydrogen sulphide
Authors: Brittain Thomas , Yosaatmadja Yuliana , Henty Kristen
Published: April 2008

Neuroglobin has been identified to protect brain neurons from apoptotic stress. Hydrogen sulphide has a role in the brain as a neuromodulator, involving NMDA receptor activation. Here we report on studies of the in vitro interaction of ferric neuroglobin with hydrogen sulphide. Hydrogen sulphide binds very tightly to the heme group of neuroglobin in a biphasic reaction. The faster of the two reaction processes is concentration dependent whilst the slower process is not. The rate of hydrogen sulphide binding is pH sensitive and as the pH is reduced over the physiological range the rate of reaction increases by a factor of ∼10. This change in reactivity appears to reflect the ionisation of the heme distal His ligand rather than a preference for the binding of H2S. We discuss the potential role of neuroglobin in the modulation of hydrogen sulphide sensitivity of neurons in the brain. © 2008 IUBMB IUBMB Life, 60(2): 135–138, 2008
Signaling mechanisms in skeletal muscle: Acute responses and chronic adaptations to exercise
Authors: Röckl Katja S.C. , Witczak Carol A. , Goodyear Laurie J.
Published: April 2008

Physical activity elicits physiological responses in skeletal muscle that result in a number of health benefits, in particular in disease states, such as type 2 diabetes. An acute bout of exercise/muscle contraction improves glucose homeostasis by increasing skeletal muscle glucose uptake, while chronic exercise training induces alterations in the expression of metabolic genes, such as those involved in muscle fiber type, mitochondrial biogenesis, or glucose transporter 4 (GLUT4) protein levels. A primary goal of exercise research is to elucidate the mechanisms that regulate these important metabolic and transcriptional events in skeletal muscle. In this review, we briefly summarize the current literature describing the molecular signals underlying skeletal muscle responses to acute and chronic exercise. The search for possible exercise/contraction‐stimulated signaling proteins involved in glucose transport, muscle fiber type, and mitochondrial biogenesis is ongoing. Further research is needed because full elucidation of exercise‐mediated signaling pathways would represent a significant step toward the development of new pharmacological targets for the treatment of metabolic diseases such as type 2 diabetes. © 2008 IUBMB IUBMB Life, 60(3): 145–153, 2008
Microtubules: A dynamic target in cancer therapy
Authors: Pasquier Eddy , Kavallaris Maria
Published: April 2008

The tubulin/microtubule system is an important target for anticancer therapy. Two of the most clinically valuable groups of these agents are the vinca alkaloids and taxanes. In recent years, new tubulin‐binding agents have been under preclinical or clinical development. One of these classes of agents, epothilones, has shown great promise in phase III clinical trials. What all these agents share in common, is that they bind to β‐tubulin and disrupt microtubule function during mitosis which in turn leads to mitotic arrest and cell death. In addition, these agents can inhibit angiogenesis. Not withstanding their effectiveness, drug resistance can pose a major clinical problem. This review provides an overview of the mechanisms mediating resistance to tubulin‐binding agents related to the cellular target and discusses strategies to overcome this important clinical problem. © 2008 IUBMB IUBMB Life, 60(3): 165–170, 2008
The role of PAS kinase in regulating energy metabolism
Authors: Hao Huai‐Xiang , Rutter Jared
Published: April 2008

Metabolic disorders, such as diabetes and obesity, are fundamentally caused by cellular energy imbalance and dysregulation. Therefore, understanding the regulation of cellular fuel and energy metabolism is of great importance to develop effective therapies for metabolic disease. The cellular nutrient and energy sensors, AMPK and TOR, play a key role in maintaining cellular energy homeostasis. Like AMPK and TOR, PAS kinase (PASK) is also a nutrient responsive protein kinase. In yeast, PAS kinase phosphorylates the enzyme Ugp1 and thereby shifts glucose partitioning toward cell wall glucan synthesis at the expense of glycogen synthesis. Consistent with this function, yeast PAS kinase is activated by both cell integrity stress and growth in non‐fermentative carbon sources. PASK is also important for proper regulation of glucose metabolism in mammals at both the hormonal and cellular level. In cultured pancreatic β‐cells, PASK is activated by elevated glucose concentrations and is required for glucose‐stimulated transcription of the insulin gene. PASK knockdown in cultured myoblasts causes increased glucose oxidation and elevated cellular ATP levels. Mice lacking PASK exhibit increased metabolic rate and resistance to diet‐induced obesity. Interestingly, PGC‐1 expression and AMPK and TOR activity were not affected in PASK deficient mice, suggesting PASK may exert its metabolic effects through a new mechanism. We propose that PASK plays a significant role in nutrient sensing, metabolic regulation, and energy homeostasis, and is a potential therapeutic target for metabolic disease. © 2008 IUBMB IUBMB Life, 60(4): 204–209, 2008
SWAP‐70 is important for invasive phenotypes of mouse embryo fibroblasts transformed by v‐Src
Authors: Murugan Avaniyapuram Kannan , Ihara Sayoko , Tokuda Emi , Uematsu Kimio , Tsuchida Nobuo , Fukui Yasuhisa
Published: April 2008

SWAP‐70 is a protein involved in actin rearrangement, especially in membrane ruffling. Mouse embryo fibroblasts (MEFs) deficient in SWAP‐70 show impaired membrane ruffling and fail to grow in soft agar after transformation by v‐Src. Here, we show that v‐Src transformed MEFs expressing SWAP‐70 are highly invasive. MEFs expressing SWAP‐70 or v‐Src alone were far less invasive, suggesting that both proteins were required for the cells to be invasive. Expression of both SWAP‐70 and v‐Src induced constant membrane ruffling, which may cause vigorous cell movement, probably required for invasiveness of the cells. Expression of v‐Src alone morphologically transformed MEFs but formed lamellipodia rather than membrane ruffles, suggesting less aggressive nature of the cells compared with those expressing both SWAP‐70 and v‐Src. These results suggest that v‐Src and SWAP‐70 act synergistically in the invasion activity of MEFs. © 2008 IUBMB IUBMB Life, 60(4): 236–240, 2008
Steroid and thyroid hormone receptors in mitochondria
Authors: Psarra Anna‐Maria G. , Sekeris Constantine E.
Published: April 2008

Receptors for glucocorticoids, estrogens, androgens, and thyroid hormones have been detected in mitochondria of various cell types by Western blotting, immunofluorescence labeling, confocal microscopy, and immunogold electron microscopy. A role of these receptors in mitochondrial transcription, OXPHOS biosynthesis, and apoptosis is now being revealed. Steroid and thyroid hormones regulate energy production, inducing nuclear and mitochondrial OXPHOS genes by way of cognate receptors. In addition to the action of the nuclearly localized receptors on nuclear OXPHOS gene transcription, a parallel direct action of the mitochondrially localized receptors on mitochondrial transcription has been demonstrated. The coordination of transcription activation in nuclei and mitochondria by the respective receptors is in part realized by their binding to common trans acting elements in the two genomes. Recent evidence points to a role of the mitochondrial receptors in cell survival and apoptosis, exerted by genomic and nongenomic mechanisms. The identification of additional receptors of the superfamily of nuclear receptors and of other nuclear transcription factors in mitochondria increases their arsenal of regulatory molecules and further underlines the central role of these organelles in the integration of growth, metabolic, and cell survival signals. © 2008 IUBMB IUBMB Life, 60(4): 210–223, 2008
The Poisson‐Boltzmann model for tRNA: Assessment of the calculation set‐up and ionic concentration cutoff
Authors: Gruziel Magdalena , Grochowski Pawel , Trylska Joanna
Published: April 2008

Using tRNA molecule as an example, we evaluate the applicability of the Poisson‐Boltzmann model to highly charged systems such as nucleic acids. Particularly, we describe the effect of explicit crystallographic divalent ions and water molecules, ionic strength of the solvent, and the linear approximation to the Poisson‐Boltzmann equation on the electrostatic potential and electrostatic free energy. We calculate and compare typical similarity indices and measures, such as Hodgkin index and root mean square deviation. Finally, we introduce a modification to the nonlinear Poisson‐Boltzmann equation, which accounts in a simple way for the finite size of mobile ions, by applying a cutoff in the concentration formula for ionic distribution at regions of high electrostatic potentials. We test the influence of this ionic concentration cutoff on the electrostatic properties of tRNA. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008
Inclusion of the quadrupole moment when describing polarization. The effect of the dipole‐quadrupole polarizability
Authors: Holt Asbjørn , Karlström Gunnar
Published: April 2008

A method to compute distributed dipole–quadrupole polarizabilities is suggested. The method is based on numerical differentiation of distributed quadrupole moments, using finite field perturbation calculations. It is tested using two different multicenter multipole expansions, and compared with results using polarizabilities obtained via the uncoupled Hartree–Fock approximation. The accuracy of these dipole–quadrupole polarizabilities are tested for different molecules and basis sets, by comparing the induced electrostatic potential of the Hartree–Fock density with the induced electrostatic potential of the polarization models. This is done by perturbing the molecules with an external homogeneous field and with an external dipole. It is found that inclusion of the dipole–quadrupole polarizability significantly improves the accuracy of the response of the molecule to these external perturbations. This suggests that inclusion of higher‐order induced moments can be of importance when improving the description of intermolecular interactions using force fields. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Treatment of methanol vapours in biofilters packed with inert materials
Authors: Avalos Ramirez Antonio , Bénard Sandrine , Giroir‐Fendler Anne , Jones J Peter , Heitz Michèle
Published: April 2008

BACKGROUND: Methanol is a major pollutant emitted in Canada. Methanol is toxic to humans and it is associated with environmental problems such as smog generation. Biofiltration is a treatment method of considerable interest for controlling methanol emissions, because of its characteristics: no production of hazardous wastes, low energy consumption and low operating costs. The present study analyzed the effects of porous and non‐porous packing materials, the nitrogen concentration in nutrient solution and the methanol inlet load on biofilter performance and biofilm characteristics.

RESULTS: The biofilter packed with porous material presented a removal efficiency up to 95%, which was higher than the 35% removal efficiency with the non‐porous material. Inlet load (IL) influenced the biomass and carbon dioxide production rates. The critical inlet load (ILcrit) occurred at 80 g m−3 h−1. The cellular densities of methylotrophs and non‐methylotrophs were affected by all operating variables examined.

CONCLUSION: Biofiltration can be applied for controlling methanol emissions with high removal efficiency. The cellular density of methylotrophs is correlated with the performance of the biofilter. Copyright © 2008 Society of Chemical Industry
Larval morphology of the brooding clam Lasaea adansonii (Gmelin, 1791) (Bivalvia, Heterodonta, Galeommatoidea)
Authors: Altnöder Andreas , Haszprunar Gerhard
Published: April 2008

The strongly modified mode of development of the small and brooding galeommatoid bivalve Lasaea adansonii (Gmelin, 1791) [syn. Lasaea rubra (Montagu, 1803)] has been studied by means of transmission and scanning electron microscopy and by fluorescent staining of the muscular system and of two neurotracers, FMRFamide and serotonin. In addition, two developmental stages were visualized using computer‐aided 3D‐reconstruction. All larval stages of L. adansonii lack ciliary rings. The apical organ appears invaginated: the base of the duct contacts the cerebral ganglia and opens on the preoral region. Larval protonephridia are lacking. The adult kidneys develop independently of the pericardial cavity and contain a protonephridial part that enables excretory function until the pericardium is formed. The larval muscular system is composed of smooth muscle fibers; striated fibers are lacking. Posteriorly and immediately below the ligament, a paired cell of unknown function is present that contains serotonin and FMRFamide. In summary, L. adansonii exhibits the direct mode of development. Only few truly larval structures (e.g., the modified apical organ) are elaborated. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.
Surface topology and structural integrity of the Theromyzon tessulatum (Annelida: Hirudinea: Glossiphoniidae) cocoon
Authors: Coleman Jon'elle , Marotta Roberto , Shain Daniel H.
Published: April 2008

Cocoons secreted by the aquatic leech Theromyzon tessulatum comprise a tubular, membranous ovoid, sealed at each end by a glue‐like substance, called an operculum. Scanning electron microscopy showed surface features of the T. tessulatum cocoon that included a circuitous bulge, cups that conformed to the shape of embryos, relief folds that radiated from opercula, and asymmetric distributions of protuberances on the upper aspect of the cocoon surface. The structural integrity of the T. tessulatum cocoon was assessed after exposure to a variety of denaturing conditions (e.g., extreme heat, detergents, acids). Although both the fibrous cocoon membrane and opercula were strikingly resilient, the membrane/operculum boundary appeared to be the weakest structural component of the cocoon, consistent with its functional role as an escape hatch for juvenile leeches. The operculum itself was more sensitive to denaturation than the cocoon membrane, and thus was probably the source of a major protein component isolated from the T. tessulatum cocoon (i.e., Tcp; Theromyzon cocoon protein). J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.
Effects of estrogen on basal forebrain cholinergic neurons and spatial learning
Authors: Ping Sophie E. , Trieu Jennifer , Wlodek Mary E. , Barrett Graham L.
Published: April 2008

Estrogen receptors are expressed in several areas of the brain associated with cognition, including the basal forebrain cholinergic nuclei, and numerous reports have described improvements in memory in response to estrogen supplementation. The relationship between estrogen's effects on the basal cholinergic system and improvements in cognitive function, however, are obscure. We therefore undertook a study to determine the effects of estrogen on several parameters of the cholinergic system in ovariectomized rats and measured the concomitant effects on performance in the Barnes maze, a test of spatial memory. Six weeks of estradiol treatment caused an increase in choline acetyltransferase activity throughout the projection fields of the basal forebrain, including the hippocampal formation (14%), olfactory bulb (30%), and cerebral cortex (35%). Estrogen treatment also caused an increase in cell soma size of cholinergic neurons in the horizontal diagonal limb of the band of Broca and in the basal nucleus of Meynert. There was no change in the number of neurons positive for p75NTR, nor in the level of p75NTR expression per neuron. Barnes maze performance was markedly improved after estradiol treatment, reinforcing the view that estrogen has beneficial cognitive effects, particularly on spatial memory. The beneficial cognitive effect was likely mediated in part by stimulation of the basal forebrain cholinergic system, especially in its neocortical projection, but was not associated with changes in the level of p75NTR expression. © 2008 Wiley‐Liss, Inc.
Basis for the new challenges of growing broccoli for health in hydroponics
Authors: Moreno Diego A , López‐Berenguer Carmen , Martínez‐Ballesta M. Carmen , Carvajal Micaela , García‐Viguera Cristina
Published: April 2008

BACKGROUND: Variations in the contents of phytochemicals with biological activity in broccoli could originate as a result of genetic and environmental factors. An understanding of the effects of growth conditions on the bioactive compounds in broccoli is essential for improving its quality and nutritive value. Using salinity (40 mmol L−1 NaCl), and foliar sprayed compounds (methionine, tryptophan and chitosan) as different stress conditions, broccoli developed in soilless culture in the greenhouse was analysed for biologically active phytochemicals (glucosinolates, caffeoyl‐quinic, ferulic and sinapic derivatives and vitamin C).

RESULTS: The application of elicitors during head formation could be beneficial for the enrichment in phytochemicals in broccoli. Management practices for increasing a given phytochemical (e.g., glucoraphanin or glucobrassicin) may be related to a decreased level of natural antioxidants (hydroxycinnamic acids). Growing broccoli hydroponically in the greenhouse in winter (Mediterranean climate) needs the supporting treatment of abiotic stress during development (i.e., NaCl, elicitors).

CONCLUSION: The use of hydroponic growth conditions for broccoli and the application of stress factors (elicitors) at head induction and during development may serve the purpose of enhancing its nutritional quality to deliver a health‐promoting food. Copyright © 2008 Society of Chemical Industry
Local perceptions and regional climate trends on the Central Plateau of Burkina Faso
Authors: West C. T. , Roncoli C. , Ouattara F.
Published: April 2008

Due to devastating droughts in the 1970s and 1980s, climatic and environmental change in the West African Sahel has attracted a great deal of scientific research. While many of these studies documented a long‐term trend of declining rainfall, analyses conducted in the last few years suggest that a ‘recovery’ is underway. Drawing on ethnographic interviews, focus groups, and participant observation in two Provinces of the Central Plateau of Burkina Faso, we elicited local perspectives on these rainfall trends from the people who are most directly affected, namely local farmers. Fieldwork revealed that farmers in the research sites perceive that both overall seasonal rainfall and the number of ‘big rains’ during the rainy season have decreased over the last 30 years. We then tested these perceptions against rainfall records from nearby meteorological stations and found them to be corroborated. This paper illustrates how farmers of the Central Plateau now view drought as ‘normal’, having incorporated drought‐mitigation adaptations into their agricultural systems. Our case study highlights the need for ground truthing scientific analyses and assessing livelihood implications at the local level. It also advocates for sustained institutional support for rural communities, to increase their ability to adapt to climate change. Copyright © 2008 John Wiley & Sons, Ltd.
Genipin‐Modified Silk‐Fibroin Nanometric Nets
Authors: Silva Simone S. , Maniglio Devid , Motta Antonella , Mano João F. , Reis Rui L. , Migliaresi Claudio
Published: April 2008

Nanometric silk‐fibroin nets were fabricated by electrospinning from regenerated Bombyx mori silk‐fibroin (SF)/formic acid solutions with the addition of genipin (GE), 2, 15 and 24 h after the solution preparation. After spinning, the pure fibroin nanofibers were water soluble and needed a further stabilization process, whereas the reaction of fibroin with genipin resulted in water‐insoluble fibroin nets due to conformational changes induced in the fibroin by the genipin. SFGE nanofibers presented diameters ranging from 140 to 590 nm and were generally thinner than pure SF nanofibers. The secondary structure of SF into SFGE nanofibers showed the presence of a β‐sheet conformation together with β‐turn intermediates (turns and bends). The approach described in this paper provides an alternative method of designing SF nanofibers that are already water insoluble, without any stability post‐treatment needed.

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Tri‐band compact antenna array for MIMO user mobile terminals at GSM 1800 and WLAN bands
Authors: Gómez‐Calero Carlos , González Luis , Martínez Ramón
Published: April 2008

Multiple‐Input Multiple‐Output (MIMO) systems have been widely studied in recent years as a solution to improve the radio link reliability. To introduce MIMO in mobile communications, it is necessary to design antennas with differential features to introduce multiple elements in the space reserved for the antenna, such as the type of element or array configuration. In this article, a 2 × 2 MIMO system has been considered according to the next‐generation WLAN (802.11n) frequencies band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1914–1918, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23472
A novel compact microstrip bandpass filter using folded stepped impedance resonators
Authors: Yang Tao , Xu Ruimin , Xia Lei , Guo Yunchuan
Published: April 2008

A folded quarter‐wavelength stepped impedance resonator (SIR) is proposed with a largely reduced size. A bandpass filter with center frequency of 1.85 GHz using the SIRs is designed, fabricated, and measured. This compact filter covers an area less than 10 mm × 10 mm, which makes it suitable for compact and high‐performance microwave circuit applications. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1864–1867, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23476
The effect of FET soft turn‐on on a Doherty amplifier
Authors: Smith Karla J. I. , Eccleston Kimberley W. , Gough Peter T. , Mann Stephen I.
Published: April 2008

A Doherty amplifier's theoretical gain and efficiency characteristics significantly exceed those achieved by practical simulations and implementations. Analysis and simulation demonstrates that the FET gate voltage to drain current transfer characteristic has a significant detrimental effect on these characteristics, indicating it is the major factor in the difference between ideal and practical results. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1861–1864, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23477
ADI‐FDTD method perturbed by the second order cross derivative terms
Authors: Kong Ki‐Bok , Kim Jong‐Sung , Park Seong‐Ook
Published: April 2008

A two‐step FDTD method as a compromise of conditional stability and reduced splitting error is formulated and its numerical stability is investigated. It is the perturbed form to the ADI‐FDTD method by the addition of second order cross derivative term. It is validated from the comparison of numerical anisotropy and numerical error over the ADI‐FDTD that numerical performances can be improved by controlling the perturbed term within the stable region of the cross derivative term. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1822–1826, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23479
New perturbation technique to generate split modes in electromagnetically coupled notch filters using different ring resonators
Authors: Hari Krishna J. V. S , Karekar R. N , Aiyer R. C
Published: April 2008

A new method for generating split modes in ring resonators, used as notch filters with three geometries (square, triangular, and circular), is introduced by varying the feed position of electromagnetically coupled feed line. The resonators are fabricated (all at 2.4 GHz nominally) on TMM4 (εr = 4.5, h = 0.762 mm) substrates and coupled electromagnetically to a 50 Ω microstrip feed line on separate TMM4 substrate. Only the latter has ground plane under it. The offset distance between the center of feed line and center of resonator is varied and changes in the resonant (notch) frequency, rejection (S21) of single and split modes are recorded at each offset position for all resonators. Experimental results are found to agree with simulated results to a greater degree for square and lesser for other two geometries. Frequency variations have much more disagreements. The angle of crossing between feed line and ring edges appears to be a critical factor. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1747–1752, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23483
Design of ultra wideband microstrip 180 degree phase shifter
Authors: Eldek Abdelnasser A.
Published: April 2008

A Ultra Wideband microstrip 180 degree phase shifter is presented. It is obtained by a novel design of Microstrip‐to‐Coplanar Waveguide (CPW)‐to‐Microstrip transition. Via holes are used to transfer the current from the top to the bottom substrate layer and vice versa. The presented phase shifter is operating in a wide bandwidth between 5.5 and 17.2 GHz, with low insertion loss and reflection coefficients. This phase shifter can be used in phased arrays and power combiners. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1841–1844, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23487
Criteria for negative refraction in active and passive media
Authors: Kinsler P. , McCall M. W.
Published: April 2008

We review three commonly used conditions that characterize negative refraction in isotropic dielectric‐magnetic materials. We show that while all the different conditions are equivalent for passive media, they are distinct for different types of active media. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1804–1807, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23489
Permittivity measurement of biological materials with improved microwave cavity perturbation technique
Authors: Wang Zhanxian , Che Wenquan , Chang Yumei
Published: April 2008

The resonant cavity perturbation technique is usually used to measure the complex permittivity of various dielectric materials at microwave frequency. The values of real and imaginary part of the complex permittivity of the material under test can be deduced from the measured shift of resonant frequency and the change of quality factor (Q factor) of the resonance cavity with inserted samples. In this article, an improved resonance cavity perturbation technique is employed to measure the complex permittivity of biological materials, including porcine fat, marrow, and liver, etc. The measured results agree well with the known data, demonstrating the potential validity of our method. This method can be expected to extend to permittivity measurement of other biological material even the tissues from human body. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1800–1804, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23490
Design of a 5.8 GHz narrow band‐pass filter with second harmonic suppression using the open stubs
Authors: Yoon Ki‐Cheol , Lee Jong‐Chul
Published: April 2008

In this article, λg/2 open stub bandpass filters with flexible narrow bandwidth on duroid substrate are presented. This filters show flexible bandwidth with variation of the position of the open stubs using the external quality factor, Qe without changing the impedance value at microwave range. On the other hand, by replacing the series quarter‐wavelength connecting‐lines with the equivalent T‐shaped line, a compact stub bandpass filter with second harmonic suppression can be obtained. This filter shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1763–1766, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23492
A broadband, circular switched parasitic array for portable and vehicular mobile DVB‐T applications at the V UHF band
Authors: Panagiotou Stylianos C. , Mitilineos Stelios A. , Dimousios Themistoklis D. , Capsalis Christos N.
Published: April 2008

A broadband, circular switched parasitic array with two active elements, suitable for DVB‐T applications at the V‐UHF band is designed with the aid of a genetic algorithm. Numerical as well as measurements results are presented for a single switch position. Simulation results are also presented for switched‐beam array operation, using the measured antenna radiation patterns. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1727–1732, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23494
Broadband planar dipole antenna for DTV/GSM operation
Authors: Lee Cheng‐Tse , Wong Kin‐Lu
Published: April 2008

This article presents a new broadband planar dipole antenna for DTV signal reception in the UHF band (470 ∼ 862 MHz) and mobile communications in the GSM850/900 band (824 ∼ 894/890 ∼ 960 MHz), which requires an operating bandwidth (3:1 VSWR) of 490 MHz or about 69% centered at 715 MHz. The antenna has two radiating arms (arm 1 and arm 2) with a total length 230 mm and a width 14 mm, which are easily printed on an FR4 substrate. Broadband operation is obtained from successful excitation of the half‐ and one‐wavelength modes of the antenna, which is achieved by shifting the antenna's feeding point away from the dipole center through adding a tuning strip to arm 1 and embedding a tuning slot to arm 2. The tuning strip is extended across the tuning slot, and both are also formed as an internal matching circuit for achieving good impedance matching of the excited half‐ and one‐wavelength modes of the antenna. The proposed antenna is presented and studied. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1900–1905, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23500
Exact design of evanescent‐wave amplification using bilayer periodic circuit structures
Authors: Lin Xian Qi , Feng Ma Hui , Liu Ruopeng , Cheng Qiang , Cui Tie Jun
Published: April 2008

An efficient method is presented to design the evanescent wave amplification exactly by cascading two layers of periodic series‐shunt capacitors and inductors, which simulate a bilayer of magnetic and electric plasmas. Based on the presented method, equivalent lumped parameters of circuit structures are retrieved, from which the evanescent‐wave amplification (EWA) is obtained at a designed frequency. Full‐wave simulations show that the relative offset of the EWA frequency is less than 0.1%. The structure has been fabricated and measured, and the measurement results have good agreements with the simulation results. The proposed method can be used to design other periodic circuit structures, and the exact design of EWA can be used in the fabrication of novel components. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1870–1873, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23501
Compact cross‐coupled hairpin filter design using ceramic substrates
Authors: Huang Cheng‐Liang , Shen Chun‐Hsu , Lin Ling‐Mei
Published: April 2008

Cross‐coupled hairpin filter design using electrical‐coupling with asymmetric feed on ceramics was reported. The band‐pass filters are designed at center frequency of 2.0 (GHz) with bandwidth of 10%. In addition, this article presents an analytical technique for positioning the locations of two transmission zeros for a microstrip band‐pass filters. The band‐pass filter uses two resonators with two transmission zeros to obtain lower insertion loss than a conventional cross‐coupled microstrip filter. Also, by using high Q, high permittivity dielectric materials as substrates, the filters demonstrate high selectivity, compact size, and can be used in many wireless communication systems. A bandwidth of 10% with −0.75 dB insertion loss and −34 dB attenuation was achieved with chip size of 2.5 × 0.85 cm2. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1795–1800, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23505
Broadband and high gain slot antenna with adjustable polarization
Authors: Chu Yu‐Yi , Row Jeen‐Sheen
Published: April 2008

This article presents a wide slot antenna whose polarization can be adjusted by rotating a conducting strip. To obtain an optimum gain of the slot antenna, a parasitic patch and a metallic reflector were placed at the front and rear of the wide slot, respectively. A prototype of the proposed antenna was implemented and measured. Experimental results exhibit that the prototype can provide one linear polarization and dual circular polarization operations over a 10 dB‐return‐loss impedance bandwidth of 21%; moreover, the antenna gain is around 10 dBi for each polarization operation. Simulation results performed by HFSS are also shown and they agree with the measured results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1793–1795, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23506
MIMO handheld antenna design approach using characteristic mode concepts
Authors: Ethier Jonathan , Lanoue Eric , McNamara Derek
Published: April 2008

In handheld communications devices there is not much room for the placement of antennas. This problem is exacerbated when more than one antenna is needed for use in a MIMO communications system. It is then useful to be able to utilize some of the existing device structure to form the required antennas. In this article, we show how the characteristic mode theory can be used to achieve this in a way that results in antennas with the low envelope correlation preferred for MIMO antennas. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1724–1727, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23509
Implementation of tunable erbium doped fiber laser using a broadband fiber mirror
Authors: Liaw Shien‐Kuei , Jhong Guo‐Sing , Cho Li‐Ting , Chang Chu‐Lin
Published: April 2008

By using a broadband fiber mirror (BFM), a wavelength tunable erbium‐doped fiber laser (TEDFL) is demonstrated composed with tunable fiber Bragg grating (TFBG). The BFM acts as a broadband reflector both for the lasing signal and pump source. At pumping power of 100 mW, stable laser output power of 21.35 dBm is obtained at a low threshold pumping power of 4.7 mW. A side mode suppression ratio (SMSR) of 57.9 dB and 16 nm wavelength scan range are demonstrated using a single TFBG. The tunable fiber laser may be a good candidate for vast applications in optical network technologies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1722–1724, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23510
Even/odd mode resonance frequency of electromagnetically coupled microstrip ring resonator with flexible positional overlay of dielectric strips
Authors: Ghanbari H.
Published: April 2008

Effect of perturbation by flexible dielectric strip overlay (Alumina εr = 9.8) on even/odd mode resonance frequency of electromagnetically coupled microstrip ring resonator (EMC‐MRR) is reported. Change in even and odd mode resonance frequencies is found to obey cosine and sine wave function, respectively. Even mode resonance frequency tends to vary linearly with both width and thickness of the strip overlay while for odd mode it is independent of overlay thickness. Based on the experimental results empirical equations for both the even and odd mode resonance frequencies are reported. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1931–1934, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23513
Broadband dual‐band CPW‐fed closed rectangular ring monopole antenna with a vertical strip for WLAN operation
Authors: Zhang Li , Jiao Yong‐Chang , Zhao Gang , Song Yue , Zhang Fu‐Shun
Published: April 2008

A novel CPW‐fed closed rectangular ring monopole antenna with a vertical strip is proposed for WLAN applications. The antenna with a very simple structure is easily fabricated. The measured results explore broadband dual‐frequency operation with (10 dB) impedance bandwidths of 23.4%, range from 2.24 to 2.82 GHz, and 22.9%, ranging from 4.86 to 6.18 GHz, at bands of 2.48 and 5.76 GHz, respectively, which cover the 2.4/5.2/5.8 GHz WLAN operating bands. Also, good omni‐directional radiation patterns and antenna gains over the operating bands have been obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1929–1931, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23514