bluuebunny/crossref_metadata_2025 huggingface dataset:
Tbx1 regulation of myogenic differentiation in the limb and cranial mesoderm
Authors: Dastjerdi Akbar , Robson Lesley , Walker Rebecca , Hadley Julia , Zhang Zhen , Rodriguez‐Niedenführ Marc , Ataliotis Paris , Baldini Antonio , Scambler Peter , Francis‐West Philippa
Published: November 2006

The T‐box transcription factor Tbx1 has been implicated in DiGeorge syndrome, the most frequent syndrome due to a chromosomal deletion. Gene inactivation of Tbx1 in mice results in craniofacial and branchial arch defects, including myogenic defects in the first and second branchial arches. A T‐box binding site has been identified in the Xenopus Myf5 promoter, and in other species, T‐box genes have been implicated in myogenic fate. Here we analyze Tbx1 expression in the developing chick embryo relating its expression to the onset of myogenic differentiation and cellular fate within the craniofacial mesoderm. We show that Tbx1 is expressed before capsulin, the first known marker of branchial arch 1 and 2 muscles. We also show that, as in the mouse, Tbx1 is expressed in endothelial cells, another mesodermal derivative, and, therefore, Tbx1 alone cannot specify the myogenic lineage. In addition, Tbx1 expression was identified in both chick and mouse limb myogenic cells, initially being restricted to the dorsal muscle mass, but in contrast, to the head, here Tbx1 is expressed after the onset of myogenic commitment. Functional studies revealed that loss of Tbx1 function reduces the number of myocytes in the head and limb, whereas increasing Tbx1 activity has the converse effect. Finally, analysis of the Tbx1‐mesoderm‐specific knockout mouse demonstrated the cell autonomous requirement for Tbx1 during myocyte development in the cranial mesoderm. Developmental Dynamics 236:353–363, 2007. © 2006 Wiley‐Liss, Inc.
Loss of Fgfr3 leads to excess hair cell development in the mouse organ of Corti
Authors: Hayashi Toshinori , Cunningham Dale , Bermingham‐McDonogh Olivia
Published: November 2006

Previous studies have demonstrated the importance of FGF signaling at several stages in the development of the cochlea. At early stages of embryogenesis, Fgfr1, Fgfr2, and several FGFs are critical for both the induction of the otic vesicle and the initial development of the sensory epithelium. At late stages of cochlear development, Fgfr3 is necessary for the development of the tunnel of Corti. To determine the stage of development when Fgfr3 is required, we examined the expression of Fgfr3 and Fgf8 at various developmental stages. We also re‐examined the Fgfr3 −/− mouse with additional markers for developing supporting cells. We confirmed the previous analysis of the Fgfr3 −/− mice, indicating that there are deficiencies in support cell differentiation. Specifically, we find that the inner pillar cell never develops, while the outer pillar cell is stalled in its differentiation. In addition, we found an extra row of outer hair cells, and accompanying Deiters' cells, in the apical two thirds of the organ of Corti in the Fgfr3 mutant. Thus, in addition to controlling the fate decision between pillar cells and Deiters' cells, we find that Fgfr3 also regulates the width of the sensory epithelium. Developmental Dynamics 236:525–533, 2007. © 2006 Wiley‐Liss, Inc.
Fabrication and characterization of semicircular detection electrodes for contactless conductivity detector – CE microchips
Authors: Lee Chia‐Yen , Chen C. M. , Chang Guan‐Liang , Lin Che‐Hsin , Fu Lung‐Ming
Published: November 2006

This study uses simple and reliable microfabrication techniques to fabricate CE biochips, integrating a novel contactless conductivity detector in a miniaturized detection system in a microfluidic biochip. The off‐channel electrodes are deposited around side channels by Au sputtering and patterned using a standard “lift‐off” process. A vacuum fusion bonding process is employed to seal the lower substrate containing the microchannels and the electrodes to an upper glass cover plate. The variations in the capacitance between the semicircular detection electrodes in the side channels are measured as different samples and ions pass through the detection region of the CE separation channel. Samples of Rhodamine B, commercial sports drinks, mineral waters, and a red wine, respectively, are mixed in different buffer solutions, separated, and successfully detected using the developed device. The semicircular detection electrodes for the contactless conductivity detector have microscale dimensions and provide a valuable contribution to the realization of the lab‐on‐a‐chip concept.
Floating electrode dielectrophoresis
Authors: Golan Saar , Elata David , Orenstein Meir , Dinnar Uri
Published: November 2006

In practice, dielectrophoresis (DEP) devices are based on micropatterned electrodes. When subjected to applied voltages, the electrodes generate nonuniform electric fields that are necessary for the DEP manipulation of particles. In this study, electrically floating electrodes are used in DEP devices. It is demonstrated that effective DEP forces can be achieved by using floating electrodes. Additionally, DEP forces generated by floating electrodes are different from DEP forces generated by excited electrodes. The floating electrodes' capabilities are explained theoretically by calculating the electric field gradients and demonstrated experimentally by using test‐devices. The test‐devices show that floating electrodes can be used to collect erythrocytes (red blood cells). DEP devices which contain many floating electrodes ought to have fewer connections to external signal sources. Therefore, the use of floating electrodes may considerably facilitate the fabrication and operation of DEP devices. It can also reduce device dimensions. However, the key point is that DEP devices can integrate excited electrodes fabricated by microtechnology processes and floating electrodes fabricated by nanotechnology processes. Such integration is expected to promote the use of DEP devices in the manipulation of nanoparticles.
Improvements on the electrokinetic injection technique for microfluidic chips
Authors: Wu Chien‐Hsien , Yang Ruey‐Jen
Published: November 2006

This paper presents a T‐form electrokinetic injection system for the discrete time‐based loading and dispensing of samples of variable‐volume in a microfluidic chip. A novel push–pull effect is produced during the loading and dispensing processes by the application of an appropriate control voltage distribution. The experimental and numerical results show that this push–pull loading technique produces compact sample plugs and hence improves the detection resolution of the microfluidic device. The injection system is integrated with a microflow switch, and a suitable voltage control scheme is proposed to guide the sample to the desired outlet port such that the microfluidic device can function as a microdispenser. The time‐based variable‐volume T‐form injection method presented in this study is performed using a compact geometry and a simple control scheme and can be readily integrated with other microfluidic devices to form a microfluidic system capable of continuous monitoring and analysis of bioreactions in the life science and biochemistry fields.
Numerical analysis of an electrokinetic double‐focusing injection technique for microchip CE
Authors: Zhuang Gui‐Sheng , Li Gang , Jin Qing‐Hui , Zhao Jian‐Long , Yang Meng‐Su
Published: November 2006

The injection techniques in electrophoresis microchips play an important role in the sample‐handling process, whose characteristics determine the separation performance achieved, and the shape of a sample plug delivered into the separation channel has a great impact on the high‐quality separation performance as well. This paper describes a numerical investigation of different electrokinetic injection techniques to deliver a sample plug within electrophoresis microchips. A novel double‐focusing injection system is designed and fabricated, which involves four accessory arm channels in which symmetrical focusing potentials are loaded to form a unique parallel electric field distribution in the intersection of injection channel and separation channel. The parallel electric field effectuates virtual walls to confine the spreading of a sample plug at the intersection and prevents sample leakage into separation channel during the dispensing step. The key features of this technique over other injection techniques are the abilities to generate regular and nondistorted shape of sample plugs and deliver the variable‐volume sample plugs by electrokinetic focusing. The detection peak in the proposed injection system is uniform regardless of the position of the detection probe in the separation channel, and the peak resolution is greatly enhanced. Finally, the double‐focusing injection technique shows the flexibility in detection position and ensures improved signal sensitivity with good peak resolution due to the delivered high‐quality sample plug.
A sheath‐flow nanoelectrospray interface of microchip electrophoresis MS for glycoprotein and glycopeptide analysis
Authors: Mao Xiuli , Chu Ivan K. , Lin Bingcheng
Published: November 2006

Microchip was coupled with MS through a stable, sensitive, and controllable sheath‐flow nanoelectrospray (nES) interface for glycoprotein and glycopeptide analysis. The nano‐ESI (nESI) was made with a delivery capillary, a commercial nES capillary, and a stainless steel (SS) tube which were connected together through a tee unit. High voltage for nES was applied on the SS tube and the commercial nES capillary was used as nES emitter. The delivery capillary was attached to the microchannel for delivering liquid from microchip to the nESI source. The flow rate of sheath liquid was optimized to be 100–200 nL/min which largely reduced the sample dilution. The detection limit of peptides on this microchip/MS platform was at femtomole level. Glycoprotein and glycopeptides were also successfully analyzed on the platform. All the glycoforms and glycopeptides of ribonuclease B (RNase B) were identified with this method. Some structures of the glycopeptides from RNase B were further characterized with MS/MS on the microchip, coupled with a quadrupole IT‐MS.
A microfluidic‐based system for analysis of single cells based on Ca2+ flux
Authors: Zhang Xunli , Yin Huabing , Cooper Jon M. , Haswell Stephen J.
Published: November 2006

A microfluidic format‐based system has been developed for in situ monitoring of the calcium flux response to agonists using Chinese hamster ovary (CHO) cells. The assay is based on measuring the fluorescent intensity of the calcium‐sensitive indicator, Fluo‐4 AM, and was performed in a modified glass chip channel, whose surface was functionalised using a silanisation method with 3‐aminopropyltriethoxysilane (APTS) (enabling the cells to be immobilised on the channel surface). CHO cells calcium flux response was measured for different agonists over a range of concentrations. Cells and reagents were introduced into the chip in a continuous flow as a series of plugs in a given sequence.
Integrated isotachophoretic preconcentration with zone electrophoresis separation on a quartz microchip for UV detection of flavonoids
Authors: Ma Bo , Zhou Xiaomian , Wang Gang , Huang Huaiqing , Dai Zhongpeng , Qin Jianhua , Lin Bingcheng
Published: November 2006

A quartz microchip integrated isotachophoretic (ITP) preconcentration with zone electrophoresis (ZE) separation was fabricated using a novel multi‐point pressure method featured in normal temperature and lower pressure during bonding process. ITP followed by subsequential ZE of two flavonoids, quercetin and isorhamnetin on the microchip was performed consecutively on the homemade microfluidic workstation with UV detection, resulting in a decreased detectable concentration of 32‐fold, compared to the ZE mode only, and their detection limits decreased down to 0.2 µg/mL and 1.2 µg/mL, respectively
Microfluidics for multiplexed MS analysis
Authors: Foret František , Kusý Petr
Published: November 2006

Recent advances of microfluidics systems suitable for multiplexed MS analysis are reviewed with respect to fabrication technologies and applications.
Enhanced Treatment of Trace Pollutants by a Novel Electrolytic Cell
Authors: Sakakibara Y. , Senda Y. , Obanayama T. , Nagata R.
Published: November 2006

Continuous experiments were conducted to evaluate the electrolytic performance of a novel 3‐dimensional electrolytic cell consisting of granular Pt/Ti electrodes. The electric current efficiency to decompose indigotrisulfonate was approx. 96 %, while energy consumption was one to two orders of magnitude smaller than that for O3 treatment. Furthermore, the cell was successfully applied to treat trace endocrine disrupting chemicals (EDCs) and chlorinated compounds. Energy consumption was in the range of 2 to 10 Wh/m3. From these results, it was concluded that the present electrolytic cell would be a feasible alternative to conventional oxidation processes in water treatment.
Tools for Selective Enzyme Reaction Steps in the Synthesis of Laboratory Chemicals
Authors: Wohlgemuth R.
Published: November 2006

The need for more selective reactions steps and the compatibility between process steps which follow on from each other has been a major driving force for organic synthesis. The synthesis of chiral compounds, metabolites, new chemical entities and natural products by a combination of chemical and enzyme reaction steps has become well established, due the existence of stable enzymes as selective catalysts which are inherently chiral by nature. Auxiliary tools such as suitable transfer reagents for reaching complete conversion, easy and robust reaction control as well as tools for straightforward workup and purification of the final product have been developed. Selective enzyme reaction steps in the area of hydrolyses, oxidation steps including hydroxylation and the Baeyer‐Villiger oxidation, carbon‐carbon bond formation and glycosylation reactions have compared favorably with existing methods of classical organic synthesis. The tools developed during optimization and scale‐up of these enzyme reaction steps have the potential to shorten development time. The introduction of selective enzyme reactions into an entire synthetic process has resulted in harmonization of improvements in economic efficiency with resultant solutions to health, safety and environment problems. This will become even more important in industrial synthetic chemistry in the future, for convenient solutions to certain intractable synthetic problems and for expanding the repertoire of chemistry by modular biocatalysts. Efficient isolation procedures for the final product are essential to take full advantage of the biocatalytic conversion to obtain high product yields.
Generating “Tide” in Pilot‐Scale Constructed Wetlands to Enhance Agricultural Wastewater Treatment
Authors: Sun G. , Zhao Y. , Allen S. , Cooper D.
Published: November 2006

The operation of tidal flow was studied using a pilot‐scale system treating high strength piggery wastewater. Located on a farm in Staffordshire, UK, the system consisted of five wetland treatment stages vegetated with common reeds of Phragmites australis. Wastewater samples were collected from the inlet and outlet of each stage and analyzed for BOD5, COD, NH4‐N, NO3‐N, NO2‐N, SS, PO4‐P and pH. Average hydraulic and organic loadings on the system were 0.12 m3/m2 d and 240 g BOD/m2 d, respectively, which is considerably higher than the typical loadings on conventional subsurface flow systems. On average, BOD5 and COD were reduced by 82 % and 80 % from initial concentrations of 2000 mg/L and 2750 mg/L, respectively, across the whole system. The first‐order kinetics constant for BOD5 removal (KBOD in m/d) in this tidal flow system is approximately 2.5 times the rate constant obtainable in a typical horizontal flow system, demonstrating a more efficient removal of organic matter in tidal flow wetlands. The overall efficiency of the system was found to increase with time before stabilizing towards the end of a start‐up period. Straight‐line correlations were established between the loading and removal of BOD5 and COD. Contributions by individual stages to the overall treatment were analyzed. SEM images of wetland media demonstrated the formation of biofilms and microbial activities inside the matrices of the wetland system, which accounted for the degradations of organic pollutants.
High Frequency in vitro Multiplication of Centella asiatica: An Important Industrial Medicinal Herb
Authors: Sivakumar G. , Alagumanian S. , Rao M. V.
Published: November 2006

An efficient protocol was developed for rapid clonal propagation of the important medicinal plant, Centella asiatica (L.) Urban, using shoot tip culture. High frequency bud break (88 %) and multiple shoot formation (16.8 shoots/shoot tip) were induced from a shoot tip segment, which was cultured on MS medium supplemented with 6‐benzylaminopurine (BAP) (17.76 μM) and gibberillic acid (GA3) (1.44 μM). Half‐strength Murashige and Skoog (MS) medium supplemented with naphthalen acetic acid (NAA) (10.74 μM) induced the maximum (27.66) number of roots. Plantlets with 3–4 fully expanded leaves and well‐developed roots were successfully transferred to potted soil which exhibited a 95 % survival. The protocol enables the harvest of more than 25,000 plantlets within 160 days starting from a single shoot tip explant.
Effectiveness of Various Small‐Scale Constructed Wetland Designs for the Removal of Iron and Zinc from Acid Mine Drainage under Field Conditions
Authors: Wiessner A. , Kuschk P. , Buddhawong S. , Stottmeister U. , Mattusch J. , Kästner M.
Published: November 2006

A system of planted and unplanted small‐scale subsurface flow (SSF) and surface flow (SF) constructed wetlands together with hydroponic systems (HP) were installed to compare the removal efficiencies of Fe and Zn from acid mine drainage (AMD) under long‐term field conditions. Maximum removal of 94–97 % (116–142 mg/m2 d) for Fe and 69–77 % (6.2–7.9 mg/m2 d) for Zn was calculated for the planted soil systems. The planted SSF was most sensitive to heavy rain fall. Short‐term increases of the metal concentration in the outflows, short‐term breakdowns of the Fe removal and continual long‐term breakdowns of the Zn removal were observed. In contrast to Zn removal, all wetland types are applicable for Fe removal with maximum removal in the range of 60–98 %. Most of the removed Fe and Zn was transformed and deposited inside the soil bed. The amount absorbed by the plants (0.03 to 0.3 %) and gravel‐associated soil beds (0.03 to 1.7 %) of the total input were low for both metals. The response of the planted SSF to rainfall suggests a remobilization of metals accumulated inside the rhizosphere and the importance of buffering effects of the surface water layers of SF systems. The importance of plants for metal removal was shown.
Novel microdeletion in the transforming growth factor β type II receptor gene is associated with giant and large cell variants of nonsmall cell lung carcinoma
Authors: Wang Jiu‐Cun , Su Cheng‐Chang , Xu Ji‐Bin , Chen Le‐Zhen , Hu Xiao‐Hua , Wang Gui‐Ying , Bao Yang , Huang Qiang , Fu Song‐Bin , Li Pu , Lu Chen‐Qi , Zhang Rong‐Mei , Luo Z. W.
Published: November 2006

Mutations in the tumor suppressor gene transforming growth factor β (TGFB) Type II receptor (TGFBR2) are frequently found in many cancers with microsatellite instability, but are less common in lung cancer. In the present study, we looked for mutations in TGFBR2 in nonsmall cell lung carcinoma (NSCLC) cells and tissues. A novel homozygous microdeletion (c.492_507del) was identified in two cell lines derived from the same giant cell carcinoma (GCC) and was confirmed in the corresponding tumor tissues. Furthermore, a heterozygous c.492_507del was found in the germ‐line of one patient, as well as in the other GCC cases and some large cell carcinomas (LCC) but not in other subtypes of NSCLC. The 16 bp‐microdeletion introduced a premature stop codon at positions 590–592 of the cDNA, resulting in a truncated TGFBR2 protein with a mutated transmembrane domain and loss of kinase domain. The GCC cells were characterized as being unresponsive to TGFB induction both in growth inhibition and stimulation of extracellular matrix protein. Moreover, after the reconstitution of wild‐type TGFBR2 expression, the sensitivity to TGFB was restored. Therefore, mutated TGFBR2 seems to play an important role in the abrogation of TGFB signal transduction in GCC cells. © 2006 Wiley‐Liss, Inc.
Primary colorectal tumors fail to express the proapoptotic mediator PTAG and its reexpression augments drug‐induced apoptosis
Authors: Bahar Adil , Whitby Philip , Holley Sarah , Hoban Paul R. , Elder James B. , Deakin Mark , Hall Christine , Clayton Richard N. , Williams Gwyn T. , Farrell William E.
Published: November 2006

Genes implicated in tumor evolution and progression, including those in apoptotic pathways, are associated with methylation‐associated gene silencing in different tumor types. By exploiting differential methylation we recently isolated a novel pituitary tumor derived apoptosis gene (PTAG) that augments drug‐induced apoptosis. The importance of PTAG was determined in other tumor types, and these studies show that the majority of primary colorectal tumors fail to express the PTAG gene, indicating an important role for PTAG in colorectal tumorigenesis. The effects of expression of PTAG were examined through stable transfection of the colorectal cell lines HCT116 and SW480. Expression of PTAG, per se, had no discernible effects on cell viability or cell kinetics. In contrast to these findings, in cells subject to drug challenges that engaged either a death‐receptor mediated or mitochondrial pathway, all of the experiments indicated a role for PTAG in the intrinsic pathway of apoptosis. Loss of PTAG therefore contributes to a blunted apoptotic response and is likely to predispose cells toward malignant transformation and resistance to chemotherapeutic interventions. © 2006 Wiley‐Liss, Inc.
Post‐stroke dementia and depression: frontosubcortical dysfunction as missing link?
Authors: Naarding Paul , de Koning Inge , van Kooten Fop , Janzing Joost G. E. , Beekman Aartjan T. F. , Koudstaal Peter J.
Published: November 2006

Objective

Testing the hypothesis that depressive symptoms in dementia reflect dysfunction in fronto‐subcortical pathways.

Background

Both depression and dementia can be the result of vascular damage of the brain. The nature of the depressive symptomatology seems to be related to concommittant cognitive disturbances in that subjects show more so‐called motivational symptoms of depression. These symptoms can be the result of frontal‐subcortical dysfunction. It could be very helpful for clinical practice if these subjects could be identified by simple diagnostic procedures.

Methods

Associations were computed between measures of depressive symptoms and a set of neuropsychological tests in a sample of 54 subjects with a post‐stroke dementia.

Results

Allthough we used an extensive set of neuropsychological tests, most subjects were able to participate only in a small part of them, because of disease severity. Our hypothesis was supported by a negative correlation between scores on the verbal semantic fluency task and the total numbers of motivational depressive symptoms. None of the neuropsychological tests was significantly related to the number of mood symptoms neither did they correlate with the total number of depressive symptoms.

Conclusion

This study gives further evidence for the assumption that motivational‐based depressive symptoms partially originate from fronto‐subcortical dysfunction. Copyright © 2006 John Wiley & Sons, Ltd.
Efficacy of cognitive rehabilitation in patients with mild cognitive impairment treated with cholinesterase inhibitors
Authors: Rozzini Luca , Costardi Daniela , Chilovi Barbara Vicini , Franzoni Simone , Trabucchi Marco , Padovani Alessandro
Published: November 2006

Background

Individuals who have Mild Cognitive Impairment (MCI) may be in a transitional stage between aging and Alzheimer's disease (AD). The high rate of conversion from MCI to AD makes early treatment an important clinical issue. Recent evidence suggests that cognitive training intervention may reduce the rate of progression to AD.

Objectives

To evaluate the efficacy of a NeuroPsychological Training (TNP) in patients with MCI who are treated with cholinesterase inhibitors (ChEIs), compared with patients MCI treated only with ChEIs and patients not treated, in a longitudinal, one year follow‐up study.

Methods

One year longitudinal and retrospective comparison study of neuropsychological performances in 59 subjects affected by Mild Cognitive Impairment (MCI) according to Petersen's criteria. Fifteen subjects were randomised to receive TNP plus cholinesterase inhibitors; 22 subjects cholinesterase inhibitors alone and 22 subjects no treatment. All the subjects referring memory complaints, corroborated by an informant, underwent a multidimensional assessment concerning neuropsychological, behavioural and functional characteristics, at baseline and after one year follow‐up.

Results

Subjects without treatment maintained their cognitive, functional and behavioural status after one year; patients treated only with ChEIs improved in depressive symptoms whereas subjects treated with TNP and ChEIs showed significant improvements in different cognitive areas, such as memory, abstract reasoning and in behavioural disturbances, particularly depressive symptoms.

Conclusions

A long‐term TNP in ChEIs‐treated MCI subjects induces additional cognitive and mood benefits. Copyright © 2006 John Wiley & Sons, Ltd.
A double‐blind, placebo‐controlled trial of memantine in age‐associated memory impairment (memantine in AAMI)
Authors: Ferris Steven , Schneider Lon , Farmer Mildred , Kay Gary , Crook Thomas
Published: November 2006

Objectives

To determine the safety and efficacy of memantine in treating Age‐Associated Memory Impairment (AAMI).

Methods

Sixty adults between 50–79 years of age meeting diagnostic requirements for AAMI were randomly assigned to either memantine (titrated to 20 mg) or a matched placebo and treated for 90 days. An extensive battery of computerized cognitive tests was administered at screening, baseline and, thereafter, at monthly intervals.

Results and Conclusion

Study results suggest that the primary cognitive effects of memantine in this population are on attention and information processing speed, rather than on memory. There were no differences in adverse events between memantine and placebo. Copyright © 2006 John Wiley & Sons, Ltd.
New large sets of t‐designs with prescribed groups of automorphisms
Authors: Laue R. , Omidi G. R. , Tayfeh‐Rezaie B. , Wassermann A.
Published: November 2006

In this article, we investigate the existence of large sets of 3‐designs of prime sizes with prescribed groups of automorphisms PSL(2,q) and PGL(2,q) for q < 60. We also construct some new interesting large sets by the use of the computer program DISCRETA. The results obtained through these direct methods along with known recursive constructions are combined to prove more extensive theorems on the existence of large sets. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 210–220, 2007
Quantitative analysis of gemcitabine triphosphate in human peripheral blood mononuclear cells using weak anion‐exchange liquid chromatography coupled with tandem mass spectrometry
Authors: Veltkamp S. A. , Hillebrand M. J. X. , Rosing H. , Jansen R. S. , Wickremsinhe E. R. , Perkins E. J. , Schellens J. H. M. , Beijnen J. H.
Published: November 2006

Gemcitabine triphosphate (dFdCTP) is a highly active metabolite of gemcitabine. It is formed intra‐cellularly via the phosphorylation of gemcitabine by deoxycytidine kinase. The monitoring of dFdCTP in human peripheral blood mononuclear cells (PBMCs), in addition to plasma concentrations of gemcitabine and its metabolite 2′,2′‐difluorodeoxyuridine, is considered very useful in determining pharmacokinetic–pharmacodynamic relationships.

We describe a novel sensitive assay for the quantification of dFdCTP in human PBMCs. The method is based on weak anion‐exchange liquid chromatography and detection with tandem mass spectrometry (LC‐MS/MS). The assay has been validated from 1 ng/ml (lower limit of quantification, LLOQ) to 25 ng/ml (upper limit of quantification, ULOQ) using 180 µl aliquots of PBMC extracts containing ∼0.648 mg protein or 3.8 × 106 lysed PBMCs. The LLOQ is equivalent to 94 fmol/106 cells (1 ng/ml = 0.18 ng/180 µl or 0.18 ng/0.648 mg protein = 0.047 ng/106 cells or 94 fmol/106 cells). This highly sensitive assay is capable of quantifying about 200‐fold lower concentrations of dFdCTP in human PBMCs than currently available methods. Copyright © 2006 John Wiley & Sons, Ltd.
A novel low‐dispersive (2,2) collocated FDTD scheme
Authors: Bommaraju Chakrapani , Marklein Rene , Schuhmann Rolf , Weiland Thomas
Published: November 2006

The dispersion relation and the convergence of a modified finite‐difference time‐domain scheme (MFDTD), which has fourth‐order convergence and excellent broadband characteristics, are presented. The accuracy of several low‐dispersion finite‐difference time‐domain schemes in 2‐D is compared with that of the MFDTD, via direct evaluation of the dispersion relation. Convergence of the FDTD and the MFDTD in 2‐D are also examined. Copyright © 2006 John Wiley & Sons, Ltd.
Accuracy improved ADI‐FDTD methods
Authors: Ahmed Iftikhar , Chen Zhizhang (David)
Published: November 2006

FDTD method plays an important role for simulation of different structures in various fields of engineering, such as RF/microwaves, photonics and VLSI. However, due to the CFL stability constraint, the FDTD time step is still small and the related CPU time is still large for modelling fine geometry where small cell sizes are required to resolve fields. As a result, the unconditionally stable CFL‐condition‐free ADI‐FDTD method is becoming a popular alternative to the FDTD method. The ADI‐FDTD method allows the use of larger time steps; however, it comes at the cost of larger errors. To mitigate the problem of these larger errors, in this paper we propose to modify the conventional ADI‐FDTD algorithm. The modifications are based on the fact that because the ADI‐FDTD is a truncated form of the Crank–Nicolson (CN) method, the truncated terms can be re‐introduced approximately into the ADI algorithms to improve accuracy. Two accuracy‐improved ADI‐FDTD algorithms are derived and then validated for two‐dimensional cases. Unfortunately, in the three‐dimensional case the proposed methods are not found to be unconditionally stable. Copyright © 2006 John Wiley & Sons, Ltd.
PML termination of conducting media in the finite difference time domain method for bodies of revolution (BORs)
Authors: Carrión José , Farahat Nader
Published: November 2006

In this paper we discuss the use of perfectly matched layers (PMLs) for the termination of conducting media in the body of revolution finite difference time domain (BOR–FDTD) algorithm. This type of termination enables us, to accurately and efficiently model long conductors possessing rotational symmetry. The formulation is validated by investigating the propagation characteristics of two practical guiding wave structures, viz., a coaxial cable (RG‐142) and a circular waveguide operating in the TE11mode. Both the conductors as well as dielectrics are extended into the PML region in order to simulate infinitely long guides. Copyright © 2006 John Wiley & Sons, Ltd.
System identification and model order reduction for TLM analysis
Authors: Lukashevich D. , Coccetti F. , Russer P.
Published: November 2006

A system identification (SI) and Prony's model based algorithm for modelling and prediction of a time‐domain transient response is introduced and applied to time‐domain transmission line matrix (TLM) transient responses in order to extrapolate parameters of microwave circuits and accelerate the simulation process.

Application of moment matching model order reduction (MOR) techniques to the TLM method is presented with emphasis placed on Krylov subspace methods based on the Lanczos process and its modifications. The Krylov subspace methods are attractive for MOR in the TLM framework because the construction of orthonormal and biorthogonal bases for correspondent Krylov subspaces can be carried out through a direct application of the implicit TLM solver. MOR applied to TLM allows one to generate a compact macromodel of a TLM‐system and significantly reduce the computational time.

The efficiency and advantages of the SI and MOR techniques are demonstrated through their applications to the full‐wave analysis of different electromagnetic structures. In addition, a brief comparison of SI and MOR involved for modelling of a planar patch antenna is provided. Copyright © 2006 John Wiley & Sons, Ltd.
A predator–prey model with disease in the prey species only
Authors: Greenhalgh David , Haque Mainul
Published: November 2006

A predator–prey model with transmissible disease in the prey species is proposed and analysed. The essential mathematical features are analysed with the help of equilibrium, local and global stability analyses and bifurcation theory. We find four possible equilibria. One is where the populations are extinct. Another is where the disease and predator populations are extinct and we find conditions for global stability of this. A third is where both types of prey exist but no predators. The fourth has all three types of individuals present and we find conditions for limit cycles to arise by Hopf bifurcation. Experimental data simulation and brief discussion conclude the paper. Copyright © 2006 John Wiley & Sons, Ltd.
Modeling absorption of rough interface between dielectric and conductive medium
Authors: Gu Xiaoxiong , Tsang Leung , Braunisch Henning , Xu Peng
Published: November 2006

The effects of a random rough surface between dielectric and lossy conductive medium on power absorption are analyzed by considering incident plane waves impinging on the interface. We use two methods to formulate and solve the 2‐D problem: the two‐media small perturbation method to second order (SPM2) and the numerical system transfer operator matrix method, referred to as T‐matrix method. The two methods are in agreement within the regimes of validity. The results show significant difference between absorption of a rough surface and that of a smooth surface. Surface fields are further examined numerically. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 7–13, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22023
Analysis of an E‐shaped patch antenna
Authors: Pandey Vijay K. , Vishvakarma Babau R.
Published: November 2006

This paper presents the theoretical and simulation investigations of an E‐shaped patch antenna applicable in modern mobile communications. It shows marked improvement in the bandwidth when compared with rectangular patch antenna with acceptable radiation pattern. Further, the bandwidth is optimized with respect to notch length, width, and position. Typically, the antenna shows an enhanced impedance bandwidth of 32.5%. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 4–7, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22024
Transmission characteristics of dielectric loaded double trapezoidal‐ridge waveguide
Authors: Lu Mai , Persson Mikael
Published: November 2006

As a new kind of broadband microwave component, transmission characteristics of dielectric loaded double trapezoidal‐ridge waveguide have been analysed by edge element method. Variations of the cutoff wavelength, single‐mode bandwidth and field patterns with the ridge dimensions for different values of dielectric constant have been investigated in details. Numerical results in this article provide an extension to the existing design data for ridge waveguides and are considered helpful in practical applications. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1–4, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22025
Broadband CMOS mixer cell for UWB applications
Authors: Chen W. L. , Huang G. W. , Chang S. F.
Published: November 2006

A broadband mixer cell with active matching network was developed using commercial 0.25‐μm CMOS technology. From experimental results, the down‐converter with the proposed mixer cell achieves a RF input return loss greater than 10 dB from 3.1 to 23.3 GHz. For UWB low‐band application, it achieves a conversion gain of −9.2 dB and an input P1dB greater than −3 dBm at the moderate LO power level of 4 dBm. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 127–128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22026
Improving the performance of a 10 Gbit/s optical communication system with a thermally actuated chromatic dispersion compensator based on chirped fiber Bragg gratings
Authors: Neto B. , André P.
Published: November 2006

In this letter we describe the use of tunable chromatic dispersion compensator based on chirped fiber Bragg grating to improve the performance of a 10 Gbit/s optical fiber communication system. Tunable compensation is achieved by applying temperature gradients along the grating longitudinal axis. It is demonstrated that thermal gradients comprised between −40 and 40°C were able to change the grating dispersion from −84.88 to −218.30 ps/nm. Previously developed model that issued a BER variation on the system from 1.82 × 10−12to 1.62 × 10−9are consistent with the experimental evidences reported here. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 124–127, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22027
A small‐size semilumped three‐port tunable power divider
Authors: Perrier A.‐L. , Duchamp J.‐M. , Ferrari P.
Published: November 2006

In this paper, a small‐size semi‐lumped three‐port power divider with both power and frequency tune is designed and measured. The proposed topology uses complex impedance transformers in each output branch. A 3D CPW prototype is realized with varactor diodes. It exhibits a wide tunable power, from −1.3 to −17 dB, and a wide working frequency tune, from 0.8 to 1.4 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 90–94, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22029
UMTS diplexer design using dual‐mode ring resonators
Authors: Ho Min‐Hua , Xu Wei‐Qin , Chen Yu‐Wei
Published: November 2006

In this letter, we propose a novel design of a UMTS diplexer using dual‐mode rectangular ring‐resonators. The diplexer is composed of two rectangular rings, which termed as the Tx‐ and Rx‐ring, with each ring its input and output ports separated from each other by a quarter‐wavelength to create the degenerate‐mode resonance. The ratio of the long‐ and short‐side dimension of rectangular ring can be used to fine tune the passband's bandwidth and the ratio is properly chosen to achieve sufficient bandwidth required by the UMTS diplexer applications. An enhanced parallel‐coupled structure is introduced in the circuit to replace the conventional end‐gap coupling for reducing the insertion losses in the passband. The effect of the coupling‐line length is also simulated and the resulting data are used to precisely tune the positions of the zeros. In the zero assignment, one of the zeros possessed by each ring filter is managed to be implanted in the passband of its counterpart filter for increasing the isolation between the Rx‐ and Tx‐port. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 63–65, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22030
Performance of duo‐stage SOA based all‐optical multicasting switching matrix for future grid networking
Authors: Lee Bernard H. L. , Shahril S. M. , Mohamad R. , Kaharudin D.
Published: November 2006

This paper presents the performance evaluation of a duo‐stage SOA based All‐Optical Multicasting capable Switch architecture suitable for the requirements of Grid Networking. SOAs based devices are located at the input and the output ports of the switch. The SOAs located at the input port serves as a multicasting and routing device feeding the signals into an N × N arrayed waveguide gratings and the SOAs at the output are regenerators to restore the quality of the signals before sending them into the network. This design uses the non‐linearity processes in SOA such as Cross Gain Modulation and Cross Phase Modulation to achieve a maximum of 1–16 multicast at a bit‐rate of 10 Gbps within the all‐optical switch. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 59–62, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22031
Improved spiral compact microstrip resonance cell low‐pass filter with wide stopband characteristics
Authors: Che Wenquan , Deng Kuan , Xu Lei , Wang Dapeng , Geng Liang
Published: November 2006

An improved spiral compact microstrip resonance cell (SCMRC) structure is proposed in this article. Good low pass performance and wide stopband characteristics can be achieved with a simple single cell, two transmission zeros are introduced within the stopband and thus improve the bandwidth significantly. The measured results of the prototype show that the insertion loss is less than 0.55 dB in the passband, and the bandwidth of the stopband is about 90%, nearly two times of the original SCMRC structure. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 121–124, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22032
A CMOS multiphase shifting network with RC‐CR filter and bias‐level‐scaled active interpolator
Authors: Lee Mi‐Young , Yoo Changsik
Published: November 2006

A CMOS multiphase shifting network is described, which is developed for the use in a subharmonic mixing based direct‐conversion receiver of 5–6 GHz wireless LAN. Accurate phase shift and amplitude matching are simultaneously achieved with a third‐order RC–CR filter followed by the active interpolators whose bias levels are scaled for accurate phase shift. Implemented in a 0.18 μm CMOS process, the phase shifting network provides octa‐phase local oscillator (LO) signals spaced by 45°. The measured accuracy of the phase shift and amplitude matching are better than 0.8° and 0.4%, respectively. The phase shifting network excluding LO buffers dissipates 13 mW from a 1.8 V supply voltage. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 118–121, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22033
Double negative media using interconnected ω‐type metallic particles
Authors: Lheurette É. , Vanbésien O. , Lippens D.
Published: November 2006

We report on broadband low‐loss properties of Ω‐based metamaterials. It is shown that interconnecting elementary current‐loops via their arms can yield to a relative bandwidth of around 70% for infinite arrays. Combining interconnected and disconnected sections permits one to engineer the left‐handed and right‐handed dispersion branches with the prospect of composite artificial media such as those initially proposed by Itoh and coworkers (IEEE Microwave Mag 34 (2004) 34–50) in the context of transmission lines. This typical behavior is interpreted through a lumped element model. At last, some guidelines to optimize the transmission properties of Ω‐shaped arrays are presented. These results are discussed on the basis of recently published data concerning Ω‐shaped and C‐shaped particles. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 84–90, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22034
Exploring the possibility of enhancing the bandwidth of μ‐negative metamaterials by employing tunable varactors
Authors: Alù Andrea , Bilotti Filiberto , Vegni Lucio
Published: November 2006

We analyze here the performance of μ‐negative metamaterials in different configurations at microwave and optical frequencies that employ variable values of capacitances or tunable varactors, with the purpose of increasing their bandwidth of operation. The proposed method shows moderately good results both in resonant‐like and in transmission‐line configurations. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 55–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22036
Wide stopband EBG structure design based on 2D nonlinearly tapered slot array
Authors: Wu Jack , Qiu S. N. , Qiu C. X. , Shih I.
Published: November 2006

Electromagnetic bandgap structures are well known for their stopband features and can be applied at microwave frequencies. In this work, a wide stopband electromagnetic band‐gap (EBG) structure design based on 2D tapered slot array is presented. Each tapered slot length is designed to provide stopband at a specific frequency to maximize the attenuation level. The tapered slot array is positioned in the ground plane of a microstrip transmission line structure. Thus, the overall 9‐slot nonlinearly tapered array produces a wide stopband from 9.3 to 20 GHz with attenuation better than 25 dB, which is observed in both simulation and actual measurements. The nonlinearly tapered EBG structure can be applied as an efficient lowpass filter. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 31–34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22038
Characteristics of low K thin film microstrip line on standard lossy silicon substrate for radio frequency integrated circuits
Authors: Wu Hung‐Wei , Weng Min‐Hang , Su Yan‐Kuin , Yang Ru‐Yuan
Published: November 2006

In this paper, effective dielectric constant, line attenuation, and characteristic impedance of thin film microstrip line (TFML) on polyimide dielectric as interconnection for radio frequency integrated circuits is investigated. The TFML is fabricated on low cost low resistivity silicon substrate (ρ≤10 Ω cm) by incorporating a spin‐on dielectric polyimide and sputtering of aluminum. An accurate on‐wafer‐procedure for extracting the microwave characteristics of TFML up to 50 GHz is described and the method is successfully applied to low‐K polyimide deposited on the silicon. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 79–83, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22052
A 6 GHz low power differential VCO
Authors: Jang Sheng‐Lyang , Lee Shao‐hua , Chiu Chung‐Ching , Chuang Yun‐Hsueh
Published: November 2006

This paper presents a new differential CMOS voltage controlled oscillator (VCO). The topology of the proposed differential VCO is a combination of Colpitts CMOS VCO and cross‐coupled lateral BJT VCO. A symmetric transformer and differential differentially tuned MOS varactors are used to reduce phase noise. The VCO has been fabricated with the 0.18‐μm CMOS process. At the 1.2‐V supply voltage, the output frequency of VCO is from 5.99 to 6.43 GHz with 441 MHz tuning range and a phase noise of −118.5 dBc/Hz at the 1 MHz offset from the center frequency of 6.43 GHz. Its core current consumption is 2.8 mA and the core power consumption is 3.36 mW. The total power consumption of this VCO is 9.12 mW. The figure of merit (FOM) of this differential VCO is −189.4 dBc/Hz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 76–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22043