Distribution by Scientific Domains

Selected Abstracts

Weak agonist self-peptides promote selection and tuning of virus-specific T cells

Abstract Recent progress has begun to define the interactions and signaling pathways that are triggered during positive selection. To identify and further examine self-peptides that can mediate positive selection, we searched a protein-database to find peptides that have minimal homology with the viral peptide (p33) that activates a defined P14 transgenic TCR. We identified four peptides that could bind the restriction element H-2Db and induce proliferation of P14 transgenic splenocytes at high concentration. Two of the four peptides (DBM and RPP) were able to positively select thevirus-specific TCR in fetal thymic organ culture but were unable to induce clonal deletion. Reverse-phase HPLC and mass spectrometry demonstrated that these peptides were presented by H-2Db molecules on thymic epithelial cell lines. We also examined whether the selecting ligands altered T cell responsiveness in vitro. DBM-selected T cells lost their ability to respond to the positively selecting ligand DBM, whereas RPP-selected T cells only retainrd their ability to respond to high concentrations of RPP. These results demonstrate that self-peptides that mediate positiveselection can differentially "tune" the activation threshold of T cells and alter the functional repertoire of T cells. [source]

A New Sol,Gel Material Doped with an Erbium Complex and Its Potential Optical-Amplification Application,

L.-N. Sun
Abstract The crystal structure of a ternary Er(DBM)3phen complex (DBM,=,dibenzoylmethane; phen,=,1,10-phenanthroline) and its in-situ synthesis via a sol,gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er3+/DBM/phen co-doped luminescent hybrid gel, formed via an in-situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near-IR luminescence (centered at around 1.54,,m) resulting from the 4I13/2,,,4I15/2 transition of the Er3+ ion, which contributes to the efficient energy transfer from the ligands to the Er3+ ion in both the Er(DBM)3phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541,nm in the emission spectrum of the ErDP gel is 72,nm, which has potential for optical-amplification applications. Further theoretical analysis on the Er3+ ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers. [source]

Occurrence of the diamondback moth (Plutella xylostella L.) and its parasitoids in Ethiopia: influence of geographical region and agronomic traits

G. Ayalew
Abstract:, Surveys were carried out in 2001 in brassica-producing areas of Ethiopia to determine the geographic distribution and severity of diamondback moth (DBM) and occurrence of indigenous parasitoids. Principal component analysis was used to analyse the importance of nine parameters , DBM density, parasitism by different parasitoid species (Oomyzus sokolowskii, Diadegma spp., Apanteles sp. and overall parasitism), cropping systems, pesticide use, frequency of pesticide application and altitude. A total of 194 brassica fields in 13 different areas were visited. Principal component analysis showed that the first two of the nine principal components (largely DBM density and pesticide use) accounted for 70% of the variation in the data set. Higher DBM numbers were associated with pesticide usage and higher overall parasitism with intercropping. Eight parasitoid species were recorded of which three species were important both in distribution and level of parasitism. These include Oomyzus sokolowskii (Hym., Eulophidae), Diadegma spp. (Hym., Ichneumonidae) and Apanteles sp. (Hym., Braconidae). Overall parasitism ranged from 3.6% to 79.5% with big differences between areas. Apanteles sp. and Diadegma spp. were largely confined to the south-western part of Ethiopia where insecticide use is minimal. Oomyzus sokolowskii is mainly distributed in areas of the Rift Valley and northern Ethiopia with relatively heavy insecticide use. This study indicated a huge impact of repeated insecticide treatment and agronomic practices on DBM severity and its parasitoids. [source]

Control of Plutella xylostella using polymer-formulated Steinernema carpocapsae and Bacillus thuringiensis in cabbage fields

S. Schroer
Abstract:, Field trials evaluating the potential of the entomopathogenic nematode Steinernema carpocapsae and the feasibility to combine nematodes with Bacillus thuringiensis for sustainable control of the diamondback moth (DBM) Plutella xylostella were conducted in cabbage cultivated in the province Probolinggo, east Java and Indonesia. A single use of 0.5 million S. carpocapsae m,2 applied with a surfactant-polymer-formulation containing 0.3% xanthan and 0.3% Rimulgan® achieved a significant reduction of the insects per plant with >50% control after 7 days. Even 14 days after the application about 45% control was recorded and dead larvae containing nematodes were found. No significant effects were recorded when the formulation was compared with nematodes applied in water or with a surfactant alone. This was attributed to high humidity in the experimental area at the end of the rainy season and a microclimate in the cabbage heads favouring nematode survival. Weekly applications of B. thuringiensis (Turex®) or alternating applications of Turex® and the nematodes achieved >80% control. The application of both biological agents together every second week reached insignificant lower efficacy (70%). Nematodes can be used to substitute ineffective chemical insecticides and alterations with B. thuringiensis can prevent the further development of resistance against the bacterial control agent. [source]

Immunosuppression with FK506 Increases Bone Induction in Demineralized Isogeneic and Xenogeneic Bone Matrix in the Rat

Dr. Gregor Voggenreiter
Abstract The aim of the present study was to investigate a systemic induction of bone formation in rats by immunosuppression with FK506 (1 mg/kg body weight intraperitoneally [ip]) in a model of osteoinduction of isogeneic and xenogeneic demineralized bone matrix (DBM) for a period of 28 days. In particular, alterations of in vitro cytokine synthesis and changes of lymphocyte subsets were studied. DBM was implanted intramuscularly in the abdominal wall of Lewis rats (seven per group). Blood was sampled on days ,7, 0, 7, and 28 for determination of in vitro tumor necrosis factor , (TNF-,) synthesis and lymphocyte subsets by flow cytometry (CD3+, CD4+, CD8+, CD45+, ED9+, and Ia+ antibodies). Ossicles of de novo formed bone and the tibias were removed on day 28 after double tetracycline labeling for histomorphometric analysis. Immunosuppression with FK506 significantly decreased lipopolysaccharide (LPS)-stimulated in vitro cytokine synthesis after 7 days and 28 days (p < 0.05). Compared with control animals FK506 treatment significantly increased the volume of induced bone in isogeneic (2.1 ± 0.3 mm3 vs. 10.8 ± 0.9 mm3) and xenogeneic (0 mm3 vs. 4.7 ± 0.8 mm3) DBM. Bone histomorphometry of the tibias revealed that immunosuppression increased both bone formation and bone resorption, accompanied by a significant reduction in the relative trabecular area (Tb.Ar). FK506 caused a decrease in the counts of CD8+ T cells probably because of destruction or dislocation of these cells. This suggests that the amount of CD8+ cells and the degree of T cell activation in terms of mean fluorescence intensity (MFI) may be associated with bone metabolism. In support of this, statistical analysis revealed a significant positive correlation between parameters of bone formation as well as bone resorption and the CD4+/CD8+ ratio. There was a significant negative correlation between parameters of remodeling of the metaphysis of the tibia and induced bone volume (BV), respectively, and MFI values of CD3+/Ia+ cells. These findings suggest an important role of T lymphocytes in bone formation and bone resorption in vivo. FK506 caused a marked increase of bone formation in DBM. However, the conclusion that immunosuppression increases fracture healing warrants further investigation. [source]

Osteogenesis by guided tissue regeneration and demineralized bone matrix

N. Mardas
Abstract Aim:, To evaluate in a discriminating capsule model whether bone formation by guided tissue regeneration (GTR) may be influenced by concomitant implantation of demineralized bone matrix (DBM). Materials and Methods:, Thirty 4-month-old male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical, Teflon capsule (5.0 mm in diameter), loosely packed with a standardized amount of DBM, was placed with its open part facing the lateral bone surface of the ramus. At the contralateral side, an empty capsule was placed, serving as control. After healing periods of 15, 30, and 120 days, groups of 10 animals were sacrificed and 40,70 ,m thick undecalcified sections of the capsules were produced. In the sections, the cross-sectional areas of (1) the space created by the capsule, (2) newly formed bone, (3) DBM particles, (4) loose connective tissue as well as the (5) height of the capsules, and (6) that of the newly formed bone were measured. Results:, Increasing bone fill was observed in both test and control sites from 30 to 120 days. After 30 days of healing, the mean amount of bone was approx. 3% of the cross-sectional area of the capsules at the test sites while it was 8% in the control sites (p<0.05). However, no statistically significant differences were observed between the test (46%) and control (64%) sites after 120 days regarding any of the measured parameters (p>0.05). The newly formed bone in the DBM group at 120 days, on the other hand, appeared more dense than that in the control capsules. Conclusion:, DBM used as an adjunct to GTR did not provide any added effect on bone formation but increased the density of the newly formed bone. Zusammenfassung Ziel: Die Untersuchung in einem Kapselmodell, welches differenzieren kann, ob die Knochenbildung durch GTR durch die gleichzeitige Implantation von demineralisierter Knochenmatrix (DBM) beeinflusst werden könnte Material und Methoden: Dreißig männliche 4-Monate-alte Albinoratten des Wistar Stammes wurden in der Studie verwendet. Nach der chirurgischen Freilegung des Unterkieferastes wurde eine halbkugelförmige Teflonkapsel (5,0 mm Durchmesser), welche locker mit einer standardisierten Menge von DBM versehen war, wurde mit ihrer offenen Fläche auf die seitlichen Knochenfläche des Ramus gelegt. Auf der kontralateralen Seite diente eine leere Kapsel als Kontrolle. Nach Heilungsintervallen von 15, 30 und 120 Tagen wurden Gruppen von 10 Tieren geopfert und 40-70 ,m dicke nicht-entkalkte Schnitte der Kapseln wurden hergestellt. An den Schnitten wurde die Querschnittsfläche von: 1) der Fläche, die von der Kapsel geschaffen wurde, 2) dem neu gebildeten Knochen, 3) den DBM-Partikeln, 4) dem lockeren Bindegewebe gemessen, als auch 5) die Höhe der Kapseln und 6) des neu gebildeten Knochens bestimmt. Ergebnisse: Von Tag 30 zu Tag 120 wurde sowohl bei den Test- als auch bei den Kontrollstellen eine erhöhte Knochenauffüllung beobachtet. Nach 30 Tagen der Heilung betrug an den Teststellen die mittlere Knochenmenge ungefähr 3% der Querschnittsfläche der Kapseln, während sie an den Kontrollstellen 8% (p<0,05) betrug. Jedoch wurde nach 120 Tagen bei keinem der gemessenen Parameter eine statistisch signifikante Differenz zwischen den Test- (46%) und den Kontrollstellen (64%) beobachtet. Auf der anderen Seite erschien nach 120 Tagen in der DBM-Gruppe der neu gebildete Knochen dichter als in den Kontrollkapseln Schlussfolgerung: DBM welches als Zusatz bei der GTR verwendet wurde, lieferte keinen zusätzlichen Effekt bei der Knochenbildung, aber erhöhte die Dichte des neu gebildeten Knochens. Résumé Le but de cette étude a été d'évaluer dans un modèle de capsule discriminatoire si la formation osseuse par regénération tissulaire guidée (GTR) pouvait être influencée par l'implantation concomitante de matrice osseuse déminéralisée (DBM). Trente rats albinos mâles âgés de quatre mois de la souche Wistar ont été utilisés pour cette étude. A la suite de l'exposition chirurgicale de la branche montante mandibulaire, une capsule en téflon hémisphérique de 0,5 mm de diamètre remplie sans tassement avec une quantité standardisée de DBM a été placée avec sa partie ouverte contre la surface osseuse latérale de la branche. Du côté contralatéral, une capsule vide était placée servant de contrôle. Après des périodes de guérison de 15, 30 et 120 jours, des groupes de dix animaux ont été tués et des coupes non-décalcifiées de 40 à 70 ,m d'épaisseur des capsules ont été effectuées. Dans ces coupes, une aire sur coupe transversale contenant 1) l'espace créé par la capsule, 2) l'os néoformé, 3) des particules DBM, 4) du tissu conjonctif lâche; 5) la hauteur des capsules et 6) et celle de l'os néoformé ont été mesurés. Un comblement osseux de plus en plus important tant dans les sites contrôles que les sites tests a été constaté entre les jours 30 et 120. Après 30 jours de guérison, la quantité moyenne d'os formait approximativement 3% de l'aire de la coupe des capsules dans les sites tests tandis qu'elle était de 8% dans les sites contrôles (p<0,05). Cependant, aucune différence statistique n'a été observée entre les sites tests (46%) et les sites contrôles (64%) après 120 jours pour les paramètres mesurés (p>0,05). L'os néoformé dans le groupe DBM à 120 jours semblait plus dense que dans les capsules contrôles. Le DBM utilisé durant la GTR n'apportait aucun effet additionnel sur la formation osseuse mais augmentait cependant la densité du nouvel os formé. [source]

Host,parasitoid population density prediction using artificial neural networks: diamondback moth and its natural enemies

Henri E. Z. Tonnang
1An integrated pest management (IPM) system incorporating the introduction and field release of Diadegma semiclausum (Hellén), a parasitoid of diamondback moth (DBM) Plutella xylostella (L.), comprising the worst insect pest of the cabbage family, has been developed in Kenya to replace the pesticides-only approach. 2Mathematical modelling using differential equations has been used in theoretical studies of host,parasitoid systems. Although, this method helps in gaining an understanding of the system's dynamics, it is generally less accurate when used for prediction. The artificial neural network (ANN) approach was therefore chosen to aid prediction. 3The ANN methodology was applied to predict the population density of the DBM and D. semiclausum, its larval parasitoid. Two data sets, each from different release areas in the Kenya highlands, and both collected during a 3-year period after the release of the parasitoid, were used in the present study. Two ANN models were developed using these data. 4The ANN approach gave satisfactory results for DBM and for D. semiclausum. Sensitivity analysis suggested that pest populations may be naturally controlled by rainfall. 5The ANN provides a powerful tool for predicting host,parasitoid population densities and made few assumptions on the field data. The approach allowed the use of data collected at any appropriate scale of the system, bypassing the assumptions and uncertainties that could have occurred when parameters are imported from other systems. The methodology can be explored with respect to the development of tools for monitoring and forecasting the population densities of a pest and its natural enemies. In addition, the model can be used to evaluate the relative effectiveness of the natural enemies and to investigate augmentative biological control strategies. [source]

Augmentation of osseous phenotypes in vivo with a synthetic peptide

Xinhua Lin
Abstract The synthetic peptide B2A2-K-NS augmented the in vitro expression of osseous phenotypes when cells were stimulated with BMP-2, an osteoinductive growth factor. B2A2-K-NS significantly enhanced the effects of BMP-2-induced alkaline phosphatase activity and mineralization. In the absence of BMP-2, B2A2-K-NS did not have an effect on these endpoints. Based on these observations, in vivo studies were conducted to evaluate if B2A2-K-NS could augment osseous phenotypes in an osteoinductive environment in which BMP-2 should be present. In one study, human demineralized bone matrix (DBM) was used to generate an osteoinductive environment and the effects of B2A2-K-NS on ectopic mineralization of subcutaneous implants evaluated. In the second study, a noncritical sized defect in rabbit ulnas with inherent reparative capacity was used as the osteoinductive environment and was treated with or without B2A2-K-NS. In the DBM studies, B2A2-K-NS augmented mineralization as determined using a combination of radiographic analysis and von Kossa staining at 4 weeks postimplant. In the rabbit ulna model, B2A2-K-NS significantly increased the radiographic bone density in the defects compared to carrier-only or no-treatment controls after 6 weeks. Histological staining confirmed that B2A2-K-NS generated a pronounced bone repair response. The results are consistent with the hypothesis that B2A2-K-NS augments osseous phenotypes in an osteoinductive environment, and suggests that B2A2-K-NS may have clinical utility. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:531,539, 2007 [source]

Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrix

Yanchun Liu
Abstract Injectable hydrogel and porous sponge formulations of CarbylanÔ-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with CarbylanÔ-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The CarbylanÔ-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the CarbylanÔ-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. CarbylanÔ-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1454,1462, 2006 [source]

Individualized and time-variant model for the functional link between thermoregulation and sleep onset

Summary This study makes use of control system model identification techniques to examine the relationship between thermoregulation and sleep regulation. Specifically, data-based mechanistic (DBM) modelling is used to formulate and experimentally test the hypothesis, put forth by Gilbert et al. [Sleep Med. Rev.8 (2004) 81], that there exists a connection between distal heat loss and sleepiness. Six healthy sleepers each spent three nights and the following day in the sleep laboratory: an adaptation, a cognitive arousal and a neutral testing day. In the cognitive arousal condition, a visit of a television camera crew took place and subjects were asked to be interviewed. During each of the three 25-min driving simulator tasks per day, the distal-to-proximal gradient and the electroencephalogram are recorded. It is observed from these experimental data that there exists a feedback connection between thermoregulation and sleep. In addition to providing experimental evidence in support of the Gilbert et al. (2004) hypothesis, the authors propose that the nature of the feedback connection is determined by the nature of sleep/wake state (i.e. NREM sleep versus unwanted sleepiness in active subjects). Besides this, an individualized and time-variant model for the linkage between thermoregulation and sleep onset is presented. This compact model feeds on real-time data regarding distal heat loss and sleepiness and contains a physically meaningful parameter that delivers an individual- and time-depending quantification of a well known biological features in the field of thermoregulation: the thermoregulatory error signal Thypo(t),Tset(t). A validation of these physical/biological features emphasizes the reliability and power of DBM in describing individual differences related to the sleep process. [source]

Cloning and nucleotide sequencing of three heat shock protein genes (hsp90, hsc70, and hsp19.5) from the diamondback moth, Plutella xylostella (L.) and their expression in relation to developmental stage and temperature

Shoji Sonoda
Abstract Heat shock protein genes, hsp90, hsc70, and hsp19.5, were cloned and sequenced from the diamondback moth, Plutella xylostella (L.) by RT-PCR and RACE method. The cDNA sequence analysis of hsp90 and hsp19.5 revealed open reading frames (ORFs) of 2,151 and 522 bp in length, which encode proteins with calculated molecular weights of 82.4 and 19.5 kDa, respectively. Analysis of cDNA from hsc70 revealed an ORF of 1,878 bp coding a protein with a calculated molecular weight of 69.3 kDa. Furthermore, the analysis of genomic DNA from hsc70 confirmed the presence of introns while no introns were apparent in hsp90 and hsp19.5. Southern blot analysis suggested the presence of multiple copies of each gene family in the DBM genome. Detectable expression of hsp19.5 was observed at the pupal stage while expression of hsp90 and hsc70 was detected at both pupal and adult stages. At adult stage, females showed a higher expression of hsp90 and hsc70 than males. An increased expression was observed in all three genes after exposure to a high temperature in both sexes. These results suggest that in addition to a heat shock response, these HSP genes might be involved in other functions during the course of development in DBM. Arch. Insect Biochem. Physiol. 62:80,90, 2006. © 2006 Wiley-Liss, Inc. [source]

Biochemical mechanisms of insecticide resistance in the diamondback moth (DBM), Plutella xylostella L. (Lepidopterata: Yponomeutidae), in the Sydney region, Australia

Vincent Y Eziah
Abstract Following the detection of resistant diamondback moth (DBM) populations to synthetic pyrethroid, organophosphorus and indoxacarb insecticides in the Sydney Basin, a study of the major biochemical mechanisms was conducted to determine the type of resistance in these populations. The activity of cytochrome P450 monooxygenases increased two- to sixfold when compared with the susceptible strain. Up to a 1.9-fold increase in esterase activity in resistant strains compared with the susceptible strain was observed. In vitro inhibition studies showed that profenofos, methamidophos and chlorpyrifos strongly inhibited the esterases while permethrin and esfenvalerate resulted in less than 30% inhibition. Qualitative analysis of the esterases using native polyacrylamide gel electrophoresis showed four bands in both the susceptible and resistant individuals with more intense staining in the resistant individuals. The development of these bands was inhibited by methamidophos and chlorpyrifos pretreatment of the protein extract while permethrin and esfenvalerate did not exhibit this effect. Glutathione S-transferase (GST) activity was significantly higher in two field populations compared with the remaining populations. Overall, the study showed that the mechanisms of insecticide resistance in the DBM populations in the area studied were due to cytochrome P450 monooxygenases, esterase and GSTs, and possibly other non-metabolic mechanisms that were not investigated in the present study. [source]

Susceptibility of four field populations of the diamondback moth Plutella xylostella L. (Lepidoptera: Yponomeutidae) to six insecticides in the Sydney region, New South Wales, Australia

Vincent Y Eziah
Abstract Concerns about the failure of insecticides to control the diamondback moth (DBM) Plutella xylostella in the Sydney region of New South Wales, Australia, necessitated the current investigation to establish the susceptibility of four field populations of the DBM to six insecticides. These include two each of organophosphates (OPs), and synthetic pyrethroid insecticides as well as two new products with different modes of action, spinosad and indoxacarb, currently recommended for DBM control in the region. Topical application of the insecticides to the third-instar larvae showed high resistance to pyrethroids (permethrin and esfenvalerate) of 35.0- to 490.0-fold. Resistance to the OPs (methamidophos and chlorpyrifos) and indoxacarb ranged from 12.1- to 36.2-fold and from 11.4- to 34.6-fold, respectively. However, the field populations were susceptible to spinosad (resistance factors only two- to threefold compared with the susceptible strain). A 2 h pre-treatment of the esfenvalerate-resistant strain with the synergists piperonyl butoxide and diethyl maleate increased the toxicity of esfenvalerate by 30.0- and 1.9-fold, respectively, suggesting the involvement of esterases and/or monooxygenases as the key mechanism(s) of insecticide resistance with glutathione S-transferases playing a minor role. [source]

Liposome Formulations for Effective Administration of Lipophilic Malonatoplatinum(II) Complexes

CANCER SCIENCE, Issue 11 2002
Insook Han
For effective administration of lipophilic trans(±)-l,2-diaminocyclohexaneplatinum(II) complexes of malonate derivatives [(dach)PtL, L=allylmalonate (AM), diallylmalonate (DAM), allylbenzyl-malonate (ABM), or dibenzylmalonate (DBM)] in aqueous solution, we have applied three different liposome formulations and evaluated their physical and chemical properties, along with their in vitro cytotoxicity. The liposome formulations were composed of DMPC/DMPG [DMPC=1,2-dimyristoyl- sn -glycero-3-phosphocholine, DMPG=l,2-dimyristoyl- sn -glycero-3-(phospho- rac -l-glycerol) (sodium salt)] in different molar ratios (7/3 or 3/7) or an equimolar DOTAP/DOPE formulation (DOTAP=l,2-dioleoyl-3-trimethylammonium propane, DOPE=l,2-dioleoyl- sn -glycero-3-phosphoethanolamine). Preliposomal powders of the platinum complexes were prepared by lyophilization, and reconstituted in aqueous solution to obtain the final liposomal platinum complexes. Due to the lipophilicity of the malonatoplatinum complexes, the entrapment efficiency of drugs within the liposomes was over 90% except for the AM complex, and platinum drug stability was also satisfactory (>90%) in these liposomal systems. In vitro cytotoxicity was tested in human ovarian carcinoma cells sensitive (A2780) and resistant to cisplatin (A2780/PDD). In both cell lines, the liposomal DBM complex was much more cytotoxic than the corresponding DAM and ABM complexes, which means that the more hydrophobic benzyl substituent affords higher cytotoxicity than the allyl substituent in the malonato leaving group. Furthermore, the DBM complex in DMPC/DMPG formulations was effective against both sensitive and resistant A2780 cells (resistance indexes (RI)=1.10,1.49), showing lack of cross-resistance to cisplatin. Therefore, the liposomal DBM complex in the DMPC/DMPG formulations is a promising candidate for stable pharmaceutical liposomal platinum complexes. [source]

Lanthanide (Eu3+, Tb3+) Centered Mesoporous Hybrids with 1,3-Diphenyl-1,3-Propanepione Covalently Linking SBA-15 (SBA-16) and Poly(methylacrylic acid)

Ya-Juan Li Dr.
Abstract 1,3-Diphenyl-1,3-propanepione (DBM)-functionalized SBA-15 and SBA-16 mesoporous hybrid materials (DBM-SBA-15 and DBM-SBA-16) are synthesized by co-condensation of modified 1,3-diphenyl-1,3-propanepione (DBM-Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 and Pluronic F127 as a template, respectively. The as-synthesized mesoporous hybrid material DBM-SBA-15 and DBM-SBA-16 are used as the first precursor, and the second precursor poly(methylacrylic acid) (PMAA) is synthesized through the addition polymerization reaction of the monomer methacrylic acid. These precursors then coordinate to lanthanide ions simultaneously, and the final mesoporous polymeric hybrid materials Ln(DBM-SBA-15)3PMAA and Ln(DBM-SBA-16)3PMAA (Ln=Eu, Tb) are obtained by a sol-gel process. For comparison, binary lanthanide SBA-15 and SBA-16 mesoporous hybrid materials (denoted as Ln(DBM-SBA-15)3 and Ln(DBM-SBA-16)3) are also synthesized. The luminescence properties of these resulting materials are characterized in detail, and the results reveal that ternary lanthanide mesoporous polymeric hybrid materials present stronger luminescence intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary lanthanide mesoporous hybrid materials. This indicates that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system. In addition, the SBA-15 mesoporous hybrids show an overall increase in luminescence lifetime and quantum efficiency compared with SBA-16 mesoporous hybrids, indicating that SBA-15 is a better host material for the lanthanide complex than mesoporous silica SBA-16. [source]

An efficient neural network approach for nanoscale FinFET modelling and circuit simulation

M. S. Alam
Abstract The present paper demonstrates the suitability of artificial neural network (ANN) for modelling of a FinFET in nano-circuit simulation. The FinFET used in this work is designed using careful engineering of source,drain extension, which simultaneously improves maximum frequency of oscillation ,max because of lower gate to drain capacitance, and intrinsic gain AV0,=,gm/gds, due to lower output conductance gds. The framework for the ANN-based FinFET model is a common source equivalent circuit, where the dependence of intrinsic capacitances, resistances and dc drain current Id on drain,source Vds and gate,source Vgs is derived by a simple two-layered neural network architecture. All extrinsic components of the FinFET model are treated as bias independent. The model was implemented in a circuit simulator and verified by its ability to generate accurate response to excitations not used during training. The model was used to design a low-noise amplifier. At low power (Jds,10,µA/µm) improvement was observed in both third-order-intercept IIP3 (,10,dBm) and intrinsic gain AV0 (,20,dB), compared to a comparable bulk MOSFET with similar effective channel length. This is attributed to higher ratio of first-order to third-order derivative of Id with respect to gate voltage and lower gds in FinFET compared to bulk MOSFET. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Parallel-type C+L band hybrid amplifier pumped by 1480 nm laser diodes

S.-K. Liaw
Abstract A parallel-type, dispersion compensating C+L band erbium-doped fiber amplifier/Raman fiber amplifier is constructed by sharing a common 1480-nm pump source. The gain spectra of C+L band are flattened by optimally dividing the pump power ratio to 1:29 for EDFA and RFA, respectively. In a signal input power of ,20 dBm, the average gain is 14 dB for the C-band EDFA and 13.6 dB for the L-band RFA when a pump reflector is used to recycle the residual pump power in L-band. The noise figure value ranges from 4.6 to 6.5 dB and the polarization dependent gain is less than 0.14 dB. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

A linear cavity Brillouin fiber laser with multiple wavelengths output

M.R. Shirazi
Abstract A linear cavity Brillouin fiber laser (BFL) is proposed and demonstrated for multi-wavelength operation. The BFL uses a single mode fiber (SMF) as a non-linear gain medium and an optical circulator to generate a linear cavity resonator. Two couplers are used to inject the Brillouin Pump (BP) and tap the BFL output respectively. The effect of the coupler ratio on the BFL performance is studied by keeping constant the ratio of the first coupler and varying the ratio of the second coupler. 11 simultaneous lines with a line spacing of 0.8 nm are obtained at a BP of 11.7 dBm and a coupler ratio of 95:5. The laser output is stable at room temperature with 5 lines obtained at above , 30 dBm, and has the largest signal to noise ratio observed at the remaining lines. The proposed BFL has the advantage of being able to operate at any wavelength and is only dependent on the available BP wavelength. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

A new configuration of multi-wavelength Brillouin fiber laser

S.W. Harun
Abstract A multi-wavelength laser is demonstrated using stimulated Brillouin scattering in a single-mode fiber with a feedback loop using two couplers and an optical circulator. This Brillouin fiber laser can operate at any wavelength depending on the Brillouin pump (BP) wavelength used. With a BP of 14 dBm, approximately 8 to 10 BFL lines are obtained in both forward and backward directions respectively with a line spacing of 0.16 nm. The use of the 99/1 coupler and 50/50 coupler gives the highest power and number of lines for the forward and backward outputs respectively. The maximum Stokes power obtained is approximately 8.0 dBm. The anti-Stokes lines are also obtained due to four wave mixing and bidirectional operation. The combination of forward and backward output can generate a larger number of lines with channel spacing of 0.08 nm. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

An efficient gain-flattened C-band Erbium-doped fiber amplifier

S. W. Harun
Abstract An efficient gain-flattened C-band Erbium-doped fibre amplifier is demonstrated using a double-pass configuration with an IsoGainTM Erbium-doped fibre (EDF). The amplifier utilizes a double-propagation of signal provided by an optical circulator at the output end of the EDF to obtain an improved flatgain characteristic. At input signal power of ,10 dBm, a flatgain of 25 dB was obtained from wavelength region from 1528 to 1568 nm. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system because of its simplicity and low cost. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

A 60-GHz CMOS receiver front-end with integrated 180° out-of-phase Wilkinson power divider

Jen-How Lee
Abstract A 60-GHz receiver front-end with an integrated 180° out-of-phase Wilkinson power divider using standard 0.13 ,m CMOS technology is reported. The receiver front-end comprises a wideband low-noise amplifier (LNA) with 12.4-dB gain, a current-reused bleeding mixer, a baseband amplifier, and a 180° out-of-phase Wilkinson power divider. The receiver front-end consumed 50.2 mW and achieved input return loss at RF port better than ,10 dB for frequencies from 52.3 to 62.3 GHz. At IF of 20 MHz, the receiver front-end achieved maximum conversion gain of 18.7 dB at RF of 56 GHz. The corresponding 3-dB bandwidth (,3 dB) of RF is 9.8 GHz (50.8,60.6 GHz). The measured minimum noise figure (NF) was 9 dB at 58 GHz, an excellent result for a 60-GHz-band CMOS receiver front-end. In addition, the measured input 1-dB compression point (P1 dB) and input third-order inter-modulation point (IIP3) are ,20.8 dBm and ,12 dBm, respectively, at 60 GHz. These results demonstrate the adopted receiver front-end architecture is very promising for high-performance 60-GHz-band RFIC applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2688,2694, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25559 [source]

X-band low phase noise in-phase and out-of-phase injection-locked push,push DRO

Zhou Cao
Abstract An X-band push,push dielectric resonator (DR) oscillator with injection locking capability has been developed. Two injection locking methods, i.e., the in-phase method and the out-of-phase method, are studied. It is found that the out-of-phase method has wider locking range and much less effects on fundamental suppression than that of the in-phase method. The oscillator generates an output power of 9.5 dBm at 12.4 GHz and has a fundamental suppression of 32.5 dBc. Despite using a high quality (Q) factor DR, wide locking range has been obtained. SiGe HBTs with good flicker noise performance were chosen for low phase noise design. The phase noise values of the free running oscillator are ,104.4 dBc/Hz, ,120.2 dBc/Hz, and ,142.6 dBc/Hz at 10 kHz, 100 kHz, and 1 MHz offsets from the carrier frequency, respectively. The phase noise performance is superior or comparable to the reported designs. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2448,2452, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25510 [source]

An efficient CMOS power-combining technique with differential and single-ended power amplifier

Eunil Cho
Abstract This article proposes an efficient power-combining architecture with differential and single-ended power amplifiers (PAs) in a CMOS process. The single-ended amplifier is added for overall efficiency enhancement. To demonstrate this concept, a CMOS PA using the proposed architecture was fabricated with a 0.13-,m CMOS technology that delivers 30.6 dBm of output power with 42% drain efficiency and 38% power-added efficiency at 1.95 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2214,2217, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25460 [source]

Low power dual transformer injection locked frequency divider using 0.5 ,m GaAs E/D-mode PHEMTs process

Po-Yu Ke
Abstract This letter proposes a new divide-by-2 injection locked frequency divider (ILFD) fabricated by 0.5 ,m GaAs ED-Mode PHEMTs process and describes the operation principle of the dual-transformer ILFD. The first transformer is applied to replace two inductors of the cross-couple LC-tank oscillator circuit. The injection signal of the ILFD transmits into a transistor through a second transformer, which consisted of a bandpass filter achieving a high injection signal power and wide locking range. The measurement results show that the divider's free-running frequency were from 6.47 to 9.54 GHz (32.2%) with 3 V supply voltage. With an incident power of 0 dBm, the locking range is 3.07 GHz from the incident frequency 16.41 to 19.45 GHz (15.6%). The measured phase noise of free running VCO is ,92.2 dBc/Hz at 1 MHz offset frequency at 9.45 GHz and this value of the locked ILFD is ,128.4 dBc/Hz, which is 36.2 dB lower than the free running VCO. The core power consumption was 42 mW. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2302,2306, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25442 [source]

A novel CMOS distributed receiver front-end for wireless ultrawideband receivers

Xin Guan
Abstract An ultrawideband CMOS distributed receiver front-end utilizing cascade gain cell structure is designed in Jazz 0.18-,m CMOS process. The proposed distributed front-end, fully integrating a low-noise amplifier (LNA) and mixer together, demonstrates 11.5,14 dB gain, 5,6.5 dB noise figure and more than 9-dB RF/LO return loss over 2,17 GHz with a fixed IF frequency of 500 MHz and LO power of 5 dBm. The entire circuit occupies 1.7 × 1.0 mm2 including on-wafer pads and consumes 170 mA from 1.8-V voltage supply. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1790,1792, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25316 [source]

Ku-band SiGe HBT I/Q subharmonic mixer with reactive quadrature generators

Sheng-Che Tseng
Abstract This article demonstrates a high-frequency 0.35-,m SiGe HBT subharmonic downconverter with reactive in-phase and quadrature-phase (I/Q) generators. Two reactive I/Q generators are integrated in our work to provide differential quadrature RF and LO signal. The I/Q subharmonic downconverter with single-ended LO, RF, and IF (I/Q) ports has a conversion gain of 1 dB, IP1dB of ,10 dBm, IIP3 of 0 dBm, and IIP2 of 21 dBm at 16.4 GHz. The magnitude and phase errors between the I and Q channels are 1.34% and 0.6°, respectively. The dc power consumption of this I/Q mixer without output buffers is approximately 5 mW. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1516,1520, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25281 [source]

Ka-band substrate integrated waveguide voltage-controlled Gunn oscillator

Zhou Cao
Abstract A Ka-band substrate integrated waveguide (SIW) voltage-controlled oscillator (VCO) is demonstrated using GaAs Gunn diode.GaAs hyperabrupt varactor is employed in parallel to the Gunn diode for low phase noise and wideband tuning. The VCO achieves a tuning range of more than 1 GHz by varying the varactor tuning voltage between 0 V and 9 V, and phase noise of ,102.1 dBc/Hz at 1 MHz offset from a 36 GHz carrier frequency. The output power varies from 9.3 dBm to 11.3 dBm within the tuning range. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1232,1235, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25169 [source]

A variable gain amplifier using a very-high speed OTA

You Zheng
Abstract A variable gain amplifier is demonstrated using only one fully-differential operational transconductance amplifier (OTA) as the core circuit element.Gain control is achieved by varying the transconductance of the OTA and by using an output buffer circuit to sum the output signals of the OTA in the correct phase relationship. The circuit was designed and fabricated using 0.18 ,m CMOS technology. Measured results show a gain control range of 15 dB between 1 GHz and 3 GHz and the input and output reflection coefficients are below ,10 dB and ,20 dB, respectively. The output power of the amplifier is +2.3 dBm at its 1-dB compression point. The chip has a maximum DC power consumption 12.6 mW and it measures 0.25 mm2 including bonding pads. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1112,1116, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25114 [source]

60 GHz SoC/SoP radio system for high data-rate transmission

K. C. Eun
Abstract We present the 60 GHz CMOS and system-on-package (SoP) research activities in Korea Advanced Institute of Science and Technology for high data-rate and short-range wireless communication. A low-power single-chip resonant frequency CMOS receiver for 60 GHz mobile terminals consists of four-stage current reuse LNA, resistive mixer, Ka-band low-phase noise VCO, high-suppression frequency doubler, and two-stage current reuse drive amplifiers. The receiver conversion gain and input P1dB are ,9.5 dB and ,12.5 dBm, respectively, with a size of 2.67 × 0.75 mm2 and power consumption of 21.9 mW. The integration and communication tests of a transmitter/receiver (Tx/Rx) radio have been demonstrated at a data rate of 3 Gbps for short-range transmission and with a communication distance of over 3.5 m at 650 Mbps data rate. The design and fabrication of mmW subcircuits, such as low-loss transmission lines and transitions with noble air cavity structures, a high-Q resonator using zigzagged dual-row via posts and a ,/4 short stub, and the monolithic integration of band-pass filter and antennas, have been performed for low-temperature cofired ceramic SoP integration with a size of 37 × 11 mm2 for the whole Tx or Rx radio. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 667,673, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25024 [source]

A highly efficient class-F power amplifier for wideband linear power amplifier applications

Jangheon Kim
Abstract In this letter, a highly efficient class-F power amplifier (PA) is developed as a new main block of the wideband base-station linear power amplifier. The class-F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10-W peak envelop power. The nonlinearity and memory effects of class-F PA are explored to apply the wideband application. The maximum power-added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14-GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide-band code division multiple access 3FA signal with 15-MHz bandwidth, and the linearity can be improved to about ,48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323,2326, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24631 [source]