Blocked diisocyanates as reactive coupling agents: Application to pine fiber-polypropylene composites

In this paper, composites from polypropylene and Kraft pulp (from Pinus radiata) were prepared. Phenyl isocyanate, unblocked and phenol blocked derivatives of 4,4`-methylenebis (phenyl isocyanate) (MDI) were used as coupling agents and the mechanical properties of the obtained composites analyzed. The results showed that the addition of such compatibilizers readily improved the tensile and flexural strengths of the composites. However, no significant variation in the mechanical properties was observed for composite formulations comprising different isocyanate compounds. Accordingly, the chemical structure of isocyanate derivatives did not affect extensively the mechanical properties of MDI-coupled pine fiber reinforced composites. These results were similar to those obtained in previous studies regarding the efficiency of organosilane coupling agents. In comparison to monoreactive isocyanates, the addition of MIDI increased considerably the mechanical properties of pine fiber-polypropylene composites. The mechanical anchoring of polymeric PP chains onto the irregular reinforcement surface supported this result. Non-isothermal DSC analysis showed a slowing effect of MDI on the crystallization kinetics of the coupled composites. This may have been the result of diminished polymer chain mobility in the matrix due to mechanical anchoring onto the fiber surface. Considering these results, the occurrence of strong bonds between the composite components was stated, rather than the unique existence of Van der Waals interactions among the non-polar structures. (c) 2008 Elsevier Ltd. All rights reserved.

Acoustic Simulation of a Special Switched Reluctance Drive by Means of Field-Circuit Coupling and Multiphysics Simulation

The approach presented in this paper consists of an energy-based field-circuit coupling in combination with multi-physics simulation of the acoustic radiation of electrical machines. The proposed method is applied to a special switched reluctance motor with asymmetric pole geometry to improve the start-up torque. The pole shape has been optimized, subject to low torque ripple, in a previous study. The proposed approach here is used to analyze the impact of the optimization on the overall acoustic behavior. The field-circuit coupling is based on a temporary lumped-parameter model of the magnetic part incorporated into a circuit simulation based on the modified nodal analysis. The harmonic force excitation is calculated by means of stress tensor computation, and it is transformed to a mechanical mesh by mapping techniques. The structural dynamic problem is solved in the frequency domain using a finite-element modal analysis and superposition. The radiation characteristic is obtained from boundary element acoustic simulation. Simulation results of both rotor types are compared, and measurements of the drive are presented.

Characterization of electrical penetration graphs of Bucephalogonia xanthophis, a vector of Xylella fastidiosa in citrus

The sharpshooter Bucephalogonia xanthophis (Berg) (Homoptera: Cicadellidae) is a vector of the xylem-limited bacterium, Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner), which causes citrus variegated chlorosis. Despite the importance of citrus variegated chlorosis, the probing behavior of vectors on citrus and its implications for transmission of X. fastidiosa have not been studied. Here we studied electrical penetration graph (EPG-DC system) waveforms produced by B. xanthophis on Citrus sinensis (L.) Osbeck (Rutaceae), and their relationships with stylet activities and xylem ingestion. Electrical penetration graph waveforms were described based on amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration on plant tissues. The main waveforms were correlated with histological observations of salivary sheaths in plant tissues and excretion analysis, in order to determine stylet activities and their precise position. Six waveforms and associated activities are described: (S) secretion of salivary sheath and intracellular stylet pathway, (R) resting during stylet pathway, (Xc) contact of stylets with xylem vessels, (Xi) active xylem ingestion, (N) interruption within the xylem phase (during Xc or Xi), and (W) withdrawal of stylet from the plant. The sharpshooter spent 91.8% of its probing time with its stylet in the xylem, where the main activity was ingestion (Xi: 97.5%). During a probe, the most likely sequence of events is secretion of salivary sheath and pathway (S) through epidermal and parenchyma cells (all individuals), followed by contact with xylem (Xc) (67.6% of all individuals) and ingestion (Xi) (88.3% of those that exhibit waveform Xc). The mean time to contact the xylem (Xc) and initiate ingestion (Xi) after onset of the first probe was 27.8 and 34.2 min, respectively. However, sustained xylem ingestion (Xi > 5 min) was established after 39.8 min, on average. This information is basic for future studies on the transmission mechanisms of X. fastidiosa and in order to establish control strategies aimed at interfering with this process.

Vector within-host feeding preference mediates transmission of a heterogeneously distributed pathogen

2. We documented the within-host distribution of two vector species that differ in transmission efficiency, the leafhoppers Draeculacephala minerva and Graphocephala atropunctata, and which are free to move throughout entirely caged alfalfa plants. The more efficient vector D. minerva fed preferentially at the base of the plant near the soil surface, whereas the less efficient G. atropunctata preferred overwhelming the top of the plant. 3. Next we documented X. fastidiosa heterogeneity in mechanically inoculated plants. Infection rates were up to 50% higher and mean bacterial population densities were 100-fold higher near the plant base than at the top or in the taproot. 4. Finally, we estimated transmission efficiency of the two leafhoppers when they were confined at either the base or top of inoculated alfalfa plants. Both vectors were inefficient when confined at the top of infected plants and were 20-60% more efficient when confined at the plant base. 5. These results show that vector transmission efficiency is determined by the interaction between leafhopper within-plant feeding behaviour and pathogen within-plant distribution. Fine-scale vector and pathogen overlap is likely to be a requirement generally for efficient transmission of vector-borne pathogens.

Irrigation requirements and transpiration coupling to the atmosphere of a citrus orchard in Southern Brazil

Crop evapotranspiration (ETc) was measured as evaporative heat flux from an irrigated acid lime orchard (Citrus latifolia Tanaka) using the aerodynamic method. Crop transpiration (T) was determined by a stem heat balance method. The irrigation requirements were determined by comparing the orchard evapotranspiration (ETc) and T with the reference evapotranspiration (ETo) derived from the Penman-Monteith equation, and the irrigation requirements were expressed as ETc/ETo (Kc) and T/ETo (Kcb) ratios. The influence of inter-row vegetation on the ETc was analyzed because the measurements were taken during the summer and winter, which are periods with different regional soil water content. In this study, the average Mc values obtained were 0.65 and 0.24 for the summer and winter, respectively. The strong coupling of citrus trees to the atmosphere and the sensitivity of citrus plants to large vapor pressure deficits and air/leaf temperatures caused variations in the Kcb in relation to the ETo ranges. During the summer, the Kcb value ranged from 0.34 when the ETo exceeded 5 mm d(-1) to 0.46 when the ETo was less than 3 mm d(-1). (C) 2011 Elsevier B.V. All rights reserved.

Endophytic population of Pantoea agglomerans in citrus plants and development of a cloning vector for endophytes

Harmless bacteria inhabiting inner plant tissues are termed endophytes. Population fluctuations in the endophytic bacterium Pantoea agglomerans associated with two species of field cultured citrus plants were monitored over a two-year period. The results demonstrated that populations of P. agglomerans fluctuated in Citrus reticulata but not C. sinensis. A cryptic plasmid pPA3.0 (2.9 kb) was identified in 35 out of 44 endophytic isolates of P. agglomerans and was subsequently sequenced. The origins of replication were identified and nine out of 18 open reading frames (ORFs) revealed homology with described proteins. Notably, two ORFs were related to cellular transport systems and plasmid maintenance. Plasmid pPA3.0 was cloned and the gfp gene inserted to generate the pPAGFP vector. The vector was introduced into P. agglomerans isolates and revealed stability was dependent on the isolate genotype, ninety-percent stability values were reached after 60 hours of bacterial cultivation in most evaluated isolates. In order to definitively establish P. agglomerans as an endophyte, the non-transformed bacterium was reintroduced into in vitro cultivated seedlings and the density of inner tissue colonization in inoculated plants was estimated by bacterium re-isolation, while the tissue niches preferred by the bacterium were investigated by scanning electronic microscopy (SEM). Cells from P. agglomerans (strain ARB18) at similar densities were re-isolated from roots, stems and leaves and colonization of parenchyma and xylem tissues were observed. Data suggested that P. agglomerans is a ubiquitous citrus endophyte harboring cryptic plasmids. These characteristics suggest the potential to use the bacterium as a vehicle to introduce new genes in host plants via endophytic bacterial transformation.

Copper salt-catalyzed homo-coupling reaction of potassium alkynyltrifluoroborates: a simple and efficient synthesis of symmetrical 1,3-diynes

The copper-catalyzed dimerization of alkynyltrifluoroborates proceeds readily with good yields. The homo-coupling reaction can be effected in DMSO, in the open air, using Cu(OAc)(2) as catalyst in the absence of any other additives. A variety of functional groups are tolerated. (C) 2008 Elsevier Ltd. All rights reserved.

Ultrasound-assisted synthesis of functionalized 1,3-enynes by palladium-catalyzed cross-coupling reaction of alpha-styrylbutyltelluride with alkynyltrifluoroborate salts

An ultrasound-assisted synthesis of functionalized 1,3-enyne scaffolds is described and illustrated by palladium-catalyzed cross-coupling of potassium alkynyltrifluoroborate salts and alpha-styrylbutyltellurides. This procedure offers easy access to 1,3-enyne architecture that contains aliphatic and aromatic groups in good to excellent yields.

Functionalization of (2S)-Isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones by a Suzuki-Miyaura Cross-Coupling Reaction Using Aryltrifluoroborate Salts: Convenient Enantioselective Preparation of alpha-Substituted beta-Amino Acids

A simple protocol for the Pd(OAc)(2)-catalyzed cross-coupling reaction of 1-benzoyl-(2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones with potassium aryltrifluoroborates was developed. The reaction is performed at 110 degrees C with a ligand-free catalyst. In all cases, complete conversion of the 1-benzoyl-(2S)-isopropyl-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones and aryltrifluoroborates into the C-C coupling products was observed within 30-360 min. It is noteworthy that a large variety of groups present in the potassium aryltrifluoroborates (-CF(3), -OMe, -SEt, -CN, -CHO, -Cl, -Cbz, -NCbz, -OH, -CO(2)H) could be tolerated. Hydrogenation of the endocyclic double bonds in the Suzuki-Miyaura products followed by acid hydrolysis afforded highly enantioenriched alpha-aryl-substituted beta-amino acids.

alpha-Arylation and Alkynylation of Cyclic alpha-Iodoenones Using Palladium-Catalyzed Cross-Coupling Reactions with Trifluoroborate Salts

An expeditious synthesis of alpha-aryl- and alpha-alkynylcyclo-hexenones is described and illustrated by palladium-catalyzed cross-coupling reaction of cyclic alpha-iodoenones with potassium aryltrifluoroborate salts. This procedure offers easy access to alpha-arylated and alkynylated cyclohexenones functionalized with electrondonor and -acceptor substituents in good yields.

Calcium Carbonate Particle Growth Depending on Coupling among Adjacent Layers in Hybrid LB/LbL Films

There are practical and academic situations that justify the study of calcium carbonate crystallization and especially of systems that are associated with organic matrices and a confined medium. Despite the fact that many different matrices have been studied, the use of well-behaved, thin organic films may provide new knowledge about this system. In this work, we have studied the growth of calcium carbonate particles on well-defined organic matrices that were formed by layer-by-layer (LbL) polyelectrolyte films deposited on phospholipid Langmuir-Blodgett films (LB). We were able to change the surface electrical charge density of the LB films by changing the proportions of a negatively charged lipid, the sodium salt of dimyristoyl-sn-glycero-phosphatidyl acid (DMPA), and a zwitterionic lipid. dimyristoyl-sn-glycero-phosphatidylethanolamine (DMPE). This affects the subsequent polyelectrolyte LbL film deposition, which also changes the the nature of the bonding (electrostatic interaction or hydrogen bonding). This approach allowed for the formation of calcium carbonate particles of different final shapes, roughnesses, and sizes. The masses of deposited lipids, polyelectrolytes, and calcium cabonate were quantified by the quartz crystal microbalance technique. The structures of obtained particles were analyzed by scanning electron microscopy.

Retrograde delivery of photosensitizer (TPPp-O-beta-GluOH)(3) selectively potentiates its photodynamic activity

Photodynamic therapy involves administration of a photosensitizing drug and its subsequent activation by visible light of the appropriate wavelength. Several approaches to increasing the specificity of photosensitizers for cancerous tissues and, in particular, through their conjugation to ligands that are directed against tumor-associated antigens have been investigated. Here, we have studied the delivery of the photocytotoxic porphyrin compound TPP(p-O-beta-D-GluOH)(3) into tumor cells that overexpress the glycosphingolipid Gb3, using the Gb3-binding nontoxic B-subunit of Shiga toxin (STxB) as a vector. To allow for site-directed chemical coupling, an STxB variant carrying a free sulfhydryl moiety at its C-terminal end has been used. Binding affinity, cellular uptake, singlet oxygen quantum yield, and phototoxicity of the conjugate have been examined. Despite some effect of coupling on both the photophysical properties of TPP(p-O-beta-D-GluOH)(3) and the affinity of STxB for its receptor, the conjugate exhibited a higher photocytotoxic activity than the photosensitizer alone and was exquisitely selective for Gb3-expressing tumor cells. Furthermore, our data strongly suggest that STxB-mediated retrograde delivery of the photosensitizer to the biosynthetic/secretory pathway is critical for optimal cytotoxic activity. In conclusion, a strong rationale for using retrograde delivery tools such as STxB in combination with photosensitizing agents for the photodynamic therapy of tumors is presented.

Synthesis of (Z)-tributylstannyl enynes: systematic studies of Sonogashira cross-coupling reactions between (E)-1-iodovinyl-1-tributylstannanes and terminal acetylenes using amines or tetrabutylammonium hydroxide (TBAOH) as activator

Sonogashira cross-coupling reactions involving (E)-iodo vinyl stannanes and terminal acetylenes were carried out in the presence of Pd(PPh(3))(4), Cul and several amines, affording (Z)-tributylstannyl enynes in moderate to good yields (62-91%). Utilizing the catalytic system containing Pd(PPh(3))(4) (5%), Cul (10%), and TBAOH (40% in aqueous media) as activator, better yields (72-91%) and lower reaction times were achieved. (C) 2011 Elsevier Ltd. All rights reserved.

Endostatin- and interleukin-2-expressing retroviral bicistronic vector for gene therapy of metastatic renal cell carcinoma

Background Metastatic renal cell carcinoma (mRCC) is one of the most treatment-resistant malignancies. Despite all new therapeutic advances, almost all patients develop resistance to treatment and cure is rarely seen. In the present study, we evaluated the antitumor effect of a bicistronic retrovirus vector encoding both endostatin (ES) and interleukin (IL)-2 using an orthotopic metastatic RCC mouse model. Methods Balb/C-bearing Renca cells were treated with NIH/3T3-LendIRES-IL-2-SN cells. In the survival studies, mice were monitored daily until they died. At the end of the in vivo experiment, serum levels of IL-2 and ES were measured, the lung was weighed, and the number of metastatic nodules, nodule area, tumor vessels and proliferation of tumor-infiltrating Renca cells were determined. Results Inoculation of NIH/3T3-LendIRES-IL-2-SN cells resulted in an increase in ES and IL-2 levels in the treated group (p < 0.05). There was a significant decrease in lung wet weight, lung nodule area and tumor vessels in the treated group compared to the control group (p < 0.001). The proliferation of Renca cells in the bicistronic-treated group was significantly reduced compared to the control group (p < 0.05). Kaplan-Meier survival curves showed that the probability of survival was significantly higher for mice submitted to bicistronic therapy (log-rank test, p = 0.0016). Bicistronic therapy caused an increase in the infiltration of CD4, CD4 interferon (IFN)gamma-producing, CD8, CD8 IFN gamma-producing and natural killer (CD49b) cells. Conclusions Retroviral bicistronic gene transfer led to the secretion of functional ES and IL-2 that was sufficiently active to: (i) inhibit tumor angiogenesis and tumor cell proliferation and (ii) increase the infiltration of immune cells (C) Copyright. 2011 John Wiley & Sons, Ltd.

An fMRI Normative Database for Connectivity Networks Using One-Class Support Vector Machines

The application of functional magnetic resonance imaging (fMRI) in neuroscience studies has increased enormously in the last decade. Although primarily used to map brain regions activated by specific stimuli, many studies have shown that fMRI can also be useful in identifying interactions between brain regions (functional and effective connectivity). Despite the widespread use of fMRI as a research tool, clinical applications of brain connectivity as studied by fMRI are not well established. One possible explanation is the lack of normal pattern, and intersubject variability-two variables that are still largely uncharacterized in most patient populations of interest. In the current study, we combine the identification of functional connectivity networks extracted by using Spearman partial correlation with the use of a one-class support vector machine in order construct a normative database. An application of this approach is illustrated using an fMRI dataset of 43 healthy Subjects performing a visual working memory task. In addition, the relationships between the results obtained and behavioral data are explored. Hum Brain Mapp 30:1068-1076, 2009. (C) 2008 Wiley-Liss. Inc.