Lateralization of amygdala activation in fMRI may depend on phase-encoding polarity

Object

Susceptibility artifacts along the phase-encoding (PE) direction impact the activation pattern in the amygdala and may lead to systematic asymmetries. We implemented a triple-echo echo-planar imaging (EPI) sequence, acquiring opposite PE polarities along left?Cright PE direction in a single shot, to investigate its effects on amygdala lateralization.

Materials and Methods

Twelve subjects viewed emotional faces to evoke amygdala activation.

Results and Conclusion

A region of interest analysis revealed that the lateralization of amygdala responses depended on the PE polarity thus representing a pure method artifact. Alternating PE with multi-echo EPI reduced the artifact. Lateralized fMRI activation in areas with magnetic field inhomogeneities need to be interpreted with caution.     

The use of long-chain plant polyprenols as a means to modify the biological properties of new biodegradable polyurethane scaffolds for tissue engineering. A pilot study

Microporous membranes for tissue engineering were produced from new biodegradable polyurethane based on hexamethylene diisocyanate, poly(ε-caprolactone) diol and 1,4:3,6-dianhydro-d-sorbitol. The interconnected pores had an average size in the range of 5–100 μm. The tensile strength at break, the Young’s modulus and elongation at break of the membranes were 3.2 ± 0.3 MPa, 25.2 ± 1.5 MPa and 190 ± 12%, respectively, while nonporous foils from the same polymers had a tensile strength at break of 40 ± 2 MPa, a Young’s modulus of 91 ± 6 MPa, and an elongation at break of 370 ± 10%. The membranes were incubated for 10 days in a 2.65 vol% solution of long-chain plant polyprenol in n-hexane to promote their interaction with cells and tissues. The polyprenol was isolated from leaves of Magnolia cobus and was a mixture of prenol-10 and prenol-11. The prenol-impregnated membranes and nonimpregnated membranes (control) were tested in cell culture to assess whether impregnation has a beneficial effect on cell-material interaction. The cells used in the test were chondrocytes isolated from the articular-epiphyseal cartilage of leg bones of 5-day-old inbred LEW rats. The time of culture was 2 and 5 weeks. Both, the nonimpregnated and impregnated polyurethane membranes supported attachment and growth of rat chondrocytes. The cells firmly attached to the surface of the microporous membranes, invaded the pores and maintained the round shape characteristic for chondrocyte-like-morphology. Abundant fibrillar extracellular matrix produced by the cells resembled the network formed by chondrocytes in vivo. The cells produced relatively more extracellular matrix in the membranes impregnated with polyprenol than in the control membranes. Impregnation of polyurethane scaffolds with biologically active amphiphilic polyprenols may be a route to facilitate the cell–material interaction.     

Relating nutrient and herbicide fate with landscape features and characteristics of 15 subwatersheds in the Choptank River watershed

Excess nutrients and agrochemicals from non-point sources contribute to water quality impairment in the Chesapeake Bay watershed and their loading rates are related to land use, agricultural practices, hydrology, and pollutant fate and transport processes. In this study, monthly baseflow stream samples from 15 agricultural subwatersheds of the Choptank River in Maryland USA (2005 to 2007) were characterized for nutrients, herbicides, and herbicide transformation products. High-resolution digital maps of land use and forested wetlands were derived from remote sensing imagery. Examination of landscape metrics and water quality data, partitioned according to hydrogeomorphic class, provided insight into the fate, delivery, and transport mechanisms associated with agricultural pollutants. Mean Nitrate-N concentrations (4.9 mg/L) were correlated positively with percent agriculture (R² = 0.56) and negatively with percent forest (R² = 0.60). Concentrations were greater (p = 0.0001) in the well-drained upland (WDU) hydrogeomorphic region than in poorly drained upland (PDU), reflecting increased denitrification and reduced agricultural land use intensity in the PDU landscape due to the prevalence of hydric soils. Atrazine and metolachlor concentrations (mean 0.29 μg/L and 0.19 μg/L) were also greater (p = 0.0001) in WDU subwatersheds than in PDU subwatersheds. Springtime herbicide concentrations exhibited a strong, positive correlation (R² = 0.90) with percent forest in the WDU subwatersheds but not in the PDU subwatersheds. In addition, forested riparian stream buffers in the WDU were more prevalent than in the PDU where forested patches are typically not located near streams, suggesting an alternative delivery mechanism whereby volatilized herbicides are captured by the riparian forest canopy and subsequently washed off during rainfall. Orthophosphate, CIAT (6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine), CEAT (6-chloro-N-ethyl-1,3,5-triazine-2,4-diamine), and MESA (2-[(2-ethyl-6-methylphenyl) (2-methoxy-1-methylethyl)amino]-2-oxoethanesulfonic acid) were also analyzed. These findings will assist efforts in targeting implementation of conservation practices to the most environmentally-critical areas within watersheds to achieve water quality improvements in a cost-effective manner.     

Synthesis and activity of zirconocene catalysts supported on silica-type sol-gel carrier for ethylene polymerization

Summary Synthesis and activity of bis(cyclopentadienyl)zirconium dichloride catalyst supported on unconventional silica-type material obtained in sol-gel process and activated by organoaluminium co-catalyst were studied. The effect of support modification conditions (thermal dehydration and/or modification by organoaluminium compound) and a type of co-catalyst on an activity of the catalytic system in ethylene polymerization and properties of resulting polymers were investigated and compared with results obtained earlier for vanadium catalysts supported on mentioned sol-gel carrier. The most appropriate method of the sol-gel silica-type support preparation is thermal pre-treating (200°C) followed by modification with AlEt₂Cl. Metallocene catalyst supported on such sol-gel product and activated by MAO appeared to be most active among studied systems. Studied Cp₂ZrCl₂/MAO supported on silica-type sol-gel carrier allow to obtain polyethylene (at 50°C polymerization temperature) with yield up to 30·10⁶ g/(mol_Zr·h), molecular weight below 300 000 and MWD=2−4. Received: 4 September 2000/Revised version: 3 January 2001/Accepted: 3 January 2001     

Synthesis and catalytic properties for olefin polymerization of new vanadium complexes containing silsesquioxane ligands with different denticity

A series of new vanadium‐silsesquioxanes ( 2a ? 2d ) was prepared by reacting VCl₄ with not fully condensed silsesquioxanes (having from one to four silanol groups) and evaluated as pre‐catalysts in olefin polymerization. The activation of 2a ? 2d with EtAlCl₂ generated highly active catalysts for ethylene polymerization, yielding high molar mass polymers with narrow dispersity. Ultra‐high molar mass polyethylenes, M _w up to 4 × 10⁶ g mol^?1, were obtained with methylaluminoxane and Al(i Bu)₃/[Ph₃C][B(C₆F₅)₄] as activators. Upon treatment with methylaluminoxane and boron compounds, all vanadium pre‐catalysts were active in 1‐octene polymerization as well, and produced isotactic‐rich poly(1‐octene)s with moderate monomer conversion (up to 23%). The polymerization parameters were optimized and the effect of the silsesquioxane structure on the catalytic activity and polymer properties was studied. © 2017 Society of Chemical Industry     

Synthesis of linear polysiloxanes with electron-donating organophosphorus pendant groups by kinetically controlled ring-opening polymerization

Six-membered ring siloxane monomers containing a phosphorus electron-donating groupR=–CH₂CH₂PPh₂ (1), –CH₂CH₂P(S)Ph₂ (2), and –CH₂CH₂P(O)Ph₂ (3) were synthesized. The anionic ring-opening polymerization of these monomers with kinetic control of products has been studied using tetrahydrofuran (THF) as solvent and lithium silanolates as initiators. The polymerization leads to a high molecular weight linear polymer with a very good yield in the case of2 and with a fairly good yield in the case of1 and3. The presence of the phosphorus group enhances the cyclization and broadens the molecular weight distribution of the linear polymer. This effect is relatively weak for the thiophosphinoyl group. At least in the case of the polymer obtained from2, phosphorus groups are distributed uniformly in the macromolecule, however, their arrangement along the chain is not regular. The interaction of polymers obtained from monomers1, 2, and3 with some electrophiles such as alkyl or silyl halides was demonstrated to lead to generation of polyelectrolytes.     

Properties of anionic polymerized ε‐caprolactam in the presence of carbon nanotubes

The results of the investigations of the relations between structure, physical and usage properties of polyamide 6 (PA6) reinforced with multiwall carbon nanotubes (MWNTs) are presented. A method of in situ anionic bulk polymerization of ε‐caprolactam in the presence of MWNTs was used for the preparation of reinforced PA6. The polymerization product was crushed, and the pellets of PA6 and PA6/MWNTs composites were injection molded to produce the standard test specimens for various measurements. The surface morphology (SEM), thermal (DSC, TGA, DMTA), and mechanical properties (tensile strength, Charpy's notched impact strength) of these materials were examined. Some differences between our specimens and those obtained by hydrolytic polymerization of ε‐caprolactam (CL) were found. It was found that a small amount of carbon nanotube decreases the crystallinity degree of PA6 matrix in the composites. The thermal stability was higher than that for neat PA6. DMTA results showed that the magnitudes of the storage modulus are higher for the PA6/MWNTs composites than for the unmodified PA6 in the temperature range between ?90 and 200°C. The tensile strength and tensile modulus are higher compared with the neat PA6. The elongation at break showed no noticeable change in the range of MWNTs loading considered, while the Charpy's notched impact strength slightly decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Reactive polymeric microspheres: Catalytic reduction of a nitrobenzene derivative

Polymeric microspheres have been demonstrated as a potentially useful vehicle for targeted delivery applications. In this work we report on the preparation of polymer microspheres capable of performing specific reaction chemistry. The microspheres are modified with silver nanoparticles in a two‐step reaction. The first step involves formation of the microsphere by UV‐induced polymerization of pyrrole and the second step is the reduction of silver cations to metallic silver in situ. The resulting Ag‐decorated microspheres were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X‐ray, and thermogravimetry analysis. The catalytic reaction behavior of the decorated microspheres was illustrated through the reduction reaction of m‐nitrobenzene sulfonate acid in the presence of sodium borohydride. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43653.     

Relaxation of magnetoelastic phenomena in electrodeposited nickel-iron films

Cylindrical 5 μm films of Ni-8% Fe alloy electrodeposited onto a substrate wire, with the easy axis of magnetization in a circumferential direction and the hard axis coinciding with the substrate axis, can be used as sensors of tension. The change of the anisotropy field H_k is proportional to the strain produced in the film and can be observed as a change of the current in a measuring circuit. However, at constant load (and strain) a considerable relaxation occurs, which can be represented as an exponential function of time, at least for periods shorter than 10 min. The rate of relaxation is temperature dependent with an apparent activation energy of 0.3 eV. It is suggested that the observed phenomena are due to the migration of defects and to their interaction.     

Starch modified by high-pressure homogenisation of the pastes – Some structural and physico-chemical aspects

According to literature data, high-pressure homogenisation of starch paste in the optimum conditions gives a product of digestibility reduced by 50%. This product has been analysed from the point of view of its resistance to enzyme activity. Results obtained by X-ray diffraction, scanning electron microscopy, optical microscopy and measurements of surface activity prove that reduction in the product digestibility is not related to changes in its crystalline structure and morphology of its particles. The product of high-pressure homogenisation of the paste is also found to be characterised by very slow kinetics of wetting. In comparison to the native starch, the aqueous solutions of the product of homogenisation show significantly different surface activity and different mode of iodine complexation.