Unusual magnetic properties of NiO nanoparticles embedded in a silica matrix

We have observed unusual magnetic properties of NiO (nickel oxide) nanoparticles embedded in a silica matrix. The sample was synthesized by a method based on the contribution of sol-gel and combustion processes. X-ray powder diffraction (XRPD) of the sample shows the formation of the nanocrystalline NiO phase whereas transmission electron microscope (TEM) reveals spherical-shaped nanoparticles of about 4 nm diameter. Moreover, HRTEM images show lattice fringes of the nanoparticles and defects in the crystal structure. The temperature and field dependence of the magnetization are also measured. The zero-field-cooled (ZFC) measurements show two maximums, one sharp and narrow at low temperatures ∼6.5 K and an other broad one at higher temperature ∼64 K. The FC magnetization shows a continuous increase upon lowering the temperature. The M(H) measurements reveal that NiO nanoparticles display anomalous hysteretic behaviors at low temperatures (below the low temperature maximum in the ZFC curve, 2 K and 5 K) showing that the magnetization initial curve lies below the hysteresis loop for a certain field range. Moreover, jump of the magnetization at low temperatures (2 K and 5 K) are also observed. These features represent novel magnetic properties for nanosized NiO which may be attributed to the surface spins. Moreover, these results indicate that the NiO nanoparticle consists of magnetically disorder shell and antiferromagnetically order core with an uncompensated magnetic moment.     

Supercritical carbon dioxide extraction of sesquiterpenes from valerian root

Supercritical carbon dioxide extraction of sesquiterpenes from valerian root was investigated. Extractions from cultivar Arterner züctung and two wild grown valerian subspecies were performed. The influence of extraction conditions on extraction yield and chemical composition of obtained extracts was investigated at temperatures from 40 °C to 50 °C and pressures from 10 MPa to 20 MPa. Chemical composition of obtained extracts was analyzed by GC/FID and GC/MS methods. The influence of particle size on extraction process was investigated at 40 °C and 10 MPa. The major constituents of supercritical extracts were valerianol, valerenal, bornyl acetate and kessanyl acetate. Optimal extraction conditions for the cyclopentanoid sesquiterepenes isolation, referred to the content of cyclopentanoid sesquiterpenes in extract, were found to be 50 °C and 15 MPa. Extract obtained from the cultivar was characterized by the higher content of cyclopentanoid sesquiterpenes, as well as valerenal comparing to extracts from wild grown species. At 40 °C and 20 MPa 19.6% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. At 40 °C and 10 MPa, 17.4% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. However, the extract obtained with methanol was characterized by the high content (42.51%) of unwanted isovaleric as well as by the lower content of cyclopentanoid sequiterpenes than the extracts obtained with supercritical carbon dioxide. The process of supercritical extraction was influenced by particle size. In order to simulate the process, mathematical model on the secretory structure scale was derived. Results of the model showed good agreement with the experimental data.     

Cuticular Surface Hydrocarbons of Desert Locust Nymphs, Schistocerca gregaria, and Their Effect on Phase Behavior

The quantity of cuticular hydrocarbons is higher in solitarious nymphs of the desert locust, Schistocerca gregaria, compared to gregarious nymphs, but the total hydrocarbon fraction of solitarious nymphs does not significantly divert behavioral transition of isolated nymphs to the gregarious phase, while gregarious hydrocarbon extracts do. This suggests that qualitative differences in composition are responsible for the biological effect. The profile of cuticular hydrocarbon components is similar in the two phases, but some peak ratios differ. Crowding of solitarious nymphs leads to rapid changes in the profile of the hydrocarbon fraction, suggesting that specific hydrocarbons are produced and secreted as a consequence. Isolating previously crowded nymphs has an opposite effect. The composition of cuticular hydrocarbons from the migratory locust, Locusta migratoria, which differs considerably from that of S. gregaria, does not induce the gregarious behavioral phase in solitarious nymphs of the latter.     

Use of conifer volatiles to reduce injury caused by carrot psyllid,Trioza apicalis,Förster (Homoptera,Psylloidea)

The feeding and oviposition of the carrot psyllid,Trioza apicalis, were reduced by the application of fresh spruce and pine sawdust along the seedling rows in carrot fields. Turpentine and separate monoterpene hydrocarbons, mixed into old sawdust and/or placed in polyethylene tubes, were also effective. At a dose of 0.5 liter/m, fresh sawdust reduced the damage to 18% of the plants, compared to 100% damage in untreated plants. The sawdust materials were spread on the soil surface at four- or seven-day intervals during the oviposition period. The tubes were placed along the carrot rows before the oviposition started. Turpentine and separate monoterpene hydrocarbons afforded a protective effect of the same order of magnitude as that obtained from fresh sawdust. The volatile profiles of the spruce and pine sawdust as well as of the turpentine used were determined.     

Poly(dimethylaminoethylmethacryloylpropanesulfonate)‐suitable polymer additive for pulsed electrodeposition of nanocrystalline nickel

Nano‐nickel (n‐Ni) is deposited by a pulsed electrodeposition (PED) in the presence of nonionogenic (poly(ethylene glycol), poly(N‐vinylpyrrolidone), starch), anionogenic (gum arabic, sodium alginate), cationic (quaternized guar gum), and polyampholytic (polyzwitterionic) poly(dimethylaminoethylmethacryloylpropanesulfonate) (PDMAEMPS) polymers. It is established that, by PED (40 mA/cm², t_on = 1 ms, t_off = 50 ms, 323 K), the size of the nanocrystalline particles produced in the presence of PDMAEMPS is far less (by a factor of 6–10) than those obtained in the presence of other polymer additives. These comparative results emphasize a new possibility of controlling the nanograin size of the electrodeposited metals by PED. The dramatic difference in the size of the nickel particles and the unique ability of the polyzwitterionic (PZI) additives are connected by the specific for the polyzwitterionic macromolecular conformation response to the pulsatile electric potential. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2967–2971, 2006     

Oxidation and adsorption of arsenic species by means of hybrid polymer containing manganese oxides

The aim of this work was a comprehensive study of the oxidative and sorptive properties of a hybrid polymer containing manganese oxide toward As(III) and As(V). A poly(styrene‐divinylbenzene) copolymer containing oxidative functional groups (? SO₂NBrNa) was used as the supporting material for MnO₂. The inorganic component was deposited as a result of the oxidation reaction of Mn(II) with oxidative groups of the host polymer. The surface of the polymer matrix was evenly covered with a thin layer of manganese oxide. The obtained product (R/S/Mn) exhibited high oxidative capacity over a wide pH range (2–12); however, under acidic and neutral conditions, the reaction ran significantly faster. The studied material shows some sorption properties but its sorption capacity is much lower than its oxidation capacity. The treatment, in a column regime, of the arsenic solution containing 1 mg As(III) dm^?3 and coexisting ions in concentrations similar to those in natural waters, confirmed the excellent oxidation capacity of the obtained product. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39489.     

Effects of hemodialysis on ventricular activation time in children with end‐stage renal disease

Patients with end‐stage renal disease are affected by cardiovascular complications, including disturbances of the heart intraventricular conduction. Body surface potential mapping is a non‐invasive electrocardiographic detection method of initial disturbances in heart activation propagation. A goal of the study was to analyze the effects of single hemodialysis (HD) session on ventricular activation time (VAT) maps obtained from hemodialyzed children. The study group consisted of 13 hemodialyzed children (age: 6–18 years). The control group is composed of 26 healthy subjects. In each HD patient, 12‐lead electrocardiogram and echocardiography examinations were performed. Isochrone heart maps, reflecting body surface distribution of VAT isolines, were recorded from an 87‐electrode HPM‐7100 system for body surface potential mapping, before (group B) and after HD session (group A). The distribution of isochrones and VAT values, as recorded in the HD patients, differed significantly from the reference VAT map for controls. The highest VAT maximal value was noted in group B (Me: 110 vs. 62 ms in the control group; P < 0.001), becoming significantly lower after HD session (Me: 98 ms for group A vs. 110 ms for group B; P < 0.001). Ventricular activation time maps, recorded before HD session, showed significant VAT delays with isochrone arrangement specific for the left bundle branch block. After HD session, VAT maps presented significant changes, suggesting a normalization process. Ventricular activation time maps in children with end‐stage renal disease exhibited disturbances of intraventricular conduction within the left bundle branch block, undetectable on standard electrocardiogram. A single HD session resulted in VAT map improvement related to overall HD treatment duration.