A multivariate study: variation in uptake of trace and toxic elements by various varieties of Sorghum bicolor L

The aim of present study was to evaluate the variation in uptake of elements (As, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn) by different varieties of Sorghum bicolor L., plants grown in soil amended with untreated industrial waste water sewage sludge (SUIS), on same experimental plots. The power of chemometrics was also used in exploring the potential natural and/or anthropogenic sources responsible for elemental contents in different varieties of sorghum. Hierarchical cluster analysis was used to explore the different variety of sorghum grouping according to corresponding their SUIS samples as additional information to the output obtained by principal component analysis. Significant genotypic variation was detected in the fourteen elements concentrations in sorghum grains, indicating the possibility to reduce the concentration of toxic elements in grains through breeding approach. It was observed that high tolerance limit of toxic elements was observed in sorghum variety PARC-SV-1.     

Hazardous impact of toxic metals on tobacco leaves grown in contaminated soil by ultrasonic assisted pseudo-digestion: multivariate study

Tobacco leaves (Nicotiana tabacum L.), agricultural soil and pollute irrigated lake water samples were collected during 2005–2006 and analyzed for Cd and Ni by electrothermal atomic absorption spectrometry (ETAAS). A simple and efficient procedure was investigated for the complete decomposition of tobacco leaves using ultrasonic assisted acid pseudo-digestion method (UPDM). A Plackett–Burman experimental design was used as a multivariate strategy for the evaluation of seven factors/variables at once, while central composite were used to found optimum values of significant variables. The accuracy of the proposed methods was assessed by analyzing certified reference (CRM); Virginia tobacco leaves (CTA-VTL-2). The results being compared with those obtained by conventional wet acid digestion method. The result obtained by optimized method showed good agreement with the certified values and sufficiently high recovery 97.8 and 98.7% for Cd and Ni, respectively. Under optimal conditions, the detection limits (3σ) were evaluated to be 0.019 μg g⁻¹ for Cd and 0.37 μg g⁻¹ for Ni. The proposed method was successfully applied to the determination of Cd and Ni in raw, processed tobacco and different branded cigarettes samples.     

The spray drying of unfractionated heparin: optimization of the operating parameters

Unfractionated heparin is an anti-inflammatory mucoactive agent, with the potential to treat the inflamed and mucus-obstructed airways in patients with cystic fibrosis. In this study, unfractionated heparin has been spray-dried to produce spherical micronized particles in the size range 1-5 microm, which is suitable for delivery by dry-powder inhalation. Spray drying parameters have been optimized using a 2(4) factorial experimental design. The feed concentration and atomization spray flow rate have the greatest effects on recovery (typically 60%) and particle size.     

Towards a controlled photopolymerization of dental dimethacrylate monomers: EPR studies on effects of dilution, filler loading, storage and aging

Electron paramagnetic resonance (EPR) was used to study the kinetics of methacrylate radical formation in the monomer mixture 2,2-bis [4-(2-hydroxy-3-methacryloxyprop-1-oxy) phenyl] propane (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA), in the presence of a photo-initiator system (camphorquinone, CQ/N,N-dimethyl-p-toluidine, DET). Curing-time dependences on the filler (0–40 wt%) and TEGDMA content (15–90 wt%) were evaluated; the influence of irradiation protocol, uncured sample storage time and aging of cured systems were also studied. EPR enabled observing at least two different kinetic regimes during polymerization. The final radical concentration decreased both with Bis-GMA and filler content. However, a reverse trend was obtained when the relative photo-initiator concentrations were considered. Filler also showed a significant effect on the radical life-time reduction. Irradiation protocol and storage time of uncured matrices showed to affect the free radical concentration. The observed changes on the EPR signal lineshape with post-curing time suggests that the distribution of CH₂ conformations also changes with time.     

A figure of merit for optimization of nanocrystal flash memory design

Nanocrystals can be used as storage media for carriers in flash memories. The performance of a nanocrystal flash memory depends critically on the choice of nanocrystal size and density as well as on the choice of tunnel dielectric properties. The performance of a nanocrystal memory device can be expressed in terms of write/erase speed, carrier retention time and cycling durability. We present a model that describes the charge/discharge dynamics of nanocrystal flash memories and calculate the effect of nanocrystal, gate, tunnel dielectric and substrate properties on device performance. The model assumes charge storage in quantized energy levels of nanocrystals. Effect of temperature is included implicitly in the model through perturbation of the substrate minority carrier concentration and Fermi level. Because a large number of variables affect these performance measures, in order to compare various designs, a figure of merit that measures the device performance in terms of design parameters is defined as a function of write/erase/discharge times which are calculated using the theoretical model. The effects of nanocrystal size and density, gate work function, substrate doping, control and tunnel dielectric properties and device geometry on the device performance are evaluated through the figure of merit. Experimental data showing agreement of the theoretical model with the measurement results are presented for devices that has PECVD grown germanium nanocrystals as the storage media.     

Structural and optical properties of ge nanocrystals embedded in Al2O3

Ge nanocrystals (NCs) embedded in aluminum oxide were grown by RF-magnetron sputtering. Raman, high resolution transmission electron microscopy (HRTEM), selected area diffraction (SAD), and X-ray diffraction (XRD) techniques confirmed good cristallinity of the NCs from samples annealed at 800 degrees C. The average NC size was estimated to be around 7 nm. Photoluminescence (PL) measurements show an emission related to the NCs. The temperature dependence of the PL confirms the confinement phenomenon in the Ge NCs.     

Integration of multianalyte sensing functions on a capillary-assembled microchip: simultaneous determination of ion concentrations and enzymatic activities by a "drop-and-sip" technique

A general and simple implementation of simultaneous multiparametric sensing in a single microchip is presented by using a capillary-assembled microchip (CAs-CHIP) integrated with the plural different reagent-release capillaries (RRCs), acting as various biochemical sensors. A novel "drop-and-sip" technique of fluid handling is performed with a microliter droplet of a model sample solution containing proteases (trypsin, chymotrypsin, thrombin, elastase) and divalent cations (Ca2+, Zn2+, Mg2+) that passes through the microchannel with the aid of a micropipette as a vacuum pump, concurrently filling each RRC via capillary force. To avert the evaporation of the nanoliter sample volume in each capillary, PDMS oil is dropped on the outlet hole of the CAs-CHIP exploiting the capillary force that results in spontaneous sealing of all the RRCs. In addition, this high-speed sample introduction alleviates the possibility of protein adsorption and capillary cross-contamination, allowing a reliable and multianalyte determination of a sample containing many different proteases and divalent cations by using the fluorescence image analysis. Presented results suggested the possible application of this microchip in the field of drug discovery and systems biology.     

Employing spectra of polycrystalline materials for the verification of optical constants obtained from corresponding low-symmetry single crystals

The determination of optical constants from spectra of low-symmetry single crystals or from spectra stemming from unfavorable crystal faces by dispersion analysis is a difficult task. Besides oscillator frequencies, band positions can additionally depend on oscillator strength as well as on the relative orientation of the transition moment. Therefore the results of the analysis are highly prone to errors. We present an easy method to validate the oscillator data resulting from dispersion analysis by the comparison of measured and simulated spectra of randomly oriented polycrystalline materials. Depending on the crystallite size, either average reflectance and transmittance theory (ARTT) or average refractive index theory (ARIT) can be applied to model the spectra of polycrystalline compounds. As an alternative to ARIT, effective medium theory (EMA) can also be employed. However, since principal dielectric functions do not exist in the general triclinic case, which are needed for the application of EMA, we suggest using the eigenvalues of the dielectric tensor function instead. Our method for the verification of optical constants of single crystals is validated using monoclinic CuO as an example.     

Stress birefringent, space-variant wave plates for vortex illumination

We describe the use of stress birefringence in the creation of vortex illumination. A trifold symmetric stress pattern will provide an annular region that exhibits polarization vortices when illuminated with linearly polarized light and scalar vortices when illuminated with circularly polarized light. A finite element plane-stress model is used to analyze the space-variant anisotropy.     

Structural and spatially resolved studies on the hardening of a commercial resin-modified glass-ionomer cement

A commercial photopolymerizable resin-modified glass-ionomer (Fuji II LC) was studied using a variety of nuclear magnetic resonance (NMR) techniques. ¹H and ¹⁹F stray-field imaging (STRAFI) enabled to follow the acid–base reaction kinetics in self-cured (SC) samples. Gelation and maturation processes with 25 min and 40 h average time constants, respectively, were distinguished. In self- & photo-cured (SPC) samples, two processes were also observed, which occurred with 2 s and 47 s average time constants. ¹H, ²⁷Al and ²⁹Si magic angle spinning (MAS) NMR, ¹³C cross-polarization (CP)/MAS NMR and ²⁷Al multiple quanta (MQ)MAS NMR spectroscopy were used to obtain structural information on the glass and cements that were either SC or SPC. The presence of methacrylate groups was identified in the solid component. Unreacted hydroxyl ethylmethacrylate (HEMA) was detected in self-cured cement. ²⁷Al data showed that approximately 28% and 20% of Al is leached out from glass particles in SC and SPC samples, respectively. The upfield shift detected in ²⁹Si MAS NMR spectra of the cements is consistent with a decrease in the number of Al species in the second coordination sphere of the silicon structures. Scanning electron microscopy (SEM) showed existence of 3D shrinkage of the cement matrix in photo-cured cements.