Concentrations and Source Identification of Polycyclic Aromatic Hydrocarbons (PAHs) in Mangrove Sediments from North of Persian Gulf

The concentrations of 16 Environmental Protection Agency (EPA) priority polyaromatic hydrocarbons (PAHs) were quantified in surface sediments from Hormozgan Province mangroves, south of Iran in dry and wet seasons. Sampling stations were selected in Laft and Khamir mangroves with international importance. Polyaromatic hydrocarbons varied from 75.24 ± 11.24 to 581.94 ± 637.39 ng/g dry weight basis. Pollution sources and their contribution for polyaromatic hydrocarbons pollution in sediments of Hormozgan mangroves were appointed based on molecular ratios and statistical methods, including principal components analysis (PCA) and multiple linear regression/principal components analysis (PCA/MLR) tests. Both of pyrogenic and petrogenic sources contributed in detected concentrations of PAHs. Contribution percentages of pyrogenic and petrogenic origins were estimated at 73.20 and 26.79%, respectively. Temporal variations showed that sediments contained higher levels of ∑PAHs in wet season than dry time. However, the mean detected ∑PAHs was lower than international quality guidelines; the high concentration of PAHs was found in Laft mangrove, suggesting the presence of PAH polluted localized area.     

Grain refinement in nanostructured Al–Mg alloys subjected to high pressure torsion

Nanostructures of three binary Al–Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion at room temperature were comparatively investigated using transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray line profile analysis. Grain size distributions, dislocation densities, and densities of planar defects including stacking faults and microtwins were quantified. The average subgrain size decreased considerably from 120 to 55 nm as the Mg content increased from 0.5 to 4.1 wt%. The average dislocation density in the alloys first increased to a maximum and then decreased as the Mg content increased and the average subgrain size decreased. The role of Mg solute on these features and the refinement mechanisms associated with the typical nanostructures and faults were interpreted.     

Synthesis and characterization of single-walled carbon nanotubes filled with the superionic material SnF2

We report X-ray powder diffraction, high resolution transmission electron microscopy and Raman spectroscopy of the semiconducting single-walled carbon nanotubes filled with the superionic material SnF₂. We first have obtained the Raman spectra of filling SWCNTs using the near-infrared excitation (1064 nm). Our results show that SnF₂ behaves as an electron acceptor with small charge transfer from nanotubes to SnF₂. We interpret the large high-frequency shift of radial breathing modes as due to both charge transfer and the increasing interaction between filling material and nanotubes.     

Iron-included carbon nanocapsules coated with biocompatible poly(ethylene glycol) shells

Nanoparticles of iron carbides wrapped in multilayered graphitic sheets (carbon nanocapsules) were synthesized by electric plasma discharge in an ultrasonic cavitation field in liquid ethanol and purified by selective oxidation and magnetic separation. The particles had 100–200 nm in diameter after centrifuging for 10 min at 4000 rpm. Carbon nanocapsules were covered by wispy poly(ethylene glycol) PEG coating about 7–10 nm in thickness. The number of PEG chains coated on carbon nanocapsules could be estimated as 9.15%. The values of saturation magnetization Ms and coercivity Hc of purified carbon nanocapsules without PEG coating were 112 emu g⁻¹ and 75 Oe respectively. Magnetically soft carbon nanocapsules with a poly(ethylene glycol) coating on the surface may possibly be used as biocompatible magnetic nanoparticles in medical applications.     

A Phosphorescent Nanoparticle‐Based Probe for Sensing and Imaging of (Intra)Cellular Oxygen in Multiple Detection Modalities

Monitoring cell and tissue oxygenation is important for the analysis of cell development and differentiation, mitochondrial function, and common (patho)physiological conditions such as ischemia, cancer, neurodegenerative disorders. A number of materials for sensing cellular oxygen (O₂) by optical means have been described in recent years, but the diverse range of biological models and measurement tasks demands more versatile, flexible, and simple O₂ sensors. A new cell‐penetrating phosphorescent nanosensor material called MM2 probe is presented. In it, the highly photostable phosphorescent reporter dye Pt(II)‐5,10,15,20‐tetrakis‐(2,3,4,5,6‐pentafluorophenyl)‐porphyrin (PtTFPP; emission at 650 nm) and poly(9,9‐dioctylfluorene) (PFO) fluorophore act as Förster resonance energy transfer (FRET) donor and two‐photon antennae are embedded in cationic hydrogel nanoparticles. Such probe formulation provides efficient delivery into the cell and subsequent sensing and high‐resolution imaging of cellular O₂ in different detection modalities, including ratiometric intensity and phosphorescence lifetime‐based sensing under one‐photon and two photon excitation. MM2 probe combines high brightness, photo‐ and chemical stability, low toxicity, and ease of fabrication and use. Its versatility and analytical performance are demonstrated in physiological experiments with adherent cells and neurospheres representing 2D and 3D respiring objects and detection on time‐resolved fluorescent readers, confocal and multiphoton microscopes, and customized microsecond fluorescence/phosphorescence lifetime imaging microscopy (FLIM) systems.     

Suppression of overtone oscillation and low‐current operation using novel‐design scheme for quartz crystal oscillators

A novel design is proposed for a low‐frequency quartz crystal oscillator circuit. Negative resistance in a low‐frequency CMOS‐inverter quartz oscillator was reviewed for the fundamental mode at 32 kHz and the overtone oscillation at 200 kHz. Suppression of the overtone oscillation, appropriate gain, and drive current reduction are realized by adding only three circuit components. Experimental results and an estimate of the absolute value of the negative resistance are presented for the conventional Colpitts circuit and two types of the quartz crystal oscillator circuit. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Research and development of transgenic plants in Malaysia: an example from an Asian developing country

In 2000, agriculture contributed 13% to the national gross domestic product of Malaysia. The country of 23 million people has created a competitive program coordinated by the Ministry of Science, Technology and the Environment, research institutions, and universities to undertake biotechnology research in several areas. Intensified research efforts are under way on oil palm, rubber, rice, papaya, and orchids. Although the most progress has been made in rice and papaya, no transgenic crop is ready for field trials. Nonetheless, preliminary steps have been taken to prepare for the trials, and detailed testing protocols are being developed.     

Improvement of Thermal Stability via Outer-Loop Ion Pair Interaction of Mutated T1 Lipase from Geobacillus zalihae Strain T1

Mutant D311E and K344R were constructed using site-directed mutagenesis to introduce an additional ion pair at the inter-loop and the intra-loop, respectively, to determine the effect of ion pairs on the stability of T1 lipase isolated from Geobacillus zalihae. A series of purification steps was applied, and the pure lipases of T1, D311E and K344R were obtained. The wild-type and mutant lipases were analyzed using circular dichroism. The T_m for T1 lipase, D311E lipase and K344R lipase were approximately 68.52 °C, 70.59 °C and 68.54 °C, respectively. Mutation at D311 increases the stability of T1 lipase and exhibited higher T_m as compared to the wild-type and K344R. Based on the above, D311E lipase was chosen for further study. D311E lipase was successfully crystallized using the sitting drop vapor diffusion method. The crystal was diffracted at 2.1 Å using an in-house X-ray beam and belonged to the monoclinic space group C2 with the unit cell parameters a = 117.32 Å, b = 81.16 Å and c = 100.14 Å. Structural analysis showed the existence of an additional ion pair around E311 in the structure of D311E. The additional ion pair in D311E may regulate the stability of this mutant lipase at high temperatures as predicted in silico and spectroscopically.