The Concept of Folic Acid in Health and Disease

Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells.     

Using the Isalos platform to develop a (Q)SAR model that predicts metal oxide toxicity utilizing facet-based electronic,image analysis-based,and periodic table derived properties as descriptors

Structural Chemistry - Engineered nanoparticles (NPs) are being studied for their potential to harm humans and the environment. Biological activity, toxicity, physicochemical properties, fate, and...     

Fast- and ultra-fast laser pulse induced reactions between carbon dioxide and methane

The direct excitation of CO_2 using fast (nanosecond) and ultrafast (femtosecond) pulsed lasers was investigated. A gas reaction cell was used to excite CO_2 in a 50:50 mixture of CO_2 and CH_4 using nano- and femtosecond laser systems, to induce a reaction between these two compounds. FT-IR spectra showed that CO was formed using the nanosecond and femtosecond laser systems. It was also found that hydrocarbons, containing C-C bonds were formed. For both the nanosecond and femtosecond laser, it was found that more C-C higher hydrocarbons were formed after 5 h compared to 3 h of irradiation. Irradiation at pressures of 250, 350 and 500 kPa with the femtosecond laser system showed the expected increase in the amount of CO formed with an increase in pressure. Results from this study showed that carbon dioxide and methane can be activated successfully using nanosecond laser pulses at 2000 run and femtosecond laser pulses at 795 or 2000 nm and that these activated species react to form CO and C-C containing products.     

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

We study self-assembly on a spherical surface of a model for a binary mixture of amphiphilic dimers in the presence of guest particles via Monte Carlo (MC) computer simulation. All particles had a hard core, but one monomer of the dimer also interacted with the guest particle by means of a short-range attractive potential. We observed the formation of aggregates of various shapes as a function of the composition of the mixture and of the size of guest particles. Our MC simulations are a further step towards a microscopic understanding of experiments on colloidal aggregation over curved surfaces, such as oil droplets.     

Fe–Ni Nanoparticles supported on carbon nanotube-co-cyclodextrin polyurethanes for the removal of trichloroethylene in water

Nanoscale bimetallic particles of nickel on iron were supported on carbon nanotubes and then co-polymerized with β-cyclodextrin (CNTs/CD) and the resulting polymers applied to the degradation of pollutants in water. The bimetallic nanoparticles (BMNPs) were first embedded on functionalized carbon nanotubes (f-CNTs) before being copolymerized with beta cyclodextrin (β-CD) and hexamethylene diisocyanate (HMDI) forming a water-insoluble polyurethane. The particle size and distribution of BMNPs were determined by Transmission Electron Microscopy (TEM), and the surface area was determined by using the Brunauer–Emmett–Teller (BET) method. Energy dispersive X-ray spectroscopy (EDXS) was used to confirm the formation of the BMNPs. Degradation of trichloroethylene (TCE) as a model pollutant was studied and more than 98% reduction in TCE was achieved by the polymers. Polymers with the BMNPs maintained their efficiency in degrading TCE after several cycles compared to metal-free polymers. The degradation was monitored by using gas chromatography-mass spectrometry (GC-MS), while the production of chlorides was verified by using ion chromatography (IC). Atomic absorption spectroscopy (AAS) was employed to determine the possible leaching of the BMNPs from the polymer, and confirmed to be extremely low.     

Magnetism in iron implanted oxides: a status report

Emission Mössbauer spectroscopy on ⁵⁷Fe fed by ⁵⁷Mn ions implanted in the metal oxides ZnO, MgO and Al₂O₃ has been performed. The implanted ions occupy different lattice sites and charge states. A magnetic part of the spectra in each oxide can be assigned to Fe^3?+? ions in a paramagnetic state with unusually long relaxation time observable to temperatures up to several hundreds Kelvin. Earlier expectations that the magnetic spectra could correspond to an ordered magnetic state could not be confirmed. A clear decision for paramagnetism and against an ordered magnetic state was achieved by applying a strong magnetic field of 0.6 Tesla. The relaxation times deduced were compared to spin–lattice relaxation times from electron paramagnetic resonance (EPR).     

A new multistage spectral relaxation method for solving chaotic initial value systems

In this paper, we present a new pseudospectral method application for solving nonlinear initial value problems (IVPs) with chaotic properties. The proposed method, called the multistage spectral relaxation method (MSRM) is based on a novel technique of extending Gauss–Siedel type relaxation ideas to systems of nonlinear differential equations and using the Chebyshev pseudo-spectral methods to solve the resulting system on a sequence of multiple intervals. In this new application, the MSRM is used to solve famous chaotic systems such as the such as Lorenz, Chen, Liu, Rikitake, Rössler, Genesio–Tesi, and Arneodo–Coullet chaotic systems. The accuracy and validity of the proposed method is tested against Runge–Kutta and Adams–Bashforth–Moulton based methods. The numerical results indicate that the MSRM is an accurate, efficient, and reliable method for solving very complex IVPs with chaotic behavior.     

Effect of precipitating agent on the catalytic behaviour of precipitated iron catalysts

Hyperfine Interactions - Iron precipitated catalysts have been prepared using different precipitating agents (NH4OH, K2CO3) at different pH values. In situ Mössbauer (MES) study of the reduced...     

Mössbauer study of 57Fe in GaAs and GaP following 57Mn+ implantation

Ion implantation provides a precise method of incorporating dopant atoms in semiconductors, provided lattice damage due to the implantation process can be annealed and the dopant atoms located on regular lattice sites. We have undertaken ⁵⁷Fe emission Mössbauer spectroscopy measurements on GaAs and GaP single crystals following implantation of radioactive ⁵⁷Mn^?+? ions, to study the lattice sites of the implanted ions, the annealing of implantation induced damage and impurity–vacancy complexes formed. The Mössbauer spectra were analyzed with four spectral components: an asymmetric doublet (D1) attributed to Fe atoms in distorted environments due to implantation damage, two single lines, S1 assigned to Fe on substitutional Ga sites, and S2 to Fe on interstitial sites, and a low intensity symmetric doublet (D2) assigned to impurity–vacancy complexes. The variations in the extracted hyperfine parameters of D1 for both materials at high temperatures (T?> 400 K) suggests changes in the immediate environment of the Fe impurity atoms and different bonding mechanism to the Mössbauer probe atom. The results show that the annealing of the radiation induced damage is more prominent in GaAs compared to GaP.     

The effect of uranium speciation on the removal of gross alpha activity from acid mine drainage using anion exchange resin

The study was conducted to understand, (a) the effect of pH on the speciation of uranium in acid mine drainage and (b) determine the effect of uranium speciation on the removal of gross alpha activity from acid mine drainage. Speciation modeling predicted a dominance of neutral and positively charged species under acidic and neutral conditions. Negative species become dominant from pH 8. The effectiveness of the anionic exchange resin to remove gross alpha activity was lower under acidic conditions (pH < 6) compared to alkaline conditions (pH ≥ 8).