A new method in the production of protective sheets against X-ray radiation.

Today, the use of X-rays in diagnosing and sometimes treating patients is inevitable. Despite the many benefits of using X-rays in medical and other sciences, the harmful effects of this radiation on human tissue should not be neglected. One of the best ways to prevent the harmful effects of X-rays on the human body is to use appropriate covers against these rays. It seems that it is necessary to find effective particles to weaken X-rays and choose a suitable substrate with high mechanical resistance to scatter particles in it. In this study, the synthesis of SnO2 nanoparticles from SnCl2.2H2O precursor and BaSO4 nanoparticles from BaCl2.2H2O precursor using neem tree extract (Azadirachta indica) as a reducing and stabilizing agent is reported. After the synthesis of nanoparticles, their structure was investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Then the desired composite and nanocomposite were prepared in the polymer substrate. The sheets were prepared using an extruder and then a hot hydraulic press. The output sheets had a thickness of 1 mm. The structural characteristics of the produced sheets such as surface morphology, density of prepared composites, mechanical properties, thermal gravimetric analysis and retention of loaded particles after three times washes were investigated. The X-ray attenuation capability of each sample was evaluated by calculating the linear attenuation coefficient for each prepared sample. The results show that all sheets filled with tin and barium micro and nano particles have more X-ray attenuation capabilities than pure polymer. Among the prepared sheets, the nanocomposite prepared from low-density polyethylene (77 %) + SnO2 (10 %) + BaSO4 (10 %) + multi-walled carbon nanotubes (3 %) showed the highest X-ray attenuation.

Understanding the kinetics and atmospheric degradation mechanism of chlorotrifluoroethylene (CF2CFCl) initiated by OH radicals.

The atmospheric degradation of chlorotrifluoroethylene (CTFE) by OH˙ was investigated using density functional theory (DFT). The potential energy surfaces were also defined in terms of single-point energies derived from the linked cluster CCSD(T) theory. With an energy barrier of -2.62 to -0.99 kcal mol-1 using the M06-2x method, the negative temperature dependence was determined. The OH˙ attack on Cα and Cß atoms (labeled pathways R1 and R2, respectively) shows that reaction R2 is 4.22 and 4.42 kcal mol-1, respectively, more exothermic and exergonic than reaction R1. The main pathway should be the addition of OH˙ to the ß-carbon, resulting in ˙CClF-CF2OH species. At 298 K, the calculated rate constant was 9.87 × 10-13 cm3 molecule-1 s-1. The TST and RRKM calculations of rate constants and branching ratios were performed at P = 1 bar and in the fall-off pressure regime over the temperature range of 250-400 K. The formation of HF and ˙CClF-CFO species via the 1,2-HF loss process is the most predominant pathway both kinetically and thermodynamically. With increasing temperature and decreasing pressure, the regioselectivity of unimolecular processes of energized adducts [CTFE-OH]˙ gradually decreases. Pressures greater than 10-4 bar are often adequate for assuring saturation of the estimated unimolecular rates when compared to the RRKM rates (in high-pressure limit). Subsequent reactions involve the addition of O2 to the [CTFE-OH]˙ adducts at the α-position of the OH group. The [CTFE-OH-O2]˙ peroxy radical primarily reacts with NO and then directly decomposes into NO2 and oxy radicals. "Carbonic chloride fluoride", "carbonyl fluoride", and "2,2-difluoro-2-hydroxyacetyl fluoride" are predicted to be stable products in an oxidative atmosphere.

Zr(HSO4)4: Green, efficient and reusable catalyst for one-pot synthesis of 1,8-dioxooctahydroxanthene under solvent-free conditions.

Many methods have been used to synthesize xanthene derivatives using different catalysts. However, some of these methodologies have not been entirely satisfactory. Most of the mentioned methods have disadvantages such as low yields, prolonged reaction times, harsh reaction conditions and the requirement of expensive catalysis and use of toxic organic solvent. In this research, a green and highly efficient procedure for the one-pot synthesis of 1,8-dioxo-octahydro-xanthenes has been developed. Zr(HSO4)4 catalyst was used as an efficient and recoverable catalyst for synthesis of 1,8-dioxo-octahydro-xanthene derivatives via cyclocondensation of dimedone and aromatic aldehydes in solvent-free conditions. There are no examples of the use of Zr(HSO4)4 for the synthesis of 1,8-dioxo-octahydro-xanthene derivatives. The present method offers several advantages such as green, highly efficient, recoverable, reusable, simple work-up and simple purification of products. The structure of the synthesized products was confirmed by Fourier Transform Infrared (Ft-IR) and Proton nuclear magnetic resonance (1HNMR) analyzes. The antibacterial activity of the synthesized compounds was determined by agar disk diffusion method against gram-positive (S. aureus bacteria) and gram-negative (E. coli bacteria) microorganisms. Among the synthesized compounds (3a-3j), 3h compound showed the highest antibacterial effect by forming an inhibitory diameter zone of 15 mm around the disc containing 2000 mg of 3h-compound against gram-positive (S. aureus bacteria). 1. Use of Zr(HSO4)4 as a green and highly efficient and reusable heterogeneous catalyst. 2. Under solvent-free condition. 3. Simple work-up and Simple purification of products.

Microwave-assisted Synthesis of Novel Pyrazole Derivatives and their Biological Evaluation as Anti-Bacterial Agents.

AIMS AND OBJECTIVES: Microwave-assisted condensation of acetophenone 1 and aromatic aldehydes 2 gave chalcone analogs 3, which were cyclized to pyrazole derivatives 6a-f via the reaction with hydrazine hydrate and oxalic acid in the presence of the catalytic amount of acetic acid in ethanol. MATERIALS AND METHODS: The structural features of the synthesized compounds were characterized by melting point, FT-IR, 1H, 13C NMR and elemental analysis. RESULTS: The antibacterial activities of the synthesized pyrazoles were evaluated against three gram-positive bacteria, such as Enterococcus durans, Staphylococcus aureus, Bacillus subtilis and two gram-negative bacteria such as Escherichia coli and Salmonella typhimurium. CONCLUSION: All the synthesized pyrazoles showed relatively high antibacterial activity against S. aureus strain, and none of them demonstrated antibacterial activity against E. coli.

DFT study on tautomerism and natural bond orbital analysis of 4-substituted 1,2,4-triazole and its derivatives: solvation and substituent effects.

Density functional theory investigations at the DFT-B3LYP/6-311++G** theoretical level employed to determine the tautomerism, substituent effects of 4-substituted 4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione, and its derivatives (4-R-H, 4-R-CH3, 4-R-F, 4-R-NO2) in the selected solvent (acetone, acetonitrile, and dichloromethane) and gas phases using the polarizable continuum method (PCM) model. The substituted 1,2,4-triazoles have two main different tautomers namely N2-H and S7-H. For considered derivatives, thione forms are more energetically stable and dominant form in the studied solvent and gas phases. In addition, geometrical parameters, charges on atoms, dipole moments, energetic properties, and the nucleus-independent chemical shifts (NICS) are investigated. It has been seen that these molecular features of the studied compound and its derivatives are mostly solvent dependent. For electron-releasing and -withdrawing derivatives in the solution and gas phases, 2-H forms are the more stable and dominant form. The relative stability of the C4-substituted 1,2,4-triazole tautomerism is influenced by the possibility for intramolecular interactions between substituent and electron-donor or electron-acceptor centers of the triazole ring.

Synthesis and evaluation of single-wall carbon nanotube-paclitaxel-folic acid conjugate as an anti-cancer targeting agent.

Single-wall carbon nanotubes (SWCNT) represent a novel nanomaterial applied in various nanotechnology fields because of their surface chemistry properties and high drug cargo capacity. In this study, SWCNT are pre-functionalized covalently with paclitaxel (PTX) - an anticancer drug, and folic acid (FA), as a targeting agent for many tumors. The samples are investigated and evaluated by different analyses such as Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), absorption spectroscopic measurements (UV-Visible), elemental analysis, and cell analyses with cancer cell line cultures. The results show good conjugation of the targeting molecule and the anticancer drug on the surface of the carbon nanotubes (CNT). This work demonstrates that the SWCNT-PTX-FA system is a potentially useful system for the targeted delivery of anticancer drugs.

Types of neural guides and using nanotechnology for peripheral nerve reconstruction.

Peripheral nerve injuries can lead to lifetime loss of function and permanent disfigurement. Different methods, such as conventional allograft procedures and use of biologic tubes present problems when used for damaged peripheral nerve reconstruction. Designed scaffolds comprised of natural and synthetic materials are now widely used in the reconstruction of damaged tissues. Utilization of absorbable and nonabsorbable synthetic and natural polymers with unique characteristics can be an appropriate solution to repair damaged nerve tissues. Polymeric nanofibrous scaffolds with properties similar to neural structures can be more effective in the reconstruction process. Better cell adhesion and migration, more guiding of axons, and structural features, such as porosity, provide a clearer role for nanofibers in the restoration of neural tissues. In this paper, basic concepts of peripheral nerve injury, types of artificial and natural guides, and methods to improve the performance of tubes, such as orientation, nanotechnology applications for nerve reconstruction, fibers and nanofibers, electrospinning methods, and their application in peripheral nerve reconstruction are reviewed.

Cell engineering: nanometric grafting of poly-N-isopropylacrylamide onto polystyrene film by different doses of gamma radiation.

Poly-N-isopropylacrylamide was successfully grafted onto a polystyrene cell culture dish and γ-preirradiated in air. In this study, the effect of a γ-pre-irradiation dose of radiation (radiation absorbed dosages of 10, 20, 30, 40 KGy) under appropriate temperature and grafting conditions was investigated. The Fourier transform infrared spectroscopy analysis showed the existence of the graft poly-N-isopropylacrylamide (PNIPAAm) on the substrate. The optimal value of the dose for grafting was 40 KGy at 50°C. The scanning electron microscopy and atomic force microscopy (AFM) images clearly showed that increasing the absorbed dose of radiation would increase the amount of grafting. Surface topography and graft thickness in AFM images of the radiated samples showed that the PNIPAAm at the absorbed dose of radiation was properly grafted. The thickness of these grafts was about 50-100 nm. The drop water contact angles of the best grafted sample at 37°C and 10°C were 55.3 ± 1.2° and 61.2 ± 0.9° respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. Differential scanning calorimetry analysis also revealed the low critical solution temperature of the grafted sample to be 32°C. Thermoresponsive polymers were grafted to dishes covalently which allowed fibroblast cells to attach and proliferate at 37°C; the cells also detached spontaneously without using enzymes when the temperature dropped below 32°C. This characteristic proves that this type of grafted material has potential as a biomaterial for cell sheet engineering.

The effect of acetaminophen nanoparticles on liver toxicity in a rat model.

Acetaminophen, a pain-reliever, is one of the most widely used medications in the world. Acetaminophen with normal dosage is considered a nontoxic drug for therapeutic applications, but when taken at overdose levels it produces liver damage in human and various animal species. By a high energy mechanically activated method, we produced acetaminophen in a nanometer crystalline size (24 nm). Forty-eight hours after injection of crystalline particles with normal and reduced size of our drug, the effect of liver toxicity was compared by determination of liver transferase enzymes such as alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase (ALT). These enzymes were examined by routine colorimetric methods using commercial kits and pathologic investigations. Statistical analysis and pathological figures indicated that ALT delivery and toxicity in reduced size acetaminophen was significantly reduced when compared with normal size acetaminophen. Pathology figures exhibited reduced necrosis effects, especially the confluent necrosis, in the central part of the lobule in the reduced size acetaminophen samples when compared with the normal samples.