Experimental study and simulation of 63Zn production via proton induce reaction.

The 63Zn was produced by16.8 MeV proton irradiation of natural copper. Thick target yield for 63Zn in the energy range of 16.8 →12.2 MeV was 2.47 ± 0.12 GBq/µA.h. Reasonable agreement between achieved experimental data and theoretical value of thick target yield for 63Zn was observed. A simple separation procedure of 63Zn from copper target was developed using cation exchange chromatography. About 88 ± 5% of the loaded activity was recovered. The performance of FLUKA to reproduce experimental data of thick target yield of 63Zn is validated. The achieved results from this code were compared with the corresponding experimental data. This comparison demonstrated that FLUKA provides a suitable tool for the simulation of radionuclide production using proton irradiation.

Spectrofluorimetric determination of cefixime using terbium-danofloxacin probe.

OBJECTIVES: Cefixime (Cfx), is a semi-synthetic third-generation oral cephalosporin antibiotic that is prescribed for the treatment of susceptible infections. There are some procedures for the determination of Cfx in pharmaceutical formulations and biological samples. Herein a spectrofluorimetric method was proposed for Cfx determination based on the fluorescence quenching of terbium-danofloxacin (Tb(3+)-Dano) in the presence of Cfx. MATERIALS AND METHODS: Cfx was detected based on fluorescence quenching of terbium-danofloxacin (Tb(3+)-Dano) in the presence of Cfx with maximum excitation and emission wavelengths at 347 nm and 545 nm, respectively. The quenched fluorescence intensity of Tb(3+)- Dano system is proportional to the concentration of Cfx. The optimum conditions for the determination of Cfx were studied. RESULTS: The maximum response was achieved under optimum conditions of [Tris buffer]= 0.008 mol/l (pH 6.5), [Tb(3+)]=1×10(-4) mol/l and [Dano]=1×10(-4) mol/l. The developed method was evaluated in terms of accuracy, precision and limit of detection. The linear concentration ranges for quantification of Cfx were 8.8×10(-8)-8.8×10(-7) mol/l and 1.1×10(-7)-8.8×10(-7) mol/l in standard and human serum samples with the detection limits (S/N=3) of 2.8×10(-8) mol/l and 3.9×10(-8) mol/l, respectively. The Cfx was determined in pharmaceutical tablets and spiked serum samples and the results were satisfactory. CONCLUSION: This method is simple, practical and relatively interference-free for determination of Cfx in pharmaceutical tablets and serum samples.

Analysis of losartan and carvedilol in urine and plasma samples using a dispersive liquid-liquid microextraction isocratic HPLC-UV method.

BACKGROUND: A simple, precise and sensitive HPLC method has been developed for simultaneous determination of carvedilol and losartan in human plasma and urine samples. The analytes were extracted by a dispersive liquid-liquid microextraction method. A mobile phase of 15 mM sodium dihydrogen phosphate buffer (pH 4.0)/acetonitrile/2-propanol (70/27.5/2.5, v/v/v) was used to separate the drugs using a Waters® ODS column (250 × 4.6 mm) and detected by a UV detector at 222 nm. RESULTS: The developed method is selective for studied drugs possessing a linearity range of 0.1-1.0 and 0.05-0.75 µg/ml, respectively, for losartan and carvedilol with precision <15%. The accuracy is better than 15% and the mean recovery of carvedilol and losartan was 98.9 and 100.2% for plasma and 100.7 and 100.5% for urine samples, respectively. CONCLUSION: The developed method is applicable for therapeutic drug monitoring and PK analyses.

Comparison of stresses induced by fiber post, parapost and casting post in root canals by photoelasticity method.

INTRODUCTION: Many studies have been performed to evaluate the stress distribution around endodontic posts; those which compared posts composed of different materials are rare. The aim of this study was to compare stresses induced in dentin by three structurally different posts using photoelasticity method. MATERIALS AND METHODS: Nine blocks of PSM-5 Photoelastic material with 45×45×10 mm dimension were prepared. In each block, a canal 9 mm in length and 0.8 mm in width was drilled. Blocks were divided into 3 groups of three each. In the first group, the canals were prepared for insertion of Fiber Post with 1.25 mm width. In the second group, the canals were prepared for insertion of ParaPost with 1.25 mm width and the canals in the third group were prepared for casting post similar to the above samples. Casting Post pattern was made by Duralay resin and casted by Ni-Cr alloy. All posts were cemented in canals with Panavia cement. The stresses were evaluated in the polariscope under three different conditions: 1) without load, 2) with 135 N vertical load, and 3) with 90 N oblique load (26° inclination to post long axis). The fringe orders in the cervical, middle and apical regions of the posts were evaluated and compared with each other. RESULTS: Application of the vertical load induced a high stress concentration (FO=4) in the apical region of the ParaPost, while lower stress was observed in the middle (FO=2) and cervical region (FO=2+). Fiber Post and Casting Post showed even stress distribution (FO=2+). High stress concentration was detected with the application of oblique force in the cervical region of ParaPost (FO=5) and Casting Post (FO=3+). Fiber Posts fractured before reaching 90-N loading force. CONCLUSION: The stress distribution around Fiber Post and Casting Post were constant in comparison with ParaPost. Fiber Post with 1.25 mm width was not recommended in situations with high oblique stresses.