The application of high resolution delayed K X-ray spectrometry to proton,alpha, thermal and fast neutron activation analysis: A comparison of sensitivities

High resolution (K) X-ray spectrometry preceded by activation with fast neutrons, neutrons from an isotope-source, and charged particles, is a novel development in the field of activation analysis. This paper describes the capabilities of these techniques and evaluates their analytical potential for the specific determination of the rare earths and Platinum Group Elements (PGE's) in small samples. The investigation took the form of a feasibility study which relied heavily on the low energy sensitivity of the detector used. Detection of the delayed X-rays was achieved with a 100 mm² Ge detector whose ability to produce optimum photopeak-to-noise ratios formed the basis exploited in this investigation. Analytical conditions are demonstrated over a range of concentrations for the elements of interest and the potential of the technique for application to the general routine analysis of the rare earths and PGE's are discussed.     

Crystal and molecular structure of 1-methyl-2,3,5,6-tetraphenylpiperidin-4-ol,C30H29NO

The structure of the the title compound, C₃₀H₂₉NO, was determined by X-rays.M _r =419.57, triclinic, space groupP1,a=5.8922(12),b=8.5855(11),c=12.2216(20) Å,=78.145(12)°,=79.181(15)°, =76.108(14)°,V _c =581.1(1) ų,Z=1,D _x =1.199 Mg m^–3. CuK radiation (graphite crystal monochromator, =1.54184 Å),(CuK)=5.17 cm^–1,T=290K. Final conventionalR-factor=0.039,R _w =0.042 for 2795 observed reflections and 377 variables. The structure was solved usingMultan andDirdif. With a view to determining the conformational preference of the piperidine ring when it is highly sustituted with a bulky group like the phenyl group, the present X-ray investigation was undertaken.     

Elliptic and Hyperelliptic Curves Over Supersimple Fields

It is proved that if F is an infinite field with characteristicdifferent from 2, whose theory is supersimple, and C is an ellipticor hyperelliptic curve over F with generic ‘modulus’,then C has a generic F-rational point. The notion of generityhere is in the sense of the supersimple field F.     

Transition metal analysis: A comparison between ICP-AES and deuteron activation

The analytical capabilities of ICP-AES (ICP) and deuteron activation (associated with prompt gamma-rays and delayed X-rays) for the determination of certain transition metals, were investigated. The sensitivities of the three methods are given, and the general applicability of each technique is evaluated. In the case of ICP, numerical data were obtained from aqueous solutions containing digested plant material. These experimental results were assessed against minimum detectable limits attained in relevant solid matrices that were subjected to prompt gamma-ray and delayed X-ray spectrometry using 5 MeV ²H⁺ ions. The analytically useful lines originated mainly from (d,p) and (d,n) reactions. The potential of the three techniques for routine analysis is discussed and detailed methodologies are presented.     

Mössbauer studies in reentrant spin glass (Pd x Pt1−x )3Fe

Mössbauer and Magnetization studies in the reentrant spin glass regime of the series (Pd_x Pt_1–x)₃ Fe clarifies some aspects of the multiple magnetic phase transitions. The data presented refute the presence of a long range ferromagnetic order at temperatures between the spin glass and the paramagnetic states. The ferromagnetic-like response can arise from the presence of magnetic clusters.     

XHSTT: an XML archive for high school timetabling problems in different countries

We present the progress on the benchmarking project for high school timetabling that was introduced at PATAT 2008. In particular, we announce the High School Timetabling Archive XHSTT-2011 with 21 instances from 8 countries and an evaluator capable of checking the syntax of instances and evaluating the solutions.     

Nanostructured Cobalt(II) Tetracarboxyphthalocyanine Complex Supported Within the MWCNT Frameworks: Electron Transport and Charge Storage Capabilities

The electrochemical redox properties of a surface‐confined thin solid film of nanostructured cobalt(II) tetracarboxyphthalocyanine integrated with multiwalled carbon nanotube (nanoCoTCPc/MWCNT) have been investigated. This novel nanoCoTCPc/MWCNT material was characterized using SEM, TEM, zeta analysis and electrochemical methods. The nanoCoTCPc/MWCNT nanohybrid material exhibited an extra‐ordinarily high conductivity (15 mS cm^?1), which is more than an order of magnitude greater than that of the MWCNT‐SO₃H (527 µS cm^?1) and three orders of a magnitude greater than the nanoCoTCPc (4.33 µS cm^?1). The heterogeneous electron transfer rate constant decreases as follows: nanoCoTCPc/MWCNT (k_app≈19.73×10^?3 cm s^?1)>MWCNT‐SO₃H (k_app≈11.63×10^?3 cm s^?1)>nanoCoTCPc (k_app≈1.09×10^?3 cm s^?1). The energy‐storage capability was typical of pseudocapacitive behaviour; at a current density of 10 µA cm^?2, the pseudocapacitance decreases as nanoCoTCPc/MWCNT (3.71×10^?4 F cm^?2)>nanoCoTCPc (2.57×10^?4 F cm^?2)>MWCNT‐SO₃H (2.28×10^?4 F cm^?2). The new nanoCoTCPc/MWCNT nanohybrid material promises to serve as a potential material for the fabrication of thin film electrocatalysts or energy‐storage devices.     

Polymeric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drug carriers

This study focused on evaluating four emulsion-based processing strategies for polymeric nanoparticle synthesis to explicate the mechanisms of nanoparticle formation and the influence on achieving sustained-release of two anti-tuberculosis drugs, isoniazid and rifampicin. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles were formulated with and without sorbitan mono-oleate as a stabilizer using emulsion-solvent-surfactant-evaporation (ESSE) and emulsion-solvent-evaporation (ESE) approaches. An alginate solution gelled by ionic crosslinking with calcium chloride was employed to prepare alginate hydrogel nanoparticles via reverse-emulsion-cationic-gelification (RECG) and reverse-emulsion-surfactant-cationic-gelification (RESCG) approaches. In vitro drug release analysis was performed. The size, zeta potential and morphology of the nanoparticles were analyzed. Molecular mechanics energy relationships (MMER) were employed to explore the spatial disposition of alginate and PLGA with respect to the emulsifying profile of sorbitan monooleate and to corroborate the experimental findings. Results revealed that particle size of the PLGA nanoparticles was influenced by the stabilizer concentration. Nanoparticles synthesized by the ESSE approach had smaller sizes of 240±8.7 nm and 195.5±5.4 nm for rifampicin- and isoniazid-loaded nanoparticles, respectively. This was a substantial size reduction from nanoparticles generated by the ESE approach (>1000 nm). The RESCG approach produced stable and higher nanoparticle yields with desirable size (277±1.0 nm; 289±1.2 nm), a low polydispersity index (27.1±0.3 mV; 28.5±0.5 mV) and drug entrapment efficiency of 73% and 75% for isoniazid and rifampicin, respectively. Drug release from the ESSE and RESCG synthesized nanoparticles displayed desirable release of the two anti-TB drugs with sustained zero-order kinetics over a period of 8h. MMER supported the mechanisms of nanoparticle formation with a sphericalized interlaced network configuration.     

Depth Profiling (ICP-MS) Study of Trace Metal ‘Grains’ in Solid Asphaltenes

Knowledge of trace metal ‘grains’ in asphaltenes could play a significant role in enhancing refining and processing of crudes and also in providing useful information on mechanistic and migratory features linked to asphaltenes. These metals originate directly from interaction of oils with source-rock, mineral matter, and formation water and their accumulation in asphaltene matrices could vary from oil well to oil well. Suitable asphaltene samples were subjected to high-performance ICP-MS laser depth profiling (213 nm) to depths of 50 μm at 5 μm intervals. The study was conducted in the absence of standardization and characteristic intensities originating from the metals of interest were measured. Ten metal profiles were investigated (Na, Mg, Al, Mn, Fe, Zn, Sr, Pb, V, and Ni). The experimental results showed non-uniform distribution of trace metals and identified areas where such metals agglomerate. The data suggested that certain chemical and physical conditions within the structure of asphaltenes are favorable for metal ‘grain’ formation at specific points. The exact mechanism for this behavior is not clear at this stage, and has considerable scope for future studies, including mathematical modeling simulations of asphaltenes. We also found that solid asphaltenes could be a useful forerunner of scale formation.