Rapid parameter optimization of low signal‐to‐noise samples in NMR spectroscopy using rapid CPMG pulsing during acquisition: application to recycle delays

A method is presented that combines Carr–Purcell–Meiboom–Gill (CPMG) during acquisition with either selective or nonselective excitation to produce a considerable intensity enhancement and a simultaneous loss in chemical shift information. A range of parameters can theoretically be optimized very rapidly on the basis of the signal from the entire sample (hard excitation) or spectral subregion (soft excitation) and should prove useful for biological, environmental, and polymer samples that often exhibit highly dispersed and broad spectral profiles. To demonstrate the concept, we focus on the application of our method to T₁ determination, specifically for the slowest relaxing components in a sample, which ultimately determines the optimal recycle delay in quantitative NMR. The traditional inversion recovery (IR) pulse program is combined with a CPMG sequence during acquisition. The slowest relaxing components are selected with a shaped pulse, and then, low‐power CPMG echoes are applied during acquisition with intervals shorter than chemical shift evolution (RCPMG) thus producing a single peak with an SNR commensurate with the sum of the signal integrals in the selected region. A traditional ¹³C IR experiment is compared with the selective ¹³C IR‐RCPMG sequence and yields the same T₁ values for samples of lysozyme and riverine dissolved organic matter within error. For lysozyme, the RCPMG approach is ~70 times faster, and in the case of dissolved organic matter is over 600 times faster. This approach can be adapted for the optimization of a host of parameters where chemical shift information is not necessary, such as cross‐polarization/mixing times and pulse lengths. Copyright © 2013 John Wiley & Sons, Ltd.     

Mathematical analysis of the dynamics of visceral leishmaniasis in the Sudan

In this paper we develop a mathematical model to study the dynamics of visceral leishmaniasis in the Sudan. To develop this model we consider the dynamics of the disease between three different populations, human, reservoir and vector populations. The model is analyzed at equilibrium and the stability of the equilibria is analyzed. The basic reproduction number is derived, and the threshold conditions for disease elimination established. Results show that the disease can be eliminated under certain conditions. Simulations of the model show that human treatment helps in disease control, and its synergy with vector control will more likely result in the elimination of the disease.     

Microemulsion method: A novel route to synthesize organic and inorganic nanomaterials: 1st Nano Update

Synthesis of nanoparticles by microemulsion method is an area of considerable current interest. Since the discovery of microemulsions, they have attained increasing significance both in basic research and in different industrial fields. Due to their unique properties, namely, ultralow interfacial tension, large interfacial area, thermodynamic stability and the ability to solubilize otherwise immiscible liquids. The uses and applications of microemulsions are numerous in chemical and biological fields. The nanoparticles not only are of basic scientific interest, but also have resulted in important technological applications, such as catalysts, high-performance ceramic materials, microelectronic devices, high-density magnetic recording and drug delivery. The microemulsion technique promises to be one of the versatile preparation method which enables to control the particle properties such as mechanisms of particle size control, geometry, morphology, homogeneity and surface area. This review aims to give a vivid look on the use of microemulsions for synthesizing and controlling the grain size and morphology of the nanoparticles and at the same time will summarize some recent works carried out in the synthesis of organic and inorganic nanoparticles by this method.     

Vaccination model for visceral leishmaniasis with infective immigrants

In this paper, we present and analyzed a mathematical model that describes the dynamics of visceral leishmaniasis in a population with immigration of infective humans under mass vaccination strategy. Our result shows that in order for the vaccine to play a role on disease control, it must be very effective. Results also show that vaccination coverage does not have any impact on disease control when the immigration rate is small, and it does not affect the long‐term behavior when the immigration rate is high. In the case of no immigration of infective, our system has disease‐free equilibrium, and it is globally asymptotically stable when , the basic reproduction number, is less than unity. Numerical simulation shows that in the case of no immigration of infective, our system undergoes forward bifurcation when passes throw unity. Copyright © 2012 John Wiley & Sons, Ltd.     

Physical and optical properties of Li2O-MgO-B2O3 doped with Dy3+

The study on the optical properties of alkali borate glasses doped with rare earths is an interesting area of research. Dysporosium doped lithium magnesium borate glasses were prepared by melt-quenching technique with dysporosium concentration varying from 0.3 to 1.0 mol %. Physical and optical properties of Lithium Magnesium Borate doped with different concentration of Dy³⁺ were observed based on its physical parameters, emission spectra and absorption spectra. The absorption spectra of this study exhibits eight absorption bands with hypersensitive peak at 1260 nm (⁶ H _9/2). Two emitted spectra transitions were also observed at ⁴ F _9/2 → ⁶ H _15/2, ⁴ F _9/2 → ⁶ H _13/2. Lastly, important physical parameters for each concentration of dopant such as density, ions concentration, polaron radius, inter-nuclear distance, refractive index, oscillator strength and other parameters were determined.     

Effect of ultrasound on different quality parameters of apple juice

Fresh apple juice treated with ultrasound (for 0, 30, 60 and 90 min, at 20 °C, 25 kHz frequency) was evaluated for different physico-chemical, Hunter color values, cloud value, antioxidant capacity, scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical, ascorbic acid, total phenolics, flavonoids, flavonols and microbial characteristics. No significant effect of sonication was observed on pH, total soluble solids (°Brix) and titratable acidity of apple juice. Sonication significantly improved ascorbic acid, cloud value, phenolic compounds, antioxidant capacity, DPPH free radical scavenging activity and differences in Hunter color values. Moreover, significant reduction in microbial population was observed. Findings of the present study suggested that sonication treatment could improve the quality of apple juice. It may successfully be employed for the processing of apple juice with improved quality and safety from consumer’s health point of view.     

Measurement of ablative laser propulsion parameters for aluminum, Co–Ni ferrite and polyurethane polymer

Laser ablation propulsion is a form of beam-powered propulsion in which a pulsed laser ablates a target material thus producing thrust. We report in this work the measurements of various parameters related to laser-induced micropropulsion in toluene diisocyanate-based polyurethane polymer, aluminum and Co–Ni ferrite. The targets were irradiated by a Q-switched pulsed Nd–YAG laser at 1064 nm (pulse duration 5 ns) under atmospheric conditions. A contact-free optical triangulation method was used to measure the laser ablation induced thrust in the samples. The measurements and calculations depict that Co–Ni ferrite is better in terms of critical propulsion parameters C _m and I _sp. It has been observed that the propulsion parameters depend on the energy per pulse of the incident laser beam.     

Homotopy analysis method for singular IVPs of Emden–Fowler type

In this paper, approximate and/or exact analytical solutions of singular initial value problems (IVPs) of the Emden–Fowler type in the second-order ordinary differential equations (ODEs) are obtained by the homotopy analysis method (HAM). The HAM solutions contain an auxiliary parameter which provides a convenient way of controlling the convergence region of the series solutions. It is shown that the solutions obtained by the Adomian decomposition method (ADM) and the homotopy-perturbation method (HPM) are only special cases of the HAM solutions.     

Solutions of Emden–Fowler equations by homotopy-perturbation method

In this paper, approximate and/or exact analytical solutions of the generalized Emden–Fowler type equations in the second-order ordinary differential equations (ODEs) are obtained by homotopy-perturbation method (HPM). The homotopy-perturbation method (HPM) is a coupling of the perturbation method and the homotopy method. The main feature of the HPM is that it deforms a difficult problem into a set of problems which are easier to solve. In this work, HPM yields solutions in convergent series forms with easily computable terms, and in some cases, only one iteration leads to the high accuracy of the solutions. Comparisons with the exact solutions and the solutions obtained by the Adomian decomposition method (ADM) show the efficiency of HPM in solving equations with singularity.     

Variational iteration method for fractional heat- and wave-like equations

This paper applies the variational iteration method to obtaining analytical solutions of fractional heat- and wave-like equations with variable coefficients. Comparison with the Adomian decomposition method shows that the VIM is a powerful method for the solution of linear and nonlinear fractional differential equations.