Analytical model for the magnetophoretic capture of magnetic microspheres in microfluidic devices

Magnetic microspheres are used as mobile substrates in micro-total-analysis systems (μTAS), since the particles can be selectively functionalized to attach different bioconjugates and can be precisely manipulated using external magnetic field gradients. A large number of MEMS-based bio-analytical devices employ magnetophoretic separation as an important step during their operation. An analytical technique is proposed in this paper that describes the magnetophoretic transport of magnetic microspheres under an imposed magnetic field when there is a pressure-driven or electroosmotic flow through a microchannel. Successful magnetophoretic capture occurs if the strength of the field-inducing magnetic dipole exceeds a critical value, or if the particles are larger than a critical size. The magnetophoretic separator performance is characterized in terms of capture efficiency. The analysis shows that the capture efficiency is a function of two independent non-dimensional parameters, λ and γ that in turn involve all the physical design and operating parameters of the microfluidic separator, e.g., the dipole strength, particle size and susceptibility, fluid viscosity and velocity, channel height, and the separation of the dipole. Parametric plots of capture efficiency as function of λ and γ helps in choosing the right design and operation parameter of a practical microfluidic separator for a target level of performance.     

Fully automated radiosynthesis of [<Superscript>18</Superscript>F]Fluoromisonidazole with single neutral alumina column purification: optimization of reaction parameters

1-H-1-(3-[¹⁸F]fluoro-2-hydroxypropyl)-2-nitroimidazole ([¹⁸F]FMISO), is the most used hypoxia-imaging agent in oncology and we have recently reported a fully automated procedure for its synthesis using the Nuclear Interface FDG module and a single neutral alumina column for purification. Using 1-(2′-nitro-1′-imidazolyl)-2-O-tetra-hydropyranyl-3-O-toluenesulfonylpropanediol (NITTP) as the precursor, we have investigated the yield of [¹⁸F]FMISO using different reaction times, temperatures, and the amount of precursor. The overall yield was 48.4 ± 1.2% (n = 3), (without decay correction) obtained using 10 mg NITTP with the radio-fluorination carried out at 145 °C for 3 min followed by acid hydrolysis for 3 min at 125 °C in a total synthesis time of 32 ± 1 min. Increasing the precursor amount to 25 mg did not improve the overall yield under identical reaction conditions, with the decay uncorrected yield being 46.8 ± 1.6% (n = 3), but rather made the production less economical. It was also observed that the yield increased linearly with the amount of NITTP used, from 2.5 to 10 mg and plateaued from 10 to 25 mg. Radio-fluorination efficiency at four different conditions was also compared. It was also observed by radio thin layer chromatography (radio-TLC) that the duration of radio-fluorination of NITTP, not the radio-fluorination temperature favoured the formation of labeled thermally degraded product, but the single neutral alumina column purification was sufficient enough to obtain [¹⁸F]FMISO devoid of any radiochemical as well as cold impurities.     

Magnetohydrodynamic stagnation-point flow of a power-law fluid towards a stretching surface

Steady two-dimensional stagnation-point flow of an electrically conducting power-law fluid over a stretching surface is investigated when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point. We have discussed the uniqueness of the solution except when the ratio of free stream velocity and stretching velocity is equal to 1. The effect of magnetic field on the flow characteristic is explored numerically and it is concluded that the velocity at a point decreases/increases with increase in the magnetic field when the free stream velocity is less/greater than the stretching velocity. It is further observed that for a given value of magnetic parameter M, the dimensionless shear stress coefficient |F^″(0)| increases with increase in power-law index n when the value of the ratio of free stream velocity and stretching velocity is close to 1 but not equal to 1. But when the value of this ratio further differs from 1, the variation of |F^″(0)| with n is non-monotonic.     

Stability of dual solutions in stagnation-point flow and heat transfer over a porous shrinking sheet with thermal radiation

An analysis is carried out to study the steady two-dimensional stagnation-point flow and heat transfer of an incompressible viscous fluid over a porous shrinking sheet in the presence of thermal radiation. A set of similarity transformations reduce the boundary layer equations to a set of non-linear ordinary differential equations which are solved numerically using fourth order Runge-Kutta method with shooting technique. The analysis of the result obtained shows that as the porosity parameter β increases, the range of region of existence of similarity solution increases. It is also observed that multiple solutions exist for a certain range of the ratio of the shrinking velocity to the free stream velocity (i.e., α) which again depends on β. We then discuss the stability of the unsteady solutions about each steady solution, showing that one steady state solution corresponds to a stable solution whereas the other corresponds to an unstable solution. The stable solution corresponds to the physically relevant solution. Further we obtain numerical results for each solution, which enable us to discuss the features of the respective solutions.     

Separation of Palladium by Extraction Chromatographic Technique Using Cyanex 471X (Tri Isobutyl Phosphine Sulfide) on Chromosorb-102

In a preliminary study performed with the waste rocks from the future uranium mine to be explored in Brazil, 106 samples were taken from the eight main lithologies found in the massif and analysed by instrumental neutron activation analysis (INAA) for 20 elements. For samples from the same lithology, a high variability in the concentration of most of the elements was found (coefficient of variation larger than 20%), which might be attributed to either insufficient homogenisation of minerals or to local variation within lithology. The hypothesis that the variability within the lithology does not have an influence to the total variability was tested by analysing 5 replicates of the 5 most contrasting samples from the predominant lithology (plagioclase-microcline-gneiss), chosen after applying statistical evaluation (principal components and cluster analyses). Results indicated that homogenisation of samples was adequate due to low variation among replicates. The hypothesis tested was rejected with a confidence level higher than 99% for all the elements, corroborating the large intra-lithology variability.     

Use of EM algorithm for data reduction under sparsity assumption

Recent scientific applications produce data that are too large for storing or rendering for further statistical analysis. This motivates the construction of an optimum mechanism to choose only a subset of the available information and drawing inferences about the parent population using only the stored subset. This paper addresses the issue of estimation of parameter from such filtered data. Instead of all the observations we observe only a few chosen linear combinations of them and treat the remaining information as missing. From the observed linear combinations we try to estimate the parameter using EM based technique under the assumption that the parameter is sparse. In this paper we propose two related methods called ASREM and ESREM. The methods developed here are also used for hypothesis testing and construction of confidence interval. Similar data filtering approach already exists in signal sampling paradigm, for example, Compressive Sampling introduced by Candes et al. (Commun Pure Appl Math 59(8):1207–1223, 2006) and Donoho (IEEE Trans Inf Theory 52: 1289–1306, 2006). The methods proposed in this paper are not claimed to outperform all the available techniques of signal recovery, rather our methods are suggested as an alternative way of data compression using EM algorithm. However, we shall compare our methods to one standard algorithm, viz., robust signal recovery from noisy data using min-\(\ell _{1}\) with quadratic constraints. Finally we shall apply one of our methods to a real life dataset.     

Carbohydrate assisted fluorescence turn-on gluco-imino-anthracenyl conjugate as a Hg(II) sensor in milk and blood serum milieu

A new anthracenyl-imino-glucosyl conjugate (L) selectively senses Hg(2+) by turn-on fluorescence with a 13 ± 1 fold enhancement by forming a 2?:?1 complex in pH 5 to 10 even in the presence of several biologically and ecologically relevant metal ions, with a 25 ± 2% fluorescence enhancement at the EPA limit of 2 ppb. L is equally sensitive towards Hg(2+) in the presence of albumin proteins and in blood serum and milk.     

Testing for the Absence of Random Effects in a Two-way Nested Design with Mixed Effects Model: A Nonparametric Approach

Two-way nested design with mixed effects model arises in many practical situations. In the classical analysis of variance set-up, a test for the absence of the random effects is obtained under the assumption that the random effects and the errors are normally distributed. The present paper avoids this assumption and provides an asymptotically distribution-free test procedure for the above problem. The asymptotic null distribution of the test statistic is obtained. Actual implementation of the test is straight forward given the prior information on quantiles of the intra-block differences of observations. In the absence of such information, working test procedures are proposed. The performances of these tests are compared with the classical analysis of variance test through simulations. The tests are then illustrated by some real data sets.     

Biocompatibility of gold nanoparticles and their endocytotic fate inside the cellular compartment: a microscopic overview

Macrophages are one of the principal immune effector cells that play essential roles as secretory, phagocytic, and antigen-presenting cells in the immune system. In this study, we address the issue of cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. The cytotoxicity of gold nanoparticles has been correlated with a detailed study of their endocytotic uptake using various microscopy tools such as atomic force microscopy (AFM), confocal-laser-scanning microscopy (CFLSM), and transmission electron microscopy (TEM). Our findings suggest that Au(0) nanoparticles are not cytotoxic, reduce the production of reactive oxygen and nitrite species, and do not elicit secretion of proinflammatory cytokines TNF-alpha and IL1-beta, making them suitable candidates for nanomedicine. AFM measurements suggest that gold nanoparticles are internalized inside the cell via a mechanism involving pinocytosis, while CFLSM and TEM studies indicate their internalization in lysosomal bodies arranged in perinuclear fashion. Our studies thus underline the noncytotoxic, nonimmunogenic, and biocompatible properties of gold nanoparticles with the potential for application in nanoimmunology, nanomedicine, and nanobiotechnology.     

On total photon cross sections and contributions of the new quark states

The vector dominance model is used to calculate the contributions of the ψ-family to total photon cross sections, the parameters being estimated from the radiative and leptonic decays of the ψ-states. This is found to be rather small when compared to the recent data of Caldwell et al. on σ_tot(γp) at Fermilab energies. To explain this discrepancy, it is then conjectured that, within the context of VDM, one may have to invoke the recently hypothesized multiquark states to give the observed increase in σ_tot(γp); upper limits are set on their contributions.