Nanoparticles decorated with a Schiff's base for the microextraction of Cd,Pb, Ni,and Co in environmental samples

In this paper, we report a new liquid–liquid microextraction procedure called “nanoparticles decorated with a Schiff's base for the microextraction of Cd, Pb, Ni, and Co in environmental samples”. The developed procedure was utilized for the extraction of Cd, Pb, Ni, and Co in environmental samples. The Schiff's base was formed by reacting salicylaldehyde with 3‐aminopropyltriethoxysilane‐functionalized iron oxide nanoparticles. Analyte extraction was conducted in a capillary column system loaded with modified nanoparticles and triton X‐114 as dispersion medium. 1‐Butyl‐3‐methylimidazolium hexafluorophosphate was employed as an extraction solvent. Acidified methanol in ultrasonic bath was used as desorption solvent, and elemental determination was carried out with flame atomic absorption spectrometer. Characterization of modified nanoparticles was performed with FTIR spectroscopy and transmission electron microscopy. Solution pH, nanoparticles amount, dispersant concentration, ionic liquid, and temperature were optimized for the extraction. Detection limits obtained for Cd, Pb, Ni, and Co were 0.183, 0.201, 0.241, and 0.192 μg L^?1, respectively, and enhancement factors were 79.1, 86.4, 95.7, and 82.0, respectively. The reproducibility of the developed procedure was in the range of 3.98–5.10%. Validation was checked by applying the developed procedure on certified reference water samples. The microextraction based on nanoparticles decorated with Schiff's base was successfully applied for the extraction of Cd, Pb, Ni, and Co in real environmental water samples.     

Isolating stem cells in the inter-follicular epidermis employing synchrotron radiation-based Fourier-transform infrared microspectroscopy and focal plane array imaging

Normal function and physiology of the epidermis is maintained by the regenerative capacity of this tissue via adult stem cells (SCs). However, definitive identifying markers for SCs remain elusive. Infrared (IR) spectroscopy exploits the ability of cellular biomolecules to absorb in the mid-IR region (λ?=?2.5–25?μm), detecting vibrational transitions of chemical bonds. In this study, we exploited the cell’s inherent biochemical composition to discriminate SCs of the inter-follicular skin epidermis based on IR-derived markers. Paraffin-embedded samples of human scalp skin (n?=?4) were obtained, and 10-μm thick sections were mounted for IR spectroscopy. Samples were interrogated in transmission mode using synchrotron radiation-based Fourier-transform IR (FTIR) microspectroscopy (15?×?15?μm) and also imaged employing globar-source FTIR focal plane array (FPA) imaging (5.4?×?5.4?μm). Dependent on the location of derived spectra, wavenumber–absorbance/intensity relationships were examined using unsupervised principal component analysis. This approach showed clear separation and spectral differences dependent on cell type. Spectral biomarkers concurrently associated with segregation of SCs, transit-amplifying cells and terminally-differentiated cells of epidermis were primarily PO ₂ ^? vibrational modes (1,225 and 1,080?cm^?1), related to DNA conformational alterations. FPA imaging coupled with hierarchical cluster analysis also indicated the presence of specific basal layer cells potentially originating from the follicular bulge, suggested by co-clustering of spectra. This study highlights PO ₂ ^? vibrational modes as potential putative SC markers.

A Thermodynamic Study of Complexation of Iron Ions with Clarithromycin and Roxithromycin in Methanol Using a Conductometric Method

The formation constants K _ML of Clarithromycin (CLA) and Roxithromycin (ROX) with Fe(III) and Fe(II) ions in methanol have been determined at various temperatures using a conductometric technique. The interaction yields complexes with metal-to-ligand compositions of 1:1. The conductivity data were analyzed using a computer program based on 1:1 stoichiometry from which the stability constants and the limiting molar conductance were obtained. The stability of these complexes was found to increase with temperature. Compared with Fe(II), Fe(III) forms more stable complexes with ROX and CLA. The values of the thermodynamic parameters enthalpies (??H ^°), entropies (??S ^°), and the derived Gibbs energies (??G ^°) were deduced from the dependence of the formation constants on temperature. The positive values of ??H ^° and ??S ^° indicate that the complexation processes is enthalpically unfavorable but entropically favored. The negative values of ??G ^° show the ability of the studied ligand to form stable complexes and that the complexation process is favorable.     

Flow-induced deformation of shallow microfluidic channels

We study the elastic deformation of poly(dimethylsiloxane) (PDMS) microchannels under imposed flow rates and the effect of this deformation on the laminar flow profile and pressure distribution within the channels. Deformation is demonstrated to be an important consideration in low aspect ratio (height to width) channels and the effect becomes increasingly pronounced for very shallow channels. Bulging channels are imaged under varying flow conditions by confocal microscopy. The deformation is related to the pressure and is thus non-uniform throughout the channel, with tapering occurring along the stream-wise axis. The measured pressure drop is monitored as a function of the imposed flow rate. For a given pressure drop, the corresponding flow rate in a deforming channel is found to be several times higher than expected in a non-deforming channel. The experimental results are supported by scaling analysis and computational fluid dynamics simulations coupled to materials deformation models.     

Absence of reptation in the high-temperature folding of the trpzip2 beta-hairpin peptide

We have carried out extensive all atom explicit solvent simulations of the high-temperature folding and unfolding of the trpzip2 beta-hairpin peptide and examined the resulting trajectories for evidence of folding via a reptation mechanism. Over 300 microcanonical simulations of 10 ns each were initiated from a Boltzmann ensemble of conformations at 425 K. Though we observed numerous folding and unfolding events, no evidence of reptation was found. The diffusional dynamics of the peptide are orders of magnitude faster than any observed reptation-like motion. Our data suggest that the dominant mechanisms for beta-hairpin folding under these conditions are hydrophobic collapse and turn formation, and that rearrangements occur via significant expansion of the polypeptide chain.     

A study of a special family of analytic functions at infinity

In the present work we introduce certain new subclasses of analytic functions in the open unit disk U. Then by using a quasi-Hadamard product we discuss their applications in the space of analytic functions.     

Some new exact analytical solutions for helical flows of second grade fluids

The helical flow of a second grade fluid, between two infinite coaxial circular cylinders, is studied using Laplace and finite Hankel transforms. The motion of the fluid is due to the inner cylinder that, at time t = 0⁺ begins to rotate around its axis, and to slide along the same axis due to hyperbolic sine or cosine shear stresses. The components of the velocity field and the resulting shear stresses are presented in series form in terms of Bessel functions J₀(•), Y₀(•), J₁(•), Y₁(•), J₂(•) and Y₂(•). The solutions that have been obtained satisfy all imposed initial and boundary conditions and are presented as a sum of large-time and transient solutions. Furthermore, the solutions for Newtonian fluids performing the same motion are also obtained as special cases of general solutions. Finally, the solutions that have been obtained are compared and the influence of pertinent parameters on the fluid motion is discussed. A comparison between second grade and Newtonian fluids is analyzed by graphical illustrations.     

Vibration modelling of helical springs with non-uniform ends

Helical springs constitute an integral part of many mechanical systems. Usually, a helical spring is modelled as a massless, frequency independent stiffness element. For a typical suspension spring, these assumptions are only valid in the quasi-static case or at low frequencies. At higher frequencies, the influence of the internal resonances of the spring grows and thus a detailed model is required. In some cases, such as when the spring is uniform, analytical models can be developed. However, in typical springs, only the central turns are uniform; the ends are often not (for example, having a varying helix angle or cross-section). Thus, obtaining analytical models in this case can be very difficult if at all possible. In this paper, the modelling of such non-uniform springs are considered. The uniform (central) part of helical springs is modelled using the wave and finite element (WFE) method since a helical spring can be regarded as a curved waveguide. The WFE model is obtained by post-processing the finite element (FE) model of a single straight or curved beam element using periodic structure theory. This yields the wave characteristics which can be used to find the dynamic stiffness matrix of the central turns of the spring. As for the non-uniform ends, they are modelled using the standard finite element (FE) method. The dynamic stiffness matrices of the ends and the central turns can be assembled as in standard FE yielding a FE/WFE model whose size is much smaller than a full FE model of the spring. This can be used to predict the stiffness of the spring and the force transmissibility. Numerical examples are presented.     

Holographic dark energy in Brans–Dicke theory with logarithmic correction

In the derivation of holographic dark energy density, the area law of the black hole entropy plays a crucial role. However, the entropy-area relation can be modified from the inclusion of quantum effects, motivated from the loop quantum gravity, string theory and black hole physics. In this paper, we study cosmological implication of the interacting entropy-corrected holographic dark energy model in the framework of Brans–Dicke cosmology. We obtain the equation of state and the deceleration parameters of the entropy-corrected holographic dark energy in a non-flat Universe. As system’s IR cutoff we choose the radius of the event horizon measured on the sphere of the horizon, defined as L = ar(t). We find out that when the entropy-corrected holographic dark energy is combined with the Brans–Dicke field, the transition from normal state where w _D > −1 to the phantom regime where w _D < −1 for the equation of state of interacting dark energy can be more easily achieved for than when resort to the Einstein field equations is made.     

Reliable iris localization using integral projection function and 2D-shape properties

Iris recognition technology recognizes a human based on his/her iris pattern.However,the accuracy of the iris recognition technology depends on accurate iris localization.Localizing a pupil region in the presence of other low-intensity regions,such as hairs,eyebrows,and eyelashes,is a challenging task.This study proposes an iris localization technique that includes a localizing pupillary boundary in a sub-image by using an integral projection function and two-dimensional shape properties(e.g.,area,geometry,and circularity).The limbic boundary is localized using gradients and an error distance transform,and the boundary is regularized with active contours.Experimental results obtained from public databases show the superiority of the proposed technique over contemporary methods.