Synthesis and morphology of nanosized zeolite L

AFM is a powerful tool for imaging nanoscale surface features; it provides two and three dimensional crystal structure images and other information about actual surface of zeolite crystallites. In this paper, nanosized zeolite L is synthesized in different crystallization times and a study of crystal growth of zeolite L is reported using atomic force microscopy (AFM). X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques are used for characterization of the as synthesized samples. TEM and two‐dimensional AFM images indicate that the zeolite particles are in a nano‐range and they have hexagonal structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Finite element buckling analysis of multi-layered graphene sheets on elastic substrate based on nonlocal elasticity theory

Graphene-polymer nano-composites are one of the most applicable engineering nanostructures with superior mechanical properties. In the present study, a finite element (FE) approach based on the size dependent nonlocal elasticity theory is developed for buckling analysis of nano-scaled multi-layered graphene sheets (MLGSs) embedded in polymer matrix. The van der Waals (vdW) interactions between the graphene layers and graphene-polymer are simulated as a set of linear springs using the Lennard-Jones potential model. The governing stability equations for nonlocal classical orthotropic plates together with the weighted residual formulation are employed to explicitly obtain stiffness and buckling matrices for a multi-layered super element of MLGS. The accuracy of the current finite element analysis (FEA) is approved through a comparison with molecular dynamics (MD) and analytical solutions available in the literature. Effects of nonlocal parameter, dimensions, vdW interactions, elastic foundation, mode numbers and boundary conditions on critical in-plane loads are investigated for different types of MLGS. It is found that buckling loads of MLGS are generally of two types namely In-Phase (INPH) and Out-of-Phase (OPH) loads. The INPH loads are independent of interlayer vdW interactions while the OPH loads depend on vdW interactions. It is seen that the decreasing effect of nonlocal parameter on the OPH buckling loads dwindles as the interlayer vdW interactions become stronger. Also, it is found that the small scale and polymer substrate have noticeable effects on the buckling loads of embedded MLGS.     

Study of the ZnO crystal growth by vapour transport methods

The crystal growth of ZnO by vapour transport is classically made with the assistance of additional species that produce a gaseous mixture, the role of which remains often uncertain in the transport and growth process. Initially, in order to study the mass transport process, a numerical simulation is made to analyse which are the requirements to have an effective transport. As the pressure of each gaseous species is generally unknown, the numerical study has been performed for different total pressures. It is found that, if congruent and equilibrium conditions are assumed at the sublimation and crystallisation interfaces, effective growth conditions can only be attained for a narrow range of total pressures. Nevertheless, it is well known that ZnO growth by vapour transport is possible for a wide range of pressures of gaseous species. As a consequence, partial pressures higher than the equilibrium ones must be present in order to justify the experimental results. We suggest that the thermal decomposition of ZnO is given by an activated process. The analysis of different mechanisms that could justify the activated decomposition, in accord with a systematic set of growth experiments, suggests that some additional species in the growth of ZnO by vapour transport promote the generation of an additional Zn pressure. This zinc pressure would act autocatalytically inducing O₂ and Zn partial pressures higher than the equilibrium ones and promoting thermal decomposition. The above-cited set of experimental growth experiences, that include the presence of C, Zn, Fe, Cu and H₂, will be analysed and interpreted according to this approach.     

New integrable cases of a Cremona transformation: a finite-order orbits analysis

We analyse the properties of a particular birational mapping of two variables (Cremona transformation) depending on two free parameters ( and ), associated with the action of a discrete group of non-linear (birational) transformations on the entries of a q × q matrix. This mapping originates from the analysis of birational transformations obtained from very simple algebraic calculations, namely taking the inverse of q × q matrices and permuting some of the entries of these matrices. It has been seen to yield weak chaos and integrability. We have found new integrable cases of this Cremona transformation, corresponding to the values of = 0 when , besides the already known values = 0 and = −1, and also arbitrary when = 0. For these cases, one has a foliation of the parameter space in elliptic curves. We give the equations of these elliptic curves. Based on this very example we show how one can find these integrability cases of the Cremona transformation and actually integrate it using a method based on the systematic study of the finite-order conditions of the Cremona transformation. The method is shown to be efficient and straightforward. The various integrability cases are revisited using many different representations of this very mapping (birational transformations, recursion in one variable, …).     

Modified carbon nanotubes as a sorbent for solid-phase extraction of gold,and its determination by graphite furnace atomic absorption spectrometry

A simple, sensitive and accurate method was developed for solid-phase extraction and preconcentration of trace levels of gold in various samples. It is based on the adsorption of gold on modified oxidized multi-walled carbon nanotubes prior to its determination by graphite furnace atomic absorption spectrometry. The type and volume of eluent solution, sample pH value, flow rates of sample and eluent, sorption capacity and breakthrough volume were optimized. Under these conditions, the method showed linearity in the range of 0.2–6.0 ng L⁻¹ with coefficients of determination of >0.99 in the sample. The relative standard deviation for seven replicate determinations of gold (at a level of 0.6 ng L⁻¹) is ±3.8 %, the detection limit is 31 pg L⁻¹ (in the initial solution and at an S/N ratio of 3; for n = 8), and the enrichment factor is 200. The sorption capacity of the modified MWCNTs for gold(III) is 4.15 mg g⁻¹. The procedure was successfully applied to the determination of gold in (spiked) water samples, human hair, human urine and standard reference material with recoveries ranging from 97.0 to 104.2 %.

A sorbent based on modified carbon nanotubes was prepared and used to extract gold ion from various samples prior to its determination by graphite furnace atomic absorption spectrometry

     

Electrophoretic fingerprint metallothionein analysis as a potential prostate cancer biomarker

Prostate-specific antigen (PSA) is a routinely used marker of prostate cancer; however, the cut-off values for unambiguous positive/negative prostate cancer diagnoses are not defined. Therefore, despite the best effort, certain percentage of misdiagnosed cases is being recorded every year. For this reason, search for more specific diagnostic markers is of great interest. In this study, systematic comparison of PSA and metallothionein (MT) levels in blood serum of 46 prostate cancer-diagnosed patients is presented. It is clearly demonstrated that PSA levels vary significantly and despite normal total PSA values in the range of 0 - 4?ng/mL were obtained in over 36.9% of cases, positive prostate cancer was diagnosed by biopsy. In contrary, MT levels were considerably elevated in all tested samples and no significant variations were observed. These results are indicating the potential of MT as an additional prostate cancer marker reducing, in combination with PSA, the probability of false positive/negative diagnosis. To increase the throughput of the screening, chip-based capillary electrophoresis was suggested as a rapid and effective method for the fingerprinting analysis of prostate cancer from diseased blood sera.     

Shears band in the 105Sn nucleus

The structure of ¹⁰⁵Sn has been investigated through the ⁵⁰Cr(⁵⁸Ni,2pn) reaction at a beam energy of 210 MeV. In addition to an extension of the spherical level scheme, a regular sequence of dipole transitions has been found. The experimental results are in agreement with the prediction of Tilted Axis Cranking calculations, which satisfactorily explain the properties of the band.     

G-espaces topologiques

In this paper we define a topologicalG-space, whereG is a monoid, and we extend the notion of bounded sets in this spaces.