Degradation of 4-hydroxybenzoic acid by combined ultrasound irradiation and catalytic wet peroxide oxidation

The aim of this study is to explore the potential benefits from the combined use of ultrasound irradiation and catalytic wet peroxide oxidation for the degradation of 4-hydroxybenzoic acid (4-HBA). The target compound degradation was studied under direct and indirect sonication, while silent conditions were employed as reference. The catalyst, a mixed (Al-Fe) pillared clay named FAZA, was in the form of powder and of extrudates. In the case of extrudates it was observed that ultrasound improves the catalyst performance due to reduction of diffusion resistance, thereby increasing the conversion after 4 h by 12-15 times. Increasing the initial concentration of 4-HBA was found to lead to lower conversion. The combined ultrasonic/catalytic process appears very promising for environmental applications.     

Charged cosmic strings interacting with gravitational and electromagnetic waves

Under a particular choice of the Ernst potential, we solve analytically the Einstein–Maxwell equations to derive a new exact solution depending on five parameters: the mass, the angular-momentum (per unit mass), α, the electromagnetic-field strength, k, the parameter-p and the Kerr-NUT parameter, l. This (Petrov Type D) solution is cylindrically symmetric and represents the curved background around a charged, rotating cosmic string, surrounded by gravitational and electromagnetic waves, under the influence of the Kerr-NUT parameter. A C-energy study in the radiation zone suggests that both the incoming and the outgoing radiation is gravitational, strongly focused around the null direction and preserving its profile. In this case, the absence of the k-parameter from the C-energy implies that, away from the linear defect the electromagnetic field is too weak to contribute to the energy-content of the cylindrically symmetric space-time under consideration. In order to explain this result, we have evaluated the Weyl and the Maxwell scalars near the axis of the linear defect and at the spatial infinity. Accordingly, we have found that the electromagnetic field is concentrated (mainly) in the vicinity of the axis, while falling-off prominently at large radial distances. However, as long as k ≠ 1, the non-zero Kerr-NUT parameter enhances those scalars, both near the axis and at the spatial infinity, introducing some sort of gravitomagnetic contribution.     

Guided e-MRI prostate biopsy can solve the discordance between Gleason score biopsy and radical prostatectomy pathology

Introduction

The aim of this study is to examine if guided prostate biopsies based on abnormalities detected by conventional and functional endorectal magnetic resonance imaging (MRI) yield a more reliable representation of the radical prostatectomy pathology and to identify probable preoperative clinical variables that stratified patients likely to harbor significant upgrading.

Patients and Methods

From April 2004 to April 2009, a review of N=70 patients records diagnosed with prostate cancer by a 3-6 core guided transrectal ultrasound (TRUS) prostate biopsy based on abnormalities detected by conventional and functional endorectal MRI and who subsequently underwent radical prostatectomy and exhibited a significant upgrading was conducted. Additionally, a multivariate analysis with a significant upgrading as the outcome was performed including the following parameters: prostate specific antigen (PSA) level, clinical stage, prostate size and duration from biopsy to radical prostatectomy.

Results

A significant upgrading was noted in only 8.5% of patients, with 1.4% exhibiting a significant downgrading and the rest 90.1% exhibiting an exact Gleason score match. No preoperative clinical variables that stratified patients likely to harbour significant upgrading were identified.

Conclusions

This type of biopsy method seems to solve the discordance between the biopsy Gleason score and radical prostatectomy pathology regardless of known preoperative clinical variables that can affect it.     

Application of stable isotopes and hydrochemical analysis in groundwater aquifers of Argolis Peninsula (Greece)

The present study examines the isotopic and hydrochemical composition of 18 inland spring waters and 3 coastal karstic spring waters, covering the period between October 2005 and March 2008. The stable isotopes (¹⁸O, ²H) processing has revealed the absence of significant evaporation phenomena and that the origin of fresh water samples is meteoric. Using ¹⁸O values in rainfall waters, an average line of isotopic depletion with altitude has been constructed, extracting a rate of?0.45‰/100 m as typical for the study area. Furthermore, the mean altitude of recharge of the springs has been estimated by plotting the groundwater sampling points on a δ¹⁸O versus altitude diagram. Hydrochemistry results have shown that the dissolution of carbonate, flysch and ophiolitic formations defines the hydrochemical characteristics of groundwater. Moreover, seawater intrusion in the coastal area is significantly high, causing the water in the three karstic springs to be brackish.     

Synthesis and Self-Assembly of 2nd Generation Dendritic Homopolymers and Copolymers of Polydienes with Different Isomeric Microstructures

Synthesis of 2^nd generation dendritic polymeric materials via anionic polymerization procedures in combination with chlorosilane chemistry, consisting either from one polydienic segment (homopolymers) or from two chemically different polydienic components (copolymers), is described. The polydienes used were poly(butadiene) (PB) with ∼90% 1,4-isomerism and poly(isoprene) (PI) with increased 3,4-isomerism (∼60%). Molecular characterization of intermediate products and the final dendritic materials was made with Gel Permeation Chromatography (GPC), Membrane and Vapour Pressure Osmometry (MO and VPO respectively), Gas Chromatography –Mass Spectroscopy (GC-MS) and ¹H-Nuclear Magnetic Resonance (¹H-NMR) Spectroscopy, leading to the conclusion that they can be considered model polymers. Morphological studies solely with Transmission Electron Microscopy (TEM) have been conducted on two of the four synthesized copolymer samples exhibiting microphase separation between the two polydiene segments.     

On the geometry of complete intersection toric varieties

In this paper we give a geometric characterization of the cones of toric varieties that are complete intersections. In particular, we prove that the class of complete intersection cones is the smallest class of cones which is closed under direct sum and contains all simplex cones. Further, we show that the number of the extreme rays of such a cone, which is less than or equal to 2n − 2, is exactly 2n − 2 if and only if the cone is a bipyramidal cone, where n > 1 is the dimension of the cone. Finally, we characterize all toric varieties whose associated cones are complete intersection cones. Received: 4 July 2005     

Optimal block iterative schemes for certain large,sparse, and nonsymmetric linear systems

The problem of determining fast iterative solutions of certain large, sparse, and nonsymmetric linear systems, arising in applications, is addressed here. Several iterative schemes, from the accelerated overrelaxation family, are considered. Different geometrical algorithms are used for the explicit determination of the optimal factors. Direct comparisons of the spectral radii of the resulting optimal schemes reveal that the optimal extrapolated accelerated Gauss-Seidel (EAGS) is always asymptotically faster than the optimal successive overrelaxation, while the optimal EAGS and extrapolated Gauss-Seidel strongly compete. Application of the collocation method on simple boundary-value problems is used to demonstrate our results numerically.     

On the existence of approximate solutions for singular integral equations of Cauchy type discretized by Gauss-Chebyshev quadrature formulae

It is shown that the direct Gauss-Chebyshev method used for the numerical solution of singular integral equations of Cauchy-type possesses a unique solution for sufficiently largen.     

Nuclear magnetic resonance relaxometry as a spectroscopic probe of the coordination sphere of a paramagnetic metal bound to a humic acid mixture

Protons on water molecules are strongly affected by paramagnetic ions. Since the acid-base properties of water facilitate rapid proton exchange, a single proton nuclear magnetic resonance (NMR) signal is seen in aqueous solutions of paramagnetic ions. Proton relaxation times are significantly affected by paramagnetic species and the readily detectable single signal serves as a powerful amplifier of the information contained concerning the protons in the paramagnetic environment. Where water molecules coordinated to free paramagnetic ions and to metal complexes of ligands that form non-labile (on the NMR time scale) complexes, the effects on water in the two environments can be distinguished. This can provide information on the nature of the ligand binding sites. The example of Cu²⁺ bound to the Laurentian humic acid mixture reported here using convenient low field NMR relaxometers shows that the information can enrich our understanding of complexation and speciation in the presence of complex mixture ligands characteristic of natural water systems. In this case, the data underline the role of aggregation and conformation in defining the complexation sites.