Elastic anomalies in HoNi2B2C single crystals

We have measured temperature and magnetic field dependencies of the sound velocities and the sound attenuation in HoNi2B2C single crystals. The main result is a huge softening the velocity of C66 mode due to a cooperative Jahn-Teller effect, resulting in a tetragonal-orthorhombic structural phase transition. Anomalies in the behavior of the C66 mode through various magnetic phase transitions permit us to revise the low temperature H-T phase diagrams of this compound.Comment: v2: a discussion of the C44 mode with the comparison to Y borocarbide was adde

Magnus force and acoustic Stewart-Tolman effect in type II superconductors

At zero magnetic field we have observed an electromagnetic radiation from superconductors subjected by a transverse elastic wave. This radiation has an inertial origin, and is a manifestation of the acoustic Stewart-Tolman effect. The effect is used for implementing a method of measurement of an effective Magnus force in type II superconductors. The method does not require the flux flow regime and allows to investigate this force for almost the whole range of the existence of the mixed state. We have studied behavior of the gyroscopic force in nonmagnetic borocarbides and Nb. It is found that in borocarbides the sign of the gyroscopic force in the mixed state is the same as in the normal state, and its value (counted for one vortex of unit length) has only a weak dependence on the magnetic field. In Nb the change of sign of the gyroscopic force under the transition from the normal to the mixed state is observed.Comment: 4 pages, 5 figure

Magnesium oxide loaded mesoporous silica: Synthesis, characterisation and use in removing lead and cadmium from water supplies

Water pollution by potentially toxic elements such as cadmium (Cd) and lead (Pb) is a persistent problem in many parts of the world. It continues to have profound implications for drinking water supplies, wastewater discharge and environmental quality of rivers and lakes. Treatment is routinely needed but is not always accessible or practical for a given location or situation, hence new treatment options are the focus of much research. Nanotechnology has great potential to enhance water purification and decontamination efficiency. Nanomaterials have been shown to efficiently remove organic and inorganic pollutants, including metals, from contaminated waters but they can have a tendency to flocculate and thereby lose removal efficiency. Research aimed at stabilising nanoparticles into matrices such as silica offers a way forward. In this study, mesoporous silica (mSiO2, also referred to as MCM-41) was prepared and loaded with magnesium oxide nanoparticles (MgO-NP) to form a MgO-silica composite (MgO-mSiO2) and characterised using UV–Vis, FTIR, XRD, BET, and SEM techniques. The MgO-NP, mSiO2 and MgO-mSiO2 were then evaluated for their Cd and Pb removal capacity across varying conditions of pH, metal concentration, adsorbent: solution volume ratio and contact time. Sorption data were evaluated using the Freundlich, Langmuir and Temkin isotherm models. The MgO-mSiO2 was found to have a very high sorption capacity across the conditions tested, with >99% Cd removal across pH range 3–9 and >99% Pb removal across pH range 5–9. When tested at pH 6–7, the MgO-mSiO2 achieved nearly 100% adsorption efficiencies across the contact times tested (15–180 min)

Elastic constants of borocarbides. New approach to acoustic Measurement technique

A new version of the phase method of determining the sound velocity is proposed and implemented. It utilizes the ``Nonius'' measurement technique and can give acceptable accuracy (~1%) in samples of submillimeter size. Measurements of the sound velocity are made in single-crystal samples of the borocarbides RNi2B2C (R = Y,Lu,Ho). The elastic constants and the Debye temperature are calculated.Comment: 5 figures, 2 table

Synthesis of Nanostructured Catalysts by Surfactant-Templating of Large-Pore Zeolites

Zeolites and related crystalline molecular sieves are utilised in a wide range of reactions and processes due to their regular microporous structure, strong acidity, shape selectivity and ion-exchange properties. However, their practical applications can be limited by the small size of the channels and cavities of the microporous structures, and therefore, a great deal of effort have been devoted to enhancing the transport of large-sized molecules in the host pores. Several commercially available zeolites, including faujasite (FAU), mordenite (MOR), beta (BEA), ZSM-5 (MFI) and zeolite L (LTL) have been exposed to a variety of acid and base treatments in the presence of a surfactant (cetyltrimethyl ammonium bromide, CTAB), which led to the controlled introduction of intracrystalline mesoporosity. A detailed characterisation of the obtained mesostructured zeolites has been carried out using FTIR spectroscopy, high resolution TEM, XRD, N2 adsorption, 29Si and 27Al MAS NMR. This work demonstrates a successful application of the supramolecular templating approach for generating tuneable mesoporosity in a range of zeolites possessing 12-membered ring channels, which has been applied to zeolite L for the first time, thus producing hierarchical meso-microporous materials with improved accessibility of active sites and enhanced catalytic performance in dealkylation of tri-isopropylbenzene

Nanostructured Zeolites: The Introduction of Intracrystalline Mesoporosity in Basic Faujasite-Type Catalysts

A combination of postsynthesis modifications and ion exchange aiming to obtain basic cation-rich hierarchical zeolites X and Y was utilized in this work for the preparation of catalysts for biofuel production from vegetable oils. The secondary mesopore system with a narrow pore size distribution in the 4 nm range was introduced by successive acid and base treatments accompanied by surfactant templating. This was followed by ion exchange with Cs+ and K+ cations to produce strong basic catalysts. The prepared hierarchical zeolites were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, Fourier transform infrared spectroscopy, and solid-state NMR. The transesterification reaction over the zeolite catalysts was performed in a microwave batch-type reactor, and the effects of the reaction conditions, basic properties, and pore structure of the hierarchical faujasites were studied in detail. The conversion of triglycerides increased with increasing concentration of Cs and K in modified zeolites but declined with decreasing framework aluminum content. The balance between the strength of the basic sites and their accessibility in hierarchical zeolites and its effect on the catalytic performance of these nanostructured materials is discussed

On the enhancing effect of Ce in Pd-MOR catalysts for NOx CH4-SCR: a structure-reactivity study

The effect of palladium and cerium species on the selective catalytic reduction (SCR) of NOx using methane as reductant (NOx CH4-SCR) has been investigated using Pd-HMOR and PdCe-HMOR system. The catalysts have been characterised by H2-TPR, DRS UV–Vis, TEM/EDS and FTIR using CO and pyridine as probe molecules. The oxidation of NO and CH4-SCR catalytic tests have been conducted using monometallic and bimetallic formulations.Above 0.3 wt.% Pd, the increase in Pd loading leads to a decrease in NOx selectivity towards N2, with the formation of N2O, and a decrease in the CH4 selectivity towards SCR, due to CH4 direct combustion. H2-TPR and FTIR-CO studies indicate that palladium is stabilised as Pd2+ in ion-exchange position, probably in two different sites within the MOR framework.The addition of cerium to Pd-HMOR enhances its catalytic performance for NOx CH4-SCR. With 1 wt.% Ce, both NOx conversion into N2 and CH4 selectivity towards SCR have increased. Small CeO2 clusters interacting with palladium are likely to play a major role in this catalytic reaction. The number of such species increases up to Ce loading of ca. 2 wt.%. However, above 3 wt%, NOx conversion values decrease with Ce loading, which is attributed to the formation of bulk CeO2 species not interacting with palladium

Cardiomiopatia hipertrófica felina

A Cardiomiopatia Hipertrófica (CMH) é uma doença é a doença cardíaca primária mais comum em gatos causada por uma mutação genética autossómica de dominância incompleta com apresentações clínicas variadas que apresenta uma grande dispersão mundial e racial. O carácter hereditário desta doença cardíaca resulta de uma mutação genética autossómica dominante com penetração incompleta, sendo mais exuberante em situações de homozigotia. A mutação mais comum ocorre em genes que codificam para a Proteína C3 de Ligação à Miosina, com alterações estruturais do mesmo e consequente hipertrofia concêntrica parcial ou total do ventrículo esquerdo. Com o aumento do septo interventricular, dos músculos papilares e/ou da parede do ventrículo esquerdo, ocorre comprometimento tanto do enchimento ventricular como do seu relaxamento, o que por sua vez contribui para a progressão da hipertrofia. A diminuição da câmara cardíaca, a diminuição do débito cardíaco, o aumento compensatório do ritmo, o aumento da pressão de enchimento diastólico e o aumento do átrio esquerdo predispõem para uma insuficiência cardíaca congestiva, formação trombos e até morte súbita. A avaliação clínica de um gato com suspeita de Cardiomiopatia Hipertrófica deve ser exaustiva, mesmo que o diagnóstico definitivo apenas possa ser confirmado através de ecocardiografia e de métodos de biologia molecular no sentido de identificar a mutação genética. A ecocardiografia pode ainda ser útil para direcionar a terapêutica em função do grau de hipertrofia estabelecer prognóstico. Atualmente, em medicina humana, existem outras formas de terapêutica, como o novo MYK 461, que se revelam bastante promissores.The Hypertrophic Cardiomyopathy is the heart disease more common in cats caused by a genetic autossomic mutation with imcomplete penetrance, having several clinic findings worldwide and inbreed. This disease assumes an hereditary character associated with a genetic mutation autossomic dominant with incomplete penetrance, being more exuberant in homozigotic. It’s a common mutation in genes that codify for the Myosin Binding Protein C (MYBPC3), with structural alteration of itself and leading to the partial or total concentric hypertrophy os left ventricule. With the increase of the interventricular septum and/or papillary muscles and/or left ventricle hall there is a compromise of the ventricular filling and it’s relaxation, which in other hand contributes to the progression of the hypertrophy. The decrease of the cardiac chamber, the decrease of cardiac output, the compensatory increase of rhythm, the increase of pressure in diastolic filling and the increase of the left atrium predispose to congestive heart failure and even sudden death. Cats clinical evaluation under the suspect of Hypertrophic Cardiomyopathy should be exhaustive, even if the definite diagnostic can only be confirmed throght Ultrasound and bio molecular methods looking for identification of genetic mutations. Ultrasound can also be useful to direct the therapeutics accordingly to the level of Hypertrophy, and better prognostics. Nowadays, there are other new therapeutic drugs, like MYK 461, that are showing promissing results