Long-term results of extracorporeal peizoelectric shock wave lithotripsy of parotid stones

OBJECTIVE: To evaluate prospectively the recently developed method of extracorporeal shock-wave treatment of stones of the parotid gland. PATIENTS AND METHODS: 76 patients with symptomatic, sonographically proven, solitary stones of the parotid gland (36 females, 40 males; aged 2-80 years) were treated with extracorporeal piezoelectric shock-wave lithotripsy (ESWL) after failed conservative management (sialagogues, gland massage, duct bougie dilation). RESULTS: Parotid stones were no longer demonstrable after a mean follow-up time of 48 (6-71) months in 38 of the 76 patients; they were symptom-free and no new stones had formed. A residual, but symptom-free, stone was found in another 20 patients (26%) of whom 13 (17%) reported marked improvement after ESWL. No change from pretreatment symptoms occurred in five patients (7%) so that operative removal had to be performed. The success rate of the lithotripsy was independent of size and site of the stone. CONCLUSION: ESWL is the method of first choice in the treatment of parotid gland stones after unsuccessful conservative treatment and obviates operative gland removal in most cases.     

Equipment and transducer-independent 3D ultrasound in the maxillofacial area

AIM: The use of a new 3D ultrasound system should reduce the drawbacks of former 3D workstations (long image generation time, limited use due to the need for special 3D transducers), so that it is now applicable in daily clinical routine. METHOD: An ultrasound 3D workstation was used based on a pentium PC platform, employing a magnetoelectronic position detection system for spatial reconstruction of conventional 2D B-scan image sequences. RESULTS: Better assessment of topographico-anatomical spatial relationships was achieved when presenting pathological findings, especially in assessing lymph nodes and salivary stones. Pathological processes in the maxillofacial area occurring during a period of five months were visualised. CONCLUSION: The method of 3D reconstruction of standard two-dimensional electronic scans, as presented here, is the first method of its kind enabling applicability in daily clinical routine thanks to rapid imaging. The images can be produced with any ultrasound unit or transducer. First clinical results in maxillofacial surgery clearly show improved diagnostic possibilities although there still room for an improvement of the image quality. The possibility of semi-automatic exact volumetry appears meaningful especially in the investigation of lymph nodes. Integration of colour duplex sonography will further enhance the diagnostic value of this method.     

Top-down lipidomic screens by multivariate analysis of high-resolution survey mass spectra

Direct profiling of total lipid extracts on a hybrid LTQ Orbitrap mass spectrometer by high-resolution survey spectra clusters species of 11 major lipid classes into 7 groups, which are distinguished by their sum compositions and could be identified by accurately determined masses. Rapid acquisition of survey spectra was employed as a "top-down" screening tool that, together with the computational method of principal component analysis, revealed pronounced perturbations in the abundance of lipid precursors within the entire series of experiments. Altered lipid precursors were subsequently identified either by accurately determined masses or by in-depth MS/MS characterization that was performed on the same instrument. Hence, the sensitivity, throughput and robustness of lipidomics screens were improved without compromising the accuracy and specificity of molecular species identification. The top-down lipidomics strategy lends itself for high-throughput screens complementing ongoing functional genomics efforts.     

The reduction of NO with H2 over Ru/MgO

Ruthenium supported on magnesia was found to be a highly active and selective catalyst for the reduction of NO to N₂ with H₂. The adsorption of NO on Ru/MgO was studied at room temperature by applying frontal chromatography with a mixture of 2610 ppm NO in He. Subsequently, temperature‐programmed desorption (TPD) and temperature‐programmed surface reaction (TPSR) experiments in H₂ were performed. The adsorption of NO was observed to occur partly dissociatively as indicated by the formation of molecular nitrogen. The TPD spectrum exhibited a minor NO peak at 340 K indicating additional molecular adsorption of NO during the exposure to NO at room temperature, and two N₂ peaks at 480 K and 625 K, respectively. The latter data are in good agreement with previous results with Ru(0001) single‐crystal samples, where the interaction with NH₃ was found to lead to two N₂ thermal desorption states with a maximum coverage of atomic nitrogen of about 0.38. Heating up the catalyst after saturation with NO at room temperature in a H₂ atmosphere revealed the self‐accelerated formation of NH₃ after partial desorption of N₂, whereby sites for reaction with H₂ become available. As a consequence, the observed high selectivity towards N₂ under steady‐state reduction conditions is ascribed to the presence of a saturated N+O coadsorbate layer resulting in an enhanced rate of N₂ desorption from this layer and a very low steady‐state coverage of atomic hydrogen. The formation of H₂O by reduction of adsorbed atomic oxygen is the slow step of the overall reaction which determines the minimum temperature required for full conversion of NO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modeling of Temperature-Programmed Surface Reactions

Temperature-programmed surface reaction (TPSR) experiments with a ruthenium-based catalyst supported on MgO were conducted in a microreactor flow system. The hydrogenation of preadsorbed atomic nitrogen obtained under various experimental conditions has been studied followed by a detailed microkinetic analysis including an evaluation of the influence of backmixing. The shape of the TPSR profile was found to depend strongly on the initial surface coverage and on the presence of coadsorbates.     

A Simple Chemical Route toward Monodisperse Iron Carbide Nanoparticles Displaying Tunable Magnetic and Unprecedented Hyperthermia Properties

We report a tunable organometallic synthesis of monodisperse iron carbide and core/shell iron/iron carbide nanoparticles displaying a high magnetization and good air-stability. This process based on the decomposition of Fe(CO)(5) on Fe(0) seeds allows the control of the amount of carbon diffused and therefore the tuning of nanoparticles magnetic anisotropy. This results in unprecedented hyperthermia properties at moderate magnetic fields, in the range of medical treatments.     

A new class of organosilane-modified polycarboxylate superplasticizers with low sulfate sensitivity

It is well-established that a competitive adsorption exists between polycarboxylate superplasticizers (SP) and sulfate ions solubilized in the interstitial solution of cement paste, which may cause a loss of the dispersing properties. This has been explained by competitive weak ionic interactions between functional carboxyl groups and sulfate ions with cement grains. In this study, SPs including trialkoxysilane functional groups have been synthesized. Adsorption and dispersing properties of these SPs were evaluated in the presence of different concentrations of Na₂SO₄ added in aqueous solution. It appeared that a partial substitution of carboxyl groups by trialkoxysilane in the polymer makes them more resistant to sulfate ions. We suggested that the high adsorption capacity of these SPs results from the formation of strong bonds between hydroxysilane groups and calcium silicate hydrate phases. The improved compatibility of these new silylated SPs has been demonstrated through the formulation of two different concrete equivalent mortars.     

On the mechanism of the selective catalytic reduction of NO to N2 by H2 over Ru/MgO and Ru/Al2O3 catalysts

Steady-state and transient kinetic experiments were performed in a versatile microreactor flow set-up with magnesia- and alumina-supported ruthenium catalysts in order to elucidate the mechanism of the selective catalytic reduction (SCR) of nitric oxide with hydrogen. Both Ru/MgO and Ru/γ-Al₂O₃ were found to be highly active catalysts converting NO and H₂ into N₂ and H₂O with selectivities close to 100% at full conversion, although Ru-based catalysts are known to be active in the synthesis of NH₃ from N₂ and H₂. Frontal chromatography experiments with NO at room temperature revealed that NO and its dissociation products displace adsorbed atomic hydrogen (H−*) almost completely from hydrogen-precovered Ru surfaces. Obviously, NO and H₂ compete for the same adsorption sites, H−* being the weaker bound adsorbate. Temperature-programmed surface reaction (TPSR) experiments in H₂ subsequent to NO exposure demonstrated that higher heating rates and lower partial pressures of H₂ shift the selectivity from NH₃ to N₂. Therefore, the coverage of H−* is concluded to govern the branching ratio between the rate of associative desorption of N₂ (2N−*→N₂ + 2*) and the rate of hydrogenation of N−* (N−* + 3H–* →NH₃ + 4*). Finally, the steady-state coverages of N- and O-containing adsorbates were derived by interrupting the SCR reaction and hydrogenating the adsorbates off as NH₃ and H₂O. By solving the site balance, the Ru surfaces were found to be essentially N₂ is attributed to the very low coverage of H−* due to site blocking by a N + O coadsorbate layer, favouring the recombination of N−* instead of its hydrogenation to NH₃. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Blown Fiber Cable

A radically new approach to optical fiber cable design and installation is described. Packages containing a number of optical fibers were drawn into preinstalled empty bores (tubes) using the viscous drag of air. The drag force acting on the fiber package is distributed along its length, which makes it possible to introduce fibers into complicated routes, with low strain. In this paper, we will concentrate mainly on the design of the fiber package, first from the point of view of the hydrodynamic forces acting on it during installation. This leads to a theoretical model for the installation process. Second, we shall consider the package as a subminiature optical fiber cable, and examine its optical performance during manufacture and temperature cycling, which leads to a theoretical model of the temperature performance of the package. Finally, we will describe a trial field installation using this cabling technique.