The structure and oxidation of two palladium ceramic fusing alloys

The oxides formed at the surface of an alloy during preheating at about 1000 degrees C prior to the firing of ceramic are vital for the formation of a strong chemical bond between alloy and porcelain. Replacing Au used as the basic constituent in the ceramic fusing alloys with Pd seems to have a rather small effect on the behaviour of the elements Sn and In which were found to oxidize internally. However, no external oxidation of the transition metal component Co was found, in contrast to Ni in Au-based alloys. After ceramic firing a zone enriched with Co and In is found in the interaction area between alloy and ceramic. In another alloy Ga was observed to oxidize internally and much more easily than Cu due to its much lower free energy of formation. A solid solution was produced in both the alloys by ceramic firing as shown by SEM studies.     

Low-frequency stimulation of the external globus palladium produces anti-epileptogenic and anti-ictogenic actions in rats

Aim:

To investigate the anti-epileptic effects of deep brain stimulation targeting the external globus palladium (GPe) in rats.

Methods:

For inducing amygdala kindling and deep brain stimulation, bipolar stainless-steel electrodes were implanted in SD rats into right basolateral amygdala and right GPe, respectively. The effects of deep brain stimulation were evaluated in the amygdala kindling model, maximal electroshock model (MES) and pentylenetetrazole (PTZ) model. Moreover, the background EEGs in the amygdala and GPe were recorded.

Results:

Low-frequency stimulation (0.1 ms, 1 Hz, 15 min) at the GPe slowed the progression of seizure stages and shortened the after-discharge duration (ADD) during kindling acquisition. Furthermore, low-frequency stimulation significantly decreased the incidence of generalized seizures, suppressed the average stage, and shortened the cumulative ADD and generalized seizure duration in fully kindled rats. In addition, low-frequency stimulation significantly suppressed the average stage of MES-induced seizures and increased the latency to generalized seizures in the PTZ model. High-frequency stimulation (0.1 ms, 130 Hz, 5 min) at the GPe had no anti-epileptic effect and even aggravated epileptogenesis induced by amygdala kindling. EEG analysis showed that low-frequency stimulation at the GPe reversed the increase in delta power, whereas high-frequency stimulation at the GPe had no such effect.

Conclusion:

Low-frequency stimulation, but not high-frequency stimulation, at the GPe exerts therapeutic effect on temporal lobe epilepsy and tonic-colonic generalized seizures, which may be due to interference with delta rhythms. The results suggest that modulation of GPe activity using low-frequency stimulation or drugs may be a promising epilepsy treatment.     

Contact dermatitis from metallic palladium in patients reacting to palladium chloride

1307 consecutive patients were patch tested with PdCl2 1% pet. 32 patients were positive; 29 also showed a reaction to NiSO4. 470 patients were additionally tested with a metallic palladium disc. 3 had a positive reaction, and none of them reacted to PdCl2 or NiSO4 pet. A positive patch test to PdCl2 pet. is in most cases probably due to a cross-reaction with nickel in nickel-sensitive subjects. Patients positive to PdCl2 tolerate skin contact with metallic palladium.     

Contact stomatitis due to palladium and platinum in dental alloys

We report a patient with contact stomatitis due to combined sensitization to palladium and platinum. Patch testing showed strong and persistent allergic patch test reactions to palladium chloride (1% pet.) ammonium tetrachloroplatinate (0.25% pet), and a palladium metal plate. A platinum metal plate showed a weaker reaction. Histological examination of a biopsy from the test site of palladium chloride (1% pet.) at D3 showed both eczematous and lichenoid changes.     

A metallurgical approach to metal contact dermatitis

It is well-known that some metals/alloys are sensitizing on skin contact, but it is not so well appreciated that sensitization is dependent on the reaction of the metal/alloy with sweat. The first step in skin sensitization by metals/alloys is a corrosion process and the formation of soluble metal ions. The nature of this process has implications with respect to occurrence of metal contact dermatitis, to testing techniques and to classification of metals/alloys as skin sensitizers.     

The Effect of Sibunit Carbon Surface Modification with Diazonium Tosylate Salts of Pd and Pd-Au Catalysts on Furfural Hydrogenation

Herein, we investigated the effect of the support modification (Sibunit carbon) with diazonium salts of Pd and Pd-Au catalysts on furfural hydrogenation under 5 bars of H₂ and 50 °C. To this end, the surface of Sibunit (Cp) was modified with butyl (Cp-Butyl), carboxyl (Cp-COOH) and amino groups (Cp-NH₂) using corresponding diazonium salts. The catalysts were synthesized by the sol immobilization method. The catalysts as well as the corresponding supports were characterized by Fourier transform infrared spectroscopy, N₂ adsorption-desorption, inductively coupled plasma atomic emission spectroscopy, high resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Hammet indicator method and X-ray photoelectron spectroscopy. The analysis of the results allowed us to determine the crucial influence of surface chemistry on the catalytic behavior of the studied catalysts, especially regarding selectivity. At the same time, the structural, textural, electronic and acid–base properties of the catalysts were practically unaffected. Thus, it can be assumed that the modification of Sibunit with various functional groups leads to changes in the hydrophobic/hydrophilic and/or electrostatic properties of the surface, which influenced the selectivity of the process.     

Size-Controlled Synthesis of Soluble-Conjugated Polymeric Nanoparticles in Dendritic Mesoporous Silica Nanospheres

A size-controlled method has been exploited to synthesize 20 kinds of soluble-conjugated polymeric nanoparticles (SCPNs) through cross-coupling polymerizations between various combinations of symmetrical multifunctional monomers (A_x+B_y, x > 2, y ≥ 2). Unlike the classical polycondensation of these kinds of monomers where infinite polymer networks and insoluble polymeric products are typically formed, this confined polymerization in palladium nanoparticles-loaded dendritic mesoporous silica nanospheres produced SCPNs with good to high yields, narrow particle size distribution, and high solubility in common organic solvents. The controlled size of SCPNs characterized with gel permeation chromatography shows narrow distribution and various molecular weight ranging from 2164 to 14 234 Da, transmission electron microscopy and dynamic light scattering analyses range from 5 to 15 nm, suggesting the confined polymerization occurring inside of the mesopores. By simply adjusting the monomer structure and selecting an appropriate cross-coupling polymerization method among Suzuki, Stille, Sonogashira, and direct arylation polymerizations, the obtained SCPNs show bright fluorescence emission varying from blue to red. The SCPNs with long alkyl chain substituents in monomer units show good processability and smooth polymer films are formed by the simple spin-casting method. The repeatable and straightforward synthesis of SCPNs endows them with wide application prospects in light-emission, fluorescence sensing, and bioimaging.