Corrosion-stable nickel- and cobalt-based alloys for dental applications

In a comparative study the in vitro corrosion behavior of a selection of nickel- and cobalt-based alloys for application in dentistry containing no noble metals was studied with slow scan cyclic voltammetry. The obtained breakthrough potentials, the repassivation behavior and further typical features of the cyclic voltamograms are correlated with the chemical composition as measured with electron beam microanalysis. Surface inhomogenities detected with the latter method are discussed with respect to the electrochemical behavior. For all alloys stabilities in terms of breakthrough potential superior to previously reported data for nickel-base alloys are found.     

Combinatorial synthesis of benztropine libraries and their evaluation as monoamine transporter inhibitors

A combinatorial synthesis of benztropine analogues is presented. Radical azidonation of 3-benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 3 to 3-(1-azidobenzyloxy)-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 4 was used as a key step in the synthesis. This step was optimized by adding 10% DMF to the reaction. Reaction of 4 with phenyl magnesium bromide followed by Boc removal and N-methylation gave benztropine 1. Reaction of five-component Grignard reagents with 4 was used to create a two-dimensional library of 25 N-normethylbenztropine analogues. Further reaction of this library with five alkyl bromides was carried out to create a three-dimensional library containing 125 compounds. Screening of the libraries towards binding and inhibition of uptake of the human dopamine (hDAT), serotonin (hSERT) and norepinephrine transporters (hNET) was carried out. None of the synthesized compounds were found to be stronger than benztropine, and none were selective for inhibition of binding over monoamine uptake.     

Thiobromokomplexe von Arsen und Antimon Darstellung und Kristallstrukturen von (PPh4)2[As2SBr6] · CH2Br2 und (PPh4)2[Sb2SBr6] · CH2Br2

Thiobromo Complexes of Arsenic and Antimony. Preparation and Crystal Structures of (PPh₄)₂[As₂SBr₆] · CH₂Br₂ and (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂ (PPh₄)₂[As₂SBr₆] · CH₂Br₂ is formed by the reaction of As₂S₃, PPh₄I and HI in dibromomethane. It can also be obtained, as well as (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂, from (PPh₄)₂[As₂Br₈] and (PPh₄)₃[Sb₂Br₉], respectively, with bistrimethylsilylsulfide. The crystal structures of the title compounds were determined by X-ray diffraction. They are isotypic with (PPh₄)₂[As₂SCl₆] · C₂H₄Cl₂. In the anions [M₂SBr₆]^2? the M atoms (As or Sb) have a distorted octahedral coordination, the two octahedra share acommon face with one bridging S and two Br atoms; the lone electron pairs occupy the trans positions to the S atom. Crystal data: triclinic, space group P1 , Z = 2; (PPh₄)₂[As₂SBr₆] · CH₂Br₂, a = 119.1, b = 1203.6, c = 2067.5 pm α= 94.89, β = 97.78, γ = 112.20°, 3046 independent observed reflexions, R = 0.083; (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂, a = 1198.9, b = 1224.3, c = 2085.5pm, α = 95.04, β = 98.48, γ = 112.13°C, 2380 reflexions, R = 0.079.     

Mechanical damping by intercrystalline diffusion of hydrogen in metallic polycrystals

Anelastic relaxation by intercrystalline atomic diffusion-analogous to thermal diffusion (i.e., thermoelastic) effects but never observed hitherto-was recently suggested as a new mechanism to explain part of the hydrogen damping spectra in intermetallic compounds. A critical experimental test of this model is now presented using a Zr65Cu17.5Ni10Al7.5 alloy, which allows for a quantitative kinetic analysis in comparison to a closely related reorientation process. The results are in full agreement with the predictions of the model and clearly corroborate the proposed "intercrystalline Gorsky effect" as a new type of mechanical damping in sufficiently fine-grained polycrystals.     

Tetraphenylphosphonium-tetraiodotrithiotriarsenat,PPh4[As3S3I4]

Tetraphenylphosphonium tetraiodotrithiotriarsenate, PPh₄[As₃S₃I₄] PPh₄[As₃S₃I₄] is formed along with PPh₄I₃ and other unidentified compounds by the reaction of As₂S₃, PPh₄I and HI in CH₂I₂ at 80°C. PPh₄[As₃S₃I₄] was characterized by its IR spectrum and an X-ray crystal structure determination (3684 unique observed reflexions, R = 0.083). Crystal data: a = 1390.3, b = 1548.9, c = 1505.4 pm, β = 91.08°, monoclinic, P2₁/c, Z = 4. The crystals are not isotypic with the corresponding chloro and bromo compounds, although the anion constitutions are of the same type. The [As₃S₃I₄]^? ion consists of an As₃S₃ ring in the chair conformation, the three As atoms are commonly linked to a bridging I atom and each As atom is bonded to one terminal I atom. Cations and anions are packed in alternating layers.     

Low-frequency internal friction of metallic glasses near Tg A critique of the use of the torsion pendulum

The application of the torsion pendulum to internal friction measurements on metallic glasses near the glass transition is critically analysed. It is pointed out that a difference between the measured damping Q_t⁻¹ and the real internal friction Q_s⁻¹ of the mterial must be taken into account; quantitative expression are given for the inverted and Collette types of torsion pendulum. The Collette pendulum is found particularly useful for measuring the internal friction of metallic glasses during slow heating through the glass transition. The results obtained with this instrument on six different Pd- and Ni-based glasses, as well as theoretical evidence, suggest that the extremely large internal friction “peak” above T_g is generally due to the intervention of crystallization after a large eand monotonous increase of viscoelastic damping in the supercooled liquid. In particular, there is no vidence for a real internal friction peak due to the glass transition. This conclusion is contradictory to some internal friction results found in the literature which have been obtained with a conventional inverted torsion pendulum. For this type of pendulum, the difference between Q_t⁻¹ and Q_s⁻¹ has obviously not been sufficiently tajen into account.     

micro-Hotplate enhanced optical heating by infrared light for single cell treatment

In this study we present a simple approach for fast and localised heating that relies on the strong absorbance of infrared light by microsized patterned surfaces ("micro-hotplates"). Two different materials, micro-arrays of carbon and gold, were tested with respect to their absorbance of the 830 nm diode laser light and their applicability. Both materials were found to be suitable for inducing controlled heating to a temperature increase of more than 10 degrees C within less than a second. The effect of optical heating on living cells (colon cancer cell line SW 480) was investigated with a modified fluorescence microscope. The temperature was controlled by varying the intensity and the exposure time of the laser light. Depending on temperature, induced death of cells in direct contact with the absorbent material was observed, or otherwise cells were kept alive. Cells survive the direct exposure of IR light without the use of the micro-hotplates. In contrast to common heating systems, the optical heating does not need direct contact to a temperature control device. Therefore, it is a very flexible method that can easily be implemented within any microchip. We believe that it will be a versatile tool for initiation and modulation of biochemical or cellular reactions, reversible cell membrane opening, and for control of cell growth.     

Synthesis of 3,7-disubstituted imipramines by palladium-catalysed amination/cyclisation and evaluation of their inhibition of monoamine transporters

We describe a novel approach for the synthesis of a series of 3,7-difunctionalised symmetric and unsymmetrical analogues of the tricyclic antidepressant (TCA) imipramine, which uses a key palladium-catalysed amination/cyclisation of an ester-functionalised dibromide. Of the ester, methyl, hydroxymethyl and methoxymethyl disubstituted compounds prepared, 3,7-dimethyl-imipramine was found to be the most potent against the human serotonin transporter (hSERT). The inhibitory potency of 3,7-dimethyl imipramine was found to be at least as high as the parent imipramine. This novel TCA also exhibits an increased selectivity (relative to imipramine) in binding to hSERT versus the human norepinephrine transporter (hNET). Even higher selectivity could be obtained with 3,7-dihydroxymethyl imipramine, which was found to be 167-fold more selective for hSERT over hNET, representative of a 120-fold gain in selectivity relative to the parent imipramine. These results further validate our previous model for the binding of imipramine and high-affinity analogues of imipramine to the central binding site of hSERT.