Measuring unification

If supersymmetry is observed at the LHC its model parameters can be measured at the electroweak scale. We discuss the expected precision on the parameter determination, including a proper treatment of experimental and theoretical errors. Particular attention is paid to degenerate solutions. Using the SFitter framework we perform a bottom–up reconstruction of the unified parameters at the high scale, including a full error propagation.     

Syntheses and pharmacological characterization of achiral and chiral enantiopure C/Si/Ge-analogous derivatives of the muscarinic antagonist cycrimine: a study on C/Si/Ge bioisosterism

The C/Si/Ge-analogous compounds rac-Ph(c-C₅H₉)El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, rac-3a; El=Si, rac-3b; El=Ge, rac-3c) and (c-C₅H₉)₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 5a; El=Si, 5b; El=Ge, 5c) were prepared in multi-step syntheses. The (R)- and (S)-enantiomers of 3a–c were obtained by resolution of the respective racemates using the antipodes of O,O′-dibenzoyltartaric acid (resolution of rac-3a), O,O′-di-p-toluoyltartaric acid (resolution of rac-3b), or 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (resolution of rac-3c). The enantiomeric purities of (R)-3a–c and (S)-3a–c were ≥98% ee (determined by ¹H-NMR spectroscopy using a chiral solvating agent). Reaction of rac-3a–c, (R)-3a–c, (S)-3a–c, and 5a–c with methyl iodide gave the corresponding methylammonium iodides rac-4a–c, (R)-4a–c, (S)-4a–c, and 6a–c (3a–c→4a–c; 5a–c→6a–c). The absolute configuration of (S)-3a was determined by a single-crystal X-ray diffraction analysis of its (R,R)-O,O′-dibenzoyltartrate. The absolute configurations of the silicon analog (R)-4b and germanium analog (R)-4c were also determined by single-crystal X-ray diffraction. The chiroptical properties of the (R)- and (S)-enantiomers of 3a–c, 3a–c·HCl, and 4a–c were studied by ORD measurements. In addition, the C/Si/Ge analogs (R)-3a–c, (S)-3a–c, (R)-4a–c, (S)-4a–c, 5a–c, and 6a–c were studied for their affinities at recombinant human muscarinic M₁, M₂, M₃, M₄, and M₅ receptors stably expressed in CHO-K1 cells (radioligand binding experiments with [³H]N-methylscopolamine as the radioligand). For reasons of comparison, the known C/Si/Ge analogs Ph₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 7a; El=Si, 7b; El=Ge, 7c) and the corresponding methylammonium iodides 8a–c were included in these studies. According to these experiments, all the C/Si/Ge analogs behaved as simple competitive antagonists at M₁–M₅ receptors. The receptor subtype affinities of the individual carbon, silicon, and germanium analogs 3a–8a, 3b–8b, and 3c–8c were similar, indicating a strongly pronounced C/Si/Ge bioisosterism. The (R)-enantiomers (eutomers) of 3a–c and 4a–c exhibited higher affinities (up to 22.4 fold) for M₁–M₅ receptors than their corresponding (S)-antipodes (distomers), the stereoselectivity ratios being higher at M₁, M₃, M₄, and M₅ than at M₂ receptors, and higher for the methylammonium compounds (4a–c) than for the amines (3a–c). With a few exceptions, compounds 5a–c, 6a–c, 7a–c, and 8a–c displayed lower affinities for M₁–M₅ receptors than the related (R)-enantiomers of 3a–c and 4a–c. The stereoselective interaction of the enantiomers of 3a–c and 4a–c with M₁–M₅ receptors is best explained in terms of opposite binding of the phenyl and cyclopentyl ring of the (R)- and (S)-enantiomers. The highest receptor subtype selectivity was observed for the germanium compound (R)-4c at M₁/M₂ receptors (12.9-fold).     

A high pressure,low temperature system for μSR studies

A high pressure, low temperature system for μSR studies is described which compresses gases like He or Ar up to 14 kbar at temperatures between 10K and room temperature. The present construction of the cell, made of hardened CuBe, limits the pressure range to 7 kbar. The sample space is approximately 4 cm³. Pressure generation up to 14 kbar is accomplished in about 15 minutes while cool-down to 10K requires about 2 hours.     

Regio-and Stereoselectivity of Transition-Metal-Ion-Mediated Single and Double Dehydrogenation of Tetraline

Labeling experiments provide evidence that the Fe¹- and CO¹-mediated losses of H₂ and 2 H₂ from tetraline are extremely specific in that both reactions follow a clear syn-1,2-elimination involving C(1)/C(2) and C(3)/C(4), respectively. In the course of the multi-step reaction, the metal ions do not move from one side of the π-surface to the other. Independent experiments confirm that the kinetic isotope effect (KIE) associated with the loss of the first H₂ molecule is indeed larger than the KIE for the elimination of the second H₂ molecule.     

Comment on “mössbauer studies of the 6.2 keVγ-rays of 181 Ta in Ta-dichalcogenides”

The reported discrepancy between TDPAC and Mössbauer measurements of the electric field gradient at Ta in 2H-TaS₂ is shown to be an artifact. Combining both results a new value for the 482 keV state quadrupole moment of ¹⁸¹Ta is derived: Q(5/2) = (+)2.36(5) b.     

Intercalation reaction kinetics: a TDPAC study of 2H-TaS2 intercalation

Summary We report on thein situ observation of the¹⁸¹Ta nuclear quadrupole interaction during electrointercalation of 2H-TaS₂ with hydrated gadolinium ions by means of time differential perturbed angular correlations (TDPAC). Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

The effect of lattice vibrations on the pressure dependence of the electric field gradient in cadmium metal

We determined the pressure dependence of the electric field gradientq in Cd at 150, 300, and 575 K by perturbed angular correlations on¹¹¹Cd. Close to the melting point,q varies less with pressure than at low temperature, although Cd becomes more anisotropic. We attribute this to volume effects which grow with increasing lattice vibration amplitudes.     

The temperature dependence of the nuclear quadrupole interaction of 44Ti(EC)44Sc in rutile

The temperature dependence of the Nuclear Quadrupole Interaction on ⁴⁴Sc in rutile was measured by Time Differential Perturbed Angular Correlation in the temperature range from 300 K to 945 K. Whereas $\upomega _{\rm Q} = \mathrm{eQV}_{\rm zz}/4\rm \hbar$ with V_zz denoting the largest component of the electric field gradient tensor in magnitude increases with increasing temperature, the asymmetry parameter η remains essentially constant. This observation fits into the systematic with other probes provided the sign of V_zz is negative.