Retention of configuration in Lewis acid mediated α-alkylation of carbonyl compounds using SN1 reactive alkyl halides

Certain S_N1 reactive alkyl halides undergo CC bond formation in Lewis acid induced α-alkylations of carbonyl compounds with formal retention of configuration     

Investigations on the cold-work peak of hydrogen in iron by means of the magnetic after-effect

The magnetic after-effect of hydrogen-charged iron was investigated in the temperature range between 77 and 200 K. The hydrogen cold-work peak, known so far only from internal friction measurements, has been observed at about 130 K together with a less pronounced relaxation peak at 80 K. The activation energy of ∼0.29 eV, determined for the cold-work peak, is explained by a thermally activated motion of dislocations, the cores of which are closely decorated by a condensed atmosphere of hydrogen atoms.     

Observation of the Askaryan effect: coherent microwave Cherenkov emission from charge asymmetry in high-energy particle cascades

We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6 GHz detected strong, subnanosecond radio-frequency pulses produced by the showers. Measurements of the polarization, coherence, timing, field strength vs shower depth, and field strength vs frequency are completely consistent with predictions. These measurements thus provide strong support for experiments designed to detect high-energy cosmic rays such as neutrinos via coherent radio emission from their cascades.     

Synthesis and biological activity of hydroxamic acid-derived vasopeptidase inhibitor analogues

[structure: see text] Syntheses of novel hydroxamic acid-derived azepinones containing pendant mercaptoacyl groups or formyl hydroxamates are described. These new analogues of therapeutically important ACE and NEP inhibitors include unprecedented changes at the previously assumed essential acid component.     

The Effect of Nanoscale Roughness on Long Range Interaction Forces

A model was developed to calculate the long range van der Waals and electrostatic energies between a rough colloidal particle and a smooth solid plate in aqueous solutions. The particle roughness was modeled as hemispherical asperities distributed uniformly over the surface. Because of the assumption of additive potentials used in calculating the electrostatic force, the model is most accurate when the particle/plate separation is larger than several Debye screening lengths, such as near the location of the secondary minimum. The model predicts that such roughness reduces the depth of the secondary minimum and pushes it to larger separation distances. The model also predicts that the height of the primary energy barrier, which controls the dispersion stability, is substantially lowered by the asperities.Experimental validation of the model was achieved by measuring the potential energy profile between individual, 15µm diameter polystyrene latex spheres and a smooth glass plate around the location of the secondary energy minimum using the optical technique of total internal reflection microscopy (TIRM). When compared to predictions made assuming perfectly smooth surfaces, the measured well depths are consistently found to be lower than expected. Excellent agreement can be achieved, however, by adding asperities with a height of order 25nm to the particle surface. These measurements are some of the first direct measurements of the effect of roughness on interaction energies.     

A Proposal to Measure Antimatter Gravity Using Ultracold Antihydrogen Atoms

The gravitational acceleration of antimatter has never been measured directly. Antihydrogen atoms, being both stable and neutral, are an ideal system for investigating antimatter gravity. Ultralow temperatures in the 10–100 K range are desirable for practical experiments. It is proposed to cool positive antihydrogen ions using laser-cooled ordinary ions. Ultracold neutral antihydrogen atoms might then be obtained by photodetachment. The gravitational acceleration can readily be determined from the time-of-flight between the photodetachment laser pulse and an annihilation detector.     

Synthesis of 8-methoxy-1-methyl-1H-benzo[de][1,6]naphthyridin-9-ol (Isoaaptamine) and analogues

8-Methoxy-1-methyl-1H-benzo[de][1,6]naphthyridin-9-ol, isoaaptamine, a PKC inhibitor isolated from sponge was synthesized. The synthesis parallels a synthesis of 8,9-dimethoxybenzo[de][1,6]naphthyridine, aaptamine, but uses a nitromethyl substituent as a precursor of the key 5-(2-aminoethyl)-1H-quinolin-4-one intermediate. The quinolone intermediates were prepared by thermolysis (220-240 degrees C) of anilinomethylene derivatives of Meldrum's acid. The quinolone intermediates were N-methylated prior to cyclization to the benzo[de][1,6]naphthyridine derivatives. Aaptamine and several analogues of aaptamine and isoaaptamine were prepared including 9-demethylaaptamine, 1-methyl-8-demethylaaptamine, 1-methylaaptamine, and the 8,9-methylenedioxy analogues of aaptamine and 1-methylaaptamine.     

Bildung und Molekülstruktur von [{(CH3)3Si}3C(nC3H7)In(μ‐OH)]3

Formation and Structure of [{(CH₃)₃Si}₃C(ⁿC₃H₇)In(μ‐OH)]₃ The title compound has been prepared in low yield by the reaction of [(THF)₂LiC(SiMe₃)₃]₂with humid di(n‐propyl) indium bromide and purified by sublimation at 110–115 °C/10^–3 hPa. This organo indium hydroxo compound forms a trimer via In–OH–In bridges and crystallizes in the triclinic space group P 1 with two trimers and one toluene molecule per unitcell. The In₃O₃ heterocycle has chair‐, the n‐propyl ligand has trans‐conformation, respectively.