Observation of a parity violation in cesium

We have measured a parity violation in the 6S–7S transition of Cs in an electric field. Our result is Im $\text{E}{}_1{}^{\mathrm{<mtext>pv</mtext>}}\text{β}\text{= -1.34 ± 0.22}$$\text{(}\text{rms statistical deviation}\text{) ± ～0.11 (}\text{systematic uncertainty}\text{)}\text{mV}\text{cm;}\text{E}{}_1{}^{\mathrm{<mtext>pv</mtext>}}$ is the parity violating electric dipole amplitude, ß is the vector polarizability. This result is consistent with the Weinberg-Salam prediction.     

Observation of a multiply ionized plasma with index of refraction greater than one

We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser-created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms shows that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can affect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.     

Limit on the electron electric dipole moment in gadolinium-iron garnet

A new method for the detection of the electron electric dipole moment (EDM) using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the sample's magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron EDM of 5 x 10(-24)e cm, which is a factor of 40 below the limit obtained from the only previous solid-state EDM experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.     

Quantifying intermolecular interactions: guidelines for the molecular recognition toolbox

Molecular recognition events in solution are affected by many different factors that have hampered the development of an understanding of intermolecular interactions at a quantitative level. Our tendency is to partition these effects into discrete phenomenological fields that are classified, named, and divorced: aromatic interactions, cation-pi interactions, CH-O hydrogen bonds, short strong hydrogen bonds, and hydrophobic interactions to name a few.1 To progress in the field, we need to develop an integrated quantitative appreciation of the relative magnitudes of all of the different effects that might influence the molecular recognition behavior of a given system. In an effort to navigate undergraduates through the vast and sometimes contradictory literature on the subject, I have developed an approach that treats theoretical ideas and experimental observations about intermolecular interactions in the gas phase, the solid state, and solution from a single simplistic viewpoint. The key features are outlined here, and although many of the ideas will be familiar, the aim is to provide a semiquantitative thermodynamic ranking of these effects in solution at room temperature.     

A three-dimensional model of vocal fold abduction/adduction

A three-dimensional biomechanical model of tissue deformation was developed to simulate dynamic vocal fold abduction and adduction. The model was made of 1721 nearly incompressible finite elements. The cricoarytenoid joint was modeled as a rocking-sliding motion, similar to two concentric cylinders. The vocal ligament and the thyroarytenoid muscle's fiber characteristics were implemented as a fiber-gel composite made of an isotropic ground substance imbedded with fibers. These fibers had contractile and/or passive nonlinear stress-strain characteristics. The verification of the model was made by comparing the range and speed of motion to published vocal fold kinematic data. The model simulated abduction to a maximum glottal angle of about 31 degrees. Using the posterior-cricoarytenoid muscle, the model produced an angular abduction speed of 405 degrees per second. The system mechanics seemed to favor abduction over adduction in both peak speed and response time, even when all intrinsic muscle properties were kept identical. The model also verified the notion that the vocalis and muscularis portions of the thyroarytenoid muscle play significantly different roles in posturing, with the muscularis portion having the larger effect on arytenoid movement. Other insights into the mechanisms of abduction/adduction were given.     

Discrimination of components in atherosclerotic plaques from human carotid endarterectomy specimens by magnetic resonance imaging ex vivo

Specific MRI techniques have been used to determine the dimensional and compositional properties of atherosclerotic lesions in carotid endarterectomy tissues. A quantitative comparison of areas of specific features in typical tissue segments was performed using MR images and histologic images. The mean difference for the measurements by the two methods was 4.5% for the total vessel, 5.3% for the internal carotid artery lumen, and 5.0% for the external carotid lumen. For other less abundant components, the mean difference was 14.2%. For direct characterization, individual tissue components were isolated by microdissection and their T1 and T2 relaxation times measured. Highly calcified areas typically had rather short T1 (452-837 ms) and short T2 (10.4-18.4 ms). In contrast, regions enriched in lipid had much longer T1 (1,380-1,480 ms) and longer T2 (35.3-49.0 ms). Other components such as thrombus had intermediate T1 (1,180 ms) and short T2 (15.4 ms). T2 parametric imaging was used as a complementary approach for segmentation and quantitation of tissue components. In fresh tissue, several different components exhibited different T2 ranges: calcified/solid lipid (13-18 ms). cellular/ECM (9-30 ms), fluid lipid (35-40 ms): fibrous (50-60 ms). These results demonstrate the utility of MRI for identifying and quantifying specific components of atherosclerotic plaque ex vivo, and suggest its value for these measurements in vivo as well.     

The role of the counteranion in the cation-pi interaction

Chemical double mutant cycles have been used to quantify cation-pi interactions in chloroform as a function of the nature of the counteranion. The cation-pi interaction is -2.5 +/- 0.4 kJ mol(-1) and independent of the anion, even though the overall stability of the complexes varies by an order of magnitude due to competition of the anion for alternative binding sites.     

Multivalent recognition of bis- and tris-Zn-porphyrins by N-methylimidazole functionalized gold nanoparticles

N-Methylimidazole-functionalized gold nanoparticles behave as multivalent ligands for porphyrin arrays with an increase in binding strength of up to three order of magnitude with respect to a monovalent system.     

Synthesis of 2-Acetoxy-2-Methoxy-4-Acetoxymethyl-3,5-Cyclohexadien-1-One by Lead Tetraacetate Oxidation of Homovanillic Acid

An efficient synthesis of the title compound is achieved when homovanillic acid is reacted with lead tetraacetate.