A search for fractional electric charge in sea water

The magnetic levitation technique has been used to test for fractional electric charge in sea water, using steel balls coated with sea water residue by evaporation. The objective was to reach concentration levels below 1 g^?1 which might result from cosmic ray interactions. Four stages of increasing sensitivity are reported: (1) residue from direct evaporation of unprocessed sea water, (2) residue from sea water samples enriched by ion exchangen, (3) residue reduced by high temperature evaporation, and (4) hypothetical enrichment by dilution and separation of soluble residue. Stages 1–3 are based on the generally accepted preferential retention of fractional charge during evaporation, but stage 4 limits are subject to uncertainties in the enrichment process. No evidence for fractional charge was found in a total of about 130 samples tested in these four stages. Samples containing positive and negative ions were tested separately, and concentration limits are reported for each of the stages. Levels in the region 0.01–0.1g^?1 were reached in stage 3, and 0.001 g^?1 in stage 4.     

Observation of persistent α‐helical content and discrete types of backbone disorder during a molten globule to ordered peptide transition via deep‐UV resonance Raman spectroscopy

The molten globule (MG) state can aid in the folding of a protein to a functional structure and is loosely defined as an increase in structural disorder with conservation of the ensemble secondary structure content. Simultaneous observation of persistent secondary structure content with increased disorder has remained experimentally problematic. As a consequence, modeling how the MG state remains stable and how it facilitates proper folding remains difficult due to a lack of amenable spectroscopic techniques to characterize this class of partially unfolded proteins. Previously, deep‐UV resonance Raman (dUVRR) spectroscopy has proven useful in the resolution of global and local structural fluctuations in the secondary structure of proteins. In this work, dUVRR was employed to study the MG to ordered transition of a model four‐helix bundle protein, HP7. Both the average ensemble secondary structure and types of local disorder were monitored, without perturbation of the solvent, pH, or temperature. The MG to ordered transition is induced by stepwise coordination of two heme molecules. Persistent dUVRR spectral features in the amide III region at 1295–1301 and 1335–1338 cm⁻¹ confirm previous observations that HP7 remains predominantly helical in the MG versus the fully ordered state. Additionally, these spectra represent the first demonstration of conserved helical content in a MG protein. With successive heme binding, significant losses are observed in the spectral intensity of the amide III₃ and S regions (1230–1260 and 1390 cm⁻¹, respectively), which are known to be sensitive to local disorder. These observations indicate that there is a decrease in the structural populations able to explore various extended conformations with successive heme binding events. DUVRR spectra indicate that the first heme coordination between two helical segments diminishes exploration of more elongated backbone structural conformations in the inter‐helical regions. A second heme coordination by the remaining two helices further restricts protein motion. Copyright © 2013 John Wiley & Sons, Ltd.     

Texture development and deformation mechanisms during uniaxial straining of U–Nb shape-memory alloys

The shape–memory effect is well documented in uranium–niobium alloys near the α″–γ^o metastable phase boundary. In situ neutron diffraction measurements during uniaxial loading indicate that U–14?at.%?Nb (in the α″ monoclinic phase field) deforms by stress–induced twin reorientation. Alternatively, U–16?at.%?Nb (initially γ^o tetragonal) undergoes a stress–induced phase transformation to the α″ monoclinic phase. The crystallographic texture of the monoclinic phase of both compositions has been measured and qualitatively interpreted by considering the orientation relationship between the most favoured α′′ variant and the parent phase. In addition, previously published observations of deformation structures within the shape–memory regime of a U–13?at.%?Nb alloy are discussed within the context of the same model.     

Measurement of B --> K*gamma branching fractions and charge asymmetries

The branching fractions of the exclusive decays B0-->K(*0)gamma and B+-->K(*+)gamma are measured from a sample of (22.74+/-0.36)x10(6) BB decays collected with the BABAR detector at the PEP-II asymmetric e(+)e(-) collider. We find B (B0-->K(*0)gamma) = [4.23+/-0.40(stat)+/-0.22(syst)]x10(-5), B(B+-->K(*+)gamma) = [3.83+/-0.62(stat)+/-0.22(syst)]x10(-5) and constrain the CP-violating charge asymmetry to be -0.170K(*)gamma)<0.082 at 90% C.L.     

Analysis of the CH3D Nonad from 2000 to 3300 cm

As part of the simultaneous analysis of line positions and intensities of the first two polyads of monodeuterated methane, the results achieved for the region 3-5 μm are reported. It involves the three highest fundamentals, (ν₁, ν₂, ν₄), overlapped by overtone (2ν₃, 2ν₅, 2ν₆) and combination (ν₃+ν₆, ν₃+ν₅, ν₅+ν₆) bands. The theoretical model was based on the global tensorial model implemented in the MIRS package. Some 10 000 line positions and 2400 line intensities have been modeled to ±0.000 88 cm⁻¹ and ±3.6% respectively, using measurements obtained at 0.0056 and 0.011 cm⁻¹ resolution with the Fourier transform spectrometer at National Solar Observatory located at Kitt Peak. The strongest band in this polyad is ν₄(E) at 3016.7 cm⁻¹ with a strength of 6.3×10⁻¹⁸ cm⁻¹/(molecule cm⁻²) at 296 K; the weakest band is 2ν₃(E) at 2597.7 cm⁻¹ with a strength of 1.9×10⁻²⁰ cm⁻¹/(molecule cm⁻²) at 296 K. The total calculated absorption arising from the CH₃D nonad is 8.95×10⁻¹⁸ cm⁻¹/(molecule cm⁻²) at 296 K.     

Measurement of B0-B-0 flavor oscillations in hadronic B0 decays

Flavor oscillations of neutral B mesons have been studied in e+e- annihilation data collected with the BABAR detector at center-of-mass energies near the upsilon(4S) resonance. The data sample used for this purpose consists of events in which one B0 meson is reconstructed in a hadronic decay mode, while the flavor of the recoiling B0 is determined with a tagging algorithm that exploits the correlation between the flavor of the heavy quark and the charges of its decay products. From the time development of the observed mixed and unmixed final states, we determine the B0-B-0 oscillation frequency deltamd to be 0.516+/-0.016(stat)+/-0.010(syst) ps-1.     

Vibrational Dynamics Studies by Nuclear Resonant Inelastic X-Ray Scattering

Nuclear resonant inelastic X-ray scattering of synchrotron radiation is being applied to ever widening areas ranging from geophysics to biophysics and materials science. Since its first demonstration in 1995 using the ⁵⁷Fe resonance, the technique has now been applied to materials containing ⁸³Kr, ¹⁵¹Eu, ¹¹⁹Sn, and ¹⁶¹Dy isotopes. The energy resolution has been reduced to under a millielectronvolt. This, in turn, has enabled new types of measurements like Debye velocity of sound, as well as the study of origins of non-Debye behavior in presence of other low-energy excitations. The effect of atomic disorder on phonon density of states has been studied in detail. The flux increase due to the improved X-ray sources, crystal monochromators, and time-resolved detectors has been exploited for reducing sample sizes to nano-gram levels, or using samples with dilute resonant nuclei like myoglobin, or even monolayers. Incorporation of micro-focusing optics to the existing experimental setup enables experiments under high pressure using diamond-anvil cells. In this article, we will review these developments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nucleation and growth of cavities in soft viscoelastic layers under tensile stress

The process of growth of an individual cavity in a viscoelastic adhesive layer has been investigated experimentally. The formation of cavities was caused by the application of a negative pressure on a very confined layer with a flat-ended probe. The cavities appeared in the bulk of the adhesive layer and were observed for a range of values of applied stress approximately ten times higher than the shear modulus of the adhesive layer. Depending on the loading rate, the shape of the growing cavity changed from a flat disc to a more spherical shape. Furthermore, the growth rate of the cavity radius was consistent with a constant strain rate at the edge of the cavity, which suggests a constant level of stress at the edge of the cavity. Received 5 June 2002 RID="a" ID="a"Current address: Ethicon, Johnson & Johnson, Route 22 West, P.O. Box 151, Somerville, NJ 08876-0151, USA. RID="b" ID="b"e-mail: costantino.creton@espci.fr     

NMR spectral quantitation by principal component analysis. III. A generalized procedure for determination of lineshape variations

We present a general procedure for automatic quantitation of a series of spectral peaks based on principal component analysis (PCA). PCA has been previously used for spectral quantitation of a single resonant peak of constant shape but variable amplitude. Here we extend this procedure to estimate all of the peak parameters: amplitude, position (frequency), phase and linewidth. The procedure consists of a series of iterative steps in which the estimates of position and phase from one stage of iteration are used to correct the spectra prior to the next stage. The process is convergent to a stable result, typically in less than 5 iterations. If desired, remaining linewidth variations can then be corrected. Correction of (typically) unwanted variations of these types is important not only for direct peak quantitation, but also as a preprocessing step for spectral data prior to application of pattern recognition/classification techniques. The procedure is demonstrated on simulated data and on a set of 992 (31)P NMR in vivo spectra taken from a kinetic study of rat muscle energetics. The proposed procedure is robust, makes very limited assumptions about the lineshape, and performs well with data of low signal-to-noise ratio.