Orbital dependent nucleonic pairing in the lightest known isotopes of tin

By studying the (109)Xe→(105)Te→(101)Sn superallowed α-decay chain, we observe low-lying states in (101)Sn, the one-neutron system outside doubly magic (100)Sn. We find that the spins of the ground state (J=7/2) and first excited state (J=5/2) in (101)Sn are reversed with respect to the traditional level ordering postulated for (103)Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell-model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations dominate.     

Anomalous hybridization in the In-rich InAs(0 0 1) reconstruction

The surface bonding arrangement in nearly all the confirmed reconstructions of InAs(0 0 1) and GaAs(0 0 1) have only two types of hybridization present. Either the bonds are similar to those in the bulk and the surface atoms are sp³ hybridized or the surface atoms are in a tricoordinated bonding arrangement and are sp² hybridized. However, dicoordinated In atoms with sp hybridization are observed on the InAs(0 0 1), In-rich, room temperature and low temperature surfaces. Scanning tunneling microscopy (STM) images of the room temperature (300 K) InAs(0 0 1) surface reveal that the In-rich surface reconstruction consists of single-atom rows with areas of high electron density that are separated by ∼4.3 Å. The separation in electron density is consistent with rows of undimerized, sp hybridized, In atoms, denoted as the β3′(4 × 2) reconstruction. As the sample is cooled to 77 K, the reconstruction spontaneously changes. STM images of the low temperature surface reveal that the areas of high electron density are no longer separated by ∼4.3 Å but instead by ∼17 Å. In addition, the LEED pattern changes from a (4 × 2) pattern to a (4 × 4) pattern at 77 K. The 77 K reconstruction is consistent with two (4 × 2) subunit cells; one that contains In dimers on the row and another subunit cell that contains undimerized, sp hybridized, In atoms on the row. This combination of dimerized and undimerized subunit cells results in a new unit cell with (4 × 4) periodicity, denoted as the β3(4 × 4) reconstruction. Density functional theory (DFT) and STM simulations were used to confirm the experimental findings.     

Structure of rotational bands in 253No

In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the ²⁵³ No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.     

Velocity calibration for in-situ Mössbauer data from Mars

Beginning in August 2004, raw data acquired by the Mössbauer spectrometers on the Mars Exploration Rovers (MERs) have been released to the science community as Experimental Data Records (EDRs) for each Martian day (sol) on which measurements were made. To provide convenient direct access to the EDR data, to enable independent assessment and analysis, and to allow confirmation of MER-team scientific conclusions, a new Windows-based computer program, MERView, has been developed. Direct inspection of the binary structure of an EDR file, conversion of the binary data to decimal column format for display or export, and full-screen graphical displays are included, allowing, in a highly transparent and user-friendly manner, immediate and thorough overview of the entire EDR data set. MERView also includes automated procedures for velocity calibration. Correction for non-linearity is done using the EDR-provided drive error signal, a phase shift, and the requirement that the two halves of a reference spectrum must overlap exactly when plotted on a correct velocity scale. Absolute velocity calibration (mm/s) is then accomplished by comparing each reference spectrum with known peak positions of standard reference materials.     

Strategies for Mars remote Laser-Induced Breakdown Spectroscopy analysis of sulfur in geological samples

The key to understanding the sulfur history on Mars is to identify and determine sulfate and sulfide compositions and then to draw from them geologic clues about their environments of formation. To lay a foundation for use of remote LIBS to sulfur analysis in planetary exploration, we have undertaken a focused study of sulfur LIBS in geological samples in a simulated Mars atmosphere, with experimental parameters replicating the ChemCam LIBS instrument. A suite of twelve samples was selected, including rocks rich in minerals representative of sulfates and sulfides that might be encountered on Mars. Univariate analysis of sulfur emission lines did not provide quantitative information. Partial least squares (PLS) analysis was successful at modeling sulfur concentrations for a subset of samples with similar matrices. Sulfide minerals were identified on the basis of other siderophile or chalcophile peaks, such as those arising from Zn and Cu. Because the S lines are very weak compared to those of other elements, optimal PLS results were obtained by restricting the wavelength range to channels close to the most intense sulfur lines ~ 540-570 nm. Principal components analysis was attempted on the dataset, but did not differentiate the samples into meaningful groups because the sulfur lines are not strong enough. However, areas of the relatively weak S, H, and O peaks may be used to correctly classify all samples. Based on these outcomes, a flowchart that outlines a possible decision tree for identification and quantification of sulfur in remote LIBS analysis was constructed. Results suggest that LIBS data acquired under Mars conditions can meet the science requirements for the ChemCam instrument.     

Weak correction to the muon magnetic moment in a gauge model

The weak correction, a_μ^w, to the anomalous magnetic moment of the muon is calculated in an SU(2) ? U(1) ? U(1) gauge model of weak and electromagnetic interactions. The R_ξ gauge is used and Ward-Takahashi indentities are utilized eliminating all ξ-dependence before the loop integration is performed. a_μ^w,expt places no constraint on the mass of one of the neutral vector mesons, which may be arbitrarily small.     

Multivariate analysis of remote laser-induced breakdown spectroscopy spectra using partial least squares,principal component analysis,and related techniques

Quantitative analysis with laser-induced breakdown spectroscopy traditionally employs calibration curves that are complicated by chemical matrix effects. These chemical matrix effects influence the laser-induced breakdown spectroscopy plasma and the ratio of elemental composition to elemental emission line intensity. Consequently, laser-induced breakdown spectroscopy calibration typically requires a priori knowledge of the unknown, in order for a series of calibration standards similar to the unknown to be employed. In this paper, three new Multivariate Analysis techniques are employed to analyze the laser-induced breakdown spectroscopy spectra of 18 disparate igneous and highly-metamorphosed rock samples. Partial Least Squares analysis is used to generate a calibration model from which unknown samples can be analyzed. Principal Components Analysis and Soft Independent Modeling of Class Analogy are employed to generate a model and predict the rock type of the samples. These Multivariate Analysis techniques appear to exploit the matrix effects associated with the chemistries of these 18 samples.     

Synthesis and Microtubule‐Destabilizing Activity of N‐Cyclopropyl‐4‐((3,4‐dihydroquinolin‐1(2H)‐yl)sulfonyl)benzamide and its Analogs

While clinically useful, microtubule‐targeting agents are limited by factors that include their susceptibility to multidrug resistance. A series of aryl sulfonamides, terminally substituted with an amide or carboxylic acid, was synthesized and assayed for biological activity in two human cancer cell lines. The resulting antiproliferative activity data demonstrated that an amide was superior to a carboxylic acid in the para position. The most potent compound ( 3 ) had an IC₅₀ for growth inhibition in the low micromolar range, caused cells to accumulate in G₂M of the cell cycle, and led to depolymerization of microtubules. It was also not susceptible to the P‐glycoprotein drug efflux pump that underpins the resistance of cells to long‐term drug treatment schedules.     

Strobovideolaryngoscopy in professional voice users: Results and clinical value

Evaluation of the vibratory margin of the vocal fold is essential for accurate diagnosis and treatment of voice patients. Traditionally, physicians have performed this evaluation using their subjective impressions of the sound of the voice in conjunction with laryngoscopy under continuous light. Strobovideolaryngoscopy is a valuable addition to the diagnostic armementarium. It allows the physician to perform a proper physical examination of the vibratory margin. A review of 486 strobovideolaryngoscopy procedures in 343 voice patients during a 2-year period reveals that stroboscopic information influenced diagnosis or treatment in approximately one-third of the entities diagnosed.     

Catalytic asymmetric silane alcoholysis: practical access to chiral silanes

A new asymmetric synthesis of chiral silanes has been developed. Chiral phosphine-modified copper complexes catalyze the alcoholysis of prochiral dihydrosilanes with good to excellent stereoselectivity at silicon. The application of this methodology to the tandem silylformylation-allylsilylation of alkynes has been demonstrated.