Measurement and interpretation of the 1-0 band of 14N16O at 1900 cm−1

The wavenumbers of the vibration rotation band lines of ¹⁴N¹⁶O are reported for the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ subbands of the 1-0 transition in the infrared. The full set of spectroscopic constants for this band has been determined by direct approach using the analysis of Zare, Schmeltekopf, Harrop, and Albritton. In addition to the band origin ν₀ and the B, D, H constants for the lower and upper vibrational levels, the following spin-orbit coupling constants have been derived: $\text{A}\text{?}{}_0\text{= 123.02772 ± 0.00011}$ and $\text{A}\text{?}{}_1\text{= 122.78248 ± 0.00011}$ (in cm^?1). Apparent centrifugal corrections to these constants have been determined and the values obtained for them are $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>0</mtext>}}\text{= (0.347573 ± 0.00051) × 10}{}^{\mathrm{?3}}$ and $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>1</mtext>}}\text{= (0.337135 ± 0.00050) × 10}{}^{\mathrm{?3}}\text{cm}{}^{\mathrm{?1}}$. Λ-Type doubling constants evaluated by using both grating and tunable laser data are also reported.     

Graphs with only caterpillars as spanning trees

A connected graph G is caterpillar-pure if each spanning tree of G is a caterpillar. The caterpillar-pure graphs are fully characterized. Loosely speaking they are strings or necklaces of so-called pearls, except for a number of small exceptional cases. An upper bound for the number of edges in terms of the order is given for caterpillar-pure graphs, and those which attain the upper bound are characterized.     

An SIS waveguide heterodyne receiver for 600 HGz-635 GHz

A waveguide SIS heterodyne receiver using a Nb/AlO_X/Nb junction has been built for astronomical observations of molecular transitions in the frequency range 600 GHz - 635 GHz, and has been successfully used at the Caltech Submillimeter Observatory (CSO). We report double sideband (DSB) receiver noise temperatures as low as 245 K at 600 GHz -610 GHz, and near 300 K over the rest of the bandwidth. These results confirm that SIS quasiparticle mixers work well at submillimeter-wave frequencies corresponding to photon energies of at least 90% of the superconductor energy gap. In addition, we have systematically investigated the effect on the receiver performance of the overlap between first-order and second-order photon steps of opposite sign at these frequencies. The receiver noise increases by as much as 40% in the region of overlap. We infer potential limitations for operating submillimeter-wave Nb/AlO_x/Nb mixers.     

Superdeformed bands in195Tl

Two superdeformed (SD) bands have been found and assigned to¹⁹⁵Tl on the basis of excitation function and cross bombardment results. The two bands are almost identical in transition energies to those observed in¹⁹³Tl. They are signature partners with a splitting, presumably due to the proton i_13/2 (=5/2) orbital, characteristic of all known SD bands in the thallium isotopes. Their alignments relative to the¹⁹³Tl bands were found to be zero.On leave from Comision National de Energia Atomica 1429 Buenos Aires, Argentina.     

Min-max theory for the Yang-Mills-Higgs equations

In each monopole sector there exist an infinite number of finite energy solutions to the Prasad-Sommerfield limit of the SU(2) Yang-Mills-Higgs equations on ³ whose energy is greater than any finite number.National Science Foundation Postdoctoral Fellow in Mathematics     

Observation of laser driven supercritical radiative shock precursors

We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations.     

Modeling the liquid–gas interface using self-assembled monolayers

Stochastic classical trajectory simulations were used to study the efficiency of the energy exchange at the gas–liquid interface. Self-assembled monolayers (SAM) of long-chain functionalized molecules were used to mimic the liquid surface. Since the molecules in the monolayers are anchored by only one end, they retain some of the mobility that they have in the liquid but lose all their fluidity. The corrugation of the surface and the stiffness of the interface were tuned by varying the length of the molecules in the monolayers. The use of longer molecules leads to increased corrugation of the surface and provides additional dissipation channels that promote more efficient momentum and energy accommodation, increase the translational–rotational energy interconversion and enhance trapping. However, this “length effect” appears to saturate, as no further significant changes are observed in those properties when the monolayer's molecules's length is elongated from six to nine carbons. This saturation effect suggests that, even though monolayers can provide some of the mobility observed in liquid surfaces, they lack the energy dissipation channel provided by the fluidity of the liquid.     

Reaction kinetics and solubility in water‐organic binary solutions are governed by similar solvation equilibria

The solvation effects observed in water‐organic solutions were studied by combining data for reaction kinetics and dissolution equilibria by means of a linear free‐energy (similarity) analysis. Kinetic data for the pH‐independent hydrolysis of (4‐methoxyphenyl)‐2,2‐dichloroacetate measured in this work and solubility data for naphthalene, and other substrates of low polarity, in aqueous binary mixtures of methanol, ethanol, acetonitrile, dimethyl sulfoxide (DMSO), and 1,4‐dioxane were used. Linear similarity relationships were discovered for these data over the full range of solvent compositions studied. To gain insight into the similarities observed between these different phenomena, molecular dynamics simulations were carried out for naphthalene and an ester in water–acetonitrile solutions. The results revealed considerable preferential solvation of these substrates by the co‐solvent. Linear relationships between the experimental data and the mole fractions of acetonitrile in the solvation shells of substrates were found. Surprisingly, a linear relationship was found between the mole fractions of acetonitrile in the solvation shells of the ester and naphthalene. This linearity indicated that a similar solvation mechanism governs even such different phenomena as dissolution and reaction kinetics. The relationships between the experimental data and the results of the molecular dynamics calculations found in this work explained the solvent effect observed in water‐organic solutions on the molecular level. Copyright © 2015 John Wiley & Sons, Ltd.     

Serial Femtosecond Crystallography

X-ray free-electron lasers produce brief flashes of X-rays that are of about a billion times higher peak brightness than achievable from storage ring sources. Such a tremendous jump in X-ray source capabilities, which came in 2009 when the Linac Coherent Light Source began operations, was unprecedented in the history of X-ray science. Protein structure determination through the method of macromolecular crystallography has consistently benefited from the many increases in source performance from rotating anodes to all generations of synchrotron facilities. But when confronted with the prospects of such bright beams for structural biology, enthusiastic proposals were tempered by trepidation of the effects of such beams on samples and challenges to record data [1 M. Wilmanns, J. Synchr. Rad. 7, 41 (2000).[Crossref], [PubMed] , [Google Scholar]]. A decade after these discussions (and others in the USA) on the applications of X-ray FELs for biology, the first experiments took place at LCLS, giving results that fulfilled many of the dreams of the early visionaries. In particular, the concept that diffraction representing the pristine object could be recorded before the X-ray pulse completely vaporizes the object was validated [2 H.N. Chapman, Nature 470, 73 (2011).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]], confirming predictions [3 R. Neutze, Nature 406, 753 (2000).[Crossref], [Web of Science ®] , [Google Scholar]] that established dose limits could be vastly exceeded using femtosecond-duration pulses. The first experiments illuminated a path to achieve room-temperature structures free of radiation damage, from samples too small to provide useful data at synchrotron facilities, as well as providing the means to carry out time-resolved crystallography at femtoseconds to milliseconds. In the five years since, progress has been substantial and rapid, invigorating the field of macromolecular crystallography [4 J.C.H. Spence and H.N. Chapman, Phi. Trans. Roy. Soc. B 369, 20130309 (2014).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 5 I. Schlichting, IUCrJ 2, 246 (2015).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]. This phase of development is far from over, but with both the LCLS and the SPring-8 Ångström Compact Free-electron Laser (SACLA) providing facilities for measurements, the benefits of X-ray FELs are already being translated into new biological insights.