In situ TEM characterisation of dislocation interactions in α-titanium

In situ straining in the transmission electron microscope and diffraction-contrast electron tomography has been applied to investigate dislocation interactions in α-Ti. Dislocation debris, in the form of small loops, was seen to form from sequential cross-slip events. Electron tomography provided direct three-dimensional visualisation of the dislocation structures, allowing accurate identification of slip planes, dislocation line directions and spatial relations between dislocations.     

Heavy atom structure and conformer stabilities of cyclopropyl carbinol from rotational spectroscopy and ab initio calculations

A remeasurement of the rotational spectra of the normal and hydroxyl deuterated isotopomers of cyclopropyl carbinol (cyclopropane methanol, (CH₂)₂CH(CH₂OH)) using Fourier-transform microwave spectroscopy has provided refined rotational constants and centrifugal distortion constants for this molecule. Rotational constants for an additional four singly substituted ¹³C isotopomers, the OD isotopomer, and the ¹⁸O isotopomer are consistent with a conformer in which the OH group forms an intramolecular hydrogen bond with the edge of the cyclopropyl ring. The observed a-type transition frequencies for the normal and deuterated species are in reasonable agreement with a previous microwave study (although some frequencies differ by several hundred kilohertz), but the few b- and c-type lines that were measured in the range of our spectrometer were found to differ by several megahertz from the previous literature measurements, leading to A rotational constants that differ significantly from those reported previously. The refined rotational constants for the normal isotopic species are A=12470.7795(23) MHz, B=3236.4678(7) MHz, C=2894.4831(7) MHz, while those of the deuterated species are A=12069.2653(24) MHz, B=3177.1540(8) MHz and C=2826.2658(7) MHz. Results of ab initio optimizations on seven conformers for this molecule carried out at the MP2/6-311+G(d,p) level will be compared with the experimentally determined structural parameters.     

Microplasma Ionization of Volatile Organics for Improving Air/Water Monitoring Systems On-Board the International Space Station

Low molecular weight polar organics are commonly observed in spacecraft environments. Increasing concentrations of one or more of these contaminants can negatively impact Environmental Control and Life Support (ECLS) systems and/or the health of crew members, posing potential risks to the success of manned space missions. Ambient plasma ionization mass spectrometry (MS) is finding effective use as part of the analytical methodologies being tested for next-generation space module environmental analysis. However, ambient ionization methods employing atmospheric plasmas typically require relatively high operation voltages and power, thus limiting their applicability in combination with fieldable mass spectrometers. In this work, we investigate the use of a low power microplasma device in the microhollow cathode discharge (MHCD) configuration for the analysis of polar organics encountered in space missions. A metal-insulator-metal (MIM) structure with molybdenum foil disc electrodes and a mica insulator was used to form a 300 μm diameter plasma discharge cavity. We demonstrate the application of these MIM microplasmas as part of a versatile miniature ion source for the analysis of typical volatile contaminants found in the International Space Station (ISS) environment, highlighting their advantages as low cost and simple analytical devices.

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Dinitrogen Splitting Coupled to Protonation

The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N₂ splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N−N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo−N₂−Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N−N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation.     

Fast computing of some generalized linear mixed pseudo-models with temporal autocorrelation

This paper considers ways to increase computational speed in generalized linear mixed pseudo-models for the case of many repeated measurements on subjects. We obtain linearly increasing computing time with number of observations, as opposed to O(n ³) increasing computing time using numerical optimization. We also find a surprising result; that incomplete optimization for covariance parameters within the larger parameter estimation algorithm actually decreases time to convergence. After comparing various computing algorithms and choosing the best one, we fit a generalized linear mixed model to a binary time series data set with over 100 fixed effects, 50 random effects, and approximately 1.5 ×  10⁵ observations.     

FloDots: luminescent nanoparticles

Luminescent dye-doped silica nanoparticles (FloDots) have been developed for ultrasensitive bioanalysis and diagnosis in the past several years. Those novel nanoparticles are highly luminescent and extremely photostable. In this paper, we review the preparation, characterization, bioconjugation and bioapplication of FloDots. All the results clearly demonstrated that FloDots have many advantages over currently used luminescent probes, such as traditional fluorophores and quantum dots.     

Musical intervals and relative pitch: frequency resolution, not interval resolution, is special

Pitch intervals are central to most musical systems, which utilize pitch at the expense of other acoustic dimensions. It seemed plausible that pitch might uniquely permit precise perception of the interval separating two sounds, as this could help explain its importance in music. To explore this notion, a simple discrimination task was used to measure the precision of interval perception for the auditory dimensions of pitch, brightness, and loudness. Interval thresholds were then expressed in units of just-noticeable differences for each dimension, to enable comparison across dimensions. Contrary to expectation, when expressed in these common units, interval acuity was actually worse for pitch than for loudness or brightness. This likely indicates that the perceptual dimension of pitch is unusual not for interval perception per se, but rather for the basic frequency resolution it supports. The ubiquity of pitch in music may be due in part to this fine-grained basic resolution.     

A sufficient condition for the existence of an anti-directed 2-factor in a directed graph

Let D be a directed graph with vertex set V, arc set A, and order n. The graph underlyingD is the graph obtained from D by replacing each arc (u,v)∈A by an undirected edge {u,v} and then replacing each double edge by a single edge. An anti-directed (hamiltonian) cycleH in D is a (hamiltonian) cycle in the graph underlying D such that no pair of consecutive arcs in H form a directed path in D. An anti-directed 2-factor in D is a vertex-disjoint collection of anti-directed cycles in D that span V. It was proved in Busch et al. (submitted for publication) [3] that if the indegree and the outdegree of each vertex of D is greater than then D contains an anti-directed Hamilton cycle. In this paper we prove that given a directed graph D, the problem of determining whether D has an anti-directed 2-factor is NP-complete, and we use a proof technique similar to the one used in Busch et al. (submitted for publication) [3] to prove that if the indegree and the outdegree of each vertex of D is greater than then D contains an anti-directed 2-factor.