Unique ergodicity of some flows related to axiom a diffeomorphisms

Continuous flows, whose orbits are the unstable manifolds of certain Axiom A attractors, are shown to be uniquely ergodic. The approach used is symbolic dynamics. Equicontinuity (and lack of it) for these flows is also discussed.     

The First in Vivo Observation of C–N Coupling in Mammalian Brain

[5-¹³C,¹⁵N]Glutamine, with ¹J(¹³C–¹⁵N) of 16 Hz, was observed in vivo in the brain of spontaneously breathing rats by ¹³C MRS at 4.7 T. The brain [5-¹³C]glutamine peak consisted of the doublet from [5-¹³C,¹⁵N]glutamine and the center [5-¹³C,¹⁴N]glutamine peak, resulting in an apparent triplet with a separation of 8 Hz. The time course of formation of brain [5-¹³C,¹⁵N]glutamine was monitored in vivo with a time resolution of 20–35 min. This [5-¹³C,¹⁵N]glutamine was formed by glial uptake of released neurotransmitter [5-¹³C]glutamate and its reaction with ¹⁵NH₃ catalyzed by the glia-specific glutamine synthetase. The neurotransmitter glutamate C5 was selectively¹³C-enriched by intravenous [2,5-¹³C]glucose infusion to ¹³C-label whole-brain glutamate C5, followed by [¹²C]glucose infusion to chase ¹³C from the small and rapidly turning-over glial glutamate pool, leaving ¹³C mainly in the neurotransmitter [5-¹³C]glutamate pool, which is sequestered in vesicles until release. Hence, the observed [5-¹³C,¹⁵N]glutamine arises from a coupling between ¹³C of neuronal origin and ¹⁵N of glial origin. Measurement of the rate of brain [5-¹³C,¹⁵N]glutamine formation provides a novel noninvasive method of studying the kinetics of neurotransmitter uptake into glia in vivo, a process that is crucial for protecting the brain from glutamate excitotoxicity.     

One-step green route to narrowly dispersed copper nanocrystals

We report a total “green” chemical method in aqueous solution for synthesizing stable narrowly distributed copper nanoparticles with average diameter less than 5 nm in the presence of Polyvinylpyrrolidone (PVP) as a stabilizer and without any inert gas protection. In our synthesis route, ascorbic acid, natural vitamin C (VC), an excellent oxygen scavenger, acts as both reducing agent and antioxidant, to reduce the metallic ion precursor, and to effectively prevent the common oxidation process of the newborn pure copper nanoclusters.     

Narrowband tuning of an injection-seeded pulsed optical parametric oscillator based on a self-adaptive, phase-conjugate cavity mirror

Narrowband tuning of a pulsed optical parametric oscillator (OPO) is achieved with a self-adaptive injection-seeded optical cavity employing a phase-conjugate reflector. This approach is used in a novel OPO system based on periodically poled KTiOPO4 and pumped at 532 nm by a pulsed Nd:YAG laser. The OPO is injection seeded at 835-855 nm by a continuous-wave tunable diode laser, which also enables a Rh:BaTiO3 photorefractive crystal to act as a wavelength-selective phase-conjugate reflector, with no need for active control of cavity length. The single-longitudinal-mode tunability and operational simplicity of this OPO system are demonstrated experimentally.     

Structural and optical properties of nanocrystalline ZnO thin films synthesized by the citrate precursor route

Nanocrystalline zinc oxide (ZnO) thin films have been deposited by spin-coating polymeric precursors synthesized by the citrate precursor route using ethylene glycol and citric acid as chelating agents. The ZnO thin films were annealed in air at different temperatures for 10 min. The films were characterized by different structural and optical techniques, including X-ray diffraction (XRD), atomic force microscopy (AFM), optical transmission spectroscopy, and photoluminescence (PL). The thermal decomposition of polymeric precursor was studied by thermogravimetric analysis (TGA). XRD analysis with grazing incidence and rocking curves indicate that the ZnO films are polycrystalline with preferential orientation along the c-axis direction with a full-width at half-maximum (FWHM) of 0.31° for 600 °C-annealed samples. On annealing, the texturing in films increased along with a decrease in FWHM. AFM micrographs illustrate that the ZnO films are crack-free with well-dispersed homogeneous and uniformly distributed spherical morphology. The synthesized ZnO thin films have transparency >85% in the visible region exhibiting band edge at 375 nm, which becomes sharper with anneal. Room temperature PL spectra of these films show strong ultraviolet (UV) emission around 392 nm with an increase in intensity with annealing temperature, attributed to grain growth. Deconvolution of the PL spectra reveals that there is coupling of free excitons with higher orders of longitudinal optical (LO) phonon replicas leading to a broad asymmetric near-band-edge peak.     

On the integration of SIC and MIMO DoF for interference cancellation in wireless networks

Recent advances in MIMO degree-of-freedom (DoF) models allowed MIMO research to penetrate the networking community. Independent from MIMO, successive interference cancellation (SIC) is a powerful physical layer technique used in multi-user detection. Based on the understanding of the strengths and weaknesses of MIMO DoF and SIC, we propose to have DoF-based interference cancellation (IC) and SIC help each other so that (i) precious DoF resources can be conserved through the use of SIC and (ii) the stringent SINR threshold criteria can be met through the use of DoF-based IC. In this paper, we develop the necessary mathematical models to realize the two ideas in a multi-hop wireless network. Together with scheduling and routing constraints, we develop a cross-layer optimization framework with joint DoF IC and SIC. By applying the framework on a throughput maximization problem, we find that SIC and DoF IC can indeed work in harmony and achieve the two ideas that we propose.     

The Impact of Sunlight on Adventitious Buying and Giving

The impact of sunlight on the income derived from spending and donations in a coastal charitable facility is examined. Data consisted of income during 2017 and 2018, together with daily sunshine hours and apparent temperature, and a multiple linear regression model was employed to determine the importance of these meteorological variables on income. Results indicated that income increased with both increasing sunshine hours and apparent temperature, but with an interaction effect (negative coefficient) between sunlight and apparent temperature such that the effect of sunlight on income is positive at lower apparent temperatures and negative at higher apparent temperatures. So, besides its many direct and indirect effects on man, it appears that sunlight also acts as a positive driver in adventitious giving and buying.     

Copper-Catalyzed Enantioselective Allylic Alkylation with a γ-Butyrolactone-Derived Silyl Ketene Acetal

Herein, we report a Cu-catalyzed enantioselective allylic alkylation using a γ-butyrolactone-derived silyl ketene acetal. Critical to the development of this work was the identification of a novel mono-picolinamide ligand with the appropriate steric and electronic properties to afford the desired products in high yield (up to 96 %) and high ee (up to 95 %). Aryl, aliphatic, and unsubstituted allylic chlorides bearing a broad range of functionality are well-tolerated. Spectroscopic studies reveal that a Cu^I species is likely the active catalyst, and DFT calculations suggest ligand sterics play an important role in determining Cu coordination and thus catalyst geometry.