Measurement of the fundamental thermal noise limit in a cryogenic sapphire frequency standard using bimodal maser oscillations

We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10(-14) tau(-1/2) with only 0.5 pW of output power.     

Non-minimal scalar-flat Kähler surfaces and parabolic stability

A new construction is presented of scalar-flat Kähler metrics on non-minimal ruled surfaces. The method is based on the resolution of singularities of orbifold ruled surfaces which are closely related to rank-2 parabolically stable holomorphic bundles. This rather general construction is shown also to give new examples of low genus: in particular, it is shown that \(\mathbb{CP}^2\) blown up at 10 suitably chosen points, admits a scalar-flat Kähler metric; this answers a question raised by Claude LeBrun in 1986 in connection with the classification of compact self-dual 4-manifolds.     

Suitability of Novel Algal Biomass as Fish Feed: Accumulation and Distribution of Omega-3 Long-Chain Polyunsaturated Fatty Acid in Zebrafish

Applied Biochemistry and Biotechnology - A 28-day feeding experiment with formulated feed using docosahexaenoic acid (DHA)-rich whole cells of freeze-dried marine microalgae Schizochytrium sp. to...     

Lead(II) Siloxides

Although Pb^II-siloxides have been known until now to decompose to oxoclusters, here [{RO^F}PbOSi(SiMe₃)₃] (RO^F=fluoroalkoxide) and, most importantly, [Pb₂{OSi(SiMe₃)₃}{μ₂-OSi(SiMe₃)₃}₃], are presented. The unusual bonding pattern in the latter thermally stable dinuclear complex was investigated by crystallographic and computational methods. Its stability is much higher than that of the simple, yet elusive “[Pb(OSiPh₃)₂]”, for which decomposition pathways towards [Pb₄(μ₄-O)(μ₂-OSiPh₃)₆] have been clearly established.     

Bis(imino)carbazolate: A Master Key for Barium Chemistry

Reported here is a readily available bis(imino)carbazole‐based proligand that constitutes a convenient entry point into the challenging synthetic molecular chemistry of barium. It enables the preparation of rare or even, up to now, unknown, solution‐stable heteroleptic barium complexes. The syntheses and structural features for the first molecular barium fluoride and the first barium stannylide, with an unsupported Ba?Sn bond, are described, along with other carbazolate barium species: an amide (both a remarkably stable starting material and an excellent hydrophosphination precatalyst), iodide, and silanylide. DFT analysis of bonding patterns in the barium stannylide and barium silanylide highlights a prevailingly ionic barium–tetrelide bond with a small covalent contribution.     

Proposition of an uncoupled approach for the identification of cyclic heat sources from temperature fields in the presence of large strains

A methodology is proposed to define an equivalent geometry allowing the use of an uncoupled algorithm to solve thermomechanical problems when cyclic large strain occurs. This methodology is set up on the case of a simple bar and is then challenged on a structural sample for cyclic loadings. It is shown that the definition of the equivalent geometry is dependent on the thermal boundary conditions, which are usually unknowns of the thermal problem. The proposed approach is finally applied to the identification of cyclic dissipation from infrared thermography measurements.     

Resonant modal conversion in a two-mode waveguide

We characterize a system consisting of a two-mode waveguide coupled to a single-mode microring resonator possibly presenting a nonlinear response of Kerr type. By using the scattering parameter formalism extended to the multimode domain, we show that in the linear regime and for an ideally transparent medium, each resonance of the system can be exploited to perform complete even-to-odd (respectively, odd-to-even) modal conversion. Moreover, when the Kerr nonlinearity is effective, the microring enables a power-dependent modal switching mediated by phase bistability. Thanks to its mode-processing capabilities, this configuration is suitable to find application as a functional building-block in mode-division multiplexing (MDM) photonic integrated circuits.