Self-compensation of third-order dispersion for ultrashort pulse generation demonstrated in an Yb fiber oscillator

Compensation of the intracavity dispersion in the mode-locked oscillator is known to be one of the most important factors for ultrashort pulse generation. However, recent investigations of a Yb-doped fiber mode-locked oscillator revealed that precise third-order dispersion (TOD) compensation is not always necessary for ultrashort pulse generation, owing to the strong nonlinearity that compensates residual TOD without reducing its spectral bandwidth. The origin of the nonlinear TOD compensation has remained unclear. To investigate the process in detail, we studied the pulse evolution inside a 30 fs Yb-doped fiber mode-locked oscillator both experimentally and numerically, and we found that the nonlinear phase shift with a temporally asymmetric pulse shape introduces an appropriate amount of TOD that exactly cancels the residual cavity dispersion.     

LP narrowing: A new strategy for finding all solutions of nonlinear equations

An efficient algorithm is proposed for finding all solutions of systems of n nonlinear equations. This algorithm is based on interval analysis and a new strategy called LP narrowing. In the LP narrowing strategy, boxes (n-dimensional rectangles in the solution domain) containing no solution are excluded, and boxes containing solutions are narrowed so that no solution is lost by using linear programming techniques. Since the LP narrowing is very powerful, all solutions can be found very efficiently. By numerical examples, it is shown that the proposed algorithm could find all solutions of systems of 5000-50,000 nonlinear equations in practical computation time.     

A simple method for preparing a diamino cellulose disk from a dialdehyde cellulose disk by reductive amination using 2-picoline-borane

Cellulose - A method for the preparation of dialdehyde cellulose disks (DACD) and subsequent diamino cellulose disks (DAmCD) was developed. DACD was prepared by oxidizing filter paper with sodium...     

Heat capacity and thermal expansion of CdCr2Se4 and CdCr2S4

The thermodynamic properties of the spinel ferromagnetic compounds CdCr₂Se₄ and CdCr₂S₄ have been investigated by making heat capacity and thermal expansion measurements on single crystals. For both compounds, the ferromagnetic transition is marked by λ-type thermal anomalies, and the results provide a pressure dependence of the transition temperatures that is in agreement with direct measurements. Below the transition, CdCr₂S₄ shows an anomalous heat-capacity contribution and negative thermal expansion, which are in contrast to the conventional behavior found in CdCr₂Se₄.     

Cascade and one-pot processes providing substituted quinolines from aldimines and allylsilanes: auto-tandem catalysis of triflic imide

We have demonstrated cascade and one-pot reactions, which constitute inverse electron demand hetero-Diels-Alder reaction and oxidative aromatization, to provide substituted quinolines to form aryl aldimines and allylsilanes. The cascade process involves an auto-tandem catalysis; Tf₂NH activates these mechanistically distinct reactions. We have found that a multicomponent process starting from aniline, aldehyde, and allylsilane is also available.