Elucidation of codoping effects on the solubility enhancement of Er3+ in SiO2 glass: striking difference between Al and P codoping

The codoping effect mechanism of Al and P on the solubility enhancement of Er(3+) ion in SiO(2) glass was clarified by electron spin-echo envelope modulation spectroscopy. It turned out that doped P ions preferentially coordinate to the Er(3+) ion to form a "solvation shell structure", and the environment is similar to that in phosphate glass, while doped Al ions do not form such a selective solvation structure, taking octahedral coordination. This striking difference indicates that the primary roles of the P-doping and the Al-doping are attributed to "enthalpy of mixing" and to "entropy of mixing", respectively.     

Exact asymptotic formulae of the stationary distribution of a discrete-time two-dimensional QBD process

We propose an analytically tractable approach for studying the transient behavior of multi-server queueing systems and feed-forward networks. We model the queueing primitives via polyhedral uncertainty sets inspired by the limit laws of probability. These uncertainty sets are characterized by variability parameters that control the degree of conservatism of the model. Assuming the inter-arrival and service times belong to such uncertainty sets, we obtain closed-form expressions for the worst case transient system time in multi-server queues and feed-forward networks with deterministic routing. These analytic formulas offer rich qualitative insights on the dependence of the system times as a function of the variability parameters and the fundamental quantities in the queueing system. To approximate the average behavior, we treat the variability parameters as random variables and infer their density by using ideas from queues in heavy traffic under reflected Brownian motion. We then average the worst case values obtained with respect to the variability parameters. Our averaging approach yields approximations that match the diffusion approximations for a single queue with light-tailed primitives and allows us to extend the framework to heavy-tailed feed-forward networks. Our methodology achieves significant computational tractability and provides accurate approximations for the expected system time relative to simulated values.     

Stereoselective alkynylation of trans-2,3-epoxy sulfides with double inversion of configuration by alkynylaluminums

A stereoselective alkynylation reaction of rans-1-phenylthio-2,3-epoxyalkanes with alkynylaluminums which proceeds via episulfonium ions, that is, with double inversion of configuration, has been developed.     

Video-Assisted Rigid Endoscopic Laryngosurgery: Application to Cases with Difficult Laryngeal Exposure

In some cases of microlaryngosurgery, laryngeal exposure with a direct laryngoscope is difficult because of a variety of reasons. In such cases, we now use a long rigid endoscope inserted into the side tube of the direct laryngoscope together with a video system. The lesion can be removed while the phonosurgeon observes the magnified images of the larynx on the video monitor. We describe the surgical procedure together with the preoperative and postoperative evaluation of vocal function in 13 patients with benign laryngeal lesions. A good surgical and vocal outcome was achieved in all cases. The method appeared to be useful for treating dysphonia in patients in whom it was difficult to expose the larynx with a direct laryngoscope.     

Structural and functional properties of designed globins

De novo design of artificial proteins is an essential approach to elucidate the principles of protein architecture and to understand specific functions of natural proteins and also to yield novel molecules for medical and industrial aims. We have designed artificial sequences of 153 amino acids to fit the main-chain framework of the sperm whale myoglobin structure based on the knowledge-based energy functions to evaluate the compatibility between protein tertiary structures and amino acid sequences. The synthesized artificial globins bind a single heme per protein molecule as designed, which show well-defined electrochemical and spectroscopic features characteristic of proteins with a low-spin heme. Redox and ligand binding reactions of the artificial heme proteins were investigated and these heme-related functions were found to vary with their structural uniqueness. Relationships between the structural and functional properties are discussed.     

Absorption spectrum of nitrous acid for the ν1+2ν3 band studied with continuous-wave cavity ring-down spectroscopy and theoretical calculations

We present the high resolution absorption measurements of gaseous HONO at room temperature using continuous-wave cavity ring-down spectroscopy in the near-infrared region between 6017 and 6067 cm⁻¹ at a resolution of 1 pm (0.037 cm⁻¹). For the trans-HONO isomer an extensive analysis of the ν₁+2ν₃ combination band 6045.8089 cm^-1 was performed starting from the results of a previous study for the 1¹ and 3¹ vibrational states [Guilmot J-M, Godefroid M, Herman M. Rovibrational parameters for trans-nitrous acid. J Mol Spectrosc 1993;160:387-400]. The present combination band is perturbed because of the existence of several dark states of HONO which could not be identified unambiguously. The rotational constants achieved for the 1¹3² state deviate slightly from the values which are predicted from the rotational constants achieved in the previous studies for the 1¹ and 3¹ vibrational states of trans-HONO.     

Recognition of Multiple Methyl Groups on Aromatic Rings by a Polyaromatic Cavity

The methyl group is a small substituent, usually showing relatively weak or no interactions with other functional groups and metal ions. Herein, we present the recognition of the number of methyl groups on synthetic and natural aromatic compounds (i.e., benzene and xanthine derivatives, respectively) by the 1 nm‐sized polyaromatic cavity of a coordination capsule in water. Detailed competitive encapsulation experiments as well as X‐ray crystallographic analysis revealed that multiple guest–host CH₃–polyaromatic interactions in the confined nanospace are key driving forces for the high selectivity.     

Anisotropic Expansion of an M2L4 Coordination Capsule: Host Capability and Frame Rearrangement

Anisotropic expansion of a spherical M₂L₄ coordination capsule through the elongation of the ligand led to a new M₂L′₄ capsule. The expanded capsule provides an elliptical cavity encircled by polyaromatic frameworks with large openings and thereby can encapsulate elliptical fullerene C₇₀ and monofunctionalized fullerene C₆₀ in high yields. In addition, selective formation of a new M₂L₂L′₂ capsule occurs by mixing the original M₂L₄ and expanded M₂L′₄ capsules in a 1:1 ratio upon addition of C₆₀ or monofunctionalized C₆₀ as a template molecule.