Interconvertible multiple photoluminescence color of a gold(i) isocyanide complex in the solid state: solvent-induced blue-shifted and mechano-responsive red-shifted photoluminescence

In this study, we report the interconvertible tetracolored solid state photoluminescence of gold(i) isocyanide complex 2 upon various external stimuli through solid state structural changes. Soaking complex 2 in acetone yields blue emission as a result of the formation of 2B. The subsequent removal of acetone yields 2G through a crystal-to-crystal phase transition, which exhibits green emission. This green-emitting solid 2G exhibits stepwise emission color changes to yellow and then to orange upon mechanical stimulation by ball-milling, which corresponds to the formation of 2Y and 2O, respectively. 2B could be recovered upon the addition of acetone to 2G, 2Y, and 2O. Thus, these four emitting solid states of 2 can be switched between repeatedly by means of acetone soaking and the application of mechanical stimulation. Importantly, single crystal and powder X-ray diffraction (PXRD) studies fully show the detailed molecular arrangements of 2B, 2G, and 2Y. This is the first mechanochromic compound to show interconvertible four color emission in the solid state. We also present the first example of using PXRD measurements and the Rietveld refinement technique for the structural analysis of a ground powder in a luminescence mechanochromism study. We obtained complete molecular-level structural information of the crystalline states of 2B, 2G, 2Y, and 2O. In comparison with a more solvophobic analogue 1, we suggest that the weak interaction of 2 with acetone in the solid state would allow a solvent inclusion/release mode, which is an important structural factor for the unprecedented multicolor mechanochromic luminescence.     

Rhodium(I)‐Catalyzed Intramolecular Carbonylative [2+2+1] Cycloaddition of Bis(allene)s: Bicyclo[6.3.0]undecadienones and Bicyclo[5.3.0]decadienones

No templates needed : The title reaction makes it easy to construct the bicyclo[6.3.0]undecadienone framework in high yields (see scheme). A template effect is not required to achieve this ring‐closing reaction efficiently. The present method can be applied to the construction of bicyclo[5.3.0] and bicyclo[4.3.0] ring systems. Ts=p‐toluenesulfonyl.

     

A hierarchical clustering scheme approach to assessment of IP-network traffic using detrended fluctuation analysis

This paper presents an approach to the assessment of IP-network traffic in terms of the time variation of self-similarity. To get a comprehensive view in analyzing the degree of long-range dependence (LRD) of IP-network traffic, we use a hierarchical clustering scheme, which provides a way to classify high-dimensional data with a tree-like structure. Also, in the LRD-based analysis, we employ detrended fluctuation analysis (DFA), which is applicable to the analysis of long-range power-law correlations or LRD in non-stationary time-series signals. Based on sequential measurements of IP-network traffic at two locations, this paper derives corresponding values for the LRD-related parameter α that reflects the degree of LRD of measured data. In performing the hierarchical clustering scheme, we use three parameters: the α value, average throughput, and the proportion of network traffic that exceeds 80% of network bandwidth for each measured data set. We visually confirm that the traffic data can be classified in accordance with the network traffic properties, resulting in that the combined depiction of the LRD and other factors can give us an effective assessment of network conditions at different times.     

A computationally efficient model selection in the generalized linear mixed model

This paper is concerned with model selection in spline-based generalized linear mixed model. Exploiting the fact that smoothing parameters can be expressed as the reciprocal ratio of the variances of random effect under the setting of estimation by regularization, we propose a computationally efficient model selection procedure. Applications to some real data sets reveal that the proposed method selects reasonable models and is very fast to implement.     

100-TW sub-20-fs Ti:sapphire laser system operating at a 10-Hz repetition rate

We developed a compact three-stage Ti:sapphire amplifier laser system that produced peak power in excess of 100 TW for a pulse duration of less than 19 fs and an average power of 19 W at a 10-Hz repetition rate. A final 40-mm-diameter Ti:sapphire amplifier is pumped by a Nd:YAG master-oscillator-power-amplifier system that produces ~7-J output of 532-nm radiation. The spatial beam quality is approximately 2 times diffraction limited for the full amplified compressed output pulse. With f/3 optics, this system should therefore be capable of producing a focused intensity of ~3x10(20) W/cm(2) .     

Transfer of photoenergy in pi-conjugated polymers. Two types of photoluminescence that involve energy transfer along a polymer chain

Two types of energy transfer in pi-conjugated polymers have been investigated using time-resolved photoluminescence (PL) techniques: type i, perpendicular-type energy transfer from the 2,3-di(p-tolyl)quinoxaline unit to the pi-conjugated main chain of poly[2,3-di(p-tolyl)quinoxaline-5,8-diyl], and type ii, parallel-type energy transfer from the oligo(pyridine-2,5-diyl) (O-Py) unit to the oligo(selenophene-2,5-diyl) (O-Se) unit in a block-type copolymer of O-Py and O-Se. Both types of energy transfer were very fast with a time constant shorter than approximately 0.1 ns; in particular, the type ii energy transfer took place with a time constant of approximately 5 ps. Both pi-conjugated polymers were considered to contain segments with various effective pi-conjugation lengths, and the energy transfer to the segment with a larger effective pi-conjugation length and a smaller pi-pi* transition energy required a longer transition time. A polarizing film was obtained by utilizing the perpendicular-type energy transfer.     

Electric dipole polarizability of the hydrogen molecule by many-body perturbation theory

Many-body perturbation theory is used to calculate the static electric dipole polarizability of the hydrogen molecule with a basis set of gaussian orbitals. Corrections complete through second order in electron correlation are calculated, and partial summation of certain classes of diagrams are extensively explored. The results are discussed in connection with the geometric approximation incorporating higher-order corrections.     

Cobalt-catalyzed intramolecular Heck-type reaction of 6-halo-1-hexene derivatives

[reaction: see text] Treatment of 6-iodo-1-hexene derivatives with trimethylsilylmethyl Grignard reagent in the presence of CoCl(2)(dppb) in refluxing THF affords Heck-type products, methylenecyclopentanes, in good yields.     

Relation between interdiffusion and polarity for MBE growth of GaN epilayers on ZnO substrates

We report on GaN growth on Zn-polar ZnO substrates using plasma-assisted molecular-beam epitaxy (P-MBE). Before GaN growth, ZnO substrate annealing conditions were optimized. Reflection high-energy electron diffraction (RHEED) patterns after low-temperature GaN buffer layer annealing changed from streaky to spotty, suggesting that zinc and oxygen atoms interdiffuse from the ZnO substrate into the GaN epilayer. This interdiffusion results in a mix-polar GaN epilayer.     

Cationic ring‐opening copolymerization behavior of trioxane and seven‐membered cyclic carbonate

Cationic ring‐opening copolymerization behavior of trioxane (TOX) and a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one (7CC) is described. When TOX and 7CC were cationically copolymerized under various feed ratios using trifluoromethane sulfonic acid (TfOH) as an initiator in nitrobenzene at 30 °C, 7CC was consumed faster than TOX and the decarboxylation was accompanied to afford the corresponding polyacetal–polycarbonate type copolymers containing poly(oxytetramethylene) units. The copolymer composition could be controlled by the feed ratio of 7CC, whose increase resulted in the high copolymer composition of the 7CC unit. The solubility of the copolymers increased as the increase of the 7CC content. Thermogravimetric, size‐exclusion chromatographic, and X‐ray analyses of the copolymers suggest that the sequences of the copolymer chains consist of the segments containing the units originated from 7CC and those with TOX unit‐rich compositions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 733–739, 2008