Mononuclear Thiolatecobalt Carbonyls

A Partial Statistically Incorporation of Ca²⁺ into the Ba₆Nd₂Al₄O₁₅-Type: Ba₅CaLa₂Fe₄O₁₅ Using high temperature reactions we succeeded in incorporating Ca²⁺ into the Ba₆Nd₂Al₄O₁₅ type. Single crystal X-ray methods reveal a partly ordered alkaline earth distribution. Ba²⁺ and Ca²⁺ occupy face connected MO₆-octahedra as well as a further point position together with La³⁺ ions (space group C−P6₃mc; a = 11.770; c = 7.039 Å; Z = 2).     

Computing determinantal representation of generalized inverses

We investigate implementation of the determinantal representation of generalized inverses for complex and rational matrices in the symbolic package MATHEMATICA. We also introduce an implementation which is applicable to sparse matrices.     

Transition from smectic-A to crystalline phase in the mean field approximation

We present here a smectic-A to crystalline phase transition curve for liquid crystals, in addition to the phase diagram previously reported which includes the isotropic, nematic, and smectic-A phases calculated in the mean field approximation.     

High-accuracy theoretical study on the thermochemistry of several formaldehyde derivatives

In the case of several formaldehyde derivatives, with importance in atmospheric and combustion chemistry, the currently available thermochemical values suffer from considerably large uncertainties. In this study a high-accuracy theoretical model chemistry has been used to provide accurate thermochemical data including heats of formation at 0 and 298 K and standard molar entropies at 298 K for CF(2)O, FCO, HFCO, HClCO, FClCO, HOCO, and NH(2)CO. For most of the thermochemical quantities studied here, this investigation delivers the best available estimate.     

On the Leverrier-Faddeev algorithm for computing the Moore-Penrose inverse

We present an improvement in the implementation of the Leverrier-Faddeev algorithm for symbolic computation of the Moore-Penrose inverse of one-variable polynomial matrices, introduced in Linear Algebra Appl. 252, 35–60 (1997). Complexity analysis of the original algorithm and its improvement is presented. Algorithm and its improvement are implemented and compared in the symbolic computational package MATHEMATICA. We compare CPU time required for computation of some test matrices by means of the original algorithm and its improvement.     

Visible and infrared luminescence properties of Er-doped Y2Ti2O7 nanocrystals

Er³⁺-doped Y₂Ti₂O₇ nanocrystals were fabricated by the sol-gel method. While the annealing temperature exceeds 757 °C, amorphous pyrochlore phase Er_xY_2−xTi₂O₇ transfers to well-crystallized nanocrystals, and the average crystal size increases from ∼70 to ∼180 nm under 800-1000 °C/1 h annealing. Er_xY_2−xTi₂O₇ nanocrystals absorbing 980 nm photons can produce the upconversion (526, 547, and 660 nm; ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively) and Stokes (1528 nm; ⁴I_13/2→⁴I_15/2) photoluminescence (PL). The infrared PL decay curve is single-exponential for Er³⁺ (5 mol%)-doped Y₂Ti₂O₇ nanocrystals but slightly nonexponential for Er³⁺ (10 mol%)-doped Y₂Ti₂O₇ nanocrystals. For 5 and 10 mol% doping concentrations, the mechanism of up-converted green light is the two-photon excited-state absorption. Much stronger intensity of red light relative to green light was observed for the sample with 10 mol% dopant. This phenomenon can be attributed to the reduced distance between Er³⁺-Er³⁺ ions, resulting in the enhancement of the energy-transfer upconversion and cross-relaxation mechanisms.     

Comprehensive molecular imaging of photolabile surface samples with synchronized dual-polarity time-of-flight mass spectrometry

This work presents the unique features of a novel configuration of a synchronized dual-polarity time-of-flight mass spectrometer for comprehensive surface imaging. Mass spectrometry imaging of surface samples covering positive and negative ion modes is difficult due to rapid signal depletion. This limitation is overcome here by dual-polarity time-of-flight mass spectrometry (DP-TOFMS) via two separate TOF mass analyzers that are installed above a sample surface. The new instrument eliminates the polarity bias characteristic of most mass spectrometers, which is important for the analysis of samples with diverse physical and chemical properties. The experimental results show for the first time that the spatial distribution of positive and negative ions of various photolabile samples can be distinguished, including pigments and conventional matrix-assisted laser desorption/ionization samples. The different positive and negative ion distributions suggest that accurate quantitative information can only be obtained when the entire sample region is examined by DP-TOFMS, which was unfeasible in the past. Such a comprehensive diagnostic method is essential for the molecular imaging of trace compositions in delicate biological tissues, as demonstrated here with a Phyllanthus urinaria leaf that only produced ion signals in the first examination and not in the subsequent measurements.