Cubic Nonlinear Optical Properties of Platinum-Terminated Polyynediyl Chains

The wavelength dependence of the cubic nonlinearity of ligated platinum-terminated polyynes trans,trans-{(p-MeC6H4) 3P}2(p-MeC6H4)Pt(C≡C) nPt(p-C6H4Me){P(p-C6H 4Me)3}2 (n = 3-6, 8, 10, 12) has been examined by femtosecond Z-scan studies in the waveleng

Zero-point vibrational corrections to isotropic hyperfine coupling constants in polyatomic molecules

The present work addresses isotropic hyperfine coupling constants in polyatomic systems with a particular emphasis on a largely neglected, but a posteriori significant, effect, namely zero-point vibrational corrections. Using the density functional restricted-unrestricted approach, the zero-point vibrational corrections are evaluated for the allyl radical and four of its derivatives. In addition for establishing the numerical size of the zero-point vibrational corrections to the isotropic hyperfine coupling constants, we present simple guidelines useful for identifying hydrogens for which such corrections are significant. Based on our findings, we critically re-examine the computational procedures used for the determination of hyperfine coupling constants in general as well as the practice of using experimental hyperfine coupling constants as reference data when benchmarking and optimizing exchange-correlation functionals and basis sets for such calculations.Research Council of Norway through a CoE[179568/V30]; Norwegian Supercomputing program; [191251

Role of the (3)(ππ*) State in Photolysis of Lumisantonin: Insight from ab Initio Studies

The CASSCF and CASPT2 methodologies have been used to explore the potential energy surfaces of lumisantonin in the ground and low-lying triplet states along the photoisomerization pathways. Calculations indicate that the (n pi*) state is the accessible low-lying singlet state with a notable oscillator strength under an excitation wavelength of 320 nm and that it can effectively decay to the (3)(pi pi*) state through intersystem crossing in the region of minimum surface crossings with a notable spin-orbital coupling constant. The 3(pi pi*) state, derived from the promotion of an electron from the pi-type orbital mixed with the sigma orbital localized on the C-C bond in the three-membered alkyl ring to the pi* orbital of conjugation carbon atoms, plays a critical role in C-C bond cleavage. Based on the different C-C bond rupture patterns, the reaction pathways can be divided into paths A and B. Photolysis along path A arising from C1-C5 bond rupture is favorable because of the dynamic and thermodynamic preferences on the triplet excited-state PES. Path B is derived from the cleavage of the C5-C6 bond, leading first to a relatively stable species, compared to intermediate A-INT formed on the ground state PES. path B is relatively facile for the pyrolytic reaction. The present results provide a basis to interpret the experimental observations.Swedish Infrastructure Committee (SNIC)[SNIC 022/09-25]; National Science Foundation of China[20733002, 20873105]; Ministry of Science and Technology[2011CB808504

Screening for low bone mass with quantitative ultrasonography in a community without dual-energy X-ray absorptiometry: population-based survey

BACKGROUND: Dual-energy x-ray absorptiometry (DXA) is the criterion standard to identify low bone mineral density (BMD), but access to axial DXA may be limited or cost prohibitive. We screened for low bone mass with quantitative ultrasonography (QUS) in a community without DXA, analyzed its reliability and obtained reference values and estimated the prevalence of low QUS values. METHODS: We enrolled 6493 residents of Kinmen, Taiwan, and a reference group (96 men and 70 women aged 20–29 years) for this cross-sectional, community-based study. All participants completed a questionnaire and underwent ultrasonographic measurements. Reliability and validity of QUS measurements were evaluated. Broadband ultrasound attenuation (BUA) values were obtained and statistically analyzed by age, sex and weight. Annual loss of BUA was determined. Trends in the prevalence of QUS scores were evaluated. RESULTS: Two QUS were used and had a correlation coefficient of 0.90 (p < 0.001). Calcaneal BUA was significantly correlated with BMD in the femoral neck (r = 0.67, p < 0.001) and BMD of the total lumbar spine (r = 0.59, p < 0.001). BUAs in the reference group were 92.72 ± 13.36 and 87.90 ± 10.68 dB/MHz for men and women, respectively. Estimated annual losses of calcaneal BUA were 0.83% per year for women, 0.27% per year for men, and 0.51% per year for the total population. The prevalence of severely low QUS values (T-score = -2.5) tended to increase with aging in both sexes (p < 0.001). Across age strata, moderately low QUS values (-2.5 < T-score < -1.0) were 31.6–41.0% in men and 23.7–38.1% in women; a significant trend with age was observed in men (p < 0.001). CONCLUSION: Age-related decreases in calcaneal ultrasonometry, which reflected the prevalence of low bone mass, were more obvious in women than in men

Origin invariant approaches to the calculation of two-photon circular dichroism

The origin dependence of the expression of two-photon circular dichroism in the length formulation employed by the authors in a recent computational study [B. Jansik , Chem. Phys. Lett. 414, 461 (2005)] is discussed in detail, and some inherently origin invariant alternative formulations are introduced. Extensive computational tests on a small reference chiral system, namely, a chiral form of H2O2, are performed at the density functional theory (DFT)/B3LYP level of theory with large diffuse correlation consistent basis sets. The results indicate that the velocity formulation originally proposed by Tinoco, Jr. [J. Chem. Phys. 62, 1006 (1975)] provides the most convenient approach for an origin invariant calculation of two-photon circular dichroism. (c) 2006 American Institute of Physics

The Preface

Non peer reviewe