56,679 research outputs found
Is SH4, the simplest 10-S-4 sulfurane, observable?
No full textThe kinetic stability of SH4 was investigated theoretically with the coupled cluster ansatz. The two possible modes of decomposition into SH2 and H-2 through either a C-2v or a C-1 transition structure (TS) were investigated using intrinsic reaction coordinate (IRC) computations; orbital interactions along the reaction paths were analyzed. The two dissociation modes are due to differences in the electron delocalization in the TSs. While the C-2v TS is bonded rather covalently by a three center-four electron (3c-4e) interaction which is lost in a strictly synchronous way (two electrons occupy the same orbital at a time along the reaction coordinate), the bonding orbital in the C-1 TS is merely occupied by a single electron. Surprisingly, this highly polarized TS has a lower barrier. Computations at the CCSD(T)/cc-pVQZ level of theory show that the zero-point corrected enthalpy (Delta H(0)double dagger) of the C-1 TS is 16 kcal mol(-1) above the C-4v symmetric ground state; the barrier along the C-2v path is 40 kcal mol(-1). The overall exothermicity for the dissociation into SH2 and H-2 was estimated to be Delta H-0 = -76 kcal mol(-1). The fundamental IR absorptions of SH4 (obtained by scaling the computed harmonic vibrational frequencies taken from the CCSD(T)/cc-pVQZ level of theory) are 1432 and 2037 cm(-1)
FiFoSiM - an integrated tax benefit microsimulation and CGE model for Germany
No full textThis paper describes FiFoSiM, the integrated tax benefit microsimulation and computable general equilibrium (CGE) model of the Center of Public Economics at the University of Cologne. FiFoSiM consists of three main parts. The first part is a static tax benefit microsimulation module. The second part adds a behavioural component to the model; an econometrically estimated labour supply model. The third module is a CGE model which allows the user of FiFoSiM to assess the global economic effects of policy measures. Two specific features distinguish FiFoSiM from other tax benefit models: First, the simultaneous use of two databases for the tax benefit module and second, the linkage of the tax benefit model to a CGE model.FiFoSiM; microsimulation; CGE
Cancer genomes tolerate deleterious coding mutations through somatic copy number amplifications of wild-type regions
No full textAbstract Cancers evolve under the accumulation of thousands of somatic mutations and chromosomal aberrations. While most coding mutations are deleterious, almost all protein-coding genes lack detectable signals of negative selection. This raises the question of how tumors tolerate such large amounts of deleterious mutations. Using 8,690 tumor samples from The Cancer Genome Atlas, we demonstrate that copy number amplifications frequently cover haploinsufficient genes in mutation-prone regions. This could increase tolerance towards the deleterious impact of mutations by creating safe copies of wild-type regions and, hence, protecting the genes therein. Our findings demonstrate that these potential buffering events are highly influenced by gene functions, essentiality, and mutation impact and that they occur early during tumor evolution. We show how cancer type-specific mutation landscapes drive copy number alteration patterns across cancer types. Ultimately, our work paves the way for the detection of novel cancer vulnerabilities by revealing genes that fall within amplifications likely selected during evolution to mitigate the effect of mutations
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Temperature and matrix effects on competitive intermolecular and intramolecular reaction of benzylchlorocarbenes in ethanol
No full textPT: J; CR: GRILLER D, 1982, J AM CHEM SOC, V104, P5549 LIN CT, 1980, TETRAHEDRON LETT, V21, P3553 LIU MTH, 1983, TETRAHEDRON LETT, P5713 MOSS RA, 1978, J AM CHEM SOC, V100, P4475 MOSS RA, 1978, J CHEM SOC CHEM COMM, P255 MOSS RA, 1981, TETRAHEDRON LETT, V22, P997 POMERANTZ M, 1973, J AM CHEM SOC, V95, P5877 SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288 SENTHILNATHAN VP, 1980, J AM CHEM SOC, V102, P7637 SENTHILNATHAN VP, 1981, J AM CHEM SOC, V103, P5503 SU DTT, 1978, J AM CHEM SOC, V100, P1872 TOMIOKA H, 1977, J AM CHEM SOC, V99, P6128 TOMIOKA H, 1979, J AM CHEM SOC, V101, P256 TOMIOKA H, 1979, J AM CHEM SOC, V101, P6009 TOMIOKA H, 1980, J AM CHEM SOC, V102, P7123 TOMIOKA H, 1980, J AM CHEM SOC, V102, P7817 TOMIOKA H, 1982, CHEM LETT, P843 TOMIOKA H, 1982, J AM CHEM SOC, V104, P3156 TOMIOKA H, 1983, J AM CHEM SOC, V105, P5053 TOMIOKA H, 1984, J AM CHEM SOC, V106, P454 TOMIOKA H, 1984, J CHEM SOC CHEM COMM, P476 TROZZOLO AM, 1973, CARBENES, V2, P185 TURRO NJ, 1982, J AM CHEM SOC, V104, P1754; NR: 23; TC: 8; J9: TETRAHEDRON LETT; PG: 4; GA: TL386Source type: Electronic(1
Mechanism of particle formation on decomposing Re2(CO)10 on NaY and NaHY zeolites : effect of prereduced Pt clusters in the supercages.
No full textWhy the critical temperature of high-<i>T<sub>c</sub></i> cuprate superconductors is so low: The importance of the dynamical vertex structure
No full textTo fathom the mechanism of high-temperature (T-c) superconductivity, the dynamical vertex approximation is evoked for the two-dimensional repulsive Hubbard model. After showing that our results reproduce well the cuprate phase diagram with a reasonable T-c and dome structure, we keep track of the scattering processes that primarily affect T-c. We find that local particle particle diagrams significantly screen the bare interaction at low frequencies, which in turn suppresses antiferromagnetic spin fluctuations and hence the pairing interaction. Thus we identify dynamical vertex corrections as one of the main oppressors of T-c which may provide a hint toward higher T-c's
1, 2-H shift in benzylchlorocarbene: isotope effect and influence of the solvent
No full textLaser flash photolysis of 3-chloro-3-benzyldiazirine and 3-chloro-3-(phenyldideuteriomethyl)diazirine in isooctane over the 60 to -80-degrees-C temperature range gives rise to curved Arrhenius plots for both 1,2-H and 1,2-D migration in benzylchlorcarbene. The k(H)/k(D) values increase smoothly from 0.87 to 2.62 when the temperature increases from -60 to +30-degrees-C. The k(H)/k(D) value is approximately 4 for most of the temperatures studied if a solvent correction is applied. Quantum mechanical tunnelling or the influence of the solvent may be a possible explanation for these observations.PT: J; CR: BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 BONNEAU R, 1992, J PHOTOCH PHOTOBIO A, V68, P97 DIX EJ, 1993, J AM CHEM SOC, V115, P10424 EVANSECK JD, 1990, J PHYS CHEM-US, V94, P5518 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JACKSON JE, 1994, ADV CARBENE CHEM JONES M, 1980, REACTIVE INTERMEDIAT, V2 KIRMSE W, 1971, CARBENE CHEM LIU MTH, 1984, TETRAHEDRON, V40, P887 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LIU MTH, 1992, J PHYS ORG CHEM, V15, P285 LIU MTH, 1994, RES CHEM INTERMEDIAT, V20, P195 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MOSS RA, 1992, TETRAHEDRON LETT, V33, P4287 MOSS RA, 1994, ADV CARBENE CHEM MUROV SL, 1973, HDB PHOTOCHEMISTRY NICKON A, 1993, ACCOUNTS CHEM RES, V26, P84 SALIS GA, 1968, J PHYS CHEM-US, V72, P752 SANDER W, 1994, UNPUB SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288 SCHOLLER WW, 1989, HOUBEN WEYL METHODEN, P41 SHIMANOUCHI T, 1972, TABLES MOL VIBRATION, V1 SUGIYAMA MH, 1992, J AM CHEM SOC, V114, P966 WIERLACHER S, 1993, J AM CHEM SOC, V115, P8943; NR: 25; TC: 20; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 5; GA: PV021Source type: Electronic(1
Millipedes and earthworms increase the decomposition rate of N-15-labelled winter rape litter in an arable field
No full textEffects of millipedes and earthworms on the decomposition of N-15-labelled litter of winter oilseed rape were investigated in a microcosm field experiment over a period of 264 days on an oat field near Gottingen managed by integrated farming. A total of 32 microcosms were filled with defaunated soil. N-15-labelled rape litter was placed either on top of the soil or buried into the soil simulating mulching and ploughing, respectively. To the microcosms nine adult individuals of Blaniulus guttulatus (Diplopoda) and two of Aporrectodea caliginosa (Lumbricidae) were added separately or in combination. In general, the presence of the animals accelerated the decomposition rate of the litter material. The effects were most pronounced in the presence of Aporrectodea caliginosa. The total amount of nitrate, ammonium and the amount of N-15 leached from the microcosms was increased in the presence of earthworms or of both earthworms and millipedes, Both species proved to be important members of the detritus food web of the agricultural system studied
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