ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Fragment rotational state distributions from the dissociation of NeIBr: Experimental and theoretical results (1992)

Stephenson, Thomas A.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 97 (1992), S. 6262-6275

add to mindlist on the mindlist

Details

ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The IBr fragment rotational state distributions that result when the NeIBr van der Waals molecule undergoes vibrational predissociation have been measured in a pump–probe laser-induced fluorescence experiment. Independent of initial vibrational state and the number of quanta of vibrational energy lost from the I–Br coordinate, the rotational distributions extend over the full range of energetically accessible states. From the observation of energetic constraints on the rotational distribution, the dissociation energy (D0) is calculated to be 65.5±1.2 cm−1 for the A electronic state, v=16. For the X electronic state, v=0, D0=71.8±1.2 cm−1. Quantum mechanical bound state calculations carried out on a model A electronic state potential energy surface are in quantitative agreement with this result. The rotational distributions are broader than that predicted by either a Franck–Condon or classical impulsive model for the dissociation. The distributions are qualitatively in accord with classical trajectory calculations. Analysis of specific rotational distributions in the context of the energy gap law shows poor quantitative agreement. The average fragment rotational energy relative to analogous Ne-containing complexes is, however, qualitatively predicted by the energy gap relations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.463688

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

2

Electronic Resource

Vibrational branching ratios from the dissociation of the NeIBr van der Waals molecule (1992)

Walter, Sarah A. ; Stephenson, Thomas A.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 96 (1992), S. 3536-3541

add to mindlist on the mindlist

Details

ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The degree of vibrational excitation in the IBr fragment from the vibrational predissociation of NeIBr (A 3Π1) has been measured using two-color pump–probe laser-induced fluorescence spectroscopy. We find that for the lowest initial vibrational states examined, Δv=−1 dissociation pathways dominate the dynamics, while this channel is closed for v≥17. From this result, the A state binding energy (D0) of the complex is determined to be 67±4 cm−1, while that in the X electronic state is found to be 73±4 cm−1. The X state binding energy is identical to that for NeI2 and NeBr2, suggesting that the potential energy surface for NeIBr can be constructed from a summation of atom–atom pair potentials; we present such a model potential energy surface. The variations in the vibrational branching ratios, when combined with the trends in the predissociation rates, point to the importance of fragment rotational excitation in the dynamics of the dissociation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.461908

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

3

Electronic Resource

Nascent product states in the photoinitiated reaction of O3 and H2O (1992)

Sauder, Deborah G. ; Stephenson, John C. ; King, David S. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 97 (1992), S. 952-961

add to mindlist on the mindlist

Details

ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The rotational, vibrational and fine-structure state distributions for the reaction 16O(1D)+ H218O →16OH +18OH, triggered by 266 nm photolysis of O3, have been measured under conditions where less than 1% of the nascent fragments experienced collisions prior to detection. The distributions are qualitatively different than those reported earlier for 266 nm photolysis, which were evidently affected by collisions. The rotational and vibrational state distributions are similar to recent 248 nm photolysis experiments, but with differences attributed to collisional and/or energetic effects in those experiments. The "new'' 16OH is formed with vibrational populations in the ratio 0.39(v=0):0.29(v=1):0.3(v≥2). Gaussian rotational energy distributions peaked near N=12 give average rotational energies of 〈Erot〉 = 3440 and 2780 cm−1 for 16OH v=0 and v=1, respectively. The "old'' 18OH is much colder with vibrational populations 0.94(v=0):0.06(v=1) and a 18OH v=0 Gaussian rotational energy distribution characterized by 〈Erot〉 = 1920 cm−1.There is negligible rotational alignment of the 16OH fragments [βμJ' = β20(02) = 5A(0)2/4 = 0.06± 0.09], which is significantly less than expected for fragment rotations aligned with respect to the O+H2O relative velocity vector. The spin-orbit propensities deviate slightly from the statistical expectation and are characterized by [F2,N]/[F1,N]=(0.89±0.06) ×N/(N + 1). The Λ-doublet distributions for 18OH (all N) and 16OH (low-to-moderate N) fragments conform to an unconstrained-dynamics prior distribution. A slight propensity for Π(A') in excess of this expectation is seen for the 16OH (high N) fragments. These new results are discussed in terms of possible insertion and abstraction mechanisms for the reaction.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.463198

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

4

Electronic Resource

Pentameral Symmetry in Echinoderms (1967)

STEPHENSON, D. G.

[s.l.] : Nature Publishing Group

Nature 216 (1967), S. 994-994

add to mindlist on the mindlist

Details

ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] Nichols has looked for a reason for pentamerism in the life of modern echinoderms, but the evolution of echino-derms is a continuous process which has gone on since Pre-Cambrian times3. Once the pentameral condition had been established at some time in the past, in many members of ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/216994a0

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

5

Electronic Resource

An AP-1-like motif in the first intron of human Proα1(I) collagen gene is a critical determinant of its transcriptional activity (1992)

Katai, Hitoshi ; Stephenson, Jane D. ; Simkevich, Carl P. ; [et al.]

Springer

Molecular and cellular biochemistry 116 (1992), S. 119-129

add to mindlist on the mindlist

Details

ISSN: 1573-4919

Keywords: collagen transcription ; intronic Ap-1 ; fos jun trans-acting factors

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Abstract The first intron of the human Proα1(I) collagen gene contains an orientation-dependent enhancer composed of both positive and negative cis-acting elements involved in the transcriptional regulation of this gene. Deletion of a 360 bp Sau 3A intronic fragment spanning nucleotide + 494 to + 854 (S360) resulted in dramatic down-regulation of pCOL-KT (Thompson et al., J Biol Chem 266: 2549–2556, 1991). Using a DNaseI protection assay, we demonstrate a single footprint located at + 590 to + 615 in the S360 fragment; nuclear extracts prepared from mesenchymal and nonmesenchymal cells exhibited similar binding characteristics. A double stranded oligonucleotide representing a consensus Ap-1 binding sequence competed with S360 for binding. In contrast to what occurred in response to S360 deletion which was always accompanied by reduced expression, the deletion of the Ap-1 binding site (+ 598 to + 604) caused either increased or decreased expression of the reporter gene depending on the target cell. Site-directed mutations in the Ap-1-like cis-element of Proα1(I) were also tested in transient expression assays. Consistent with the paradoxical results of Ap-1 deletion, we observed that the functional consequences of mutations in the Ap-1 site also varied in different cells. In A204 cells, one point mutation, which resulted in the loss of protein binding to S360, led to increased CAT activity while another point mutant, which retained binding of the Ap-1 like trans-acting factor(s), showed decreased CAT expression. The effects of these two mutations in the HFL-1 cells were exactly opposite of what was seen for A204 cells. Based on these observations, we postulate that the Ap-1 site plays a critical role in the transcriptional activity of the human Proα1(I) gene. The implications of an apparently dual mode of regulation through a single cis-regulatory element are discussed. (Mol Cell Biochem 118: 119–129, 1992)

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00299391

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

6

Electronic Resource

Leaf surface chemicals fromNicotiana affecting germination ofPeronospora tabacina (adam) sporangia (1992)

Kennedy, B. S. ; Nielsen, M. T. ; Severson, R. F. ; [et al.]

Springer

Journal of chemical ecology 18 (1992), S. 1467-1479

add to mindlist on the mindlist

Details

ISSN: 1573-1561

Keywords: Nicotiana ; Peronospora tabacina ; blue mold ; leaf surface ; chemistry ; diterpenes ; sugar esters

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract A bioassay was used to evaluate the effects of cuticular leaf components, isolated fromN. tabacum, N. glutinosa (accessions 24 and 24a), and 23other Nicotiana species, on germinationof P. tabacina (blue mold). The leaf surface compounds includedα- andβ-4,8,13,-duvatriene-l,3-diols (DVT-diols), (13-E)-labda-13-ene-8α-,15-diol (labdenediol), (12-Z)-labda-12,14-diene-8α-ol (cis-abienol), (13-R)-labda-8,14-diene-13-ol (manool), 2-hydroxymanool, a mixture of (13-R)-labda-14-ene-8α,13-diol (sclareol), and (13-S)-labda-14-ene-8α,13-diol (episclareol), and various glucose and/or sucrose ester isolates. The above in acetone were applied onto leaf disks of the blue moldsusceptibleN. tabacum cv. TI 1406, which was then inoculated with blue mold sporangia. Estimated IC50 values (inhibitory concentration) were 3.0μg/cm2 forα-DVT-diol, 2.9μ/cm2 forβ-DVT-diol, 0.4μg/cm2 for labdenediol and 4.7μg/cm2 for the sclareol mixture. Manool, 2-hydroxymanool, andcis-abienol at application rates up to 30μg/cm2 had little or no effect on sporangium germination. Glucose and/or sucrose ester isolates from the cuticular leaf extracts of 23Nicotiana species and three different fractions fromN. bigelovii were also evaluated for antimicrobial activity at a concentration of 30μg/cm2. Germination was inhibited by 〉20% when exposed to sugar esters isolated fromN. acuminata, N. benthamiana, N. attenuata, N. clevelandii, andN. miersii, and accessions 10 and 12 ofN. bigelovii. These results imply that a number of compounds may influence resistance to blue mold in tobacco.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00993221

Permalink