bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibrational spectra and assignments, normal coordinate analyses, a
b i
n
i
t
i
o calculations, and conformational stability of the propenoyl halides
Authors: Durig J. R. , Berry R. J. , Groner P. 
Published: July 2002

The infrared and Raman (3500–30 cm−1) spectra of gaseous and solid propenoyl bromide, CH2 CHCBrO, have been recorded. The Raman spectrum of the liquid has been obtained and qualitative depolarization values have been measured. The fundamental asymmetric torsion for both the s-trans and s-cis conformers has been observed along with several hot transitions. From these transitions the potential function governing the internal rotation has been determined and the s-trans to s-cis barrier is 1861 cm−1 (5.32 kcal/mol), the trans conformer being more stable by 158±20 cm−1 (452±57 cal/mol). All normal modes have been assigned for the s-trans conformer and many of those for the s-cis conformer, based on band contours, depolarization values, and group frequencies. A normal coordinate calculation has been carried out by utilizing a modified valence force field to calculate the frequencies and the potential energy distribution for both conformers. Temperature studies of the Raman spectra of gaseous propenoyl fluoride and chloride and of the liquid phases of propenoyl chloride and bromide have been used to obtain the enthalpy differences between the s-trans and s-cis conformers for these compounds. For the bromide and chloride the s-trans conformer is clearly the more stable form but the data are inconclusive for the fluoride. Complete equilibrium geometries have been determined for both rotamers of the fluoride
and chloride by ab initio Hartree–Fock gradient calculations employing both 3-21G and 6-31G* basis sets. The structural parameters are compared to those suggested from microwave and/or electron diffraction studies of these molecules. Both calculations are consistent with the s-trans conformation being thermodynamically preferred for the fluoride molecule and the s-cis conformation for the chloride, which is contrary to the experimental data for the chloride. The 3-21G basis set was used to obtain the ab initio force constants and frequencies for the s-trans and s-cis conformers of both the fluoride and chloride with fixed scaling, variable scaling, and without scaling factors. These results required several reassignments of fundamentals for both conformers of both molecules. Improved vibrational data for both the fluoride and chloride were very valuable for the reassignments. These results are compared with the corresponding quantities for some similar molecules.
A crossed laser-molecular beam study of the one and two photon dissociation dynamics of ferrocene at 193 and 248 nm
Authors: Ray Urmi , Hou Hui Qi , Zhang Zhvangjian , Schwarz Wolfgang , Vernon Matt 
Published: July 2002

A crossed laser-molecular beam study of the one and two photon dissociation mechanism of bis (cyclopentadienyl) iron (ferrocene, FeCp2) has been performed at 193 and 248 nm. By combining electron bombardment mass spectroscopy with time-of-flight (TOF) measurements, the photodissociation mechanism at 193 nm is shown to have two distinct mechanisms. (1) FeCp2+hν→FeCp*+Cp; (2) FeCp+2hν→FeCp+Cp, FeCp→Fe+Cp. For the first mechanism, which accounts for less than 5% of the photodissociation events, the FeCp* velocity distribution is quantitatively consistent with a statistical dissociation producing FeCp in an excited, ligand field electronic state. The velocity distributions of the Cp and Fe fragments produced by the second mechanism (FeCp is an unstable intermediate) are also in excellent agreement with microcanonical calculations for both Cp elimination steps using the known metal–ligand bond energies of ferrocene. For the second mechanism, dissociation occurs on the lowest potential energy surface for each Cp elimination. Although one photon is energetically sufficient to remove one Cp ligand from ferrocene, RRKM calculations of the lifetime indicate that Cp elimination is extremely slow for dissociation along the ground electronic state potential energy surface. Hence, after internal conversion to the ground electronic state, the large photon absorption cross section (∼4 Å2) for the experimental irradiation conditions allows additional photons to be absorbed until the dissociation rate exceeds the up pumping rate. The large photon energy causes the dissociation rate to increase by many orders of magnitude for each additional photon absorbed. Consequently, there is strong selectivity for the total number of photons absorbed. Both mechanisms, occurring on two different electronic potential energy surfaces, suggest that dissociation induced by excitation of the ligand-to-metal charge transfer states accessed at 193 nm can be quantitatively described as a statistical, unimolecular decomposition. At 248 nm, the measured product velocity distributions are qualitatively consistent with the mechanism deduced from the 193 nm results, but the energy available for translation at this wavelength is too small to extract quantitative product
translational energy distributions which are required to independently test the applicability of the statistical dissociation model.
Molecular dynamics simulations of the structure and dynamics of confined polymer melts
Authors: Bitsanis I. , Hadziioannou G. 
Published: July 2002

We performed a series of molecular dynamics simulations investigating the static and dynamic properties of polymer melts confined between planar solid surfaces. The solid–melt interface was found to be very narrow (approximately two segment diameters) and independent of chain length. Inside the interface the segment density profile was oscillatory, the bond orientation altered between directions parallel and normal to the solid surface, and the chain ends accumulated very close to the wall (in the absence of strong wall–segment attraction). The oscillations of the segment density profile were weaker and were dampened faster than those of a simple fluid density profile next to the same solid surface. This reflected the reduced ability of sequences of connected segments (chains) to layer themselves against a solid surface because of restrictions on their configurations imposed by the chain connectivity requirement. This effect made the solid–melt interface even narrower than that of a simple fluid. Only the chain portions lying inside the interface had their shape affected by the wall.
Chain statistical segments inside the interface assumed orientations parallel to the wall. In the absence of wall–segment attraction, the size of the statistical segments inside the interface was unaffected. This situation resulted in an apparent decrease of the radius of gyration normal to the wall an apparent increase of the radius of gyration parallel to the wall and spatial independence of the total radius of gyration. The wall effect was gradually diminished and chains assumed their bulk dimensions when their center-of-mass was so far from the solid surface that no portions of the chain could reach the interface (i.e., at a distance comparable to the bulk radius of gyration). The microscopic dynamics of chain portions inside the interface were strongly anisotropic. The mobility increased in the direction parallel to the wall and decreased normal to the wall. This fact was caused by the angular asymmetry of the segment–segment collisions inside the interface, i.e., by the same mechanism that induces the segment layering. The total mobility inside the neutral wall–melt interface was identical with that in the bulk reflecting the fact that the average segment density inside the interface had essentially the bulk value. The presence of strong wall–segment attraction increased the average interfacial density above the bulk value and lowered the mobility of the interfacial chain portions in all directions. The mean-square displacement of the chain center-of-mass during a certain time interval was affected by the solid only if the chain had a portion of itself inside the interface for a fraction of this time interval. The longest relaxation time of the chains, a property that cannnot be localized properly on a length scale smaller than the interfacial width, exhibited a weak and strongly diminishing with chain length spatial dependence.
Potential energy surfaces for Ir+H2 and Ir++H2 reactions
Authors: Balasubramanian K. , Dai Dingguo 
Published: July 2002

Potential energy surfaces of 10 electronic states of IrH2 and 12 electronic states of IrH+2 are computed. A complete active space multi-configuration self-consistent field (CAS-MCSCF) followed by multireference configuration interaction (MRCI) calculations which included up to 270 000 configurations are employed. In addition spin–orbit effects are studied using the relativistic configuration interaction (RCI) method. It is found that the Ir(2F) state inserts spontaneously into H2 to form a stable IrH2 molecule in a 2A1 ground state which is 28 kcal/mol more stable than Ir(4F)+H2 in the absence of spin–orbit effects. The spin–orbit coupling of the quartet and doublet states provides nonzero transition probability for the insertion of Ir (4F) state into H2. The 3P state of Ir+ was found to insert spontaneously into H2 to form the 3A2 ground state of IrH+2 which is 30 kcal/mol more stable than Ir+(5D)+H2.
An excited singlet state of Ir+ also was found to insert into H2 spontaneously. The spin–orbit couplings of quintet and triplet states of IrH+2 at the crossing of these curves provide nonzero transition probability for the insertion of Ir+ (5D) into H2. The bent E ground state of IrH2 in the C22v group was found to be a 63% 2A1, 16% 2B1 and 17% 2A2 mixture. This strong mixing induces a large H–Ir–H bond angle change of 9.5° in the E(III) state of IrH2. The 3A2 (A1) ground state of IrH+2 was found to be a 63% 3A2, 15% 3B2, 12% 3B1 and 7% 1A1 mixture. This strong spin–orbit mixing induces a θe change of almost 9° in the ground state of IrH+2. The adiabatic ionization potential including spin–orbit effects for IrH2 and Ir are calculated as 8.2 and 8.6 eV, respectively. The ground state of IrH2 was found to be ionic (μe=2.2 D) with Ir+H− polarity exhibiting Ir(6s0.756p0.125d8.06) hybridization. The IrH+2 ion in its 3A2 state exhibits Ir+(6s0.626p0.125d7.51) hybridization character.
Laser preparation and probing of initial and final orbital alignment in collision-induced energy transfer Ca(4s5p, 1P1) +He→Ca(4s5p, 3P2)+He
Authors: Smith Christopher J. , Driessen Jan P. J. , Eno Larry , Leone Stephen R. 
Published: July 2002

In a crossed beam atomic energy transfer experiment, relative cross sections are measured between initial and final magnetic substates of atomic orbitals in a three vector correlation experiment. A pulsed laser beam prepares Ca(4s5p 1P1) in a single magnetic sublevel ‖j1mi〉 with respect to the laser polarization vector. Subsequent collision with He at a well-defined relative velocity yields Ca(4s5p 3P2). The near-resonant Ca(4s5p 3P2) is probed by a second polarized pulsed laser, revealing its magnetic sublevel ‖j2mf〉 distribution with respect to the probe laser polarization vector. The experiment is analyzed in the collision frame where the direction of the initial relative velocity vector serves as the quantization axis. In this frame, the initial and final Ca states are characterized by substates ‖j1m1〉 and ‖j2m2〉, respectively. Fourteen collision frame cross sections are needed to describe the energy transfer completely. Eight of these cross sections are real and positive (conventional type—describing population transfer) and six are complex (coherence type—containing phase information). By symmetry, only 15 unique parameters for the real and imaginary parts of the cross sections are required, nine of which are obtained here using linear polarizations and collinear laser beams.
Possible cases for circularly polarized light are also tabulated; measurement of these cases would provide several more parameters. For initial parallel preparation of the 1P1 p orbital with respect to the relative velocity (m1=0), the final 3P2 state is highly aligned in the m2=±1 and m2=±2 sublevels. Initial preparation of the p orbital perpendicular to the relative velocity vector (m1=±1) produces an aligned 3P2 state with greater population in the m2=0 and m2=±1 sublevels compared to the m2=±2 sublevels. Using the coherence information and symmetry, orientation cross sections are obtained into the m2=±1 sublevels (i.e., m preserving 1→1 and m-changing 1→−1) and are nearly identical. Preparation of the Ca p orbital perpendicular to the initial relative velocity enhances the state-specific collisional transfer of 1P1→3P2 by a factor of 2.2±0.2 over initial parallel preparation.
Isomeric structures of the electronically excited acetylene⋅Ar complex: Spectroscopy and potential calculations
Authors: Ju S. S. , Cheng P. Y. , Hahn M. Y. , Dai H. L. 
Published: July 2002

Acetylene⋅Ar complex in the S1 state has been characterized through laser fluorescence excitation spectra in the acetylene Ã←X̃, 3n0 (n=0–4) bands region. Two isomeric structures have been determined for the acetylene(Ã)⋅Ar complex from rotational band analysis, even though only one structure was known to exist for the ground state acetylene(X̃)⋅Ar. The in-plane isomer has the Ar atom situated in the molecular plane of the trans-bent acetylene, 3.77 Å from the acetylene center of mass and tilted from the H atoms. The out-of-plane isomeric structure, directly inverted from the rotational constants, has argon 3.76 Å away from the acetylene center of mass and 18° tilted from the C2 rotational axis. This structure is most likely due to large amplitude bending motions away from the equilibrium position which is along the C2 axis. Axis switching effect in the rotational band analysis for both isomers has been examined and found to be negligible. (Formulas for calculating the three-dimensional axis switching angles are detailed in the Appendix.) Three van der Waals vibrational mode frequencies have been determined from the vibrational progressions in the spectra; the stretching fundamental of the out-of-plane isomer is 28 cm−1; the in-plane bending fundamental, and the out-of-plane bending first overtone of the in-plane isomer are 11 and 17 cm−1, respectively.
The isomeric structures have been compared with the results from a pairwise-atom potential calculation with parameters transferred from the ones previously derived for C2H4⋅Ar potential calculations. It was found that when the set of parameters that most closely reflects the electronic density distribution in C2H2(Ã) orbitals was used, two potential minima mimicking the two isomeric structures were generated. This potential calculation can even qualitatively reproduce the complex spectral shift induced by the ν3 mode excitation in acetylene. Combining the observed spectral shifts and previous experimental and theoretical studies of acetylene(X̃)⋅Ar, we have estimated the binding energy of the out-of-plane C2H2(Ã)⋅Ar isomer to be 179 cm−1, and that of the in-plane isomer to be 170 cm−1.
Influence of a macrolide antibiotic, roxithromycin, on mast cell growth and activation in vitro
Authors: Shimane Toshikazu , Asano Kazuhito , Suzuki Mayumi , Hisamitsu Tadashi , Suzaki Harumi 
Published: July 2002

Background: Long‐term administration of macrolide antibiotics is recognized to be able to favorably modify the clinical condition of inflammatory diseases, such as diffuse panbronchiolitis and cystic fibrosis. However, the precise mechanisms by which macrolide antibiotics could improve clinical conditions of the patients
are not well understood.Aim: The present study was designed to examine the influence of macrolide antibiotics on effector cell functions responsible for inflammation through the choice of roxithromycin (RXM) and mast cell.Methods: Mast cells were induced by long‐term culture of splenocytes from BALB/c mice. RXM was added to the cultures at seeding and then every 4‐5 days, when the culture medium was replaced with a fresh one. The influence of RXM on mast cell growth was evaluated by counting the number of cells grown on the 16th day. We also examined the influence of RXM on mast cell activation by examining histamine release and inflammatory cytokine secretion.Results and conclusion: RXM could not inhibit mast cell growth, even when splenocytes were exposed to 100μg/ml of RXM throughout the entire culture periods. RXM also could not suppress histamine release from cultured mast cells in response to nonimmunological and immunological stimulations. However, RXM could suppress inflammatory cytokine, interleukin‐1β, interleukin‐6, granulocyte macrophage‐colony stimulating factor and tumor necrosis factor‐α, secretions induced by concanavalin A stimulation at a concentration of as little as 0.5μg/ml. These results may suggest that RXM modulated the ability of mast cells to secrete inflammatory cytokines and results in improvement of clinical condition of chronic inflammatory diseases.
Fatty acid ethyl esters: nonoxidative metabolites of ethanol
Authors: LAPOSATA MICHAEL 
Published: July 2002

AbstractThe story of fatty acid ethyl (FAEE) encompasses nearly 40 years of research. For more than half of this time, the investigation was limited to documenting the presence of ethyl ester synthesis in different cells and tissues. In the last three years, increasing evidence has emerged that FAEE contribute to ethanol‐induced organ damage, with a variety of different mechanisms proposed for mediation of this toxic effect. In addition, multiple enzymatic activities associated with FAEE formation have been described. Independent of their role in mediating cell injury, it has very recently been shown that FAEE are useful short‐term and long‐term serum markers of ethanol intake, given their appearance in the blood rapidly after ethanol ingestion and their presence when ethanol is no longer detectable.
Reliable Establishment of Human Sarcoma Xenografts in the Nude Rat
Authors: Tinkey Peggy T. , Milas Mira , Pollock Raphael E. 
Published: July 2002

Purpose. The ability to establish consistent human tumor xenografts in
experimental animals is a crucial part of preclinical investigations.The goal of this study was
to develop a method of establishing a human tumor xenograft in the leg of a nude rat for
evaluation of new surgical and molecular methods of treatments of human extremity
sarcoma.Methods and results. Initial attempts to produce sarcoma nodules by
subcutaneous injection of a human leiomyosarcoma tumor cell suspension (SKLMS‐1)
resulted in tumor nodule formation in only four of 10 sites (40%).The xenograft method
was modified to include younger nude rats of a different source and substrain
(HSD:rnu/rnu, 5–9 weeks old), treated with 500 cGy whole‐body irradiation, and the
transplantation of tumor cells or small tumor fragments which had been embedded
in Matrigel.These changes improved the tumor take rate per site to 52/52 (100%).Tumor
nodules demonstrated rapid and progressive growth and histological features consistent
with the original human sarcoma.Discussion. Successful human leiomyosarcoma establishment in
these nude rats permits the investigation of sarcoma biology and treatment with surgical
procedures for which a mouse model would be inadequate. In this study we identified
modifications in technique which enhanced the xenografting of a leiomyosarcoma cell
line in nude rats; these techniques may increase tumor take rates for other tumor types
as well.
Malignant Hemangiopericytoma Arising in Neurofibromatosis: A CaseReport with Histological, Immunohistochemical and UltrastructuralStudies
Authors: Wang Jun , Vargas Hernan , Gaal Karl , Wang Xia , Peng Shi-Kaung 
Published: July 2002

Subject. A 27‐year‐old Hispanic male with clinical manifestation of
neurofibromatosis type 1 developed chronic constipation and urination difficulty along with
recently increased abdominal bloating and anorexia. He also noted 40 lbs weight loss
over period of 1 year. Physical and radiographic examinations revealed a large mass in the
right pelvic fossa.Results. The surgically removed tumor was demonstrated,
histologically, immunohistochemically, and ultrastructurally, to be a malignant
hemangiopericytoma.Discussion.Although non‐neurogenic tumors associated with neurofibromatosis
have been reported in these patients, only one hemangiopericytoma case has been found in the English literature. We report here another case of this rare malignant
hemangiopericytoma in a patient with neurofibromatosis.
Selenium, the Element of the Moon, in Life on Earth
Authors: Flohé Leopold , Andreesen Jan R. , Brigelius‐Flohé Regina , Maiorino Matilde , Ursini Fulvio 
Published: July 2002

AbstractThe present status of selenium biochemistry is reviewed with particular emphasis on biomedical problems related to the selenium status of humans and experimental animals. Historical milestones of selenium biochemistry starting from the identification of the first selenoenzymes up to the elucidation of prokaryotic and eukaryotic selenoprotein boisynthesis are compiled. Topical hypotheses on the biological role of selenium in general and of individual selenoproteins in respect to antioxidant defense, redox regulation of metabolic processes, thyroid function, spermatogenesis, oncogenesis, and atherogenesis are critically evaluated.
Counting solutions to trinomial Thue equations: a different approach
Authors: Thomas Emery 
Published: July 2002

We consider the problem of counting solutions to a trinomial Thue equation — that is, an equation

(

∗

)

|

F
(
x
,
y
)

|

=
1
,

\begin{equation*} |F(x,y)| = 1,\tag {$*$} \end{equation*}

where

F
F

is an irreducible form in

Z
[
x
,
y
]

Z[x,y]

with degree at least three and with three non-zero coefficients. In a 1987 paper J. Mueller and W. Schmidt gave effective bounds for this problem. Their work was based on a series of papers by Bombieri, Bombieri-Mueller and Bombieri-Schmidt, all concerned with the “Thue-Siegel principle" and its relation to

(
∗
)

(*)

. In this paper we give specific numerical bounds for the number of solutions to

(
∗
)

(*)

by a somewhat different approach, the difference lying in the initial step — solving a certain diophantine approximation problem. We regard this as a real variable extremal problem, which we then solve by elementary calculus.
Simultaneous Pell equations
Authors: Anglin W. 
Published: July 2002

Let

R
R

and

S
S

be positive integers with

R
>
S

R>S

. We shall call the simultaneous Diophantine equations

x
2

−
R

y
2

a
m
p
;
=
1
,

z
2

−
S

y
2

a
m
p
;
=
1

\begin{align*} x^2-Ry^2&=1,\ z^2-Sy^2&=1 \end{align*}

simultaneous Pell equations in

R
R

and

S
S

. Each such pair has the trivial solution

(
1
,
0
,
1
)

(1,0,1)

but some pairs have nontrivial solutions too. For example, if

R
=
11

R=11

and

S
=
56

S=56

, then

(
199
,
60
,
449
)

(199, 60, 449)

is a solution. Using theorems due to Baker, Davenport, and Waldschmidt, it is possible to show that the number of solutions is always finite, and it is possible to give a complete list of them. In this paper we report on the solutions when

R
>
S
≤
200

R>S\le 200

.
Transcription regulatory region analysis using signal detection and fuzzy clustering.
Authors: Pickert L , Reuter I , Klawonn F , Wingender E 
Published: July 2002

Abstract
MOTIVATION: Presently available programs for the recognition of potential transcription factor binding sites in genomic sequences generally yield a huge amount of output. These output lists have to be filtered to obtain biologically significant elements, which is highly laborious work to be done manually. RESULTS: We developed a strategy for systematic verification and improvement of the underlying profiles, and for their contextual analysis by a fuzzy clustering approach using non-redundant libraries of search profiles as a prerequisite. AVAILABILITY: The tools mentioned in the paper are available upon request. CONTACT: ewi@gbf.de