bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport of the new chemotherapeutic agent β-
d
-glucosylisophosphoramide mustard (D-19575) into tumor cells is mediated by the Na
+
-
d
-glucose cotransporter SAAT1
Authors: Veyhl Maike , Wagner Katharina , Volk Christopher , Gorboulev Valentin , Baumgarten Katharina , Weber Wolf-Michael , Schaper Marianne , Bertram Barbara , Wiessler Manfred , Koepsell Hermann
Published: July 2002

For β-
d
-glucosylisophosphoramide mustard (β-
d
-Glc-IPM), a new alkylating drug in which isophosphoramide mustard is stabilized, a higher selectivity and lower myelotoxicity was observed than for the currently used cytostatic ifosfamide. Because β-
d
-Glc-IPM is hydrophilic and does not diffuse passively through the lipid bilayer, we investigated whether a transporter may be involved in the cellular uptake. A variety of cloned Na
+
-sugar cotransporters were expressed in
Xenopus
oocytes, and uptake measurements were performed. By tracer uptake and electrical measurements it was found that β-
d
-Glc-IPM was transported by the low-affinity Na
+
-
d
-glucose cotransporter SAAT1, which had been cloned from pig and is also expressed in humans. At membrane potentials between −50 and −150 mV, a 10-fold higher substrate affinity (
K
m
≈ 0.25 mM) and a 10-fold lower
V
max
value were estimated for β-
d
-Glc-IPM transport than for the transport of
d
-glucose or methyl-α-
d
-glucopyranoside (AMG). Transport of β-
d
-Glc-IPM and glucose by SAAT1 is apparently performed by the same mechanism because similar sodium dependence, dependence on membrane potential, electrogenicity, and phlorizin inhibition were determined for β-
d
-Glc-IPM,
d
-glucose, and AMG. Transcription of human SAAT1 was demonstrated in various human carcinomas and tumor cell lines. In one of these, the human carcinoma cell line T84, phlorizin inhibitable uptake of β-
d
-Glc-IPM was demonstrated with substrate saturation and an apparent
K
m
of 0.4 mM. The data suggest that the Na
+
-
d
-glucose cotransporter SAAT1 transports β-
d
-Glc-IPM into human tumor cells and may accumulate the drug in the cells. They provide an example for drug targeting by employing a plasma membrane transporter.
El Niño and the related phenomenon Southern Oscillation (ENSO): The largest signal in interannual climate variation
Authors: Wang Hui-Jun , Zhang Ren-He , Cole Julie , Chavez Francisco
Published: July 2002

El Niño and the related phenomenon Southern Oscillation
(ENSO) is the strongest signal in the interannual variation of
ocean-atmosphere system. It is mainly a tropical event but its impact
is global. ENSO has been drawing great scientific attention in many
international research programs. There has been an observational system
for the tropical ocean, and scientists have known the climatologies of
the upper ocean, developed some theories about the ENSO cycle, and
established coupled ocean-atmosphere models to give encouraging
predictions of ENSO for a 1-year lead. However, questions remain about
the physical mechanisms for the ENSO cycle and its irregularity,
ENSO-monsoon interactions, long-term variation of ENSO, and increasing
the predictive skill of ENSO and its related climate variations.
Cytidine 5′-triphosphate-dependent biosynthesis of isoprenoids: YgbP protein of
Escherichia coli
catalyzes the formation of 4-diphosphocytidyl-2
-C
-methylerythritol
Authors: Rohdich Felix , Wungsintaweekul Juraithip , Fellermeier Monika , Sagner Silvia , Herz Stefan , Kis Klaus , Eisenreich Wolfgang , Bacher Adelbert , Zenk Meinhart H.
Published: July 2002

2
-C
-methylerythritol 4-phosphate has been established recently as an intermediate of the deoxyxylulose phosphate pathway used for biosynthesis of terpenoids in plants and in many microorganisms. We show that an enzyme isolated from cell extract of
Escherichia coli
converts 2
-C
-methylerythritol 4-phosphate into 4-diphosphocytidyl-2
-C
-methylerythritol by reaction with CTP. The enzyme is specified by the hitherto unannotated ORF
ygbP
of
E. coli
. The cognate protein was obtained in pure form from a recombinant hyperexpression strain of
E. coli
harboring a plasmid with the
ygbP
gene under the control of a T5 promoter and lac operator. By using the recombinant enzyme, 4-diphosphocytidyl-[2-
14
C]2
-C
-methylerythritol was prepared from [2-
14
C]2
-C
-methylerythritol 4-phosphate. The radiolabeled 4-diphosphocytidyl-2
-C
-methylerythritol was shown to be efficiently incorporated into carotenoids by isolated chromoplasts of
Capsicum annuum.
The
E. coli
ygbP
gene appears to be part of a small operon also comprising the unannotated
ygbB
gene. Genes with similarity to
ygbP
and
ygbB
are present in the genomes of many microorganisms, and their occurrence appears to be correlated with that of the deoxyxylulose pathway of terpenoid biosynthesis. Moreover, several microorganisms have genes specifying putative fusion proteins with
ygbP
and
ygbB
domains, suggesting that both the YgbP protein and the YgbB protein are involved in the deoxyxylulose pathway. A gene from
Arabidopsis thaliana
with similarity to
ygbP
carries a putative plastid import sequence, which is well in line with the assumed localization of the deoxyxylulose pathway in the plastid compartment of plants.
Diversity and distribution of nicotinic acetylcholine receptors in the
locus ceruleus
neurons
Authors: Léna Clément , de Kerchove d’Exaerde Alban , Cordero-Erausquin Matilde , Le Novère Nicolas , del Mar Arroyo-Jimenez Maria , Changeux Jean-Pierre
Published: July 2002

The neurons of the
locus ceruleus
are responsible for most of the noradrenergic innervation in the brain and nicotine potentiates noradrenaline release from their terminals. Here we investigated the diversity and subcellular distribution of nicotinic acetylcholine receptors (nAChRs) in the
locus ceruleus
both somatically, by combining single-cell reverse transcription–PCR with electrophysiological characterization, and at the level of nerve terminals, by conducting noradrenaline efflux experiments. The proportion of neurons in the
locus ceruleus
expressing the nicotinic subunit mRNAs varied from 100% (β2) to 3% (α2). Yet, two populations of neurons could be distinguished on the basis of the pattern of expression of nAChR mRNAs and electrophysiological properties. One population (type A) of small cells systematically expressed α3 and β4 mRNAs (and often α6, β3, α5, α4), and nicotinic agonists elicited large currents with a potency order of cytisine > nicotine. Another population (type B) of cells with large soma did not contain α3 and β4 mRNAs but, systematically, α6 and β3 (and often α4) and responded to nicotinic agonists in the order of nicotine > cytisine. The nicotinic modulation of noradrenaline release in the hippocampus displayed an order of potency nicotine > cytisine, suggesting that noradrenergic terminals in the hippocampus originate largely from type B cells of the
locus ceruleus
. Accordingly, immunocytochemical labeling showed that β3 is present in hippocampal terminals. The α6β3β2(α4) heterooligomer thus behaves as the main nicotinic regulator of the ceruleo–hippocampal pathway.
The Representation of Knowledge in Minds and Machines
Authors: Kintsch Walter
Published: July 2002

Human knowledge can be represented as a propositional network in which the meaning of a node is defined by its position in the network. That is, the relationship between a node and its neighbours determines how this node is used in language understanding and production, i.e., its meaning. The propositions that make up such a network are predicate‐argument structures with time and location slots. Schemas, frames, and production rules can be expressed in the same formalism. Implications for this contextual view of meaning are discussed. Since the construction of such a propositional network depends on hand coding and is therefore impractical, an alternative automatic statistical procedure is explored that yields a high‐dimensional semantic space. Vectors in this space correspond to nodes in the propositional network, in that the meaning of a vector in the Latent Semantic Analysis space is given by its neighbouring vectors in that space.
General Practitioners' views of home detoxification
Authors: ROCHE ANN M. , WATT KERRIANNE , FISCHER JANE
Published: July 2002

There is a growing movement towards community‐based health care for the treatment and management of alcohol and drug problems across Australia. In spite of substantial evidence to support the clinical efficacy, cost‐effectiveness, and the utility of home detoxification, it is not an activity that has been readily embraced by Australian General Practitioners (GPs). Thus, GPs' views on this issue are vital if there is to be any form of viable home detoxification programme for alcohol and/or other drugs. A qualitative study was undertaken to determine General Practitioners' views in regard to alcohol and drug home detoxification. A qualitative data collection method, focus groups, was used. Focus group participants were obtained from a maximum variation sampling technique. Twelve focus groups were conducted in rural and metropolitan Queensland Australia, over a four‐month period. Fifty‐two participants (43 general practitioners and 9 other health professionals, 20 females and 32 males). Mean age was 40.5 years (age range 19–70). Views about home detoxification were dependent on level of experience with substance abuse treatment. Overwhelmingly, GPs argued that for home detoxification to become viable, there would need to be a more responsive infrastructure, clear policy guidelines, training and more reasonable remuneration than currently exists. GPs require improved training in addiction and drug and alcohol problems. Revised remuneration schemes will facilitate better GP management of complex chronic problems such as addiction. Even though GPs' held quite negative views about alcohol and drug dependent patients there was a high level of willingness to become involved in their treatment and support. Although the clinical efficacy of home detox has been demonstrated GPs have understandably mixed views about their potential involvement. Improved training, support and resourcing is needed to substantially facilitate the expansion of GPs' role into this growing area of care.
A Case Study in Early Mathematical Economics: Pietro Verri and Paolo Frisi, 1772
Authors: Tubaro Paola
Published: July 2002

In eighteenth-century Italy a number of interesting efforts were made to apply mathematical methods to economic analysis. Scholars living in the Milan area were especially keen on mathematizing economic issues. R. D. Theocharis identified a common current of thought, which he called the Milanese School, in his pioneering research on early mathematical economics (Theocharis 1983, p. 2).
Gas Chromatographic and Mass Spectrometric Determination of Hemoglobin Adducts of 1,3-Dinitrobenzene and 1,3,5-Trinitrobenzene in Shrew Cryptotis Parva
Authors: Myers Steven R. , Pinorini-Godly Maria T. , Reddy Tirumuru V. , Daniel F. Bernard , Reddy Gunda
Published: July 2002

1,3-Dinitrobenzene (DNB) and 1,3,5-trinitrobenzene (TNB) are used primarily in explosive compositions and munitions and have been detected as environmental contaminants of surface waters as well as ground waters near production waste disposal sites. Hemoglobin (Hb) adducts have recently been proposed as biological markers of exposure assessment for various environmental compounds, including nitroaromatics. In the present study, we have investigated the formation of DNB and TNB hemoglobin adducts in vivo and in vitro in the blood of shrew (Cryptotis parva). DNB and TNB hemoglobin adducts were detected by gas chromatography/mass spectrometry (GC/MS) after either basic (0.1 N NaOH) or acid (2 N HCl) hydrolysis followed by organic solvent extraction and derivatization of the corresponding amines. The levels of DNB-Hb adducts detected after basic hydrolysis (238.7 & pm; 50.2 pg/mg Hb) are higher than the corresponding levels detected after acid hydrolysis (52.5 & pm; 16.2 pg/mg Hb). For the TNB-Hb the levels after acid hydrolysis (132.2 & pm; 37.8 pg/mg Hb) are higher than the levels detected after basic hydrolysis (44.7 & pm; 15.3 pg-mg Hb). These results demonstrate the effectiveness of the hemoglobin adduct model for monitoring exposure to nitroaromatics.
The resolution of lexical ambiguity with reference to context in dementia of the Alzheimer's type
Authors: Chenery Helen J. , Ingram John C. L. , Murdoch Bruce E.
Published: July 2002

The present study investigated how a dementing illness such as Alzheimer's disease, might affect an individual's recourse to higher order contextual information in the access and integration of lexical material in on‐line discourse comprehension. More specifically, the experiment investigated the priming of homophones in a discourse context, by use of a cross‐modal lexical decision task, and compared the performances of a group of six subjects with mild to moderate dementia of the Alzheimer's type (DAT) with those of a matched control group. The subjects listened to 2‐sentence paragraphs and performed a lexical decision on visually presented targets that followed ambiguous prime words (or homophones) at two inter‐stimulus intervals (ISIs): 330 and 1000msec. When the target was a word, it was either an associate of the prime word, a probable inference suggested by the discourse, or an unrelated word. The control subjects primed both the discourse‐appropriate and discourseinappropriate associate of the homophone at short (330msec) ISIs (but not an appropriate inference word), a finding which supports the exhaustive access model of ambiguity resolution. As the ISI was lengthened to 1000msec, however, the discourse‐appropriate inference word was primed, and reflects the operation of attention‐dependent integrative strategies. The subjects with DAT primed both appropriate associates and inference words at the short ISI. At ISI of 1000msec, the DAT subjects primed the appropriate associate and showed substantial inhibition priming of the inappropriate associate. These results point to disturbances in the selective automatic activation of lexical material, and in the conscious integration and elaboration of lexical material in ongoing discourse comprehension in persons with DAT.
The High Osmolarity Glycerol Response (HOG) MAP Kinase Pathway Controls Localization of a Yeast Golgi Glycosyltransferase
Authors: Reynolds Todd B. , Diane Hopkins B. , Lyons Matthew R. , Graham Todd R.
Published: July 2002

The yeast α-1,3-mannosyltransferase (Mnn1p) is localized to the Golgi by independent transmembrane and lumenal domain signals. The lumenal domain is localized to the Golgi complex when expressed as a soluble form (Mnn1-s) by exchange of its transmembrane domain for a cleavable signal sequence (Graham, T. R., and V. A. Krasnov. 1995. Mol. Biol. Cell. 6:809–824). Mutants that failed to retain the lumenal domain in the Golgi complex, called lumenal domain retention (ldr) mutants, were isolated by screening mutagenized yeast colonies for those that secreted Mnn1-s. Two genes were identified by this screen, HOG1, a gene encoding a mitogen-activated protein kinase (MAPK) that functions in the high osmolarity glycerol (HOG) pathway, and LDR1. We have found that basal signaling through the HOG pathway is required to localize Mnn1-s to the Golgi in standard osmotic conditions. Mutations in HOG1 and LDR1 also perturb localization of intact Mnn1p, resulting in its loss from early Golgi compartments and a concomitant increase of Mnn1p in later Golgi compartments.
ZASP: A New Z-band Alternatively Spliced PDZ-motif Protein
Authors: Faulkner Georgine , Pallavicini Alberto , Formentin Elide , Comelli Anna , Ievolella Chiara , Trevisan Silvia , Bortoletto Gladis , Scannapieco Paolo , Salamon Michela , Mouly Vincent , Valle Giorgio , Lanfranchi Gerolamo
Published: July 2002

PDZ motifs are modular protein–protein interaction domains, consisting of 80–120 amino acid residues, whose function appears to be the direction of intracellular proteins to multiprotein complexes. In skeletal muscle, there are a few known PDZ-domain proteins, which include neuronal nitric oxide synthase and syntrophin, both of which are components of the dystrophin complex, and actinin-associated LIM protein, which binds to the spectrin-like repeats of α-actinin-2. Here, we report the identification and characterization of a new skeletal muscle protein containing a PDZ domain that binds to the COOH-terminal region of α-actinin-2. This novel 31-kD protein is specifically expressed in heart and skeletal muscle. Using antibodies produced to a fragment of the protein, we can show its location in the sarcomere at the level of the Z-band by immunoelectron microscopy. At least two proteins, 32 kD and 78 kD, can be detected by Western blot analysis of both heart and skeletal muscle, suggesting the existence of alternative forms of the protein. In fact, several forms were found that appear to be the result of alternative splicing. The transcript coding for this Z-band alternatively spliced PDZ motif (ZASP) protein maps on chromosome 10q22.3–10q23.2, near the locus for infantile-onset spinocerebellar ataxia.
An Atp-Dependent, Ran-Independent Mechanism for Nuclear Import of the U1a and U2b′′ Spliceosome Proteins
Authors: Hetzer Martin , Mattaj Iain W.
Published: July 2002

Nuclear import of the two uracil-rich small nuclear ribonucleoprotein (U snRNP) components U1A and U2B′′ is mediated by unusually long and complex nuclear localization signals (NLSs). Here we investigate nuclear import of U1A and U2B′′ in vitro and demonstrate that it occurs by an active, saturable process. Several lines of evidence suggest that import of the two proteins occurs by an import mechanism different to those characterized previously. No cross competition is seen with a variety of previously studied NLSs. In contrast to import mediated by members of the importin-β family of nucleocytoplasmic transport receptors, U1A/U2B′′ import is not inhibited by either nonhydrolyzable guanosine triphosphate (GTP) analogues or by a mutant of the GTPase Ran that is incapable of GTP hydrolysis. Adenosine triphosphate is capable of supporting U1A and U2B′′ import, whereas neither nonhydrolyzable adenosine triphosphate analogues nor GTP can do so. U1A and U2B′′ import in vitro does not require the addition of soluble cytosolic proteins, but a factor or factors required for U1A and U2B′′ import remains tightly associated with the nuclear fraction of conventionally permeabilized cells. This activity can be solubilized in the presence of elevated MgCl2. These data suggest that U1A and U2B′′ import into the nucleus occurs by a hitherto uncharacterized mechanism.
Subunit Composition of Pre–T Cell Receptor Complexes Expressed by Primary Thymocytes: CD3δ Is Physically Associated but Not Functionally Required
Authors: Berger Marc A. , Davé Vibhuti , Rhodes Michele R. , Bosma Gayle C. , Bosma Melvin J. , Kappes Dietmar J. , Wiest David L.
Published: July 2002

Maturation of immature CD4−CD8− (DN) thymocytes to the CD4+CD8+ (DP) stage of development is driven by signals transduced through a pre–T cell receptor (TCR) complex, whose hallmark is a novel subunit termed pre-Tα (pTα). However, the precise role of pre-TCRs in mediating the DN to DP transition remains unclear. Moreover, progress in understanding pre-TCR function has been hampered thus far because previous attempts to demonstrate expression of pTα-containing pre-TCRs on the surface of normal thymocytes have been unsuccessful. In this report, we demonstrate for the first time that pTα-containing pre-TCR complexes are expressed at low levels on the surface of primary thymocytes and that these pre-TCR complexes comprise a disulfide-linked pTα–TCR-β heterodimer associated not only with CD3-γ and -ε, as previously reported, but also with ζ and δ. Interestingly, while CD3-δ is associated with the pre-TCR complex, it is not required for pre-TCR function, as evidenced by the generation of normal numbers of DP thymocytes in CD3-δ–deficient mice. The fact that any of the signaling components of the pre-TCR are dispensable for pre-TCR function is indeed surprising, given that few pre-TCR complexes are actually expressed on the surface of primary thymocytes in vivo. Thus, pre-TCRs do not require the full array of TCR-associated signaling subunits (γ, δ, ε, and ζ), possibly because pTα itself possesses signaling capabilities.
Localization of the K+ Lock-in and the Ba2+ Binding Sites in a Voltage-Gated Calcium-Modulated Channel
Authors: Vergara Cecilia , Alvarez Osvaldo , Latorre Ramon
Published: July 2002

Using Ba2+ as a probe, we performed a detailed characterization of an external K+ binding site located in the pore of a large conductance Ca2+-activated K+ (BKCa) channel from skeletal muscle incorporated into planar lipid bilayers. Internal Ba2+ blocks BKCa channels and decreasing external K+ using a K+ chelator, (+)-18-Crown-6-tetracarboxylic acid, dramatically reduces the duration of the Ba2+-blocked events. Average Ba2+ dwell time changes from 10 s at 10 mM external K+ to 100 ms in the limit of very low [K+]. Using a model where external K+ binds to a site hindering the exit of Ba2+ toward the external side (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549–568), we calculated a dissociation constant of 2.7 μM for K+ at this lock-in site. We also found that BKCa channels enter into a long-lasting nonconductive state when the external [K+] is reduced below 4 μM using the crown ether. Channel activity can be recovered by adding K+, Rb+, Cs+, or NH4 + to the external solution. These results suggest that the BKCa channel stability in solutions of very low [K+] is due to K+ binding to a site having a very high affinity. Occupancy of this site by K+ avoids the channel conductance collapse and the exit of Ba2+ toward the external side. External tetraethylammonium also reduced the Ba2+ off rate and impeded the channel from entering into the long-lasting nonconductive state. This effect requires the presence of external K+. It is explained in terms of a model in which the conduction pore contains Ba2+, K+, and tetraethylammonium simultaneously, with the K+ binding site located internal to the tetraethylammonium site. Altogether, these results and the known potassium channel structure (Doyle, D.A., J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Gulbis, S.L. Cohen, B.T. Chait, and R. MacKinnon. 1998. Science. 280:69–77) imply that the lock-in site and the Ba2+ sites are the external and internal ion sites of the selectivity filter, respectively.
The motion of oxygen ions in oxygen
Authors: J Dutton  , P Howells
Published: July 2002

The drift velocities of positive and negative ions produced in a glow discharge in oxygen were measured within the range 5 < E/p
0 < 100 v cm-1 torr-1 (E is the electric field and p
0 the gas pressure reduced to 0 °c) for values of p
0 in the range 7·71 to 0·83 torr.

The results for negative ions were in agreement with previous data on ion species generally believed to be O3
- and O2
-.

In the case of positive ions, on the other hand, the results were quite different from those obtained by previous investigators in that two species of ions were observed. For E/p
0 < 15 v cm-1 torr-1 only the faster species was present, and for E/p
0 > 28 v cm-1 torr-1 only the slower species, but in the intermediate region the results indicated that the ion species interacted with the gas molecules, the dominant species being dependent critically on the experimental conditions.

Measurements were also made of the ratio D/K (D the diffusion coefficient and K the mobility) for the positive ion species.

The drift and diffusion data for the positive ions were used to show that the binding energy of the faster ion species was 0·45 ev. Since this value is in close agreement with that of 0·42 ev previously determined for the binding energy of O4
+, the present results are consistent with the identification of the faster species as O4
+ and the slower species as O2
+, and with the view that for 19 < E/p
0 < 25 v cm-1 torr-1 the reaction between the ions and the gas molecules was of the form O4
+ &rlarr2; O2
+ + O2.

The drift and diffusion data for the slower species were also used to obtain information about the collision cross section of these ions.
R-matrix theory of atomic continuum processes
Authors: I Shimamura
Published: July 2002

A general theory for explicitly antisymmetrised wavefunctions is formulated in terms of a surface operator considered originally by Bloch (1957). A variational principle is presented which directly gives a stationary R-matrix. Using this principle, the existing R-matrix theories are reformulated from a unified point of view and the work of previous authors is re-examined and extended. The eigenchannel method is also discussed and extended with emphasis on the existence of long-range potential.
Cross sections for excitation and ionization in e-He(21,3S) collisions
Authors: D Ton-That  , M R Flannery  , S T Manson
Published: July 2002

Cross sections for the 23S-n3L(n=2-5, L=S-F) excitations and for single ionization in e-He(21,3S) collisions are determined by using the Born approximation. For a given n, the 23S-n3D transitions dominate at intermediate energies and this trend is continued for transitions to the near continuum. For larger energies epsilon of the ejected electron, higher angular momentum l waves progressively dominate. While up to nine partial waves are in general required for convergence of the bound-free form factor, as many as 30 are needed when momentum changes are in the vicinity of the Bethe ridge for large epsilon . Binary-encounter results for ionization are also obtained and agree with the Born values at intermediate energies.
Motional narrowing of Zeeman resonance lineshapes. II. Monte Carlo simulation results
Authors: S F Watanabe  , G S Hayne  , H G Robinson
Published: July 2002

For pt.I see ibid., vol.10, no.5, p.931 (1977). A simple model applicable to a class of high-resolution Zeeman spectroscopy experiments is simulated using Monte Carlo techniques. For individual Legendre polynomial field gradients, h approximately rnPnwith n=1-4, the authors find the autocorrelation function (h( tau )h(t+ tau )), correlation time, relaxation function and lineshape for a range of the narrowing parameter 0.1<< Delta tauc<<10.0. The bounds placed on the correlation time,mintaun<or= tauc<or= tau1, prove to be useful in estimating the width and frequency shift in arbitrary field gradients.
Electronic relativistic effects and Coulomb deflection of the projectile in L-shell ionization of atoms by light ions
Authors: P A Amundsen
Published: July 2002

The semiclassical approximation is applied to the calculation of L-subshell Coulomb ionization of atoms by light ions, using relativistic Coulomb wavefunctions for the electrons. The Coulomb deflection of the projectile is taken into account by the tangential approximation. Numerical results are presented both for total cross sections and for the impact dependence of the ionization probabilities. There is considerable improvement in the agreement with experiment for low-energy projectiles. At high energies the relativistic effects and the deflection effects partially cancel each other.
The spectral distribution of intermediate L-K molecular-orbital radiation in symmetric heavy-ion collisions
Authors: K -H Heinig  , H -U Jager  , H Richter  , H Woittennek  , W Frank  , P Gippner  , K -H Kaun  , P Manfrass
Published: July 2002

Two distinct X-ray continuaC1 and C2 above the characteristic lines are observed in high-energy collisions between atoms with atomic numbers of 28 to 57. This structure is explained by a superposition of K molecular-orbital (KMO) radiation and of an intermediate L-K molecular-orbital (ILKMO) radiation of high intensity which is due to 2p sigma vacancies. In the framework of the dynamical theory of intermediate molecular phenomena and using a scaling of the H2+correlation diagram with screened state-dependent charges good agreement between the shapes of the measured and calculated spectra is obtained.
Continuum electronic wavefunctions in the static-exchange approximation for resonant processes in diatomic molecules. I. Widths for electron capture in the CH+closed-shell molecular ion
Authors: G Raseev  , A Giusti-Suzor  , H Lefebvre-Brion
Published: July 2002

The wavefunction of a low-energy unbound electron in the field of a closed-shell diatomic molecular ion is calculated using a single-centre expansion in the static-exchange approximation. The evaluation is reported of the electronic capture width necessary for the calculation of the dissociative-recombination rate of the CH+ion in its ground state, with a two-centre molecular integral program. The agreement between calculated values for a very low energy (0.01 eV) and extrapolated values from Rydberg states, found both for the quantum defect and the electronic-capture width, establishes the reliability of the direct calculation.
Production of krypton L vacancies in Kr-Kr and Kr-Xe collisions
Authors: R J Fortner  , F W Saris
Published: July 2002

The X-ray production cross sections for the krypton L shell in Kr-Kr and Kr-Xe collisions are reported. The cross sections exhibit an energy dependence characteristic of 'triple-peak' structures in rapidly promoted 4f sigma molecular orbitals. The data suggest that in these collision systems for distances of closest approach less than about 0.1*101-10m the probability of producing two L-shell vacancies is unity.
Model potentials applied to complex-atom-inert-gas interactions
Authors: A R Malvern
Published: July 2002

The model-potential method of Bottcher and Dalgarno (1974, 1975) has been implemented to treat the case of a complex atom (with more than one valence electron around a closed shell) interacting with an inert-gas atom. The formulation, allowing for configuration interaction, is described, and potential curves are presented for excited states of calcium and magnesium interacting with helium and neon.
Elastic scattering of electrons on Ne atoms at intermediate energies
Authors: B L Jhanwar  , S P Khare  , A Kumar Jr
Published: July 2002

A local central potential is employed to investigate the elastic scattering of electrons by neon atoms. The potential accounts for the first-order direct and exchange effects and the second-order polarisation effects. The differential and total elastic cross sections for energies between 100-1000 eV are obtained. The results are in satisfactory agreement with the recent experimental results for E>or=200 eV.
Interpretation of the angular distribution of electrons emitted in Penning ionisation of argon by metastable helium
Authors: V Hoffmann  , H Morgner
Published: July 2002

Extends an existing theory on the angular distribution of Penning electrons to the emission of electrons which have other than sigma symmetry with respect to the internuclear axis. The formulae are applied to experimental data for He(21S, 23S)-Ar. The main results is that the Penning process leads exclusively to He-Ar+states the spatial wavefunctions of which have Sigma symmetry.
Thermal diffusion factors for binary gas systems: Ar-N2, Ar-CO2, He-H2, He-N2O, Kr-N2O and He-NH3
Authors: A G Shashkov  , A F Zolotukhina  , T N Abramenko  , B P Mathur
Published: July 2002

The thermal diffusion factors for six binary systems are measured in a two-bulb metal apparatus as a function of temperature and composition. The values are compared with the available values in the literature, wherever possible, and with the predictions of the Chapman-Enskog kinetic theory involving elastic collisions. The contribution of dipole and quadrupole moments of polar gases to the thermal diffusion factor is estimated according to the theories developed by Mason and co-workers. In general, the thermal diffusion data involving polyatomic and polar gases are not well represented by the available theories, and generation of reliable data may provide considerable guidance and much needed clues for the development of an accurate but tractable theory. A possible explanation of the minima and maxima observed in the thermal diffusion data is advanced.
Excitation of H2vibrational levels (nu⩽4) by low-energy electron impact
Authors: A Klonover  , U Kaldor
Published: July 2002

An ab initio L2-basis-set theory for low-energy electron-molecule scattering is applied to the excitation of the nu =1, 2, 3 and 4 vibrational levels of H2by slow electrons (1-10 eV), with or without simultaneous rotational excitation. An optical potential including direct, exchange and polarisation terms is expanded in a diagrammatic perturbation series and used in the framework of the T-matrix expansion method of Rescigno, McCurdy and McKoy (1975). Calculated integral and differential cross sections agree well with all available experimental data. The static-exchange approximation, on the other hand, gives poor results (2-4 times too low), with the error increasing as one goes to higher vibrational excitations. Polarisation is thus indispensable in a reliable description of vibrational excitation processes.
Energy deposition and electron energy degradation in molecular hydrogen
Authors: D A Douthat
Published: July 2002

Calculations have been made of degradation and sub-excitation spectra in dilute, molecular hydrogen produced by monoenergetic source electrons of 2, 10 and 30 keV. The cross section data of Gerhart for electronic excitation and ionisation were re-examined and refined. Absolute yields for the production of electronic excitations, positive and negative ions and vibrational and rotational excitations, are tabulated. These results were produced by a new code for computation of degradation spectra from the Spencer-Fano equation. The sensitivity of computed spectra to internally consistent variation in the input is examined.
Radial transition integrals involving low or high effective quantum numbers in the Coulomb approximation
Authors: H Van Regemorter  , Hoang Binh Dy  , M Prud'homme
Published: July 2002

A very simple method is proposed for calculating the radial matrix elements and the oscillator strengths for non-hydrogenic atoms in the Coulomb approximation. The method is valid for all cases of interest and in particular for transitions involving high Rydberg states for which previous methods cannot be applied.
Laser-induced fluorescence of gaseous PbS
Authors: B Burtin  , M Carleer  , R Colin  , C Dreze  , T Ndikumana
Published: July 2002

A molecular beam of PbS molecules was excited by a CW Ar+laser in single and multimode operation. Fluorescence spectra induced by the 4880 AA line were recorded and four fluorescence series originating from the nu =7, 8 and 9 levels of the A0+state were analysed. Using a pulsed dye laser, lifetimes of the nu =4, 5, 6, 7 and 8 level of the A0+state, the nu =0, 1, 2 and 3 levels of the B1 state and the nu =21 level of the a1 state were measured. The electronic transition moments of the a-X, A-X and B-X transitions were calculated and the lifetimes of the a, A and B states of PbS are compared with those of PbO.
Properties of Regge pole positions and residues for interatomic potentials
Authors: J N L Connor  , W Jakubetz  , D C Mackay  , C V Sukumar
Published: July 2002

A detailed investigation of the Regge properties of singular intermolecular potentials has been made. Inverse power potentials of the type r-swith s>2 and Lennard-Jones (12, 6) potentials are considered. Exact quantum and semiclassical calculations are carried out for collision systems for which the residue of maximum modulus is of order unity. Good agreement between the exact quantum and semiclassical results is found. The existence of non-linear as well as linear Regge trajectories is established. The accuracy and utility of some simple approximate formulae due to Brander (1966) and Tiktopoulos (1969) for the Regge properties of r-spotentials is investigated. A new approximate formula based on a complex harmonic oscillator formalism is also derived. It is shown that these approximate formulae can be used to understand the main Regge properties of singular intermolecular potentials.
Optical collisions and saturated radiative transition rates
Authors: G Nienhuis
Published: July 2002

The formal structure of the time dependence of the state of an atom in a perturber bath in an intense classical monochromatic radiation field is studied. The authors allow the cross sections of binary collisions to be affected by the radiation field. The result is used to derive an expression for the collision-broadened saturated fluorescence excitation spectrum and absorption rate in terms of a collisional relaxation operator. This operator can be related to the rate of collisionally aided radiative excitation.
Angular distribution in above-threshold ionisation of Xe at 0.53 μm
Authors: F Fabre  , P Agostini  , G Petite  , M Clement
Published: July 2002

The angular distribution of photoelectrons has been investigated experimentally for 'normal' multiphoton ionisation and for above-threshold ionisation of xenon at 0.53 mu m. The first is characterised by a secondary maximum, and both show an isotropic term.
A study of low-energy differential ion-atom scattering. I. Experiment: Li+-Na
Authors: F von Busch  , J Hormes  , D Liesen
Published: July 2002

An experiment is described for measuring differential cross sections of Li+ions scattered by Na atoms at laboratory energies between 25 and 134 eV. Pronounced structure in the elastic cross sections is seen arising from rotational 2 Sigma -1 Pi interactions. The data are compared with a consistent 'quantum' calculation that includes the three lowest molecular states and is based on theoretical potentials and matrix elements taken from the literature. Details of the calculation are given in an accompanying paper. Good agreement is found between experiment and theory.
High-n1Stark-state production by sudden electric-field reversal in Rydberg sodium
Authors: R G Rolfes  , D B Smith  , K B MacAdam
Published: July 2002

By applying bipolar electric-field pulses of about 10 V cm-1, dE/dt approximately=109V cm-1s-1, the authors have demonstrated the conversion of laser-excited Na(nd) Rydberg states (n=30-38) to high-n1Stark states that lie at the top of the n manifold. These states correspond in zero field to orbits of the highest allowed angular momentum l. This transition phenomenon is believed to play an important role in the microwave electric-field ionisation of non-hydrogenic atoms.
Variational study of the hydrogen molecular ion in very strong magnetic fields
Authors: M Vincke  , D Baye
Published: July 2002

The hydrogen molecular ion is studied variationally for m=0 to -4 and gamma =10 to 1000 in the infinite-proton-mass approximation. The variational basis presents respectively Gaussian and exponential behaviours in the transverse and longitudinal directions with respect to the field. Binding and dissociation energies and equilibrium distances are calculated. Except for m=0 and gamma <or=100, the authors' energies improve other results. The dissociation energies and equilibrium distances present a simple behaviour with respect to the magnetic quantum number m and to the field strength gamma .
Electron impact dissociative ionisation of hydrogen, water and hydrogen sulphide
Authors: R B Cordaro  , K C Hsieh  , L C McIntyre Jr
Published: July 2002

The dissociative ionisation of H2, H2O and H2S by electron impact was investigated between electron impact energies of 20 and 45 eV. Protons were the detected fragments, and a time-of-flight method was used to measure the proton kinetic energies. By measuring thresholds for the production of discrete energy groups of protons, it was possible to determine the dissociation limits and kinetic energy distributions for individual electronic states. It was found that autoionising states that lead to dissociation were the major contributors of proton fragments for all of the molecules investigated.
Second-order correlation energy of the argon atom using basis sets of Gaussian-type functions
Authors: B H Wells  , S Wilson
Published: July 2002

The second-order correlation energy of the ground state of the argon atoms is calculated using basis sets of Gaussian-type functions. It is demonstrated that accurate second-order correlation energies can be obtained by employing systematic sequences of even-tempered basis sets of Gaussian-type functions. The pair correlation energies are compared with those obtained by Jankowski et al. (1979) using basis sets of exponential-type functions.
Collisions of Cs-with atoms and molecules
Authors: D Scott  , R L Champion  , L D Doverspike  , M S Huq
Published: July 2002

Presents the results for measurements of the absolute total cross sections for electron detachment sigmae(E) and charge transfer sigmai(E) in low-energy collisions of Cs-with He, Ne, Ar, Kr, Xe, D2, N2, O2, CO, CO2, SO2, N2O, CH4and SF6. In the case of the rare gases, the apparent energetic threshold for detachment is rather high (near E=50 eV); a similar observation has also been made for the Na-and K-projectiles. As before, a curve-crossing model well describes the observed sigmae(E). Structure in sigmae(E) for the CO2target has been attributed to charge transfer to a metastable state of CO2-(2A1). Similarly, in the case of N2O, both sigmae(E) and sigmai(E) exhibit behaviour which suggests that charge transfer to a temporary negative-ion state of that molecule is involved in the collisional dynamics. Charge transfer is also observed to be an important exit channel for other molecules; for example, the value of sigmai(E=30 eV) is about 500 a02for the SF6target.
Breakdown of the adiabatic-nuclei approximation in the rotational excitation of H2by very slow electrons
Authors: K Jung  , K -M Scheuerlein  , W Sohn  , K -H Kochem  , H Ehrhardt
Published: July 2002

Angular dependences of the rotational excitation from ji=1 to jf=3 of H2induced by electrons with a collision energy of 0.6 or 0.2 eV are presented. Comparison with different theories shows that adiabatic-nuclei approximations are no longer valid in this energy range whereas close-coupling and off-shell calculations can qualitatively reproduce the experimental results.
Broadening and shift of the 8p2P12,3/2-7s2S1/2thallium spectral lines perturbed by neon and argon
Authors: R S Dygdaa  , E Lisicki  , J Szudy
Published: July 2002

Experimental studies of the collisional broadening and shift of the 655.0 and 671.4 nm thallium lines perturbed by neon and argon were performed. The results are compared with those calculated on the basis of the van der Waals and the Czuchaj-Sienkiewicz potentials (1984). These results demonstrate that the Lennard-Jones model potential is completely inadequate for the description of pressure effects caused by neon on higher thallium states. The measured values of the broadening and shift by argon are in poor agreement with those computed for the van der Waals potential. Calculations based on realistic potentials reported by Czuchaj and Sienkiewicz give values of the broadening coefficient in good agreement with the experimental data.
Applications of pulsed microwave-microwave double resonance. II. Broadband Fourier transform spectroscopy
Authors: D A Andrews  , J G Baker
Published: July 2002

For pt.I, see ibid., vol.20, p.5675 (1987). Pulsed Fourier transform techniques for the analysis of time-resolved absorption signals have been applied to microwave-microwave double-resonance gas spectroscopy. The resonant frequencies of connected transitions have been identified by a two-dimensional Fourier transform plot, and a novel two-pulse technique which displays spectra over a band exceeding 100 MHz has been introduced. Sample results are presented for the species OCS and ClCN. New spectral features caused by the simultaneous excitation of two pump transitions have been observed and are discussed.
CASSCF-CI potential curves of HCl2+
Authors: B J Olsson  , M Larsson
Published: July 2002

The CASSCF and contracted CI methods have been used to generate electronic wavefunctions and potential energy curves for the3Sigma-,1Delta and3Pi states of HCl2+. Calculations on the ground state of HCl at its equilibrium geometry and dissociation limit were performed and the vertical double ionisation energies were deduced. These results are compared with experimental results following recent PIPICO experiments. Molecular constants and predissociation rates for the3Sigma-and1Delta state, which both possess local minima above their dissociation limits, are given.
On detuning phenomena in cascaded cavity molecular beam masers
Authors: W S Bardo  , D C Laine
Published: July 2002

A quantum mechanical analysis is given for the complex detuning phenomena observed in cascaded cavity molecular beam masers. This interprets observed phenomena in terms of pulse excitation of the particles as they traverse the first cavity, and predicts a range of new phenomena hitherto not observed, corresponding to pulse excitation in the pi to 2 pi range. The behaviour is also explained qualitatively in terms of the geometrical representation of the Schrodinger equation for a two-level system, and by this means is related to observations of the energy states of the particles emerging from the first cavity.
Electron scattering by complex atoms
Authors: P G Burke  , A Hibbert  , W D Robb
Published: July 2002

A theory of electron scattering by complex atoms is developed in which the target atomic eigenstates and pseudostates are written as linear sums of configurations and the incident electron wave function is expanded in terms of orbitals which satisfy logarithmic boundary conditions on the surface of a sphere. The radius of the sphere is chosen so that exchange between the scattered and atomic electrons is only important within the sphere but full allowance must be made for the long range atomic potentials which exist outside of the sphere. Both the bound and the continuum calculations involve a diagonalization of the Hamiltonian in the appropriate basis and these calculations are arranged so that they use the same analytic procedures and computer codes. Finally, the construction of the S-matrix and the cross section matrix is discussed.
Electron densities and drift velocities in a positive column He-Cd laser discharge
Authors: M H Dunn
Published: July 2002

Electron densities and drift velocities have been measured in the positive column of a He-Cd laser discharge under conditions appropriate to laser oscillation at 4416 AA and 3250 AA. In a pure helium discharge the electron drift velocity is proportional to the E/p value of the discharge, and drift velocities measured (3-12 * 106cm s-1for E/p values in the range 4-16 volt cm-1Torr-1) are in agreement with those of earlier investigators for low current densities. The behaviour of drift velocity with E/p can be explained in terms of a momentum transfer cross section for electrons with helium which is inversely proportional to electron velocity. The associated electron collision frequency at unit pressure is 2*109s-1Torr-1. At constant discharge current and helium frequency at unit pressure is 2*109s-1Torr-1. At constant discharge current and helium pressure the presence of a small partial pressure of cadmium in the discharge increases the electron density (by about 40% to 2.5*1012cm-3under conditions appropriate to lasing) and decreases the electron drift velocity and E/p value.
Determination of the transition moment of the B1Σ+-X1Σ+transition in CO
Authors: R E Imhof  , F H Read  , S T Beckett
Published: July 2002

The authors have measured the lifetimes of the first two vibronic levels of the B1Sigma+state of carbon monoxide using the inelastic electron-photon coincidence technique. Their respective values are 21.8+or-0.3 and 15.5+or-0.7 ns. They attribute this dependence on the vibrational quantum number to a very strong dependence of the B-X transition moment on the internuclear distance and have determined this transition moment in the r centroid approximation.
About the electronic shifts of the Stark broadened Lyman- α lines
Authors: M Caby-Eyraud  , Nguyen-Hoe
Published: July 2002

The authors investigate shift and asymmetry of broadened hydrogen lines in plasmas. All contributing multipoles and interactions between states with different principal quantum numbers (quenching effect) have been included in the atom-perturber potential V(t). Numerical results are given for Lyalpha line in the impact limit. Especially, for T=5104K, the shift arising from quenching effect is eight times greater than that arising from quadrupole and monopole.