bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of the reactions of OH radicals with C2H2 and CO
Authors: Perry R. A. , Atkinson R. , Pitts J. N.
Published: February 2003

Absolute rate constants for the reactions of OH radicals with C2H2 (k1) and CO (k2) have been determined using a flash photolysis–resonance fluorescence technique. Rate constants k1 were determined at room temperature over the pressure range 25–400 torr total pressure of argon, and over the temperature range 298–422 °K at ∼200 torr total pressure of argon. k1 was pressure dependent below ∼200 torr total pressure of argon, but was in the high pressure kinetic region at total pressures ?200 torr. The Arrhenius expression in the high pressure region was k1=1.91×10−12e−(620±400)/RT cm3 molecule−1 sec−1. Rate constants k2 were determined at 299±1 °K with argon and SF6 as diluent gases over the pressure range 25–643 torr total pressure. With argon as the diluent gas k2 showed, within experimental error, little or no pressure dependence as reported earlier from this laboratory. However, with SF6 as the diluent gas k2 increased from (1.53±0.16) ×10−13 cm3 molecule−1 sec−1 at 25 torr total pressure to (3.43±0.35) ×10−13 cm3 molecule−1 sec−1 at 604 torr total pressure. This observation of a pressure dependence for SF6 is in agreement with other recent literature data for M=SF6, M=N2+O2 and M=H2. This pressure dependence of k2 has obvious implications regarding the conversion of CO to CO2 and the concentrations of the OH radical in the troposphere.
Quantum yields for the production of O(1D) from photodissociation of O2 at 1160–1770 Å
Authors: Lee L. C. , Slanger T. G. , Black G. , Sharpless R. L.
Published: February 2003

The quantum yield for the production of O(1D) by photodissociation of O2 was measured in the 1160–1770 Å wavelength region. For wavelengths longer than 1390 Å, the quantum yields are unity and constant, with a sharp cutoff at about 1750 Å. For wavelengths shorter than 1390 Å, the O(1D) quantum yields depend strongly on wavelength. The positions of many of the structures correspond to Rydberg states identified by various authors, and the data show by which of the two principal dissociative channels, O(3P)+O(3P) or O(1D)+O(3P), the excited molecules predissociate. The total oxygen atom yields were also measured and clearly show that all photon absorption leads to dissociation in the spectral region studied. Possible identification of absorption to the 3Πu valence state has been made, with a peak at 1356 Å (9.14 eV).
The Raman excitation profile spectrum of β-carotene in the preresonance region: Evidence for a low-lying singlet state
Authors: Thrash Robert J. , Fang Howard L. B. , Leroi George E.
Published: February 2003

The Raman excitation profile spectrum of the ν1 band of trans-β-carotene has been obtained in the preresonance region (16 900–19 000 cm−1). Five features are found in the spectrum which are interpreted as vibrational structure of a low-lying excited 1Ag state with its origin near 17 230±100 cm−1. This corresponds to a 1Bu−1Ag energy gap of 3470±100 cm−1, and may help account for the nonfluorescence of β-carotene.
Molecular beam electric resonance study of formaldehyde, thioformaldehyde, and ketene
Authors: Fabricant Barbara , Krieger David , Muenter J. S.
Published: February 2003

Molecular beam electric resonance spectroscopy has been carried out on formaldehyde, H2CO; thioformaldehyde, H2CS; and ketene, H2CCO. Transitions from 1 to 2500 MHz were studied. The high frequency work utilized a new type resonance field of microstrip line configuration. The diagonal tensor elements for all the hyperfine interactions of protons in all three molecules are reported. 13C hyperfine elements for H2 13CO and D hyperfine elements for D2CCO are also given. The electric field gradient tensor at deuterium in ketene is not coincident with cylindrical C–D bonds. Precise dipole moments are obtained for H2CO, D2CO, H2 13CO, H2CO(ν4=1), H2CO(ν6=1), H2CS, H2CCO, and D2CCO.
Electrical relaxation in amorphous protonic conductors
Authors: Hodge I. M. , Angell C. A.
Published: February 2003

The dc conductivities of seven concentrated aqueous acids, and the electrical relaxation properties of four of these, are reported. At the glass transition temperature Tg, as determined by differential thermal analysis, the dc conductivities increase with Tg for the individual acids, according to an Arrhenius function with an activation energy (at constant structure) of 8.6±0.3 kcal mole−1.A similar activation energy is approached for the conductance of individual acid glasses at temperatures low enough for the structure to be completely ’’frozen,’’ suggesting all systems conduct by the same mechanism. It is believed this is a proton transfer (Grotthuss-type) mechanism. Under conditions where the structure can change with temperature, the apparent activation energy for conduction is higher, ∼35 kcal mole−1. Electrical relaxation in these media, both supercooled liquid and glass, is found to be characterized by nonexponential response functions. Data have been analyzed using an electrical modulus formalism. The Davidson–Cole distribution function gives an excellent description of the imaginary part of the modulus. The Davidson–Cole parameters remain constant for a given glass once the structure becomes frozen. It is further demonstrated that the electrical relaxation behavior of these acids is very similar to that characterizing other amorphous ionic conductors, both liquid and glassy. The generally good description of conductivity relaxation afforded by the Davidson–Cole function is discussed in terms of an ionic diffusion mechanism, similar to that described by the Glarum model for cooperative dielectric relaxation.
Quantum versus classical dynamics in the treatment of multiple photon excitation of the anharmonic oscillator
Authors: Walker Robert B. , Preston Richard K.
Published: February 2003

The response of a one-dimensional anharmonic Morse oscillator to an intense electromagnetic field has been investigated using both a quasiclassical and quantum mechanical description of the oscillator. The anharmonic nature of the Morse potential reduces the coherence of the quantum excitation process after only a few quanta have been absorbed. The classical and quantum behavior of averaged quantities such as the energy absorbed and the oscillator displacement as a function of time are in good agreement; however, the classical description cannot reproduce the multiphoton resonances. We are led to the conclusion that classical mechanics provides an adequate description of the response of a molecule in an intense laser field provided that multiphoton resonances do not individually play a fundamental role in the process.
Piecewise polynomial electronic wavefunctions
Authors: Gázquez José Luis , Silverstone Harris J.
Published: February 2003

Piecewise polynomials are examined as basis functions for electronic wavefunctions. The spline function method is a special case, which is shown to be less accurate, for a fixed set of mesh points, than a method based directly on Hermite’s interpolation formula. The determination of a suitable mesh is discussed both inductively and deductively, and a logarithmic formula for the 1s orbital of helium is ’’derived.’’ The accuracy is shown to depend on the number of points N+1 and on the polynomial order 2s+1, approximately according to the formula, δE∼N−4s−2, for appropriate meshes. A striking result is the possibility for systematically increasing the accuracy of the energy by systematically increasing the number of points, without encountering linear dependence problems, is demonstrated by calculations on the helium atom. With a 16-point theoretically derived mesh, and with seventh order polynomials, we obtain a Hartree–Fock energy for helium of −2.8616799956122 a.u.
Pressure of Kirkwood–Alder transition in monodisperse latex
Authors: Takano Kaoru , Hachisu Sei
Published: February 2003

Monodisperse latex, a colloid system consisting of uniform sized spherical particles of synthetic resin, shows a phase transition phenomenon from ordered state to disordered state. In view of the fact that repulsive interaction prevails in stably dispersed colloid, the transition must be of Kirkwood–Alder transition type. In the present work, the pressure of phase transition has been studied, making use of sedimentation equilibrium, at several electrolyte concentrations of the medium. The magnitude of the transition pressure changed as the electrolyte concentration of the medium varied. The transition pressure expressed in terms of reduced pressure at melting point was 13 to 15 when the electrolyte concentration was around 10−2 mole/liter. These values are very close to computational value 11.6 by Alder, Hoover, and Young, indicating that the particles behave as hard spheres under such condition. At low electrolyte concentrations, the value was larger, about 30 at 10−3 mole/liter and 230 at about 10−6 mole/liter, which are in accord with the result of Hoover et al. for a soft core system.
A new tunneling path for reactions such as H+H2→H2+H
Authors: Marcus R. A. , Coltrin Michael E.
Published: February 2003

The standard tunneling path in transition state theory for reactions such as H+H2→H2+H has been the so-called reaction path, namely the path of steepest ascent to the saddle point. This path is now known to give numerical results for the reaction probability which are in disagreement with the exact quantum mechanical ones by an order of magnitude at low tunneling energies. A new tunneling path corresponding to a line of vibrational endpoints is proposed. It is much shorter and is shown to give results in agreement with the quantum ones to within about a factor of two. A semiclassical basis for choosing this new path is given.
The reaction between H2 and D2 in a shock tube: Study of the atomic vs molecular mechanism by atomic resonance absorption spectrometry
Authors: Lifshitz Assa , Frenklach Michael
Published: February 2003

The exchange reaction between hydrogen and deuterium was studied behind reflected shocks in a single pulse shock tube. A vacuum uv monochromator and a Lyman-α radiation source were attached to the end block of the driven section in order to determine the hydrogen atom profile during the hot phase. These atoms are the result of impurities which are present in the shock tube. Two calibration attempts of the It/I0 vs [H]t around 1250 °K, using the decomposition scheme of propane and the postexplosion conditions in H2/O2/Ar mixtures, were unsuccessful. A calibration method which utilizes an integrated absorption profile is described. A two parameter calibration function (modified Beer–Lambert law) was derived: It/I0=exp(−α[H]βt), where α=2.92×107 and β=0.73 in units of mole-cm. For each test, a sample was withdrawn from the tube and was analyzed mass spectrometrically for postshock distribution of product and reactants. In addition, the absorption profile at 1215.7 Å was recorded and the extent of HD produced by hydrogen atoms (which originated from impurities) was numerically integrated using the two parameter calibration function and the atomic chain reactions H+D2→HD+D and D+H2→HD+H. The mass spectrometrically measured extents of exchange were always considerably higher than the ones calculated from the absorption profile, on the average by a factor of 2–3. If the difference between the two conversions is attributed to a molecular mechanism, then if calculated on the basis of the rate law H2+D2→2HD the following rate constant is obtained: k6=1014.1±0.8 exp[−(38±5) ×103/RT] mole−1 cm3 sec−1.
Vibrational spectra and structure of 1,2-difluoroethane: G
a
u
c
h
e–t
r
a
n
s conformers
Authors: Harris W. C. , Holtzclaw J. R. , Kalasinsky V. F.
Published: February 2003

Infrared and laser-Raman spectra of 1,2-difluoroethane (FH2CCH2F) have been recorded from 4000 to 50 cm−1. Whereas the Raman spectra were measured for all three physical states, the infrared data were recorded for the gaseous and crystalline phases. Spectral transitions associated with the predominant gauche conformer have been assigned with confidence on the basis of clearly defined infrared band contours and Raman depolarization ratios. Although several fundamentals have also been assigned for trans-1,2-difluoroethane, the majority of the normal modes associated with trans-C2F2H4 appear to be unresolved or coincident with bands assigned to gauche-C2F2H4. The magnitude of ΔH separating the two conformers was determined to be 1.98±0.08 kcal/mole by measuring the temperature dependence of the Raman bands assigned to the F–C–C–F bending modes for gauche (503 cm−1) and trans (461 cm−1) C2F2H4, respectively. An overall potential function describing the torsional barriers and ΔH will be discussed on the basis of the variable temperature data and the low frequency torsional transitions. The present study is consistent with an earlier electron diffraction study but disagrees with the conclusions advanced in a previous vibrational investigation of C2F2H4. These results will be reviewed in detail since the existent data is consistent with a predominant gauche conformer.
Photodissociation of atmospheric positive ions. I. 5300–6700 Å
Authors: Smith G. P. , Cosby P. C. , Moseley J. T.
Published: February 2003

Photodissociation cross sections have been investigated for several positive ions of atmospheric importance in the wavelength region from 5300 to 6700 Å, using a drift tube mass spectrometer and a tunable dye laser. The dimer ions NONO+ and CO2CO+2 are observed to have large photodissociation cross sections (≳10−17 cm2) at these wavelengths. Three ions formed from oxygen cations O+4, CO+4, and O+2⋅H2O have photodissociation cross sections near 1×10−18 cm2, with the latter two ions exhibiting a threshold near 6200 Å. The cluster ions NO+⋅M, where M is H2O, N2, CO2, and N2O, are not observed to photodissociate, nor are H3O+⋅ (H2O)n=0,1,2. Upper limits on the photodissociation cross sections for these ions are established in the range 10−19–10−20 cm2. For many of the ions studied here reactions coupling the ion of interest with other species present in the drift tube and diffusion effects following interaction with the laser must be explicitly considered to establish values or limits for the photodissociation cross sections.
Fluctuation in adsorbed phases
Authors: Oh Byung K. , Kim Shoon K.
Published: February 2003

A study has been made of fluctuations in adsorbed phase coverage based on a model which assumes localized adsorption for the first layer and nonlocalized mobile adsorption for the second layer. For a homogeneous surface the envelopes, extremum locations, and limiting knee point of the fluctuation are calculated. An s-shaped semiloop exists in the fluctuation, if the adsorption strength c is larger than the critical value cK=28.43. The molar fluctuation (fluctuation divided by coverage) has always one minimum. In the case of adsorption on a heterogeneous surface with s-different patches there exist s maxima and minima in the fluctuation provided that [Mi]ci/Mi−1ci−1≳cK=28.43, i=2, 3,..., s, where ci and Mi are the adsorption strength and the number of lattice sites for the ith patch, respectively, and [Mi]=𝒥sk=iMk. From these extrema in the fluctuation we can estimate the characteristic constants ci’s and Mi’s of an adsorbed phase. The theory is in excellent agreement with the observed fluctuations of argon on rutile of 85 °K by Drain and Morrison and xenon on porous silver at 77.4 °K by Hobson.
Thermochromism in a polydiacetylene crystal
Authors: Chance R. R. , Baughman R. H. , Müller H. , Eckhardt C. J.
Published: February 2003

Specular reflection spectra are reported for a thermochromic polydiacetylene crystal, ETCD [substituent group – (CH2)4OCONHC2H5] over the temperature range 23–130°C. A reversible thermochromic phase change occurs at ∼120°C and is accompanied by a 2750 cm−1 blue shift in the reflection spectra. Evidence is presented which strongly suggests that the dramatic change in optical properties of ETCD at the phase transition is due to an acetylene to butatriene transformation in the bonding sequence of the polydiacetylene backbone.
Identifying differentially expressed genes using
false discovery rate controlling procedures
Authors: Reiner Anat , Yekutieli Daniel , Benjamini Yoav
Published: February 2003

Motivation: DNA microarrays have recently been used for the purpose of monitoring expression levels of thousands of genes simultaneously and identifying those genes that are differentially expressed. The probability that a false identification (type I error) is committed can increase sharply when the number of tested genes gets large. Correlation between the test statistics attributed to gene co-regulation and dependency in the measurement errors of the gene expression levels further complicates the problem. In this paper we address this very large multiplicity problem by adopting the false discovery rate (FDR) controlling approach. In order to address the dependency problem, we present three resampling-based FDR controlling procedures, that account for the test statistics distribution, and compare their performance to that of the naïve application of the linear step-up procedure in Benjamini and Hochberg (1995). The procedures are studied using simulated microarray data, and their performance is examined relative to their ease of implementation.

Results: Comparative simulation analysis shows that all four FDR controlling procedures control the FDR at the desired level, and retain substantially more power then the family-wise error rate controlling procedures. In terms of power, using resampling of the marginal distribution of each test statistics substantially improves the performance over the naïve one. The highest power is achieved, at the expense of a more sophisticated algorithm, by the resampling-based procedures that resample the joint distribution of the test statistics and estimate the level of FDR control.

Availability: An R program that adjusts p-values using FDR controlling procedures is freely available over the Internet at www.math.tau.ac.il/~ybenja

Contact: anatr@post.tau.ac.il

* To whom correspondence should be addressed.
Identification of key concepts in biomedical literature using a modified Markov heuristic
Authors: Majoros W. H. , Subramanian G. M. , Yandell M. D.
Published: February 2003

Motivation: The recent explosion of interest in mining the biomedical literature for associations between defined entities such as genes, diseases and drugs has made apparent the need for robust methods of identifying occurrences of these entities in biomedical text. Such concept-based indexing is strongly dependent on the availability of a comprehensive ontology or lexicon of biomedical terms. However, such ontologies are very difficult and expensive to construct, and often require extensive manual curation to render them suitable for use by automatic indexing programs. Furthermore, the use of statistically salient noun phrases as surrogates for curated terminology is not without difficulties, due to the lack of high-quality part-of-speech taggers specific to medical nomenclature.

Results: We describe a method of improving the quality of automatically extracted noun phrases by employing prior knowledge during the HMM training procedure for the tagger. This enhancement, when combined with appropriate training data, can greatly improve the quality and relevance of the extracted phrases, thereby enabling greater accuracy in downstream literature mining tasks.

Contact: bmajoros@tigr.org

* To whom correspondence should be addressed.
Strategic HRM: enablers and constraints in the NHS
Authors: Truss Catherine
Published: February 2003

The UK Government has frequently referred to the importance of strategic human resource management (HRM) to the success of the National Health Service (NHS). However, relatively little is known about whether HR departments within individual NHS Trusts play a strategic role and, if so, how this has been achieved. Reports on the findings of a unique study into HRM at the Chelsea and Westminster NHS Trust over the period 1994‐2000. In particular, focuses on the factors that have enabled or constrained the development of a strategic role over time. Whilst it was found that the NHS context often served as a constraining factor, also shows that much can be done at the level of the individual Trust to foster a strategic role for the HR function. Of particular importance were the HR director role, the attitudes of senior management towards HRM and the way in which HR interventions were implemented.
Building trust between growers and market agents
Authors: Batt Peter J.
Published: February 2003

In the absence of the auction as the principal mechanism for setting price in the Perth fresh fruit and vegetable market, there is a great deal of distrust between growers and the market agents who receive and distribute their produce. While most growers generally transact with more than one market agent, satisfaction with the exchange builds trust. Trust is facilitated where the grower and the market agent share similar goals. To reinforce trust, growers prefer to transact with those market agents who are prepared to invest in their relationship with the grower. Conversely, the market agents propensity to act opportunistically, to exercise power and to withhold information from the grower will have a significant negative impact on the trust that develops between growers and market agents.
Endoproteolytic Processing of the Lymphocytic Choriomeningitis Virus Glycoprotein by the Subtilase SKI-1/S1P
Authors: Beyer Winfried R. , Pöpplau Dennis , Garten Wolfgang , von Laer Dorothee , Lenz Oliver
Published: February 2003

The envelope glycoprotein (GP) of lymphocytic choriomeningitis virus (LCMV) is posttranslationally cleaved into two subunits. We show here that this endoproteolytic processing is not required for transport to the cell surface but is essential for LCMV GP to mediate infectivity of pseudotyped retroviral vectors. By systematic mutational analysis of the LCMV GP cleavage site, we determined that the consensus motif R-(R/K/H)-L-(A/L/S/T/F)
265
is essential for the endoproteolytic processing. In agreement with the identified consensus motif, we show that the cellular subtilase SKI-1/S1P cleaves LCMV GP.
N-Linked Glycosylation and Sequence Changes in a Critical Negative Control Region of the ASCT1 and ASCT2 Neutral Amino Acid Transporters Determine Their Retroviral Receptor Functions
Authors: Marin Mariana , Lavillette Dimitri , Kelly Sean M. , Kabat David
Published: February 2003

A widely dispersed interference group of retroviruses that includes the feline endogenous virus (RD114), baboon endogenous virus (BaEV), human endogenous virus type W (HERV-W), and type D primate retroviruses uses the human Na
+
-dependent neutral amino acid transporter type 2 (hASCT2; gene name, SLC1A5) as a common cell surface receptor. Although hamster cells are fully resistant to these viruses and murine cells are susceptible only to BaEV and HERV-W pseudotype viruses, these rodent cells both become highly susceptible to all of the viruses after treatment with tunicamycin, an inhibitor of protein N-linked glycosylation. A partial explanation for these results was recently provided by findings that the orthologous murine transporter mASCT2 is inactive as a viral receptor, that a related (ca. 55% identity) murine paralog (mASCT1; gene name, SLC1A4) mediates infections specifically of BaEV and HERV-W, and that N-deglycosylation of mASCT1 activates it as a receptor for all viruses of this interference group. Because the only two N-linked oligosaccharides in mASCT1 occur in the carboxyl-terminal region of extracellular loop 2 (ECL2), it was inferred that this region contributes in an inhibitory manner to infections by RD114 and type D primate viruses. To directly and more thoroughly investigate the receptor active sites, we constructed and analyzed a series of hASCT2/mASCT2 chimeras and site-directed mutants. Our results suggest that a hypervariable sequence of 21 amino acids in the carboxyl-terminal portion of ECL2 plays a critical role in determining the receptor properties of ASCT2 proteins for all viruses in this interference group. In addition, we analyzed the tunicamycin-dependent viral susceptibility of hamster cells. In contrast to mASCT1, which contains two N-linked oligosaccharides that partially restrict viral infections, hamster ASCT1 contains an additional N-linked oligosaccharide clustered close to the others in the carboxyl-terminal region of ECL2. Removal of this N-linked oligosaccharide by mutagenesis enabled hamster ASCT1 to function as a receptor for all viruses of this interference group. These results strongly suggest that combinations of amino acid sequence changes and N-linked oligosaccharides in a critical carboxyl-terminal region of ECL2 control retroviral utilization of both the ASCT1 and ASCT2 receptors.
Exonuclease-Deficient Polymerase Mutant of Herpes Simplex Virus Type 1 Induces Altered Spectra of Mutations
Authors: Hwang Ying T. , Hwang Charles B. C.
Published: February 2003

The effect of exonuclease activity of the herpes simplex virus DNA polymerase (Pol) on DNA replication fidelity was examined by using the
supF
mutagenesis assay. The recombinants with exonuclease-deficient Pol, containing an integrated
supF
gene in the thymidine kinase locus (
tk
), exhibited
supF
mutation frequencies ranging from 0.14 to 5.6%, consistent with the
tk
mutation frequencies reported previously (Y. T. Hwang, B.-Y. Liu, D. M. Coen, and C. B. C. Hwang, J. Virol. 71:7791-7798, 1997). The increased mutation frequencies were 10- to 500-fold higher than those observed for wild-type Pol recombinants. The increased mutation frequencies also were significantly higher than those of
supF
mutant replicated by exonuclease-deficient Pols in the plasmid-borne assay. Furthermore, characterization of
supF
mutants demonstrated that recombinants with a defective exonuclease induced types and distributions of
supF
mutations different from those induced by wild-type Pol recombinants. The types of
supF
mutations induced by exonuclease-deficient recombinants differed between the plasmid- and genome-based assays. The spectra of
supF
mutations also differed between the two assays. In addition, exonuclease-defective viruses also induced different spectra of
supF
and
tk
mutations. Therefore, both the assay methods and the target genes used for mutagenesis studies can affect the repication fidelity of herpes simplex virus type 1 Pol with defective exonuclease activity.
An Antiviral Peptide Targets a Coiled-Coil Domain of the Human T-Cell Leukemia Virus Envelope Glycoprotein
Authors: Piñón Josefina D. , Kelly Sharon M. , Price Nicholas C. , Flanagan Jack U. , Brighty David W.
Published: February 2003

Retrovirus entry into cells is mediated by the viral envelope glycoproteins which, through a cascade of conformational changes, orchestrate fusion of the viral and cellular membranes. In the absence of membrane fusion, viral entry into the host cell cannot occur. For human T-cell leukemia virus type 1 (HTLV-1), synthetic peptides that mimic a carboxy-terminal region of the transmembrane glycoprotein (TM) ectodomain are potent inhibitors of membrane fusion and virus entry. Here, we demonstrate that this class of inhibitor targets a fusion-active structure of HTLV-1 envelope. In particular, the peptides bind specifically to a core coiled-coil domain of envelope, and peptide variants that fail to bind the coiled-coil lack inhibitory activity. Our data indicate that the inhibitory peptides likely function by disrupting the formation of a trimer-of-hairpins structure that is required for membrane fusion. Importantly, we also show that peptides exhibiting dramatically increased potency can be readily obtained. We suggest that peptides or peptide mimetics targeting the fusion-active structures of envelope may be of therapeutic value in the treatment of HTLV-1 infections.
X-Ray Crystallographic Analysis of Lipid-Protein Interactions in the Bacteriorhodopsin Purple Membrane
Authors: Cartailler Jean-Philippe , Luecke Hartmut
Published: February 2003

▪ Abstract  The past decade has witnessed increasingly detailed insights into the structural mechanism of the bacteriorhodopsin photocycle. Concurrently, there has been much progress within our knowledge pertaining to the lipids of the purple membrane, including the discovery of new lipids and the overall effort to localize and identify each lipid within the purple membrane. Therefore, there is a need to classify this information to generalize the findings. We discuss the properties and roles of haloarchaeal lipids and present the structural data as individual case studies. Lipid-protein interactions are discussed in the context of structure-function relationships. A brief discussion of the possibility that bacteriorhodopsin functions as a light-driven inward hydroxide pump rather than an outward proton pump is also presented.
DELIBERATIVEDEMOCRATICTHEORY
Authors: Chambers Simone
Published: February 2003

▪ Abstract  Deliberative democratic theory has moved beyond the “theoretical statement” stage and into the “working theory” stage. Although this essay revisits some of the main theoretical debates, this is done via a survey and evaluation of the state of deliberative democratic theory as it is being applied in a number of research areas and as it intersects with related normative debates. Five research areas are covered: public law, international relations, policy studies, empirical research, and identity politics.
Influenza Infection Exerts Prominent Inflammatory and Thrombotic Effects on the Atherosclerotic Plaques of Apolipoprotein E–Deficient Mice
Authors: Naghavi Morteza , Wyde Philip , Litovsky Silvio , Madjid Mohammad , Akhtar Adeeba , Naguib Sameh , Siadaty Mir Said , Sanati Susan , Casscells Ward
Published: February 2003

Background—

The role of infection in the development and complications of atherosclerosis has been the focus of much attention. We reported previously that influenza vaccination was associated with reduced risk of recurrent myocardial infarction. Here, we report the effect of influenza A virus on the apolipoprotein E–deficient (apoE
−/−
) mouse, an animal model of atherosclerosis.

Methods and Results—

Twenty-four apoE
−/−
mice >24 months old were injected with 1 LD
50
(lethal dose 50) of influenza A virus. Ten wild-type C57BL/6 infected mice and 11 noninfected age-matched apoE
−/−
mice served as controls. Multiple aortic sections were studied histologically 3, 5, and 10 days later. The infected mice showed markedly increased intimal cellularity compared with the noninfected apoE
−/−
mice. No aortic abnormalities were seen in infected wild-type mice. Ten infected apoE
−/−
mice had a significant subendothelial infiltrate composed of a heterogeneous group of cells that stained positively for smooth muscle cell actin, F4/80 (macrophages), and CD3 (T lymphocytes). One case of subocclusive platelet and fibrin-rich thrombus was seen.

Conclusions—

This study shows that influenza infection promotes inflammation, smooth muscle cell proliferation, and fibrin deposition in atherosclerotic plaques.
Aging and the Exercise Pressor Reflex in Humans
Authors: Markel Troy A. , Daley Joseph C. , Hogeman Cynthia S. , Herr Michael D. , Khan Mazhar H. , Gray Kristen S. , Kunselman Allen R. , Sinoway Lawrence I.
Published: February 2003

Background—

Blood flow limitation to exercising muscles engages the muscle reflex during exercise, evoking an increase in heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA).

Methods and Results—

In the current study, we examined forearm flow and autonomic responses to ischemic handgrip in young and older subjects. We studied 6 younger subjects (mean age 23.5±2.2 years) and 7 older subjects (mean age 65.0±2.4 years). Subjects performed rhythmic handgrip (thirty 1-sec contractions/min) at 30% maximal voluntary contraction during six 1-minute stages: freely perfused exercise (E1) and exercise with forearm pressure of +10, +20, +30, +40, and +50 mm Hg (E2 through E6). We measured HR, BP, MSNA, forearm flow velocity, forearm venous oxygen saturation, H
+
, and lactate. Compared with E1, ischemic exercise (E2 through E6) increased HR, BP, and MSNA, reduced forearm velocity, lowered venous oxygen saturation, and raised venous lactate and H
+
. Compared with the younger subjects, the older subjects had attenuated BP at E6, attenuated MSNA indices (%Δbursts, bursts/100 heart beats and signal averaged MSNA), attenuated H
+
at E6, a trend toward higher levels of oxygen saturation, and similar forearm velocity and HR responses.

Conclusions—

Aging attenuates the muscle reflex.
Lupus anticoagulants are stronger risk factors for thrombosis than anticardiolipin antibodies in the antiphospholipid syndrome: a systematic review of the literature
Authors: Galli Monica , Luciani Davide , Bertolini Guido , Barbui Tiziano
Published: February 2003

To formally establish the risk of lupus anticoagulants and anticardiolipin antibodies for arterial and venous thrombosis, we ran a MEDLINE search of the literature from 1988 to 2000. Studies were selected for their case-control (11), prospective (9), cross-sectional (3), and ambispective (2) design. They provided or enabled us to calculate the odds ratio with 95% confidence interval (CI) of lupus anticoagulants and/or anticardiolipin antibodies for thrombosis in 4184 patients and 3151 controls. Studies were grouped according to the antibody investigated. Five studies compared lupus anticoagulants with anticardiolipin antibodies: the odds ratio with 95% CI of lupus anticoagulants for thrombosis was always significant. None of them found anticardiolipin antibodies were associated with thrombosis. Four studies analyzed only lupus anticoagulants: the odds ratio with 95% CI was always significant. The risk of lupus anticoagulants was independent of the site and type of thrombosis, the presence of systemic lupus erythematosus, and the coagulation tests employed to detect them. Sixteen studies served to assess 28 associations between anticardiolipin antibodies and thrombosis: the odds ratio with 95% CI was significant in 15 cases. Anticardiolipin titer correlated with the odds ratio of thrombosis. In conclusion, the detection of lupus anticoagulants and, possibly, of immunoglobulin G (IgG) anticardiolipin antibodies at medium or high titers helps to identify patients at risk for thrombosis. However, to take full advantage of the conclusions provided by the available evidence, there is an urgent need to harmonize investigational methods.
High-level ectopic HOXB4 expression confers a profound in vivo competitive growth advantage on human cord blood CD34+ cells, but impairs lymphomyeloid differentiation
Authors: Schiedlmeier Bernhard , Klump Hannes , Will Elke , Arman-Kalcek Gökhan , Li Zhixiong , Wang Zheng , Rimek Andreas , Friel Jutta , Baum Christopher , Ostertag Wolfram
Published: February 2003

Ectopic retroviral expression of homeobox B4 (HOXB4) causes an accelerated and enhanced regeneration of murine hematopoietic stem cells (HSCs) and is not known to compromise any program of lineage differentiation. However, HOXB4 expression levels for expansion of human stem cells have still to be established. To test the proposed hypothesis that HOXB4 could become a prime tool for in vivo expansion of genetically modified human HSCs, we retrovirally overexpressed HOXB4 in purified cord blood (CB) CD34+ cells together with green fluorescent protein (GFP) as a reporter protein, and evaluated the impact of ectopic HOXB4 expression on proliferation and differentiation in vitro and in vivo. When injected separately into nonobese diabetic–severe combined immunodeficient (NOD/SCID) mice or in competition with control vector–transduced cells, HOXB4-overexpressing cord blood CD34+ cells had a selective growth advantage in vivo, which resulted in a marked enhancement of the primitive CD34+ subpopulation (P = .01). However, high HOXB4 expression substantially impaired the myeloerythroid differentiation program, and this was reflected in a severe reduction of erythroid and myeloid progenitors in vitro (P < .03) and in vivo (P = .01). Furthermore, HOXB4 overexpression also significantly reduced B-cell output (P < .01). These results show for the first time unwanted side effects of ectopic HOXB4 expression and therefore underscore the need to carefully determine the therapeutic window of HOXB4 expression levels before initializing clinical trials.
Outcome of donor splice site mutations accounting for congenital afibrinogenemia reflects order of intron removal in the fibrinogen alpha gene (FGA)
Authors: Attanasio Catia , David Armelle , Neerman-Arbez Marguerite
Published: February 2003

Congenital afibrinogenemia (Mendelian Inheritance in Man #202400) is a rare, autosomal recessive disorder characterized by the complete absence of circulating fibrinogen. Our recent studies on the molecular basis of the disease showed that the most common genetic defect is a donor splice mutation in fibrinogen alpha gene (FGA)intron 4, IVS4+1G>T. Two other FGA donor splice mutations, in intron 1 (IVS1+3A>G) and intron 3 (IVS3+1_+4delGTAA), were identified in afibrinogenemia patients. Because it was impossible to directly study the effect of these mutations on mRNA splicing in patient hepatocytes, we used a transfected cell approach, which previously allowed us to show that the common IVS4 mutation causes afibrinogenemia due to the activation of multiple cryptic donor splice sites. In this study, analysis of the IVS3delGTAA mutation showed exon 3 skipping in 99% of transcripts and exons 2 and 3 skipping in 1% of transcripts. The different outcomes of these donor splice mutations appear to follow the model proposed in a study of fibrillar collagen genes, where donor splice mutations occurring in a rapidly spliced intron with respect to upstream introns lead in most cases to exon skipping, while mutations in later-spliced introns lead to intron inclusion or cryptic splice-site utilization. Indeed, we found that inFGA intron 3 was preferentially spliced first, followed by intron 2, intron 4, and intron 1.
Membrane-type matrix metalloproteinase-mediated angiogenesis in a fibrin-collagen matrix
Authors: Collen Annemie , Hanemaaijer Roeland , Lupu Florea , Quax Paul H. A. , van Lent Natascha , Grimbergen Jos , Peters Erna , Koolwijk Pieter , van Hinsbergh Victor W. M.
Published: February 2003

Adult angiogenesis, associated with pathologic conditions, is often accompanied by the formation of a fibrinous exudate. This temporary matrix consists mainly of fibrin but is intermingled with plasma proteins and collagen fibers. The formation of capillary structures in a fibrinous matrix in vivo was mimicked by an in vitro model, in which human microvascular endothelial cells (hMVECs) seeded on top of a fibrin-10% collagen matrix form capillarylike tubular structures after stimulation with basic fibroblast growth factor/tumor necrosis factor α (bFGF/TNF-α) or vascular endothelial growth factor (VEGF)/TNF-α. In the fibrin-collagen matrix the metalloproteinase inhibitor BB94 inhibited tubule formation by 70% to 80%. Simultaneous inhibition of plasmin and metalloproteinases by aprotinin and BB94 caused a nearly complete inhibition of tubule formation. Adenoviral transduction of tissue inhibitor of metalloproteinases 1 (TIMP-1) and TIMP-3 into endothelial cells revealed that TIMP-3 markedly inhibited angiogenesis, whereas TIMP-1 had only a minor effect. Immunohistochemical analysis showed the presence of matrix metalloproteinase 1 (MMP-1), MMP-2, and membrane-type 1 (MT1)–MMP, whereas MMP-9 was absent. The endothelial production of these MMPs was confirmed by antigen assays and real-time polymerase chain reaction (PCR). MT1-MMP mRNA was markedly increased in endothelial cells under conditions that induced tubular structures. The presence of MMP-1, MMP-2, and MT1-MMP was also demonstrated in vivo in the newly formed vessels of a recanalized arterial mural thrombus. These data suggest that MMPs, in particular MT-MMPs, play a pivotal role in the formation of capillarylike tubular structures in a collagen-containing fibrin matrix in vitro and may be involved in angiogenesis in a fibrinous exudate in vivo.
Synthesis and Characterization of Luminescent Rod–Coil Block Copolymers by Atom Transfer Radical Polymerization: Utilization of Novel End‐Functionalized Terfluorenes as Macroinitiators
Authors: Tsolakis Panagiotis K. , Kallitsis Joannis K.
Published: February 2003

Two novel, rigid, photoluminescent, substituted terfluorene derivatives were synthesized by utilizing direct bromination and Suzuki coupling reactions. These oligomers were used as initiators for the atom transfer radical polymerization (ATRP) of styrene andtert‐butyl acrylate. Thus, diblock and triblock rod–coil block copolymers were prepared with well‐defined structure, as far as their size and shape is concerned. Molecular weights up to approximately 21 000 and polydispersity indices not exceeding 1.5 in most cases were obtained. The copolymers emit blue light in solution, and their luminescence properties remain practically invariable when passing from solution to the solid state. No ground‐state aggregation or excimer formation were observed in the solid state, even after annealing at high temperatures.
Chemische Synthese in überkritischem Kohlendioxid: Die „bessere Lösung”︁?
Authors: Leitner Walter
Published: February 2003

Die in dieser kurzen Übersicht angeführten Beispiele verdeutlichen das Potenzial von überkritischem Kohlendioxid als Reaktionsmedium für nachhaltige Syntheseverfahren („Green Chemistry”︁). Die Forschung auf diesem Gebiet vereint in besonderer Weise anwendungsbezogene Fragestellungen mit dem grundlegenden Studium molekularer und reaktionstechnischer Zusammenhänge. Dabei zeigt sich bereits heute, dass scCO2 aufgrund seiner einzigartigen physikalisch‐chemischen Eigenschaften für die Synthesechemie weit mehr ist als nur ein „Ersatzlösungsmittel”︁ und beispielsweise gänzlich neue Methoden für die Kontrolle von Aktivität, Selektivität und Prozessdesign mit heterogenen Katalysatoren, metallorganischen Katalysatoren und Biokatalysatoren eröffnet. Besonders spannend bleibt für die Zukunft gerade auch die Suche nach neuen, in „konventionellen”︁ Lösungsmitteln nicht durchführbaren Reaktionen.
In Situ Observation of the Surface Processes Involved in Dissolution from the Cleavage Surface of Calcite in Aqueous Solution Using Combined Scanning Electrochemical–Atomic Force Microscopy (SECM‐AFM)
Authors: Jones Claire E. , Unwin Patrick R. , Macpherson Julie V.
Published: February 2003

The surface processes involved in the initial stages of the proton‐assisted dissolution of the calcite single crystal cleavage plane (10$\bar 1$4) have been identified using a combined scanning electrochemical–atomic force microscope (SECM‐AFM). This instrument employs a platinum‐coated AFM probe, which functions as an electrode as well as a high‐resolution topographical sensor. Dissolution in this arrangement is effected by the local electrogeneration of protons, produced by oxidation of water at the probe electrode. By careful control of the applied potential, it is possible to vary the magnitude of the electrogenerated flux of protons from the probe towards the calcite surface. Crucially, by generating a small proton flux for short time periods (0.5 s) it is possible to observe and monitor the initial sites in the dissolution process. Topographical images were recorded in the same area of the surface both prior to and after inducing dissolution, as a function of the proton flux. At low proton fluxes, of the order of 1 nmol cm−2 s−1 or less, the surface was observed to dissolve by the nucleation of monolayer deep pits, with densities of about 108 cm−2. These pits are likely to be formed at point vacancies or atomic (impurity, for example) defects in the crystal lattice. As the proton flux was increased (over two orders of magnitude), these same etch pits were found to open into wider macro‐pits, with an outline morphology that reflected the crystallographic orientation of the surface. At the highest proton fluxes, dissolution from macroscopic step edges became significant.
A Microscopic, Continous, Optical Monitor for Interstitial Electrolytes and Glucose
Authors: Tohda Koji , Gratzl Miklós
Published: February 2003

Ions, such as hydrogen (pH), sodium, or potassium, as well as metabolites, such as glucose or lactate, diffuse easily between blood in the capillaries and the interstitial fluid (ISF) residing between cells and tissues. This work represents a synthesis of several unique concepts to achieve accurate, continuous, in vivo monitoring of critical ions and glucose in the ISF under the human skin. Ionic levels are monitored using optode technology that translates the respective concentrations into variable colors of ionophore/dye/polymeric liquid membranes. Glucose is monitored indirectly, by coupling through immobilized glucose oxidase with pH, that is then detected using a similar color scheme. The monitor consists of a tiny plastic bar (“sliver sensor”), 100–300 μm wide and 1–1.5 mm long, placed just under the skin, with optical spots or stripes for each analyte as well as blanks for calibration. The colors are read and translated into concentration values by a watchlike device placed above the skin. Direct optical coupling between the in vivo sensing bar and the ex vivo detector device requires negligible power, and eliminates the need for wires or optical fibers crossing the skin. The microminiature sliver penetrates the skin easily and painlessly, so that the user could insert it him‐ or herself. No risk of track infection exists. We are reporting here on the first successful in vitro tests of this approach.
Mechanistic Aspects of On‐Line Electrochemical Tagging of Free L‐Cysteine Residues during Electrospray Ionisation for Mass Spectrometry in Protein Analysis
Authors: Roussel Christophe , Rohner Tatiana C. , Jensen Henrik , Girault Hubert H.
Published: February 2003

The mechanistic details behind an electrochemically induced tagging of L‐cysteine residues in peptides and proteins have been unravelled using cyclic voltammetry. It was found that when hydroquinone is oxidised in the medium used in electrospray ionisation mass spectrometry (ESI‐MS) a protonated form of benzoquinone is produced that acts as an efficient electrophile for free L‐cysteine residues. Upon substitution of L‐cysteine the reduced form of the adduct is formed, which may be further oxidised leading to further substitution of L‐cysteine. Digital simulations of the cyclic voltammograms corroborated the mechanism and allowed a determination of the homogeneous second order rate constant corresponding to the addition of L‐cysteine onto the protonated form of benzoquinone. The selectivity of the tagging process was confirmed using ESI‐MS, which showed that a protein without L‐cysteine residues does not react with benzoquinone dissolved in the medium. Finally, the kinetic information obtained in this investigation is used to discuss the optimal parameters for a nanospray capable of quantitative tagging of L‐cysteine residues.
Etched Electrochemical Detection for Electrophoresis in Nanometer Inner Diameter Capillaries
Authors: Woods Lori A. , Ewing Andrew G.
Published: February 2003

Capillary electrophoresis in nanometer inner diameter capillaries allows for the analysis of extremely small volume samples, such as the contents of single cells. However, the utilization of these ultrasmall capillaries requires a very sensitive and low volume detector. An improved method for end‐column amperometric detection for capillary electrophoresis in nanometer inner diameter (i.d.) capillaries is presented. This new method involves etching both the electrode and the detection end of the capillary. These design improvements allow for better alignment between the capillary bore and the electrode. As a result, dead volume in the detector is minimized. The etched method for electrochemical detection in ultrasmall capillaries provides average coulometric efficiencies of 70±10 % for dopamine and 40±20 % for catechol in 770 nm i.d. capillaries. Furthermore, this technique provides peak efficiencies as high as 100 000 theoretical plates and detection limits as low as 340 zmol for both dopamine and catechol.