bluuebunny/crossref_metadata_2025 huggingface dataset:
Light-coupling masks: An alternative, lensless approach to high-resolution optical contact lithography
Authors: Schmid Heinz , Biebuyck Hans , Michel Bruno , Martin Olivier J. F. , Piller Nicolas B.
Published: July 2002

We describe an approach to optical lithography using light-scattering contact masks with protruding elements that couple light into a photoresist. This method differs from conventional contact lithography in two important ways. First, because portions of the light-coupling mask (LCM) are made from a polymer, intimate contact with the resist occurs over large areas without additional load. This contact is readily reversible, and causes no observable damage or contamination of the LCM or substrate. Second, the structure formed by the protruding parts of the LCM in contact with the resist can define local optical modes that impart directionality to the light propagating through the LCM and amplify its intensity. We provide an experimental realization and theoretical description of the method, demonstrating its use for the formation of 100 nm features with light having a wavelength of 256 nm.
Five inch full color field emission displays with narrow gap studies
Authors: Kim J. M. , Lee H. W. , Choi Y. S. , Jung J. E. , Lee N. S. , Jin Y. W. , Park N. S.
Published: July 2002

Electron beam spreading and emission current density for different shapes of microtips with bias levels are simulated for the application of high voltage or low voltage phosphors. In the simulation, the morphology of micro tips and the structural parameters of a field emission display (FED) panel are optimized in the direction of enhancing panel brightness as well as avoiding cross talk between pixels. Field emitter arrays with the optimized shape of microtips were fabricated for the application to real devices. Three different technologies for phosphor screening, electrophoresis, printing, and slurry methods, are evaluated in terms of white color coordination of screened phosphor plates in a FED panel level, leading to the selection of the best screening process for FEDs. The charging effect of phosphor surface seems to have an effect on the luminance properties of phosphors, which can be suppressed with a drive circuitry in the real FED operation. It is observed that electron beam irradiation triggers serious outgassing from the phosphor surface in the narrow gap, necessitating the application of getters to absorb the outgassed molecules. Residual gases inside a panel are analyzed with the adoption of evaporable and nonevaporable getters. A 5 in. diagonal full color image is successfully demonstrated with a resultant brightness of 80 cd/m2.
Development of an Er–Ni liquid alloy ion source
Authors: Chao L. C. , Steckl A. J.
Published: July 2002

We have developed a procedure for the fabrication of Er–Ni liquid alloy ion sources. The source is tested and analyzed in a MicroBeam 150 focused ion beam system. Our experimental results show that an Er2+ target current of 95–100 pA was produced, representing 50% of the total target current. The ion emission current–voltage slope is ∼36 μA/kV. Source lifetimes are generally larger than 20 h. The alloy oxidizes quickly once it is exposed to air. This must be minimized to ensure proper source performance.
Molecular beam epitaxy growth of PbSe on BaF2-coated Si(111) and observation of the PbSe growth interface
Authors: Wu H. Z. , Fang X. M. , Salas R. , McAlister D. , McCann P. J.
Published: July 2002

Epitaxial growth of PbSe/BaF2/CaF2 heterostructures was carried out by molecular beam epitaxy (MBE) on Si(111) wafers. Successful transfer of 3-μm-thick PbSe epilayers was accomplished by bonding the MBE-grown samples face down to polished copper plates followed by the removal of the silicon substrate by dissolving the BaF2 buffer layer in water. High-resolution x-ray diffraction measurements demonstrated that the PbSe epilayer maintained high-crystalline quality after transfer. In addition, optical Nomarski characterization of the exposed growth interface showed sets of parallel straight step lines consistent with glide of dislocations in the primary {100}〈110〉 glide system. Such features are evidence of the large thermal expansion mismatch strain that occurred in these layers.
Oxygen implant isolation of n-GaN field-effect transistor structures
Authors: Dang G. , Cao X. A. , Ren F. , Pearton S. J. , Han J. , Baca A. G. , Shul R. J.
Published: July 2002

Multiple-energy (30–325 keV) O+ implantation into GaN field-effect transistor structures (n∼1018 cm−3, 3000 Å thick) can produce as-implanted sheet resistances of 4×1012 Ω/□, provided care is taken to ensure compensation of the region up to the projected range of the lowest energy implant. The sheet resistance remains above 107 Ω/□ to annealing temperatures of ∼650 °C and displays an activation energy of 0.29 eV. No diffusion of the implanted oxygen was observed for anneals up to 800 °C.
Quality of electroplated copper films produced using different acid electrolytes
Authors: Seah C. H. , Mridha S. , Chan L. H.
Published: July 2002

Copper films were electroplated on either W/TiN/Si(100) or Cu/TaN/Si(100) surfaces with copper electrolytes containing different types of acids, namely, H2SO4, HCl, HNO3, and HF. The properties of these copper films were then characterized in terms of their microstructure and electrical properties. Dense copper films were obtained from H2SO4 and HNO3-based electrolytes, which produced films consisting of small equiaxed grains with average grain sizes of 0.25 μm whereas larger grains of 0.5 μm were obtained from a HF-based electrolyte. However, a very rough Cu film with copper chloride residues was obtained from the HCl-based electrolyte. For W seeded substrates, strong 〈111〉 oriented copper films were produced while both 〈111〉 and 〈220〉 were observed as the preferred orientations of the film on Cu seeded substrates. Both H2SO4- and HNO3-based electrolytes were able to produce films with bulk resistivity as low as 1.82 μΩ cm on Cu seeded substrates. For W seed, the bulk resistivity varied between 1.92 and 2.31 μΩ cm. The HF-based electrolyte produced the highest bulk resistivity of 2.23 μΩ cm. In terms of the deposition rate, both HNO3 and HF achieved higher deposition rates than H2SO4.
Study of acid diffusion in resist near the glass transition temperature
Authors: Fryer David S. , Bollepali Srinivas , de Pablo Juan J. , Nealey Paul F.
Published: July 2002

The diffusion of p-toluene sulfonic acid (PTSA), a photoacid, in novolac was investigated at temperatures below and just above the glass transition temperature (Tg=91 °C) using a technique based on ellipsometry. Bilayer samples consisting of a blended film of novolac and PTSA and a film of pure novolac were held at a constant temperature for a known period of time and then quenched. The diffusion of PTSA from the supply layer into the initially pure novolac transforms the initial step function profile in refractive index to a more diffuse gradient in refractive index. Ellipsometry data from the samples could be analyzed to obtain diffusion coefficients using a Fickian model of diffusion and the experimentally determined dependence of the index of refraction as a function of PTSA concentration. The values of the diffusion coefficients were 10−14 to 10−12 cm2/s for temperatures between 50 and 95 °C. The activation energy for diffusion below the glass transition temperature was 67 kJ/mol. At 95 °C, just above Tg of novolac, the diffusion coefficient and activation energy increased significantly. This simple and convenient experimental technique provides useful data for the optimization of resist processing.
Maskless, parallel patterning with zone-plate array lithography
Authors: Carter D. J. D. , Gil Dario , Menon Rajesh , Mondol Mark. K. , Smith Henry I. , Anderson Erik H.
Published: July 2002

Zone-plate array lithography (ZPAL) is a maskless lithography scheme that uses an array of shuttered zone plates to print arbitrary patterns on a substrate. An experimental ultraviolet ZPAL system has been constructed and used to simultaneously expose nine different patterns with a 3×3 array of zone plates in a quasidot-matrix fashion. We present exposed patterns, describe the system design and construction, and discuss issues essential to a functional ZPAL system. We also discuss another ZPAL system which operates with 4.5 nm x radiation from a point source. We present simulations which show that, with our existing x-ray zone plates and this system, we should be able to achieve 55 nm resolution.
Cl
2
plasma passivation of etch induced damage in GaAs and InGaAs with an inductively coupled plasma source
Authors: Berg E. W. , Pang S. W.
Published: July 2002

Low energy Cl species generated in an inductively coupled plasma source have been used to passivate etch induced damage in GaAs and InGaAs. Improved electrical and optical characteristics were measured after Cl2 plasma passivation. The ideality factor and barrier height of etched GaAs Schottky diodes were improved back to the values of an unetched sample with a 10 min passivation. No etching occurred during passivation due to the presence of a surface oxide layer. The growth conditions of the oxide layer were found to have a large effect on the ability of the Cl2 plasma to passivate the surface. It was found that native oxides allow more effective passivation by Cl species as compared to plasma grown oxides. The passivation techniques were used to passivate damage along an etched sidewall for improved electrical conductivity of GaAs wires and increased photoluminescence signal from etched gratings containing an InGaAs quantum well.
Low-energy electron-beam effects on poly(methyl methacrylate) resist films
Authors: Bermudez V. M.
Published: July 2002

The effects of low-energy electron irradiation (10–50 eV, up to ∼2×1017 e cm−2) on thin films of poly(methyl methacrylate) (PMMA), deposited on air-exposed Al, have been studied in situ as a function of temperature (∼200–300 K) using polarization-modulated infrared reflection absorption spectroscopy. Near 300 K damage is seen in the form of a loss of material, as shown by a decrease in the intensity of the entire PMMA spectrum. At low temperature, in addition to damage, evidence is seen for a radiation-induced change in chain configuration leading to an increased interaction between ester groups and the Al surface. This configuration is unstable and is removed by annealing to ∼300 K.
Polycarbonate surface modified by argon cluster ion beams
Authors: Zemek J. , Yamada I. , Takaoka G. , Matsuo J.
Published: July 2002

X-ray induced photoelectron spectroscopy and atomic force microscopy were used to gain detailed information on surface topography, composition and bonding among atoms in a near-surface region of untreated and modified polycarbonate surfaces by argon cluster and argon monomer ion irradiation. As a consequence of the cluster ion beam impingement on the polycarbonates, their surfaces become rough with polymer structure partially damaged. Surprisingly, the surface irradiated by argon monomer ions was found less rough but the polymer structure in a surface region completely lost its integrity and an amorphous (hydrogenated) carbon layer was formed.
In situ atomic force microscopy observation on the decay of small islands on Au single crystal in acid solution
Authors: Hirai Nobumitsu , Watanabe Ken-ichi , Shiraki Akiko , Hara Shigeta
Published: July 2002

The decay process of small islands atop Au single crystals was observed by in situ atomic force microscopy in 50 mM H2SO4 aqueous solution at 1050 mV (vs normal hydrogen electrode, where no reaction current was detected). It was found that the area of islands on the terrace decreases linearly with time and the decay rate of the islands in solution is more than 30 times faster than that reported in air. We also found that the island in the same sulfuric solution at 1050 mV decayed more rapidly on Au(100) than on Au(111). We discuss the role of the excess charge at the metal/electrolyte interface, namely the electric double layer, which may affect the surface diffusion process of atoms atop the electrode in aqueous solution.
Effect of lateral dimensional scaling on the thermal stability of thin CoSi2 layers reacted on polycrystalline silicon
Authors: Alberti A. , La Via F. , Grimaldi M. G. , Ravesi S.
Published: July 2002

The thermal stability of patterned cobalt silicide layers grown on polycrystalline silicon was studied by electrical and morphological analyses in the temperature range of 850–1000 °C. The strip degradation upon annealing resulted in a faster resistance increase than that in blanket films, and occurred from preferential agglomeration of the grains located at the strip edges. An activation energy for this process of 3.5 eV was obtained by the increase in resistance and attributed to the growth of silicon grains from the substrate that protruded into the silicide layer.
Field emission mechanism from undoped chemical vapor deposition diamond films
Authors: Göhl A. , Günther B. , Habermann T. , Müller G. , Schreck M. , Thürer K. H. , Stritzker B.
Published: July 2002

We have investigated the field emission mechanism for nominally undoped diamond films with a thickness ranging from 3.2 to 27.5 μm, epitaxially grown on low p-doped Si(001). The experiments were performed in a field emission scanning microscope, which allows the investigation of μm-sized spots on cm2-sized samples. First, all samples were heated at 300 °C, resulting in electrically insulating properties. Then, current I versus voltage U measurements in electrode contact mode were performed at different temperatures and for both polarities as well as in noncontact mode for different electrode gaps. For local current densities up to 0.5 A/cm2 the field emission was limited by the diamond bulk properties and not by the surface barrier. Conduction through the bulk occurred by a Poole–Frenkel process for traps with overlapping Coulomb potentials. A thermally assisted electron hopping over the Coulomb barriers was proven and an activation energy of 0.43 eV and a trap density of 7.1×1018/cm3 were derived.
Real-time measurements of stress relaxation in InGaAs/GaAs
Authors: Beresford R. , Yin J. , Tetz K. , Chason E.
Published: July 2002

Real-time observations of the film stress–thickness product are presented from the growth of strained InGaAs/GaAs layers. Growth temperatures of 440 and 520 °C were used with a nominal In composition of x=0.20. The data are compared with a model of relaxation kinetics based on dislocation glide velocity. The residual strain is higher than predicted and the relaxation is not markedly temperature dependent, in contrast to the model. These discrepancies suggest that dislocation blocking causes incomplete relaxation in this material system.
Effects of hydrogen on doping of GaInNAs grown by gas-source molecular beam epitaxy
Authors: Xin H. P. , Tu C. W. , Geva M.
Published: July 2002

In this article, we investigate the effects of hydrogen (H) on doping of GaInNAs grown by gas-source molecular beam epitaxy with a rf plasma nitrogen radical beam source. Incorporating nitrogen (N) into p-Ga0.892In0.108As reduces strain and improves thermal stability. With increasing N concentration, more H, from thermally cracked AsH3, is incorporated alongside N into GaInAs. H has two effects on GaInNAs: acting as an isolated donor and passivating shallow dopants by forming complexes. With increasing N concentration, the free carrier concentration in the as-grown highly Be-doped Ga0.892In0.108NxAs1−x is decreased mainly due to H passivation. Rapid thermal annealing (RTA) increases free carrier concentration due to a reduced H level. The as-grown undoped Ga0.924In0.076N0.030As0.970 sample should be p type without H since N introduces a localized acceptor-like level. Our as-grown undoped sample in n-type 6.9×1015 cm−3 due to charge compensation with H donors. After 700 °C RTA, the film becomes p-type 5.7×1016 cm−3 due to the reduced H donors. For highly Si-doped GaInNAs (∼1×1018 cm−3), H mainly passivates the dopants, so the free carrier concentration is increased after RTA.
Controlled growth of ZnSeTe superlattices with sinusoidal compositional modulation
Authors: Lee S. , Bindley U. , Furdyna J. K. , Reimer P. M. , Buschert John R.
Published: July 2002

We have fabricated ZnSeTe sinusoidal superlattices, i.e., periodic structures in which the concentration of Se and Te varies sinusoidally along the direction of growth. This was accomplished by means of a novel molecular-beam epitaxy growth technique in which the periodic modulation is achieved by substrate rotation in the presence of nonuniform flux distributions of Se and Te, rather than by shutter openings and closings. Superlattices fabricated by this technique indeed result in remarkably regular sinusoidal (or very nearly sinusoidal) compositional profiles, as inferred from the presence of only the first superlattice harmonics in the x-ray spectra observed on these novel structures. In addition to the structural analysis, we present extensive photoluminescence data which also provide clear evidence for the formation of a superlattice by this method of growth. Finally, we discuss the special advantages of such a shutterless method of superlattice fabrication, and the consequences of commensurability or noncommensurability of the superlattice period with the underlying crystal structure.
Nonalloy Ohmic contact fabrication in a hydrothermally grown n-ZnO (0001) substrate by KrF excimer laser irradiation
Authors: Akane Toshimitsu , Sugioka Koji , Midorikawa Katsumi
Published: July 2002

A nonalloy Ohmic electrode is formed on a hydrothermally grown n-type ZnO substrate by KrF excimer laser irradiation and metal deposition without any impurity doping. Laser irradiation changes the ZnO surface layer to a Zn-rich one with lower sheet resistance than the bulk. The Zn-rich premetallized layer (ZnOx layer, x=0–1) exhibits n+-type conduction, which enables current conduction into the ZnO substrate with Ohmic characteristics. An In/ZnOx contact fabricated by single-pulse laser irradiation with 0.3 J/cm2 on the ZnO substrate has a contact resistance of 7×10−1 Ω cm2. A postheat treatment for 5 min at 300 °C increases the sheet resistance in the premetallized layer, which causes an increase of the contact resistance of the fabricated contact.
Trefoil Peptides--Less Clandestine in the Intestine
Authors: Chinery Rebecca , Coffey Robert
Published: July 2002

Trefoil peptides are small, stable peptides secreted into the gut, but their function has been obscure. Now Lefebvre
et al
. (
p. 259
) and Mashimo
et al
. (
p. 262
) report on the phenotype of two mouse lines, each missing a different trefoil peptide. The mouse line missing intestinal trefoil factor is unable to heal gut wounds properly, and the other, missing pS2, shows multiple carcinomas of the gut. Chinery and Coffey explain in their Perspective how these new results imply a function for trefoil proteins in gut-cell maturation and turnover.
Collaboration Across Continents
Authors: Williams Nigel
Published: July 2002

The Human Frontier Science Program, which focuses on molecular biology and study of the brain, provides money for items that national programs generally do not fund, such as salaries and travel expenses for the exchange of postdocs between collaborating laboratories and funds for regular meetings of international teams—giving researchers an opportunity to carry out truly global collaborative science.
Fast, Cheap, and Very Bright
Authors: Fasol Gerhard
Published: July 2002

Data communications relies as never before on high-performance lasers for generating the pulses that travel down optical fibers. In his Perspective, Fasol discusses a recently invented laser—the quantum-dot vertical-cavity surface-emitting laser. Made possible by breakthroughs in crystal growth, this laser operates at room temperature and may soon be commercially viable.
RNA Polymerase β′ Subunit: A Target of DNA Binding-Independent Activation
Authors: Miller Alita , Wood Douglas , Ebright Richard H. , Rothman-Denes Lucia B.
Published: July 2002

The bacteriophage N4 single-stranded DNA binding protein (N4SSB) activates transcription by the
Escherichia coli
σ
70
-RNA polymerase at N4 late promoters. Here it is shown that the single-stranded DNA binding activity of N4SSB is not required for transcriptional activation. N4SSB interacts with the carboxyl terminus of the RNA polymerase β′ subunit in a region that is highly conserved in the largest subunits of prokaryotic and eukaryotic RNA polymerases.
High-Resolution Water Vapor Mapping from Interferometric Radar Measurements
Authors: Hanssen Ramon F. , Weckwerth Tammy M. , Zebker Howard A. , Klees Roland
Published: July 2002

Spaceborne radar interferometric delay measurements were used to infer high-resolution maps of integrated atmospheric water vapor, which can be readily related to meteorological phenomena. Maps of the water vapor distribution associated with a precipitating cloud, a partly precipitating cold front, and horizontal convective rolls reveal quantitative measures that are not observed with conventional methods, and suggest that such radar observations can be used for forecasting and to study atmospheric dynamics.
An Aqueous Channel for Filamentous Phage Export
Authors: Marciano Denise K. , Russel Marjorie , Simon Sanford M.
Published: July 2002

Filamentous phage f1 exits its
Escherichia coli
host without killing the bacterial cell. It has been proposed that f1 is secreted through the outer membrane via a phage-encoded channel protein, pIV. A functional pIV mutant was isolated that allowed
E. coli
to grow on large maltodextrins and rendered
E. coli
sensitive to large hydrophilic antibiotics that normally do not penetrate the outer membrane. In planar lipid bilayers, both mutant and wild-type pIV formed highly conductive channels with similar permeability characteristics but different gating properties: the probability of the wild-type channel being open was much less than that of the mutant channel. The high conductivity of pIV channels suggests a large-diameter pore, thus implicating pIV as the outer membrane phage-conducting channel.
One-Dimensional Electronic Structure and Suppression of
d
-Wave Node State in (La
1.28
Nd
0.6
Sr
0.12
)CuO
4
Authors: Zhou X. J. , Bogdanov P. , Kellar S. A. , Noda T. , Eisaki H. , Uchida S. , Hussain Z. , Shen Z.-X.
Published: July 2002

Angle-resolved photoemission spectroscopy was carried out on (La
1.28
Nd
0.6
Sr
0.12
)CuO
4
, a model system of the charge- and spin-ordered state, or stripe phase. The electronic structure contains characteristic features consistent with other cuprates, such as the flat band at low energy near the Brillouin zone face. However, the low-energy excitation near the expected
d
-wave node region is strongly suppressed. The frequency-integrated spectral weight is confined inside one-dimensional segments in the momentum space (defined by horizontal momenta |

k
x

| = π/4 and vertical momenta |

k
y

| = π/4), deviating strongly from the more rounded Fermi surface expected from band calculations. This departure from the two-dimensional Fermi surface persists to a very high energy scale. These results provide important information for establishing a theory to understand the charge and spin ordering in cuprates and their relation with high-temperature superconductivity.
Prolonged Activation of Mitochondrial Conductances During Synaptic Transmission
Authors: Jonas Elizabeth A. , Buchanan JoAnn , Kaczmarek Leonard K.
Published: July 2002

Although ion channels have been detected in mitochondria, scientists have not been able to record ion transport in mitochondria of intact cells. A variation of the patch clamp technique was used to record ion channel activity from intracellular organelles in the presynaptic terminal of the squid. Electron microscopy indicated that mitochondria are numerous in this terminal and are the only organelles compatible with the tips of the pipettes. Before synaptic stimulation, channel activity was infrequent and its conductance was small, although large conductances (∼0.5 to 2.5 nanosiemens) could be detected occasionally. During a train of action potentials, the conductance of the mitochondrial membrane increased up to 60-fold. The conductance increased after a delay of several hundred milliseconds and continued to increase after stimulation had stopped. Recovery occurred over tens of seconds.
Radiation Tolerance of Complex Oxides
Authors: Sickafus K. E. , Minervini L. , Grimes R. W. , Valdez J. A. , Ishimaru M. , Li F. , McClellan K. J. , Hartmann T.
Published: July 2002

The radiation performance of a variety of complex oxides is predicted on the basis of a material's propensity to accommodate lattice point defects. The calculations indicate that a particular class of oxides possessing the fluorite crystal structure should accept radiation-induced defects into their lattices far more readily than a structurally similar class of oxides based on the pyrochlore crystal structure. Preliminary radiation damage experiments substantiate the prediction that fluorites are inherently more radiation resistant than pyrochlores. These results may permit the chemical durability and radiation tolerance of potential hosts for actinides and radioactive wastes to be tailored.
The Structural Basis of Ribosome Activity in Peptide Bond Synthesis
Authors: Nissen Poul , Hansen Jeffrey , Ban Nenad , Moore Peter B. , Steitz Thomas A.
Published: July 2002

Using the atomic structures of the large ribosomal subunit from
Haloarcula marismortui
and its complexes with two substrate analogs, we establish that the ribosome is a ribozyme and address the catalytic properties of its all-RNA active site. Both substrate analogs are contacted exclusively by conserved ribosomal RNA (rRNA) residues from domain V of 23
S
rRNA; there are no protein side-chain atoms closer than about 18 angstroms to the peptide bond being synthesized. The mechanism of peptide bond synthesis appears to resemble the reverse of the acylation step in serine proteases, with the base of A2486 (A2451 in
Escherichia coli
) playing the same general base role as histidine-57 in chymotrypsin. The unusual p
K
a
(where
K
a
is the acid dissociation constant) required for A2486 to perform this function may derive in part from its hydrogen bonding to G2482 (G2447 in
E. coli
), which also interacts with a buried phosphate that could stabilize unusual tautomers of these two bases. The polypeptide exit tunnel is largely formed by RNA but has significant contributions from proteins L4, L22, and L39e, and its exit is encircled by proteins L19, L22, L23, L24, L29, and L31e.
Antimicrobial Resistance of
Neisseria gonorrhoeae
and Emerging Ciprofloxacin Resistance in The Netherlands, 1991 to 1998
Authors: de Neeling Albert J. , van Santen-Verheuvel Marga , Spaargaren Joke , Willems Rob J. L.
Published: July 2002

Surveillance of antibiotic resistance in
Neisseria gonorrhoeae
showed a decrease in the percentage of β-lactamase-producing isolates but an increase in intermediately penicillin-resistant strains and strains resistant to a high level of tetracycline. MICs for the ciprofloxacin-resistant isolates that emerged increased, and these isolates had mutations in
gyrA
and
parC
similar to those observed in the Far East.
Levofloxacin Pharmacokinetics and Serum Bactericidal Activities against Five Enterobacterial Species
Authors: Geerdes-Fenge Hilte F. , Wiedersich Axel , Wagner S. , Lehr Karl-Heinz , Koeppe Peter , Lode Hartmut
Published: July 2002

After oral administration of 500 mg of levofloxacin to 12 volunteers, we investigated the pharmacokinetics and serum bactericidal activities (SBAs) against five strains of members of the family
Enterobacteriaceae
. Pharmacokinetic data were as follows: maximum concentration in serum, 6.36 ± 0.57 mg/liter; area under the concentration-time curve, 43.6 ± 6.23 mg · h/liter; elimination half-life 4.23 ± 0.87 h. SBAs were present for 24 h against
Escherichia coli
and
Citrobacter freundii
. The SBAs at 1, 12, and 24 h after administration against
E. coli
were 1:108, 1:29, and 1:7, respectively, and those against
Citrobacter freundii
were 1:74, 1:25, and 1:7, respectively. The SBAs were present for 12 h against the other three organisms tested. The SBAs against
Serratia marcescens
were 1:28 and 1:9 at 1 and 12 h, respectively; the SBAs against
Klebsiella pneumoniae
were 1:25 and 1:7 at 1 and 12 h, respectively; and the SBAs against
Enterobacter cloacae
were 1:24 and 1:10 at 1 and 12 h, respectively.
MICs of Oxazolidinones for
Rhodococcus equi
Strains Isolated from Humans and Animals
Authors: Bowersock Terry L. , Salmon Sarah A. , Portis Ellen S. , Prescott John F. , Robison Denise A. , Ford Charles W. , Watts Jeffrey L.
Published: July 2002

Eperezolid and linezolid are representatives of a new class of orally active, synthetic antimicrobial agents. The in vitro activity values (MICs) of linezolid, eperezolid, and comparator antibiotics against 102 strains of
Rhodococcus equi
isolated from humans and animals were determined. Linezolid was more active than eperezolid against the strains tested; premafloxacin was the most active comparator antibiotic.
In Vitro Activities of LY333328 and Comparative Agents against Nosocomial Gram-Positive Pathogens Collected in a 1997 Global Surveillance Study
Authors: Zeckel Michael L. , Preston David A. , Allen Bradley S.
Published: July 2002

The in vitro activity of LY333328 was evaluated for 1,479 nosocomial gram-positive pathogens isolated in 12 countries during 1997. LY333328 MICs at which 90% of the isolates tested were inhibited for
Enterococcus faecalis
(
n
= 351),
Enterococcus faecium
(
n
= 100),
Staphylococcus aureus
(
n
= 593), coagulase-negative
Staphylococcus
species (
n
= 325), and
Streptococcus pneumoniae
(
n
= 110) were 1, 1, 2, 2, and 0.015 μg/ml, respectively. LY333328 demonstrated potent activity against isolates of vancomycin-resistant enterococci, oxacillin-resistant staphylococci, and penicillin-resistant pneumococci.
Blocking the Receptor for Interleukin 10 Protects Mice from Lethal Listeriosis
Authors: Silva Regina A. , Appelberg Rui
Published: July 2002

High doses ofListeria monocytogenesovercome the ability of a normal mouse to control the infection, due to massive bacterial replication. Treatment with an anti-interleukin 10 (IL-10) receptor monoclonal antibody prevented the fatal course of infection with high doses of bacteria. This work shows that blocking the receptor for IL-10 may have useful therapeutic applications.
Prevention and Treatment of Lethal Murine Endotoxemia by the Novel Immunomodulatory Agent MFP-14
Authors: Nicoletti Ferdinando , Di Marco Roberto , Sacerdote Paola , Meroni PierLuigi , Mangano Katia , Edwards Carl , Bartorelli Alberto , Bendtzen Klaus , Panerai Alberto
Published: July 2002

Multifunctional protein 14 (MFP-14) is a ubiquitous protein that inhibits the production of tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ), which are involved in the pathogenesis of sepsis. Here, lipopolysaccharide (LPS)-induced lethality in mice was markedly reduced by MFP-14. The treatment also lowered LPS-induced levels of TNF-α and IFN-γ in the blood.
Population Pharmacokinetics of Intramuscular Quinine in Children with Severe Malaria
Authors: Krishna Sanjeev , Nagaraja Nelamangala V. , Planche Tim , Agbenyega Tsiri , Bedo-Addo George , Ansong Daniel , Owusu-Ofori Alex , Shroads Albert L. , Henderson George , Hutson Alan , Derendorf Hartmut , Stacpoole Peter W.
Published: July 2002

We present the first population pharmacokinetic analysis of quinine in patients with
Plasmodium falciparum
malaria. Ghanaian children (
n
= 120; aged 12 months to 10 years) with severe malaria received an intramuscular loading dose of quinine dihydrochloride (20 mg/kg of body weight). A two-compartment model with first-order absorption and elimination gave post hoc estimates for pharmacokinetic parameters that were consistent with those derived from non-population pharmacokinetic studies (clearance [CL] = 0.05 liter/h/kg of body weight; volume of distribution in the central compartment [
V
1
] = 0.65 liter/kg; volume of distribution at steady state = 1.41 liter/kg; half-life at β phase = 19.9 h). There were no covariates (including age, gender, acidemia, anemia, coma, parasitemia, or anticonvulsant use) that explained interpatient variability in weight-normalized CL and
V
1
. Intramuscular quinine was associated with minor, local toxicity in some patients (13 of 108; 12%), and 11 patients (10%) experienced one or more episodes of postadmission hypoglycemia. A loading dose of intramuscular quinine results in predictable population pharmacokinetic profiles in children with severe malaria and may be preferred to the intravenous route of administration in some circumstances.
Antibacterial Properties of Gemifloxacin and Trovafloxacin in Urine Ex Vivo: Phase I Study
Authors: Garcı́a-Calvo Gloria , Parra Araceli , Aguilar Lorenzo , Ponte Carmen , Giménez Marı́a J. , Carcas Antonio , Kinzig-Schippers Martina , Soriano Francisco
Published: July 2002

Urine bactericidal titers (UBTs) against
Escherichia coli
ATCC 25922 and
Staphylococcus saprophyticus
ATCC 1970 were determined after the administration of single oral doses of gemifloxacin at 320 mg and trovafloxacin at 200 mg to healthy volunteers. Gemifloxacin presented significantly lower experimental versus mathematically predicted UBTs over 72 h, due to the effect of urine on the susceptibility of the
E. coli
strain. Experimental UBTs were significantly higher for gemifloxacin than trovafloxacin against both strains over 72 h.
Kinetic Study of Two Novel Enantiomeric Tricyclic β-Lactams Which Efficiently Inactivate Class C β-Lactamases
Authors: Vilar Mateja , Galleni Moreno , Solmajer Tom , Turk Boris , Frère Jean-Marie , Matagne André
Published: July 2002

A detailed kinetic study of the interaction between two ethylidene derivatives of tricyclic carbapenems, Lek 156 and Lek 157, and representative β-lactamases andd-alanyl–d-alanine peptidases (dd-peptidases) is presented. Both compounds are very efficient inactivators of theEnterobacter cloacae908R β-lactamase, which is usually resistant to inhibition. Preliminary experiments indicate that various extended-spectrum class C β-lactamases (ACT-1, CMY-1, and MIR-1) are also inactivated. With theE. cloacae908R enzyme, complete inactivation occurs with a second-order rate constant,k2/K′, of 2 × 104to 4 × 104M−1s−1, and reactivation is very slow, with a half-life of >1 h. Accordingly, Lek 157 significantly decreases the MIC of ampicillin forE. cloacaeP99, a constitutive class C β-lactamase overproducer. With the other serine β-lactamases tested, the covalent adducts exhibit a wide range of stabilities, with half-lives ranging from long (>4 h with the TEM-1 class A enzyme), to medium (10 to 20 min with the OXA-10 class D enzyme), to short (0.2 to 0.4 s with the NmcA class A β-lactamase). By contrast, both carbapenems behave as good substrates of theBacillus cereusmetallo-β-lactamase (class B). TheStreptomycessp. strain R61 and K15 extracellulardd-peptidases exhibit low levels of sensitivity to both compounds.
In Vitro Activity of Telithromycin against Spanish
Streptococcus pneumoniae
Isolates with Characterized Macrolide Resistance Mechanisms
Authors: Morosini Marı́a-Isabel , Cantón Rafael , Loza Elena , Negri Marı́a-Cristina , Galán Juan-Carlos , Almaraz Felisa , Baquero Fernando
Published: July 2002

The susceptibilities to telithromycin of 203
Streptococcus pneumoniae
isolates prospectively collected during 1999 and 2000 from 14 different geographical areas in Spain were tested and compared with those to erythromycin A, clindamycin, quinupristin-dalfopristin, penicillin G, cefotaxime, and levofloxacin. Telithromycin was active against 98.9% of isolates (MICs, ≤0.5 μg/ml), with MICs at which 90% of isolates are inhibited being 0.06 μg/ml, irrespective of the resistance genotype. The corresponding values for erythromycin were 61.0% (MICs, ≤0.25 μg/ml) and >64 μg/ml. The
erm
(B) gene (macrolide-lincosamide-streptogramin B resistance phenotype) was detected in 36.4% (
n
= 74) of the isolates, which corresponded to 93.6% of erythromycin-intermediate and -resistant isolates, whereas the
mef
(A) gene (M phenotype [resistance to erythromycin and susceptibility to clindamycin and spiramycin without blunting]) was present in only 2.4% (
n
= 5) of the isolates. One of the latter isolates also carried
erm
(B). Interestingly, in one isolate for which the erythromycin MIC was 2 μg/ml, none of these resistance genes could be detected. Erythromycin MICs for
S. pneumoniae erm
(B)-positive isolates were higher (range, 0.5 to >64 μg/ml) than those for
erm
(B)- and
mef
(A)-negative isolates (range, 0.008 to 2 μg/ml). The corresponding values for telithromycin were lower for both groups, with ranges of 0.004 to 1 and 0.002 to 0.06 μg/ml, respectively. The erythromycin MIC was high for a large number of
erm
(B)-positive isolates, but the telithromycin MIC was low for these isolates. These results indicate the potential usefulness of telithromycin for the treatment of infections caused by erythromycin-susceptible and -resistant
S. pneumoniae
isolates when macrolides are indicated.
Microcin E492 Is an Unmodified Peptide Related in Structure to Colicin V
Authors: Pons Anne-Marie , Zorn Nathalie , Vignon David , Delalande François , Van Dorsselaer Alain , Cottenceau Gilles
Published: July 2002

The pore-forming microcin E492 was purified by solid-phase extraction and reversed-phase high-pressure liquid chromatography. Its molecular mass was 7,886 Da. The entire 84-amino-acid sequence was determined. There is no postranslational modification in the secreted microcin, and the sequence has homologies with the sequence of the microcin colicin V.
Quantification of
Clostridium botulinum
Toxin Gene Expression by Competitive Reverse Transcription-PCR
Authors: McGrath S. , Dooley J. S. G. , Haylock R. W.
Published: July 2002

Clostridium botulinum
produces a characteristic botulinum neurotoxin which can cause an often fatal neuroparalytic condition known as botulism. Although food-borne botulism is rare, critical screening by food companies is necessary to ensure that food products are safe. At present, the food industry assesses the risks of botulinum neurotoxin production by challenge testing to check any new food products and to check the efficacy of new storage regimes. Challenge testing involves artificial introduction of defined strains of microorganisms into food, and microbial growth and possible toxin production are then monitored. Botulinum toxin is normally analyzed by using the mouse bioassay. However, the mouse bioassay is expensive, slow, and politically sensitive because of animal rights issues. In this paper we describe adaptation of a new assay, competitive reverse transcription-PCR (RT-PCR), to monitor botulinum neurotoxin production. This method accurately measures the level of toxin-encoding mRNA in
C. botulinum
cells. Measurement of mRNA should provide a good indication of gene expression as mRNA is turned over rapidly in bacterial cells. In addition, the method is rapid, specific, and sensitive. The competitive RT-PCR method was developed to examine
C. botulinum
E VH toxin gene expression and was used to investigate the level of toxin production by
C. botulinum
E VH when the organism was grown in two different types of broth. The results which we obtained with the competitive RT-PCR method demonstrated that this method is more rapid and more sensitive than the mouse bioassay.
Molecular Cloning, Sequencing, and Expression in
Escherichia coli
of the Gene Encoding a Novel 5-Oxoprolinase without ATP-Hydrolyzing Activity from
Alcaligenes faecalis
N-38A
Authors: Nishimura Atsuhisa , Oyama Hiroshi , Hamada Takatoshi , Nobuoka Katsunori , Shin Takashi , Murao Sawao , Oda Kohei
Published: July 2002

The gene encoding a novel 5-oxoprolinase without ATP-hydrolyzing activity from
Alcaligenes faecalis
N-38A was cloned and characterized. The coding region of this gene is 1,299 bp long. The predicted primary protein is composed of 433 amino acid residues, with a 31-amino-acid signal peptide. The mature protein is composed of 402 amino acid residues with a molecular mass of 46,163 Da. The derived amino acid sequence of the enzyme showed no significant sequence similarity to any other proteins reported so far. The 5-oxoprolinase gene was expressed in
Escherichia coli
by using a regulatory expression system with an isopropyl-β-
d
-thiogalactopyranoside-inducible
tac
promoter, and its expression level was approximately 16 mg per liter. The purified enzyme has the same characteristics as the authentic enzyme, except for the amino terminus, which has three additional amino acids. The enzyme was markedly inhibited by
p
-chloromercuribenzoic acid, EDTA,
o
-phenanthroline, HgCl
2
, and CuSO
4
. The EDTA-inactivated enzyme was completely restored by the addition of Zn
2+
or Co
2+
. In addition, the enzyme was found to contain 1 g-atom of zinc per mol of protein. These results suggest that the 5-oxoprolinase produced by
A. faecalis
N-38A is a zinc metalloenzyme.
Effects of pH and Energy Supply on Activity and Amount of Pyruvate Formate-Lyase in
Streptococcus bovis
Authors: Asanuma Narito , Hino Tsuneo
Published: July 2002

The enzyme system of pyruvate formate-lyase (PFL) in
Streptococcus bovis
was investigated by isolating PFL and PFL-activating enzyme (PFL-AE) from
S. bovis
, flavodoxin from
Escherichia coli
, and chloroplasts from spinach. In this study, the PFL and PFL-AE in
S. bovis
were found to be similar to those in
E. coli
, suggesting that the activating mechanisms are similar. The optimal pH of
S. bovis
PFL was 7.5, which is in contrast to the optimal pH of
S. bovis
lactate dehydrogenase, which is 5.5. The apparent

K
m

of
S. bovis
PFL was 2 mM. The intermediates of glycolysis, dihydroxyacetone phosphate (DHAP) and
d
-glyceraldehyde-3-phosphate (GAP), were shown to inhibit PFL activity. The concentrations of intracellular DHAP and GAP in
S. bovis
ranged from 1.9 mM to less than 0.1 mM and from 0.6 mM to less than 0.05 mM, respectively, depending on the energy supply. The wide variations in DHAP and GAP levels indicated that PFL activity is allosterically regulated by these triose phosphates in vivo. The amount of PFL protein, as determined by Western blot analysis with polyclonal antibody, changed in parallel with the level of
pfl
-mRNA, responding to the culture conditions. These observations confirm that PFL synthesis is regulated at the transcriptional level and support the hypothesis that
S. bovis
shifts the fermentation pathway from acetate, formate, and ethanol production to lactate production when the pH is low and when excess energy is supplied.
β-Glutamate as a Substrate for Glutamine Synthetase
Authors: Robinson Patrice , Neelon Kelly , Schreier Harold J. , Roberts Mary F.
Published: July 2002

The conversion of β-glutamate to β-glutamine by archaeal and bacterial glutamine synthetase (GS) enzymes has been examined. The GS from
Methanohalophilus portucalensis
(which was partially purified) is capable of catalyzing the amidation of this substrate with a rate sevenfold less than the rate obtained with α-glutamate. Recombinant GS from the archaea
Methanococcus jannaschii
and
Archaeoglobus fulgidus
were considerably more selective for α-glutamate than β-glutamate as a substrate. All the archaeal enzymes were much less selective than the two bacterial GS (from
Escherichia coli
and
Bacillus subtilis
), whose specific activities towards β-glutamate were much smaller than rates with the α-isomer. These results are discussed in light of the observation that β-glutamate is accumulated as an osmolyte in many archaea while β-glutamine (produced by glutamine synthetase) is used as an osmolyte only in
M. portucalensis
.
Construction of a Xylanase-Producing Strain of
Brevibacterium
lactofermentum
by Stable Integration of an Engineered
xysA
Gene from
Streptomyces
halstedii
JM8
Authors: Adham Sirin A. I. , Campelo Ana B. , Ramos Angelina , Gil José A.
Published: July 2002

A xylanolytic strain of
Brevibacterium
lactofermentum
containing the
Streptomyces
halstedii
His-tagged
xysA
gene was generated. The new strain contains DNA derived from
S
.
halstedii
, expresses xylanolytic activity, and was obtained by an integrative process mediated by a conjugative plasmid targeted to a dispensable chromosomal region located downstream from the essential cell division gene
ftsZ
. The His-tagged Xys1 enzyme was constitutively expressed under the control of the
kan
promoter from Tn
5
and was easily purified by use of Ni-nitrilotriacetic acid-agarose. The new strain is stable for more than 200 generations, lacks any known antibiotic resistance gene, and does not need any selective pressure to maintain the integrated gene. This strategy can be used to integrate any gene into the
B
.
lactofermentum
chromosome and to maintain it stably without the use of antibiotics for selection.
Aerobic Biodegradation of Methyl
tert
-Butyl Ether by Aquifer Bacteria from Leaking Underground Storage Tank Sites
Authors: Kane S. R. , Beller H. R. , Legler T. C. , Koester C. J. , Pinkart H. C. , Halden R. U. , Happel A. M.
Published: July 2002

The potential for aerobic methyl
tert
-butyl ether (MTBE) degradation was investigated with microcosms containing aquifer sediment and groundwater from four MTBE-contaminated sites characterized by oxygen-limited in situ conditions. MTBE depletion was observed for sediments from two sites (e.g., 4.5 mg/liter degraded in 15 days after a 4-day lag period), whereas no consumption of MTBE was observed for sediments from the other sites after 75 days. For sediments in which MTBE was consumed, 43 to 54% of added [U-
14
C]MTBE was mineralized to
14
CO
2
. Molecular phylogenetic analyses of these sediments indicated the enrichment of species closely related to a known MTBE-degrading bacterium, strain PM1. At only one site, the presence of water-soluble gasoline components significantly inhibited MTBE degradation and led to a more pronounced accumulation of the metabolite
tert
-butyl alcohol. Overall, these results suggest that the effects of oxygen and water-soluble gasoline components on in situ MTBE degradation will vary from site to site and that phylogenetic analysis may be a promising predictor of MTBE biodegradation potential.
Isolation and Characterization of a Gene Specific to Lager Brewing Yeast That Encodes a Branched-Chain Amino Acid Permease
Authors: Kodama Yukiko , Omura Fumihiko , Ashikari Toshihiko
Published: July 2002

We found two types of branched-chain amino acid permease gene (
BAP2
) in the lager brewing yeast
Saccharomyces pastorianus
BH-225 and cloned one type of
BAP2
gene (Lg-
BAP2
), which is identical to that of
Saccharomyces bayanus
(by-
BAP2
-1). The other
BAP2
gene of the lager brewing yeast (cer-
BAP2
) is very similar to the
Saccharomyces cerevisiae BAP2
gene. This result substantiates the notion that lager brewing yeast is a hybrid of
S. cerevisiae
and
S. bayanus
. The amino acid sequence homology between
S. cerevisiae
Bap2p and Lg-Bap2p was 88%. The transcription of Lg-
BAP2
was not induced by the addition of leucine to the growth medium, while that of cer-
BAP2
was induced. The transcription of Lg-
BAP2
was repressed by the presence of ethanol and weak organic acid, while that of cer-
BAP2
was not affected by these compounds. Furthermore, Northern analysis during beer fermentation revealed that the transcription of Lg-
BAP2
was repressed at the beginning of the fermentation, while cer-
BAP2
was highly expressed throughout the fermentation. These results suggest that the transcription of Lg-
BAP2
is regulated differently from that of cer-
BAP2
in lager brewing yeasts.
In Vivo
23
Na Nuclear Magnetic Resonance Study of Maintenance of a Sodium Gradient in the Ruminal Bacterium
Fibrobacter succinogenes
S85
Authors: Schwaab Véronique , Matheron Christelle , Delort Anne-Marie , Gaudet Geneviève , Forano Evelyne
Published: July 2002

Sodium gradients (ΔpNa) were measured in resting cells of
Fibrobacter succinogenes
by in vivo
23
Na nuclear magnetic resonance using Tm(DOTP)
5−
[thulium(III) 1,4,7,10-tetraazacyclododecane-
N
′,
N
′′,
N
′′′-tetramethylenephosphonate] as the shift reagent. This bacterium was able to maintain a ΔpNa of −55 to −40 mV for extracellular sodium concentrations ranging from 30 to 200 mM. Depletion of Na
+
ions during the washing steps led to irreversible damage (modification of glucose metabolism and inability to maintain a sodium gradient).