bluuebunny/crossref_metadata_2025 huggingface dataset:
Inductively coupled plasma heating in a weakly magnetized plasma
Authors: Kim S. S. , Chang C. S. , Yoon N. S. , Whang Ki-Woong
Published: July 2002

A one-dimensional analysis of electron heating process in a weakly magnetized, inductively coupled plasma (MICP) is presented. It is found that the main difference in the heating process of a MICP from that of a usual unmagnetized ICP is in that circularly polarized wave modes can exist in the plasma. The right handed circularly polarized wave (R-wave) can propagate into the plasma and its amplitude can be enhanced by cavity resonance effect at an appropriate chamber length and external magnetic field strength. The enhanced R-wave amplitude can raise the heating efficiency significantly. It is also found that a bounce cyclotron-resonance effect can exist, which, however, is not as significant as the cavity resonance effect.
The Gaseous Electronic Conference (GEC) reference cell as a benchmark for understanding microelectronics processing plasmas
Authors: Brake M. L. , Pender J. , Fournier J.
Published: July 2002

A collaborative experimental effort was initiated at a workshop at the 1988 Gaseous Electronics Conference (GEC) to start a program to understand the fundamental physics of processing plasmas, as well as give researchers a baseline experiment to develop plasma diagnostics to be used on manufacturing plasma systems. The design was based on the use of 4 in. diameter, aluminum electrodes in a parallel plate configuration at 13.56 MHz, run in a capacitively coupled discharge mode. Before conclusions about commercial plasma systems can be made from experimental results from the GEC cell, the GEC cell must be shown to behave similarly to that of a commercial system. The etching performance of a GEC cell was compared to a SEMI Group 1000 TP/CC reactive ion etcher (RIE). The GEC cell and the RIE gave similar etch rates and fluorine concentrations when the electrode plate spacing and power density were the same.
Contribution of slow waves on production of high-density plasmas by m=0 helicon waves
Authors: Sakawa Y. , Takino T. , Shoji T.
Published: July 2002

The contribution of the slow waves (SWs) on high-density plasma production by m=0 helicon waves is investigated in H2, D2, He, N2, Ne, Ar, and Xe plasmas. The density-jump is observed in all the gases used at optimum external magnetic fields B0. The measured plasma density np as a function of B0 peaks at a condition close to the lower-hybrid resonance in H2, D2, He, N2, and Ne, whereas, the measured dispersion relation indicates the excitation of helicon wave. Dispersion relation of electromagnetic waves is solved using dielectric tensor elements of a cold uniform plasma including ion terms, which shows two branches: the SW and fast (helicon) wave. The transition from the ionization by SWs, which are excited in the low-density plasma produced by an antenna induction field, to that by helicon waves has been predicted to explain the mechanism to produce the high-density plasma in the helicon wave discharges.
Electron-electron interaction and high field transport in Si
Authors: Lugli P. , Ferry D. K.
Published: July 2002

We present a study of the electron-electron interaction in n-silicon, utilizing the full dielectric function to determine the contribution of the electron-plasmon scattering terms. An Ensemble Monte Carlo is used to investigate the effects of this interaction on the transient dynamic response of electrons under high electric fields.
Observation of the trend of interface formation in anodic native oxide on InSb by marker experiments
Authors: Shapira Yoram , Bregman J. , Calahorra Z.
Published: July 2002

We have investigated the trend of anodization of InSb by predeposition of a very thin Cr layer, acting as a marker. Results of Auger electron spectroscopy show that the oxidation process is carried out by oxygen in diffusion through the oxide film. The details and implications of this observation are discussed.
Kinetics of thermal nitridation processes in the study of dopant diffusion mechanisms in silicon
Authors: Fahey P. , Barbuscia G. , Moslehi M. , Dutton R. W.
Published: July 2002

The changes in diffusion rates of Sb, As, and P resulting from nitridation of SiO2 and direct nitridation of the silicon surface in NH3 ambient at 1100 °C are studied for times ranging from 7 min to 4.5 h. From analysis of these data we conclude that P must diffuse almost entirely by an interstitialcy mechanism at this temperature, and that previous formulations of dopant diffusion under nonequilibrium conditions may not be complete. We also determine that the effects seen during direct nitridation are better explained by a pure vacancy injection process than a pure self-interstitial depletion process, contrary to previous assertions by us and others.
Ar (3P2) induced chemical vapor deposition of hydrogenated amorphous silicon
Authors: Toyoshima Y. , Kumata K. , Itoh U. , Arai K. , Matsuda A. , Washida N. , Inoue G. , Katsuumi K.
Published: July 2002

Energy transfer from metastable argon [Ar (3P2)] to SiH4 was applied to prepare hydrogenated amorphous silicon films. The emission due to the transition of SiH (A2Δ–X2Π) was observed when SiH4 reacted with Ar (3P2). The electric and optical properties of the films were investigated as functions of substrate temperature. The conductivity of the film prepared at 100 °C is 10−10 Ω−1 cm−1 in the dark and 10−5 Ω−1 cm−1 under illumination with a photon flux of 1015 cm−2 s−1. Hydrogen is found to be incorporated into the films mainly in the monohydride configuration even at a substrate temperature as low as 40 °C.
Formation of Fe14La2B phase in as-cast and melt-spun samples
Authors: Hadjipanayis G. C. , Tao Y. F. , Gudimetta K.
Published: July 2002

The formation of the tetragonal Fe14La2B phase has been examined in both as-cast and melt-spun Fe-La-B alloys using thermal and magnetic techniques together with x-ray diffraction analysis. It is found that this phase exists in both types of alloys and that it is produced by annealing at relatively low temperatures. The Fe14La2B phase is unstable and is transformed to mostly α-Fe plus La-B upon annealing at higher temperatures.
I
n s
i
t
u investigation of transport in semiconductors: A contactless approach
Authors: Skumanich Andrew , Fournier Daniele , Boccara A. Claude , Amer Nabil M.
Published: July 2002

We present a spatially resolved contactless method for the study of electronic and thermal transport in semiconductors. The technique employs the deflection of a probe beam propagating through the material to measure thermal and electronic diffusivities, carrier lifetime, and surface recombination. This deflection results from both the thermally and electronically induced changes in the local index of refraction of the semiconductor.
Frequency stabilization of an InGaAsP distributed feedback laser to an NH3 absorption line at 15137 Å with an external frequency modulator
Authors: Yanagawa T. , Saito S. , Machida S. , Yamamoto Y. , Noguchi Y.
Published: July 2002

The oscillation frequency of a 1.5-μm InGaAsP distributed feedback laser is stabilized to an NH3 linear absorption line at 15137 Å. A LiNbO3 external frequency modulator is used instead of direct frequency modulation of the laser to extract error signals. An effective bandwidth of 100 kHz for the feedback loop is obtained through this external modulation scheme. Frequency stability of σ(2,τ)=4×10−11 is achieved for an averaging time of 1 s≤τ≤100 s.
Dependence of photoetching rates of polymers at 193 nm on optical absorption depth
Authors: Cole H. S. , Liu Y. S. , Philipp H. R.
Published: July 2002

Mixtures of poly(methyl methacrylate) and poly(α-methyl styrene) were prepared and their optical absorption coefficients at 193 nm were measured. A study of photoetching rate of these polymeric materials using an ArF excimer laser at 193 nm shows two regions of distinctly different etching characteristics. At relatively high fluences (>300 mJ/cm2) the photoetch rate decreased with increasing absorption in the polymer films, while at lower fluences, an optimum range of absorption coefficients was found to give the maximum photoetching rate.
Schottky barrier heights of Hg, Cd, and Zn on n-type InP(100)
Authors: Sa C. J. , Meiners L. G.
Published: July 2002

We report a study of the electrical properties of Schottky barrier heights of column IIB metals (Hg, Cd, and Zn) on chemically cleaned n-type InP(100). Hg/InP diodes were formed by using a commercially available mercury probe, while Cd/InP diodes and Zn/InP diodes were fabricated by electroplating techniques. Dark forward bias current-voltage as well as dark reverse bias capacitance-voltage measuring techniques were used to characterize the samples. The barrier heights were found to be 0.92, 0.62, and 0.43 eV for Hg/n-InP, Cd/n-InP, and Zn/n-InP, respectively. The barrier heights for Hg/n-InP and Cd/n-InP are higher than commonly thought possible on n-type InP.
20% efficiency silicon solar cells
Authors: Blakers A. W. , Green M. A.
Published: July 2002

Further improvements in crystalline silicon solar cell performance have been obtained by combining the high levels of surface recombination control demonstrated in earlier passivated emitter solar cells with an improved optical approach. This approach involves the use of microgrooved surfaces which retain the advantages of pyramidally textured surfaces while avoiding some disadvantages of the latter. The approach results in a 5–6% improvement in cell short-circuit current density for cells fabricated on 0.1 and 0.2 Ω cm ( p type) substrates. This results in an energy conversion efficiency for these devices above 20% under standard terrestrial test conditions (AM1.5, 100 mW/cm2) for the first time.
Stripe-geometry quantum well heterostructure AlxGa1−xAs-GaAs lasers defined by defect diffusion
Authors: Deppe D. G. , Guido L. J. , Holonyak N. , Hsieh K. C. , Burnham R. D. , Thornton R. L. , Paoli T. L.
Published: July 2002

Impurity-free selective layer disordering, utilizing Si3N4 masking stripes and SiO2 defect (vacancy) sources, is used to realize room-temperature continuous AlxGa1−xAs-GaAs quantum well heterostructure lasers.
Analytic Boltzmann equation approach for negative differential mobility in two-valley semiconductors
Authors: Stanton Christopher J. , Baranger Harold U. , Wilkins John W.
Published: July 2002

We present results for the negative differential mobility and the distribution function in GaAs and InP for electric fields less than 40 kV/cm based on the analytic solution of the Boltzmann equation for a model with two valleys and three relaxation times. Using the measured low field mobility, lower valley mass, and valley separation energy Δ while adjusting three upper valley parameters, we obtain good agreement with the experimental velocity-field curves. The distribution function in the lower valley shows structure at energies ≊Δ due to the intervalley scattering.
Photochemically pumped I2(D′3Π2g→A′3Π2u) emission in mixtures of I2+C3F7I and I2+O3: Implications for chemically initiated, broadband optically pumped I2(D′→A′) lasers
Authors: Stech D. J. , Muller C. H. , Czyzak S. R. , Neumann D. K.
Published: July 2002

We report the first observation of photochemically initiated I2(D′→A′) emission at 342 nm. Mixtures of I2 and C3F7I or I2 and O3 were excited by a KrF laser at 248 nm photodissociating the C3F7I or O3. The process believed responsible for the intense D′→A′ emission is rapid energy transfer from the excited I(2P1/2) or O2(a 1Δ) photodissociation products to I2(X,v″=0) producing I2(X,v″=25→43) which is optically pumped by 248 nm photons to I2(D 1∑+u) and I2(F 1∑+u). Rapid collisional redistribution results in the F,D→D′ crossover. Gain of several percent per centimeter on the D′→A′ transition may be possible with the appropriate gas mixture and pump source.
Temperature and intensity dependence of photorefractive effect in GaAs
Authors: Cheng Li-Jen , Partovi Afshin
Published: July 2002

The photorefractive effect in semi-insulating Cr-doped GaAs as measured by the beam coupling technique was investigated as functions of temperature (295–386 K) and intensity (0.15–98 mW/cm2 of 1.15 μm light beams from a He-Ne laser). Results show that the photorefractive effect deteriorates rapidly over a narrow range of temperature as temperature rises and that this characteristic temperature increases with the logarithm of beam intensity. The observed phenomenon is attributed to the competing effects of the dark- and light-induced conductivities.
Longitudinal discharge XeCl excimer laser with automatic UV preionization
Authors: Furuhashi Hideo , Hiramatsu Mineo , Goto Toshio
Published: July 2002

A longitudinal discharge XeCl 308-nm excimer laser operated with automatic spark UV preionization is reported. Laser oscillation has been obtained using a four-segmented longitudinal discharge tube of 260 mm length and 4 mm inner diameter and employing a capacitor transfer circuit with commercially available doorknob ceramic capacitors. Spark UV preionization has been found to increase the laser output energy.
Thermal stability and barrier height enhancement for refractory metal nitride contacts on GaAs
Authors: Zhang L. C. , Cheung S. K. , Liang C. L. , Cheung N. W.
Published: July 2002

Self-aligned GaAs metal-semiconductor field-effect transistor process requires a very thermally stable gate material which must maintain good Schottky contact with GaAs after high-temperature annealing. The electrical characteristics of rf-sputtered ZrN, TiN, and NbN contacts on n-GaAs substrate have been investigated as a function of annealing temperature. We show that all these refractory metal nitride contacts on GaAs have ideality factors very close to unity after annealing at temperatures as high as 850 °C. The barrier height for these contacts increases with annealing temperature and very low reverse leakage current is obtained. We also observe similar behavior from previous work on WN/GaAs contacts. Such barrier height enhancement at elevated temperatures has been attributed to the incorporation of nitrogen into GaAs near the metal/GaAs interface.
Solid-state interdiffusion reactions in Ni/Ti and Ni/Zr multilayered thin films
Authors: Meng W. J. , Fultz B. , Ma E. , Johnson W. L.
Published: July 2002

We have performed a comparative transmission electron microscopy study of solid-state interdiffusion reactions in multilayered Ni/Zr and Ni/Ti thin films. The Ni-Zr reaction product was amorphous while the Ni-Ti reaction product was a simple intermetallic compound. Because thermodynamic and chemical properties of these two alloy systems are similar, we suggest kinetic origins for this difference in reaction product.
Planar-embedded InGaAsP/InP heterostructure laser with a semi-insulating InP current-blocking layer grown by metalorganic chemical vapor deposition
Authors: Sanada T. , Nakai K. , Wakao K. , Kuno M. , Yamakoshi S.
Published: July 2002

We used metalorganic chemical vapor deposition to fabricate a planar-embedded InGaAsP/InP heterostructure laser with a semi-insulating InP current-blocking layer. The laser exhibits cw operation with a low, 20 mA threshold current and a high external differential quantum efficiency of 40% at room temperature. Measurements have also shown a small-signal frequency response of 10 GHz due to an extremely small parasitic capacitance of 3.5 pF.
Low-temperature transport properties of ultrathin CoSi2 epitaxial films
Authors: Badoz P. A. , Briggs A. , Rosencher E. , d’Avitaya F. Arnaud , d’Anterroches C.
Published: July 2002

Low-temperature transport measurements (down to 18 mK) are performed in CoSi2 ultrathin films (down to 1.4 nm) epitaxially grown on silicon substrates. The low-temperature residual resistivity exhibits little dependence on the CoSi2 film thickness down to 10 nm. However, a steep increase is found below 10 nm, which is not taken into account by the Fuchs–Sondheimer [Proc. Cambridge Philos. Soc. 34, 100 (1938)] boundary scattering theory. Correlatively, the superconducting critical temperature of these CoSi2 films is abruptly depressed in the same thickness range. These two effects are phenomenologically explained by the presence of a perturbed layer, i.e., a CoSi2 interfacial layer in which the electronic transport properties are dramatically diminished.
Raman study of an epitaxial GaAs layer on a Si [100] substrate
Authors: Huang Yihe , Yu Peter Y. , Charasse Marie-Noelle , Lo Yuhua , Wang Shyh
Published: July 2002

A bevel has been etched in a GaAs epitaxial film grown on a Si substrate, so that the Raman spectrum of the GaAs layers can be measured as a function of distance from the GaAs/Si interface. The amount of strain and disorder in the GaAs film has been estimated from the GaAs longitudinal optical phonon line shape and frequency. Both the strain and the amount of disorder were found to decrease with increase in the distance from the interface.
Second-order susceptibility of asymmetric coupled quantum well structures
Authors: Khurgin J.
Published: July 2002

Second-order susceptibility of AlxGa1−xAs/GaAs asymmetric coupled quantum well is calculated. The magnitudes of second-harmonic and linear electro-optic coefficients are found to be comparable to that of LiNbO3. Further progress can lead to engineering of novel synthetic nonlinear materials.
KrF laser controlled diffuse discharge opening/closing switches using a photoelimination reaction
Authors: Kobayashi Osamu , Sasagawa Teruo , Obara Minoru
Published: July 2002

Optical control of a diffuse discharge can potentially be used to switch inductive energy storage systems at high repetition rates. A means of optical enhancement of the electron attachment process can hopefully be used as an optically controlled switch. Vinylchloride (C2H3Cl) photoeliminates a vibrationally rotationally excited HCl(v,J) which strongly attaches low-energy electrons. In our experiment, we observed the opening and closing of a diffuse discharge in a mixture of C2H3Cl/He (C2H3Cl:He=0.7:99.3%, total pressure 1.5 Torr) by KrF laser irradiation of 5.7 mJ/cm2 (20 ns full width at half-maximum). Under these conditions, a discharge current of 200 μA could be interrupted with a time constant of 100 μs. The discharge was again initiated by KrF laser irradiation. As a result, both discharge opening and closing by the laser irradiation were demonstrated.
Field-stimulated exoelectron emission from 99.9999% pure Al
Authors: Tagawa M. , Takenobu S. , Ohmae N. , Umeno M.
Published: July 2002

Exoelectrons were emitted from a 99.9999% pure Al tip by applying an electric field as a stimulus. This occurred at lower voltages than that necessary for field emission of electrons. Field-stimulated exoelectron emission showed a characteristic storage effect in accordance with the time interval of applied voltage pulses. Based upon this storage effect and a computer calculation of the field strength at the apex of the tip, we show by analytical discussions that exoelectrons are emitted by tunneling, not by the Schottky effect.
Linewidth reduction and optical frequency stabilization of a distributed feedback laser by incoherent optical negative feedback
Authors: Yasaka Hiroshi , Kawaguchi Hitoshi
Published: July 2002

A new, incoherent, optical negative feedback method is proposed and demonstrated for spectral linewidth reduction and optical frequency stabilization of distributed feedback lasers. The spectral linewidth and the optical frequency drift are simultaneously reduced to about 50 kHz and less than 10 MHz, respectively.
Transfer RNA-dependent amino acid biosynthesis: An essential route to asparagine formation
Authors: Min Bokkee , Pelaschier Joanne T. , Graham David E. , Tumbula-Hansen Debra , Söll Dieter
Published: July 2002

Biochemical experiments and genomic sequence analysis showed that
Deinococcus radiodurans
and
Thermus thermophilus
do not possess asparagine synthetase (encoded by
asnA
or
asnB
), the enzyme forming asparagine from aspartate. Instead these organisms derive asparagine from asparaginyl-tRNA, which is made from aspartate in the tRNA-dependent transamidation pathway [Becker, H. D. & Kern, D. (1998)
Proc. Natl. Acad. Sci. USA
95, 12832–12837; and Curnow, A. W., Tumbula, D. L., Pelaschier, J. T., Min, B. & Söll, D. (1998)
Proc. Natl. Acad. Sci. USA
95, 12838–12843]. A genetic knockout disrupting this pathway deprives
D. radiodurans
of the ability to synthesize asparagine and confers asparagine auxotrophy. The organism's capacity to make asparagine could be restored by transformation with
Escherichia coli asnB
. This result demonstrates that in
Deinococcus
, the only route to asparagine is via asparaginyl-tRNA. Analysis of the completed genomes of many bacteria reveal that, barring the existence of an unknown pathway of asparagine biosynthesis, a wide spectrum of bacteria rely on the tRNA-dependent transamidation pathway as the sole route to asparagine.
Human fatty acid synthase: Role of interdomain in the formation of catalytically active synthase dimer
Authors: Chirala Subrahmanyam S. , Jayakumar Armugam , Gu Zi-Wei , Wakil Salih J.
Published: July 2002

The human and animal fatty acid synthases are dimers of two
identical multifunctional proteins (
M
r
272,000) arranged in an antiparallel configuration. This arrangement
generates two active centers for fatty acid synthesis separated by
interdomain (ID) regions and predicts that two appropriate halves of
the monomer should be able to reconstitute an active fatty acid
synthesizing center. This prediction was confirmed by the
reconstitution of the synthase active center by using two
heterologously expressed halves of the monomer protein. Each of these
recombinant halves of synthase monomer contains half of the ID regions.
We show here that the fatty acid synthase activity could not be
reconstituted when the ID sequences present in the two recombinant
halves are deleted, suggesting that these ID sequences are essential
for fatty acid synthase dimer formation. Further, we confirm that the
ID sequences are the only regions of fatty acid synthase monomers that
showed significant dimer formation, by using the yeast two-hybrid
system. These results are consistent with the proposal that the ID
region, which has no known catalytic activity, associates readily and
holds together the two dynamic active centers of the fatty acid
synthase dimer, therefore playing an important role in the architecture
of catalytically active fatty acid synthase.
Retrocyclin: A primate peptide that protects cells from infection by T- and M-tropic strains of HIV-1
Authors: Cole Alexander M. , Hong Teresa , Boo Lee Ming , Nguyen Tung , Zhao Chengquan , Bristol Greg , Zack Jerome A. , Waring Alan J. , Yang Otto O. , Lehrer Robert I.
Published: July 2002

Human bone marrow expresses a pseudogene that encodes an antimicrobial peptide homologous to rhesus monkey circular minidefensins (θ-defensins). We prepared the putative ancestral human peptide by solid-phase synthesis and named it “retrocyclin.” Retrocyclin did not cause direct inactivation of HIV-1, and its modest antibacterial properties resembled those of its rhesus homologs. Nevertheless, retrocyclin had a remarkable ability to inhibit proviral DNA formation and to protect immortalized and primary human CD4+lymphocytes fromin vitroinfection bybothT-tropic and M-tropic strains of HIV-1. Confocal fluorescent microscopy studies performed with BODIPY-FL-labeled RC-101, a close analog of retrocyclin, showed that the peptide formed patch-like aggregates on the surface of CD4+cells. These findings suggest that retrocyclin interferes with an early stage of HIV-1 infection and that retrocyclin-like agents might be useful topical agents to prevent sexually acquired HIV-1 infections.
Emission lines of [K
v
] in the optical spectra of gaseous nebulae
Authors: Keenan Francis P. , Aller Lawrence H. , Espey Brian R. , Exter Katrina M. , Hyung Siek , Keenan Michael T. C. , Pollacco Don L. , Ryans Robert S. I.
Published: July 2002

Recent R-matrix calculations of electron impact excitation rates in K
v
are used to derive the nebular emission line ratio
R
=
I
(4122.6 Å)/
I
(4163.3 Å) as a function of electron density (
N
e
). This ratio is found to be very sensitive to changes in
N
e
over the density range 10
3
to 10
6
cm
−3
, but does not vary significantly with electron temperature, and hence in principle should provide an excellent optical
N
e
diagnostic for the high-excitation zones of nebulae. The observed value of
R
for the planetary nebula NGC 7027, measured from a spectrum obtained with the Hamilton Echelle spectrograph on the 3-m Shane Telescope, implies a density in excellent agreement with that derived from [Ne
iv
], formed in the same region of the nebula as [K
v
]. This observation provides observational support for the accuracy of the theoretical [K
v
] line ratios, and hence the atomic data on which they are based. However, the analysis of a high-resolution spectrum of the symbiotic star RR Telescopii, obtained with the University College London Echelle Spectrograph on the 3.9-m Anglo–Australian Telescope, reveals that the [K
v
] 4122.6 Å line in this object is badly blended with Fe
ii
4122.6 Å. Hence, the [K
v
] diagnostic may not be used for astrophysical sources that show a strong Fe
ii
emission line spectrum.
The asymptotic distribution of canonical correlations and vectors in higher-order cointegrated models
Authors: Anderson T. W.
Published: July 2002

The study of the large-sample distribution of the canonical
correlations and variates in cointegrated models is extended from the
first-order autoregression model to autoregression of any (finite)
order. The cointegrated process considered here is nonstationary in
some dimensions and stationary in some other directions, but the first
difference (the “error-correction form”) is stationary. The
asymptotic distribution of the canonical correlations between the first
differences and the predictor variables as well as the corresponding
canonical variables is obtained under the assumption that the process
is Gaussian. The method of analysis is similar to that used for the
first-order process.
The structure of a class of finite ramified coverings and canonical forms of analytic matrix-functions in a neighborhood of a ramified turning point
Authors: Nisnevich Yevsey A.
Published: July 2002

Let
X
be the germ of a complex- or real-analytic manifold
M
at a point

x
o

∈
M
, or the henselian germ of an algebraic manifold
M
over a field
k
of characteristic zero at a point

x
o

∈
M
(
k
),
D
⊂
X
a divisor. Under some assumptions on
D
and its singularities we give a description of the structure, the singularities, and the divisor class group of all finite normal coverings of
X
ramified over
D.
Let
g
:
X
→ gl(
n
) be an analytic or a
k
-algebraic family, respectively, of semisimple matrices, the eigenvalues of which are ramified on
D
as functions of
x
∈
X.
Put
U
=
X
−
D.
Using the above results under some quite general assumptions on

g and D we construct an irreducible nonsingular variety U
c

, a finite etale morphism
a
c
:

U
c

→
U
, and a morphism

u
c

:

U
c

→ GL(
n
) (all in the same category as
X
and
g
), such that

t
c

(
x
) =

u
c

(
x
)
g
(
x
)

u
c

(
x
)
−1
is a diagonal matrix, for all
x
∈

U
c
.

This construction gives, among other things, an extension in a refined form (on the level of

U
c

-sections) of the classical one-parameter Perturbation Theory of matrices to the case of many parameters, ramified eigenvalues, not necessarily hermitian matrices, etc. We also prove the stable triviality of the eigenbundles of
g
on
U
and vanishing of their Chern classes.
Measuring the diaspora for virus-specific CD8+T cells
Authors: Marshall Dana R. , Turner Stephen J. , Belz Gabrielle T. , Wingo Suzette , Andreansky Samita , Sangster Mark Y. , Riberdy Janice M. , Liu Tiebin , Tan Ming , Doherty Peter C.
Published: July 2002

The CD8+T cell diaspora has been analyzed after secondary challenge with an influenza A virus that replicates only in the respiratory tract. Numbers of DbNP366- and DbPA224-specific CD8+T cells were measured by tetramer staining at the end of the recall response, then followed sequentially in the lung, lymph nodes, spleen, blood, and other organs. The extent of clonal expansion did not reflect the sizes of the preexisting memory T cell pools. Although the high-frequency CD8+tetramer+populations in the pneumonic lung and mediastinal lymph nodes fell rapidly from peak values, the “whole mouse” virus-specific CD8+T cell counts decreased only 2-fold over the 4 weeks after infection, then subsided at a fairly steady rate to reach a plateau at about 2 months. The largest numbers were found throughout in the spleen, then the bone marrow. The CD8+DbNP366+and CD8+DbPA224+sets remained significantly enlarged for at least 4 months, declining at equivalent rates while retaining the nucleoprotein > acid polymerase immunodominance hierarchy characteristic of the earlier antigen-driven phase. Lowest levels of the CD69 “activation marker” were detected consistently on virus-specific CD8+T cells in the blood, then the spleen. Those in the bone marrow and liver were intermediate, and CD69hiT cells were very prominent in the regional lymph nodes and the nasal-associated lymphoid tissue. Any population of “resting” CD8+memory T cells is thus phenotypically heterogeneous, widely dispersed, and subject to broad homeostatic and local environmental effects irrespective of epitope specificity or magnitude.
In vitro
evolution of a highly replicating, doxycycline-dependent HIV for applications in vaccine studies
Authors: Marzio Giuseppe , Verhoef Koen , Vink Monique , Berkhout Ben
Published: July 2002

A major concern associated with the use of vaccines based on
live-attenuated viruses is the possible and well documented reversion
to pathogenic phenotypes. In the case of HIV, genomic deletions or
mutations introduced to attenuate viral pathogenicity can be repaired
by selection of compensating mutations. These events lead to increased
virus replication rates and, eventually, disease progression. Because
replication competence and degree of protection appear to be directly
correlated, further attenuation of a vaccine virus may compromise the
ability to elicit a protective immune response. Here, we describe an
approach toward a safe attenuated HIV vaccine. The system is not based
on permanent reduction of infectivity by alteration of important viral
genomic sequences, but on strict control of replication through the
insertion of the tetracycline (Tet) system in the HIV genome.
Furthermore, extensive
in vitro
evolution was applied to
the prototype Tet-controlled HIV to select for variants with optimized
rather than diminished replication capacity. The final product of
evolution has properties uniquely suited for use as a vaccine strain.
The evolved virus is highly infectious, as opposed to a canonically
attenuated virus. It replicates efficiently in T cell lines and in
activated and unstimulated peripheral blood mononuclear cells. Most
importantly, replication is strictly dependent on the nontoxic
Tetanalogue doxycycline and can be turned on and off. These
results suggest that this
in vitro
evolved,
doxycycline-dependent HIV might represent a useful tool toward the
development of a safer, live-attenuated HIV vaccine.
Nitration of succinyl-CoA:3-oxoacid CoA-transferase in rats after endotoxin administration
Authors: Marcondes Sisi , Turko Illarion V. , Murad Ferid
Published: July 2002

The tyrosine nitration of proteins has been observed in diverse inflammatory conditions and has been linked to the presence of reactive nitrogen species. From many
in vitro
experiments, it is apparent that tyrosine nitration may alter the function of proteins. A limited number of experiments under
in vivo
conditions also demonstrate that protein nitration is associated with altered cellular processes. To understand the association of protein nitration with the pathogenic mechanism of the disease, it is essential to identify specific protein targets of nitration with
in vivo
or intact tissue models. Using anti-nitrotyrosine antibodies, we demonstrated the accumulation of nitrotyrosine in a 52-kDa protein in rat kidney after lipopolysaccharide treatment. The 52-kDa protein was purified and identified with partial sequence as succinyl-CoA:3-oxoacid CoA-transferase (SCOT; EC
2.8.3.5
). Western blot analysis revealed that the nitration of this mitochondrial enzyme increased in the kidneys and hearts of lipopolysaccharide-treated rats, whereas its catalytic activity decreased. These data suggest that tyrosine nitration may be a mechanism for the inhibition of SCOT activity in inflammatory conditions. SCOT is a key enzyme for ketone body utilization. Thus, tyrosine nitration of the enzyme with sepsis or inflammation may explain the altered metabolism of ketone bodies present in these disorders.
Hyperpolarization-activated calcium channels at the tip of
Arabidopsis
root hairs
Authors: Véry Anne-Aliénor , Davies Julia M.
Published: July 2002

The root hair elongative growth phase (“tip growth”), like that of other tip-growing systems such as pollen tubes, algal rhizoids, and fungal hyphae, is associated with an apex-high cytosolic free calcium ([Ca
2+
]
c
) gradient generated by a local Ca
2+
influx at the tip. This gradient has been shown to be a fundamental regulator of tip growth. Here, we have performed patch-clamp experiments at root hair apices of
Arabidopsis thaliana
(after localized cell wall laser ablation) to characterize the plasma membrane Ca
2+
channels implicated in the tip Ca
2+
influx. We have identified a hyperpolarization-activated Ca
2+
conductance. This conductance is selective for Ca
2+
over K
+
and Cl
−
(P
Ca
/P
K
= 15; P
Ca
/P
Cl
= 25) and is fully blocked by <100-μM trivalent cations (La
3+
, Al
3+
, Gd
3+
). The selectivity sequence among divalent cations (determined by comparisons of the channel unitary conductance) is Ba
2+
> Ca
2+
(22 pS in 10 mM) ≈ Mg
2+
> Mn
2+
. This conductance was operative at typical growing hair apical resting membrane potentials. Moreover, it was seen to be down-regulated in growing hair subapical regions, as well as at the tip of mature hairs (known not to exhibit Ca
2+
influx). We therefore propose that this inward-rectifying Ca
2+
conductance is inherently involved in the apical Ca
2+
influx of growing hairs. The observed enhancement of the conductance by increased [Ca
2+
]
c
may form part of a positive feedback system for continued apical Ca
2+
influx during tip growth.
Regulation of human heme oxygenase in endothelial cells by using sense and antisense retroviral constructs
Authors: Quan Shuo , Yang Liming , Abraham Nader G. , Kappas Attallah
Published: July 2002

Our objective was to determine whether overexpression and underexpression of human heme oxygenase (HHO)-1 could be controlled on a long-term basis by introduction of the HO-1 gene in sense (S) and antisense (AS) orientation with an appropriate vector into endothelial cells. Retroviral vector (LXSN) containing viral long terminal repeat promoter-driven human HO-1 S (LSN-HHO-1) and LXSN vectors containing HHO-1 promoter (HOP)-controlled HHO-1 S and AS (LSN-HOP-HHO-1 and LSN-HOP-HHO-1-AS) sequences were constructed and used to transfect rat lung microvessel endothelial cells (RLMV cells) and human dermal microvessel endothelial cells (HMEC-1 cells). RLMV cells transduced with HHO-1 S expressed human HO-1 mRNA and HO-1 protein associated with elevation in total HO activity compared with nontransduced cells. Vector-mediated expression of HHO-1 S or AS under control of HOP resulted in effective production of HO-1 or blocked induction of endogenous human HO-1 in HMEC-1 cells, respectively. Overexpression of HO-1 AS was associated with a long-term decrease (45%) of endogenous HO-1 protein and an increase (167%) in unmetabolized exogenous heme in HMEC-1 cells. Carbon monoxide (CO) production in HO-1 S- or AS-transduced HMEC-1 cells after heme treatment was increased (159%) or decreased (50%), respectively, compared with nontransduced cells. HO-2 protein levels did not change. These findings demonstrate that HHO-1 S and AS retroviral constructs are functional in enhancing and reducing HO activity, respectively, and thus can be used to regulate cellular heme levels, the activity of heme-dependent enzymes, and the rate of heme catabolism to CO and bilirubin.
Prime type III factors
Authors: Shlyakhtenko Dimitri
Published: July 2002

It is shown that for each 0 < λ < 1, the free
Araki–Woods factor of type III
λ
cannot be written as a
tensor product of two diffuse von Neumann algebras (i.e., is prime) and
does not contain a Cartan subalgebra.
Multiscale computing
Authors: Kobayashi Mei , Irino Toshio , Sweldens Wim
Published: July 2002

Multiscale computing (MSC) involves the computation, manipulation, and analysis of information at different resolution levels. Widespread use of MSC algorithms and the discovery of important relationships between different approaches to implementation were catalyzed, in part, by the recent interest in wavelets. We present two examples that demonstrate how MSC can help scientists understand complex data. The first is from acoustical signal processing and the second is from computer graphics.
The coactivator dTAF
II
110/hTAF
II
135 is sufficient to recruit a polymerase complex and activate basal transcription mediated by CREB
Authors: Felinski Edward A. , Quinn Patrick G.
Published: July 2002

A specific TATA binding protein-associated factor (TAF), dTAF
II
110/hTAF
II
135, interacts with cAMP response element binding protein (CREB) through its constitutive activation domain (CAD), which recruits a polymerase complex and activates transcription. The simplest explanation is that the TAF is a coactivator, but several studies have questioned this role of TAFs. Using a reverse two-hybrid analysis in yeast, we previously mapped the interaction between dTAF
II
110 (amino acid 1–308) and CREB to conserved hydrophobic amino acid residues in the CAD. That mapping was possible only because CREB fails to activate transcription in yeast, where all TAFs are conserved, except for the TAF recognizing CREB. To test whether CREB fails to activate transcription in yeast because it lacks a coactivator, we fused dTAF
II
110 (amino acid 1–308) to the TATA binding protein domain of the yeast scaffolding TAF, yTAF
II
130. Transformation of yeast with this hybrid TAF conferred activation by the CAD, indicating that interaction with yTFIID is sufficient to recruit a polymerase complex and activate transcription. The hybrid TAF did not mediate activation by VP16 or vitamin D receptor, each of which interacts with TFIIB, but not with dTAF
II
110 (amino acid 1–308). Enhancement of transcription activation by dTAF
II
110 in mammalian cells required interaction with both the CAD and TFIID and was inhibited by mutation of core hydrophobic residues in the CAD. These data demonstrate that dTAF
II
110/hTAF
II
135 acts as a coactivator to recruit TFIID and polymerase and that this mechanism of activation is conserved in eukaryotes.
Mixed model analysis of quantitative trait loci
Authors: Xu Shizhong , Yi Nengjun
Published: July 2002

We develop a mixed model approach of quantitative trait locus (QTL)
mapping for a hybrid population derived from the crosses of two or more
distinguished outbred populations. Under the mixed model, we treat the
mean allelic value of each source population as the fixed effect and
the allelic deviations from the mean as random effects so that we can
partition the total genetic variance into between- and
within-population variances. Statistical inference of the QTL
parameters is obtained by using the Bayesian method implemented by
Markov chain Monte Carlo (MCMC). This unified QTL mapping algorithm
treats the fixed and random model approaches as special cases of the
general mixed model methodology. Utility and flexibility of the method
are demonstrated by using a set of simulated data.
Monoclonal antibodies inhibit in vitro fibrillar aggregation of the Alzheimer beta-amyloid peptide.
Authors: Solomon B , Koppel R , Hanan E , Katzav T
Published: July 2002

The beta-amyloid peptide, the hallmark of Alzheimer disease, forms fibrillar toxic aggregates in brain tissue that can be dissolved only by strong denaturing agents. To study beta-amyloid formation and its inhibition, we prepared immune complexes with two monoclonal antibodies (mAbs), AMY-33 and 6F/3D, raised against beta-amyloid fragments spanning amino acid residues 1-28 and 8-17 of the beta-amyloid peptide chain, respectively. In vitro aggregation of beta-amyloid peptide was induced by incubation for 3 h at 37 degrees C and monitored by ELISA, negative staining electron microscopy, and fluorimetric studies. We found that the mAs prevent the aggregation of beta-amyloid peptide and that the inhibitory effect appears to be related to the localization of the antibody-binding sites and the nature of the aggregating agents. Preparation of mAbs against "aggregating epitopes," defined as sequences related to the sites where protein aggregation is initiated, may lead to the understanding and prevention of protein aggregation. The results of this study may provide a foundation for using mAbs in vivo to prevent the beta-amyloid peptide aggregation that is associated with Alzheimer disease.
Host range restrictions of oncogenes: myc genes transform avian but not mammalian cells and mht/raf genes transform mammalian but not avian cells.
Authors: Li R , Zhou R P , Duesberg P
Published: July 2002

The host range of retroviral oncogenes is naturally limited by the host range of the retroviral vector. The question of whether the transforming host range of retroviral oncogenes is also restricted by the host species has not been directly addressed. Here we have tested in avian and murine host species the transforming host range of two retroviral onc genes, myc of avian carcinoma viruses MH2 and MC29 and mht/raf of avian carcinoma virus MH2 and murine sarcoma virus MSV 3611. Virus vector-mediated host restriction was bypassed by recombining viral oncogenes with retroviral vectors that can readily infect the host to be tested. It was found that, despite high expression, transforming function of retroviral myc genes is restricted to avian cells, and that of retroviral mht/raf genes is restricted to murine cells. Since retroviral oncogenes encode the same proteins as certain cellular genes, termed protooncogenes, our data must also be relevant to the oncogene hypothesis of cancer. According to this hypothesis, cancer is caused by mutation of protooncogenes. Because protooncogenes are conserved in evolution and are presumed to have conserved functions, the oncogene hypothesis assumes no host range restriction of transforming function. For example, mutated human proto-myc is postulated to cause Burkitt lymphoma, because avian retroviruses with myc genes cause cancer in birds. But there is no evidence that known mutated protooncogenes can transform human cells. The findings reported here indicate that host range restriction appears to be one of the reasons (in addition to insufficient transcriptional activation) why known, mutated protooncogenes lack transforming function in human cells.
A joint hazard and time scaling model to compare survival curves.
Authors: Klawansky S , Fox M S
Published: July 2002

To provide a more general method for comparing survival experience, we propose a model that independently scales both hazard and time dimensions. To test the curve shape similarity of two time-dependent hazards, h1(t) and h2(t), we apply the proposed hazard relationship, h12(tKt)/ h1(t) = Kh, to h1. This relationship doubly scales h1 by the constant hazard and time scale factors, Kh and Kt, producing a transformed hazard, h12, with the same underlying curve shape as h1. We optimize the match of h12 to h2 by adjusting Kh and Kt. The corresponding survival relationship S12(tKt) = [S1(t)]KtKh transforms S1 into a new curve S12 of the same underlying shape that can be matched to the original S2. We apply this model to the curves for regional and local breast cancer contained in the National Cancer Institute's End Results Registry (1950-1973). Scaling the original regional curves, h1 and S1 with Kt = 1.769 and Kh = 0.263 produces transformed curves h12 and S12 that display congruence with the respective local curves, h2 and S2. This similarity of curve shapes suggests the application of the more complete curve shapes for regional disease as templates to predict the long-term survival pattern for local disease. By extension, this similarity raises the possibility of scaling early data for clinical trial curves according to templates of registry or previous trial curves, projecting long-term outcomes and reducing costs. The proposed model includes as special cases the widely used proportional hazards (Kt = 1) and accelerated life (KtKh = 1) models.
Complete replication of an animal virus and maintenance of expression vectors derived from it in Saccharomyces cerevisiae.
Authors: Price B D , Rueckert R R , Ahlouist P
Published: July 2002

Here we describe the first instances to our knowledge of animal virus genome replication, and of de novo synthesis of infectious virions by a nonendogenous virus, in the yeast Saccharomyces cerevisiae, whose versatile genetics offers significant advantages for studying viral replication and virus-host interactions. Flock house virus (FHV) is the most extensively studied member of the Nodaviridae family of (+) strand RNA animal viruses. Transfection of yeast with FHV genomic RNA induced viral RNA replication, transcription, and assembly of infectious virions. Genome replication and virus synthesis were robust: all replicating FHV RNA species were readily detected in yeast by Northern blot analysis and yields of virions per cell were similar to those from Drosophila cells. We also describe in vivo expression and maintenance of a selectable yeast marker gene from an engineered FHV RNA derivative dependent on FHV-directed RNA replication. Use of these approaches with FHV and their possible extension to other viruses should facilitate identification and characterization of host factors required for genomic replication, gene expression, and virion assembly.
Novel Gq alpha isoform is a candidate transducer of rhodopsin signaling in a Drosophila testes-autonomous pacemaker.
Authors: Alvarez C E , Robison K , Gilbert W
Published: July 2002

DGq is the alpha subunit of the heterotrimeric GTPase (G alpha), which couples rhodopsin to phospholipase C in Drosophila vision. We have uncovered three duplicated exons in dgq by scanning the GenBank data base for unrecognized coding sequences. These alternative exons encode sites involved in GTPase activity and G beta-binding, NorpA (phospholipase C)-binding, and rhodopsin-binding. We examined the in vivo splicing of dgq in adult flies and find that, in all but the male gonads, only two isoforms are expressed. One, dgqA, is the original visual isoform and is expressed in eyes, ocelli, brain, and male gonads. The other, dgqB, has the three novel exons and is widely expressed. Remarkably, all three nonvisual B exons are highly similar (82% identity at the amino acid level) to the Gq alpha family consensus, from Caenorhabditis elegans to human, but all three visual A exons are divergent (61% identity). Intriguingly, we have found a third isoform, dgqC, which is specifically and abundantly expressed in male gonads, and shares the divergent rhodopsin-binding exon of dgqA. We suggest that DGqC is a candidate for the light-signal transducer of a testes-autonomous photosensory clock. This proposal is supported by the finding that rhodopsin 2 and arrestin 1, two photoreceptor-cell-specific genes, are also expressed in male gonads.