bluuebunny/crossref_metadata_2025 huggingface dataset:
Shorted-end probes for accurate permittivity measurements with time-domain reflectometry
Authors: Cereti Annamaria , Pettinelli Elena , Galli Alessandro , Bella Francesco
Published: August 2003

An investigation is presented on the use of short-circuit terminations in two-wire transmission lines employed as probes in standard time-domain-reflectometry (TDR) setups. Experimental permittivity results are given for different configurations and materials, and these data are compared with those achievable using conventional open-type terminations. The possibility of both improving the accuracy and simplifying the procedures of TDR measurements using shorted-end probes is illustrated.
Catalytic role of boron atoms in self-interstitial clustering in Si
Authors: Hwang Gyeong S. , Goddard William A.
Published: August 2003

Using density functional theory (DFT) calculations and kinetic simulations, we have investigated the influence of boron atoms on self-interstitial clustering in Si. From DFT calculations of neutral interstitial clusters with a single B atom (BsIn, n⩽4), we find that the binding of B (BsIn→In−1+BsI) becomes substantially weaker than that of an interstitial (BsIn→BsIn−1+I) when n⩾4. This implies boron can be liberated while leaving an interstitial cluster behind. Our kinetic simulations including the boron liberation explain well experimental observations reported by J. L. Benton et al., J. Appl. Phys. 82, 120 (1997).
Continuously tunable and coherent terahertz radiation by means of phase-matched difference-frequency generation in zinc germanium phosphide
Authors: Shi Wei , Ding Yujie J.
Published: August 2003

Continuously tunable and coherent radiation has been obtained in the ranges of 66.5–300 μm and 72.7–237 μm for two configurations of phase-matched difference-frequency generation, respectively, in zinc germanium phosphide. The highest output peak powers are measured to be 36 and 19 W for the two configurations, respectively.
Magnetism in Mn-doped ZnO bulk samples prepared by solid state reaction
Authors: Han S-J. , Jang T.-H. , Kim Y. B. , Park B.-G. , Park J.-H. , Jeong Y. H.
Published: August 2003

Contrasting magnetic properties were obtained from bulk Mn-doped ZnO synthesized under different processing conditions. While a ferrimagnetic phase transition was observable in a Zn0.95Mn0.05O sample processed at 1170 K, no such transition was found for a sample with the same composition processed at 1370 K. The detailed magnetic, structural, and spectroscopic studies of these two samples have revealed that the ferrimagnetic transition in the former sample is attributable to the secondary phase, (Mn,Zn)Mn2O4, in the system. For the latter sample processed at higher temperature, no secondary phase was detected and the major feature of the system remained paramagnetic down to 4 K. The implication of the present results for Mn-doped ZnO thin films is discussed.
Gettering of Pd to implantation-induced nanocavities in Si
Authors: Brett D. A. , de M. Azevedo G. , Llewellyn D. J. , Ridgway M. C.
Published: August 2003

The gettering of Pd to nanocavities in Si for implantation doses ranging from 5×1013 to 1×1015 cm−2 and annealing temperatures ranging from 750 to 1050 °C was investigated using Rutherford backscattering and cross-sectional transmission electron microscopy. For a given annealing temperature, the gettering efficiency increased as the dose decreased. For a given dose, maximum gettering efficiency was achieved at the intermediate temperatures studied. Competition between silicide formation and nanocavity gettering limited gettering efficiency.
Magnetically induced phase separation and magnetic properties of Co–Mo hexagonal-close-packed structure thin films
Authors: Oikawa K. , Qin G. W. , Sato M. , Kitakami O. , Shimada Y. , Sato J. , Fukamichi K. , Ishida K.
Published: August 2003

Magnetically induced phase separation along the Curie temperature in the hexagonal-close-packed phase of a Co–Mo binary system has been predicted by thermodynamic calculations. Furthermore, the phase separation and magnetic properties of Co–Mo sputtered thin films have been investigated. Nanoscale compositional fluctuation caused by the magnetically induced phase separation has been confirmed in the films deposited on a heated substrate in the same manner as Co–Cr-based alloys. The magnetic anisotropy constant of the Co–Mo films is larger than that of Co–Cr films. From these results, it is concluded that the Co–Mo system is promising for use as a base alloy system for high density recording media.
Effects of magnetic field on two-dimensional superconducting quantum interference filters
Authors: Oppenländer J. , Caputo P. , Häussler Ch. , Träuble T. , Tomes J. , Friesch A. , Schopohl N.
Published: August 2003

We present an experimental study of two-dimensional (2D) superconducting quantum interference filters (SQIFs) in the presence of a magnetic field B. Although the nonlinear dynamics of the 2D SQIF are much more complex than those of previously studied one-dimensional SQIFs, we found for the 2D SQIF a similar dependence of the voltage V on the magnetic field applied, which is characterized by a unique delta-like dip at B=0. The voltage span of the dip depends on the distribution of areas of the individual loops, and on the bias current, and it scales proportionally to the number of rows simultaneously operating at the same working point. In addition, the voltage response of individual rows of the 2D SQIF is sensitive to the field gradient generated by a control line superimposed on the homogeneous field of a coil. This feature suggests the use of these devices as highly sensitive absolute detectors of spatial gradients of the magnetic field.
Strain analysis of a quantum-wire system produced by cleaved edge overgrowth using grazing incidence x-ray diffraction
Authors: Sztucki M. , Schülli T. U. , Metzger T. H. , Chamard V. , Schuster R. , Schuh D.
Published: August 2003

A GaAs surface layer of 10 nm thickness was grown on the cleaved edge of an In0.1Al0.9As/Al0.33Ga0.67As multilayer in order to induce a lateral periodic strain modulation. We apply surface sensitive grazing incidence x-ray diffraction to distinguish between compositional/morphological and purely strain induced modulations. The experimentally determined strain profile is confirmed by finite-element model calculations. The GaAs layer is found to be purely strain modulated with an average lattice parameter change of (0.8±0.1)% with respect to relaxed GaAs.
Magnetization-dependent rectification effect in a Ge-based magnetic heterojunction
Authors: Tsui F. , Ma L. , He L.
Published: August 2003

We report a study of a promising Ge-based magnetic heterojunction diode composed of a CoMn-doped Ge film grown epitaxially on lightly doped n-type Ge (001) substrate. The current rectification of the diode can be controlled either by the bias voltage or by the magnetic field. The findings not only demonstrate the viability of producing fully electronic spin devices, but also provide relevant parameters for one type of devices that are compatible with current Si-based device technology.
Near-field scanning microwave microscope using a dielectric resonator
Authors: Kim Jooyoung , Lee Kiejin , Friedman Barry , Cha Deokjoon
Published: August 2003

We describe a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f=4.5 GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator for the TE011 mode. We tuned the resonance cavity to match the impedance of 50 Ω by using a tunable screw and could improve sensitivity and spatial resolution to better than 1 μm. To demonstrate the ability of local microwave characterization, the surface resistance dependence of the metallic thin films on film thickness has been mapped.
Lattice parameter and energy band gap of cubic AlxGayIn1−x−yN quaternary alloys
Authors: Marques M. , Teles L. K. , Scolfaro L. M. R. , Leite J. R. , Furthmüller J. , Bechstedt F.
Published: August 2003

First-principles total energy calculations, combined with a generalized quasichemical approach to disorder and compositional effects, are used to obtain the lattice parameter and the energy band gap of cubic AlxGayIn1−x−yN quaternary alloys. It is found that the lattice parameter a(x,y) fulfills a Vegard’s-like law; that is, it shows a linear dependence on the alloy contents x and y. The range of compositions for which the alloy is lattice-matched to GaN is obtained. The energy band gap Eg(x,y) of the quaternary alloy deviates from a planar behavior displaying a two-dimensional gap bowing in the x–y plane. Analytical expressions that fit the calculated a(x,y) and Eg(x,y) surfaces are derived in order to provide ready access to the lattice parameter and energy band gap of the alloy for the entire range of compositions. The results are compared with data for the wurtzite phase alloys.
Interface recombination velocity of silicon-on-insulator wafers measured by microwave reflectance photoconductivity decay method with electric field
Authors: Kuwayama Toshio , Ichimura Masaya , Arai Eisuke
Published: August 2003

The interface recombination velocity of silicon-on-insulator (SOI) wafers was measured by the microwave-reflectance photoconductivity-decay method. The carrier lifetime was obtained with interface recombination suppressed by applying voltage between the SOI layer and the substrate. The interface recombination velocity was then estimated by comparing two lifetime values with and without voltage application. The velocity is from 500 to 1800 cm/s, relatively large as for thermally oxidized Si/SiO2 interfaces.
High current gain (>2000) of GaN/InGaN double heterojunction bipolar transistors using base regrowth of p-InGaN
Authors: Makimoto Toshiki , Kumakura Kazuhide , Kobayashi Naoki
Published: August 2003

GaN/InGaN double heterojunction bipolar transistors with a regrown p-InGaN extrinsic base have been fabricated on SiC substrates. The maximum common-emitter current gain exceeds 2000 at the collector current of 15 mA for a 50 μm×30 μm device. In addition, the offset voltage in the common-emitter current–voltage characteristics was reduced from 5 to 1 V. This indicates that the large offset voltage reported previously was mainly due to the degraded base ohmic characteristics. The regrowth of p-InGaN is effective for improving the characteristics of nitride heterojunction bipolar transistors.
Direct observation of confined states in metallic single-walled carbon nanotubes
Authors: Maltezopoulos Theophilos , Kubetzka André , Morgenstern Markus , Wiesendanger Roland , Lemay Serge G. , Dekker Cees
Published: August 2003

We investigated the local density of states (LDOS) of extended individual metallic single-walled carbon nanotubes using low-temperature scanning tunneling spectroscopy. We observed that the LDOS oscillates with energy close to the Fermi level. The oscillation period of about 50 meV varies with position on the nanotube. Maps of the LDOS reveal that the peaks in the oscillation are related to confined states. The widths of the peaks increase with increasing distance from the Fermi level.
Frequency-doubled diode laser for ultraviolet absorption spectroscopy at 325 nm
Authors: Laurila Toni , Hernberg Rolf
Published: August 2003

A frequency-doubled tunable diode laser for absorption spectroscopy in the ultraviolet is described. The device is based on an external cavity diode laser with a transmission grating. Second-harmonic generation at 320–327 nm is carried out using a lithium iodate crystal. The measured single-pass cw ultraviolet power is 60 nW and the system has a 40-GHz continuous mode-hop-free tuning range in the ultraviolet. The laser was demonstrated by measuring the 324.75-nm 42S1/2–42P3/2 transition of copper at atmospheric pressure with a single continuous scan.
Effect of boron neutralization on interface state creation after direct tunneling injections at 100 °C in 2,3-nm ultrathin gate oxides
Authors: Zander D. , Boch J. , Saigné F. , Meinertzhagen A. , Simonetti O.
Published: August 2003

Interface state creation, after different positive and negative electron direct tunneling injections at elevated temperature are studied. A degradation peak at 100 °C is observed after positive stresses. This peak is attributed to the propensity for boron to be neutralized by hydrogen at this temperature.
Experimental investigation of single voxels for laser nanofabrication via two-photon photopolymerization
Authors: Sun Hong-Bo , Maeda Makoto , Takada Kenji , Chon James W. M. , Gu Min , Kawata Satoshi
Published: August 2003

We report critical roles that are played by laser system parameters in two-photon laser nanofabrication, which are not significant in rapid prototyping at larger scale, including: (i) polarization-induced lateral deshaping of volume elements, voxels, the primitive building block of micronanostructures, and (ii) lateral size reduction of voxels at low numerical aperture lens focusing due to thresholding effect. Also interesting is (iii) simultaneous recording of zeroth- and higher-order diffraction patterns, which was not hindered by the two-order light intensity difference by taking the advantage of the large dynamic exposure time range of general resins, a concept that is proposed in contrast to dynamic power range.
Statistical entropy and density maximum anomaly in liquid water
Authors: Saija Franz , Saitta A. Marco , Giaquinta Paolo V.
Published: August 2003

We studied the configurational entropy of liquid water at ambient pressure and extracted the cumulative contribution associated with spatial correlations involving more than two particles. This quantity, the so-called residual multiparticle entropy (RMPE), is a sensitive indicator of structural modifications and incoming thermodynamic transitions, being positive in the more disordered phase and negative in the more ordered one. The vanishing of the RMPE has been successfully exploited as a rather general ordering criterion in a variety of model fluid systems. We carried out molecular-dynamics calculations on the TIP4P model at ambient pressure for temperatures between 230 K and 350 K and found that the ordering threshold estimated through the zero-RMPE criterion falls close to the temperature of maximum density.
Interstitial H and H2 in SiC
Authors: Kaukonen M. , Fall C. J. , Lento J.
Published: August 2003

The properties of hydrogen in 3C and 4H type silicon carbide (SiC) are studied theoretically at the density functional level. We find that only singly positive or negative charge states of hydrogen are thermodynamically stable in SiC. The transition from the positive to the negative charge state (+/−) is at 0.9 and 1.3 eV above the valence band maximum in 3C and 4H structures, respectively. The diffusion barrier for the proton is 0.5 eV (being, however, anisotropic in 4H). For the negative H− the diffusion barrier is found to be considerably higher, of the order of 3 eV.
Equilibrium heat capacity of the glass-forming poly(α-methyl styrene) far below the Kauzmann temperature: The case of the missing glass transition
Authors: Huang Dinghai , Simon Sindee L. , McKenna Gregory B.
Published: August 2003

The absolute specific heat capacity of poly(α-methyl styrene) and mixtures with its pentamer were found to be independent of concentration at temperatures from 240 to 480 K. Extrapolation to 100% polymer yielded the equilibrium specific heat capacity for the polymer at temperatures as much as 180 K below the glass temperature or 130 K below the Kauzmann temperature. We find no evidence of a second order transition or a smeared transition in the equilibrium heat capacity, the entropy, the excess configurational entropy or the enthalpy over the entire range of temperatures investigated. The observations indicate that the Kauzmann paradox must be resolved without invoking a thermodynamic glass transition.
Coming Out and Outcomes: Negotiating Lesbian and Gay Identities With, and in, the Family
Authors: Valentine Gill , Skelton Tracey , Butler Ruth
Published: July 2003

In late modernity there has been a shift in the ways that individuals relate to society, in which traditional ideas, expectations, and hierarchies are being reworked. Released from the constraints and social norms of tradition, individuals, it is argued, are now freer to choose between a range of options in the pursuit of their own happiness. Notably, these social changes have been understood to provide more opportunities for lesbians and gay men to ‘come out’—disclose their sexuality and live the lifestyle of their choice. Coming out is often implicitly discussed in academic literatures as an individual decision, and the consequences of coming out are also usually explored in relation to the personal narratives of the individual who has disclosed a lesbian and gay sexuality. To date, little attention has been paid to the actual processes through which sexual dissidents negotiate their identities with others, and to the consequences of such disclosures for those who are close to them or share their lives in various ways. In this paper we address this omission by focusing on young people's experiences of coming out with, and in, families of origin. We begin by examining what is at stake in the decision whether to come out or not by examining the role that families of origin play in young people's lives. We then explore how the process of coming out is actually negotiated within different families. Finally, we consider the ‘outcomes’ of these choices. In doing so we contribute to research on geographies of sexualities, geographies of the ‘family’, youth transitions, and the emerging field of social studies of emotions.
Breeders on a Golf Ball: Normalizing Sex at Ellis Island
Authors: Rand Erica
Published: July 2003

The primary offerings at Ellis Island Immigration Museum do little to indicate that the millions of immigrants and, later, tourists who have passed through Ellis Island cannot all have been reproductively focused and gender normative; the site, too, seems oddly unembodied. In this paper I consider representations and absences around sex at Ellis Island, arguing for strategies of embodiment that attend to the particular bodies inhabited and to the complexity, messiness, and contradictions of sexed bodies in their historical specificity.
‘Corralling the Virus’: Migratory Sexualities and the ‘Spread of AIDS’ in the US Media
Authors: Raimondo Meredith
Published: July 2003

In this paper I examine the emergence of a popular geography of AIDS in the US mass media in the 1980s, exploring the role of global mobility in the construction of AIDS as a national threat. Efforts to map the geography of the epidemic served to reinforce the illusion that the borders of the nation might effectively be defended against the incursions of HIV via the bodies of those marked as outside the proper citizenry. The representation of Africa as the ‘cradle of AIDS’, the images of crack houses in narratives about urban AIDS in the United States, and stories of White gay men ‘going home to die’ in the ‘heartland’ constructed a geography of danger linking race, sexuality, and ‘home’ that promised security for those within particular borders. Emphasizing the power of racialized maternal compassion as a model for the national response to AIDS, these stories described normative heterosexual domesticity as a means of fixing sexuality in place. This geography proposed that individual family units might reinforce national borders which seemed increasingly fluid in the context of global flows of populations, a construction that illustrates the intersection of space and sexuality in the representation of an emerging global health crisis and produces spatializations of danger that continue to shape the construction of ‘global AIDS’.
Queer Diffusions
Authors: Knopp Larry , Brown Michael
Published: July 2003

Critical perspectives on space and spatiality have been underdeveloped theoretically and underapplied empirically in the context of queer studies (including queer theory). In this paper we demonstrate how critical perspectives on one form of spatiality, diffusion, can enhance understandings of queer cultures, identities, and politics. We begin by reviewing traditional approaches to diffusion within geography and explicating a specifically queer approach to the topic. Our approach builds on existing critical perspectives and certain principles of structurationism. We then apply this approach to our empirical research and activism in two very different locales: Duluth, Minnesota, and Seattle, Washington. In so doing we illustrate the complex and nuanced spatialities of heteronormative power and resistances to it.
Migratory Sexualities, Diasporic Histories, and Memory in Queer Cuban-American Cultural Production
Authors: Sugg Katherine
Published: July 2003

Interrogations of diasporic relations between place, subjectivity, and sexuality have transformed representational practices and paradigms of both Cuban and Cuban-American identity on multiple fronts. Through a consideration of two texts representing the Cuban diaspora-Achy Obejas's 1996 novel Memory Mambo and Carmelita Tropicana's performance piece “Milk of amnesia/Leche de amnesia”, first developed in 1994–I explore the centrality of sexuality in constructions of self, community, and nation. These works effectively ‘queer’ notions of immigrant belonging and Cuban diasporic consciousness, particularly in the sense of exploring the spatial imaginary of diaspora to expose and question the heteropatriarchal, and hence nationalist, underpinnings of more dominant models of diaspora. In their work, Obejas and Tropicana indicate the spatial dimensions of cultural memory and the imbrication of diasporic politics and sexualities. Attending to differences in genre, each work mines a crucial interplay between diasporic and sexual histories. In Tropicana's performance piece she uses a parodic sensibility and the broad humor enabled by the stage to engage, in a new register, with the politics of memory and the uses of place and sexuality, both in relation to Cuba and to the United States. Obejas works through and against the conventions of the contemporary novel (both immigrant and lesbian coming-of-age stories, in particular) to undo many of the assumptions regarding memory, sexuality, and cultural nostalgia as they are represented in her narrative. Both Obejas and Tropicana assert an imbrication of histories of colonialism, migration, and national attachment with experiences and practices of sexuality and gender in ways that underscore the importance of space and place in the constitution of collective memories.
We're from Oz: Marking Ethnic and Sexual Identity in Chicago
Authors: Reed Christopher
Published: July 2003

In 1998 the City of Chicago installed street furniture (including twenty-two twenty-three-foot-high, illuminated, rainbow-ringed pylons) designed to mark a gay neighborhood known as Boys Town. In this paper I describe the historical context for this project and the debates it occasioned in a US context where, sociologists suggest, sexual and ethnic identities are increasingly convergent. I challenge, from a visual-studies perspective, the values attached to invisibility by critics who would prefer that sexual identity remain unmarked.
On cubic lacunary Fourier series
Authors: Gerver Joseph
Published: July 2003

For

2
>
β
>
4

2>\beta >4

, we analyze the behavior, near the rational points

x
=
p
π

/

q

x=p\pi /q

, of

∑

n
=
1

∞

n

−
β

exp
⁡
(
i
x

n

3

)

\sum ^\infty _{n=1}n^{-\beta }\exp (ixn^{3})

, considered as a function of

x
x

. We expand this series into a constant term, a term on the order of

(
x
−
p
π

/

q

)

(
β
−
1
)

/

3

(x-p\pi /q)^{(\beta -1)/3}

, a term linear in

x
−
p
π

/

q

x-p\pi /q

, a “chirp" term on the order of

(
x
−
p
π

/

q

)

(
2
β
−
1
)

/

4

(x-p\pi /q)^{(2\beta -1)/4}

, and an error term on the order of

(
x
−
p
π

/

q

)

β

/

2

(x-p\pi /q)^{\beta /2}

. At every such rational point, the left and right derivatives are either both finite (and equal) or both infinite, in contrast with the quadratic series, where the derivative is often finite on one side and infinite on the other. However, in the cubic series, again in contrast with the quadratic case, the chirp term generally has a different set of frequencies and amplitudes on the right and left sides. Finally, we show that almost every irrational point can be closely approximated, in a suitable Diophantine sense, by rational points where the cubic series has an infinite derivative. This implies that when

β
≤
(

97

−
1
)

/

4
=
2.212
…

\beta \le (\sqrt {97}-1)/4=2.212\dots

, both the real and imaginary parts of the cubic series are differentiable almost nowhere.
Twisted sums with 𝐶(𝐾) spaces
Authors: Sánchez F. , Castillo J. , Kalton N. , Yost D.
Published: July 2003

If

X
X

is a separable Banach space, we consider the existence of non-trivial twisted sums

0
→
C
(
K
)
→
Y
→
X
→
0

0\to C(K)\to Y\to X\to 0

, where

K
=
[
0
,
1
]

K=[0,1]

or

ω

ω

.

\omega ^{\omega }.

For the case

K
=
[
0
,
1
]

K=[0,1]

we show that there exists a twisted sum whose quotient map is strictly singular if and only if

X
X

contains no copy of

ℓ
1

\ell _1

. If

K
=

ω

ω

K=\omega ^{\omega }

we prove an analogue of a theorem of Johnson and Zippin (for

K
=
[
0
,
1
]

K=[0,1]

) by showing that all such twisted sums are trivial if

X
X

is the dual of a space with summable Szlenk index (e.g.,

X
X

could be Tsirelson’s space); a converse is established under the assumption that

X
X

has an unconditional finite-dimensional decomposition. We also give conditions for the existence of a twisted sum with

C
(

ω

ω

)

C(\omega ^{\omega })

with strictly singular quotient map.
Rigidity in holomorphic and quasiregular dynamics
Authors: Martin Gaven , Mayer Volker
Published: July 2003

We consider rigidity phenomena for holomorphic functions and then more generally for uniformly quasiregular maps.
Examples for the mod 𝑝 motivic cohomology of classifying spaces
Authors: Yagita Nobuaki
Published: July 2003

Let

B
G

BG

be the classifying space of a compact Lie group

G
G

. Some examples of computations of the motivic cohomology

H

∗
,
∗

(
B
G
;

Z

/

p
)

H^{*,*}(BG;\mathbb {Z}/p)

are given, by comparing with

H
∗

(
B
G
;

Z

/

p
)

H^*(BG;\mathbb {Z}/p)

,

C

H
∗

(
B
G
)

CH^*(BG)

and

B

P
∗

(
B
G
)

BP^*(BG)

.
Fitting’s Lemma for ℤ/2-graded modules
Authors: Eisenbud David , Weyman Jerzy
Published: July 2003

Letϕ:Rm→Rd\phi :\; R^{m}\to R^{d}be a map of free modules over a commutative ringRR. Fitting’s Lemma shows that the “Fitting ideal,” the ideal ofd×dd\times dminors ofϕ\phi, annihilates the cokernel ofϕ\phiand is a good approximation to the whole annihilator in a certain sense. In characteristic 0 we define a Fitting ideal in the more general case of a map of graded free modules over aZ/2\mathbb {Z}/2-graded skew-commutative algebra and prove corresponding theorems about the annihilator; for example, the Fitting ideal and the annihilator of the cokernel are equal in the generic case. Our results generalize the classical Fitting Lemma in the commutative case and extend a key result of Green (1999) in the exterior algebra case. They depend on the Berele-Regev theory of representations of general linear Lie superalgebras. In the purely even and purely odd cases we also offer a standard basis approach to the modulecoker⁡ϕ\operatorname {coker}\phiwhenϕ\phiis a generic matrix.
Semi-free Hamiltonian circle actions on 6-dimensional symplectic manifolds
Authors: Li Hui
Published: July 2003

Assume(M,ω)(M, \omega )is a connected, compact 6-dimensional symplectic manifold equipped with a semi-free Hamiltonian circle action, such that the fixed point set consists of isolated points or compact orientable surfaces. We restrict attention to the casedim⁡H2(M)>3\dim H^2(M)>3. We give a complete list of the possible manifolds, and determine their equivariant cohomology rings and equivariant Chern classes. Some of these manifolds are classified up to diffeomorphism. We also show the existence for a few cases.
Maximal complexifications of certain homogeneous Riemannian manifolds
Authors: Halverscheid S. , Iannuzzi A.
Published: July 2003

Let

M
=
G

/

K

M=G/K

be a homogeneous Riemannian manifold with

dim

C

⁡

G

C

=

dim

R

⁡
G

\dim _{\mathbb {C}} G^{\mathbb {C}} = \dim _{\mathbb {R}} G

, where

G

C

G^{\mathbb {C}}

denotes the universal complexification of

G
G

. Under certain extensibility assumptions on the geodesic flow of

M
M

, we give a characterization of the maximal domain of definition in

T
M

TM

for the adapted complex structure and show that it is unique. For instance, this can be done for generalized Heisenberg groups and naturally reductive homogeneous Riemannian spaces. As an application it is shown that the case of generalized Heisenberg groups yields examples of maximal domains of definition for the adapted complex structure which are neither holomorphically separable nor holomorphically convex.
On model complete differential fields
Authors: Hrushovski E. , Itai M.
Published: July 2003

We develop a geometric approach to definable sets in differentially closed fields, with emphasis on the question of orthogonality to a given strongly minimal set. Equivalently, within a family of ordinary differential equations, we consider those equations that can be transformed, by differential-algebraic transformations, so as to yield solutions of a given fixed first-order ODEXX. We show that this sub-family is usually definable (in particular ifXXlives on a curve of positive genus). As a corollary, we show the existence of many model-complete, superstable theories of differential fields.
Sheaf cohomology and free resolutions over exterior algebras
Authors: Eisenbud David , Fløystad Gunnar , Schreyer Frank-Olaf
Published: July 2003

We derive an explicit version of the Bernstein-Gel’fand-Gel’fand (BGG) correspondence between bounded complexes of coherent sheaves on projective space and minimal doubly infinite free resolutions over its “Koszul dual” exterior algebra. Among the facts about the BGG correspondence that we derive is that taking homology of a complex of sheaves corresponds to taking the “linear part” of a resolution over the exterior algebra. We explore the structure of free resolutions over an exterior algebra. For example, we show that such resolutions are eventually dominated by their “linear parts" in the sense that erasing all terms of degree

>
1

>1

in the complex yields a new complex which is eventually exact. As applications we give a construction of the Beilinson monad which expresses a sheaf on projective space in terms of its cohomology by using sheaves of differential forms. The explicitness of our version allows us to prove two conjectures about the morphisms in the monad, and we get an efficient method for machine computation of the cohomology of sheaves. We also construct all the monads for a sheaf that can be built from sums of line bundles, and show that they are often characterized by numerical data.
Hyperplane arrangement cohomology and monomials in the exterior algebra
Authors: Eisenbud David , Popescu Sorin , Yuzvinsky Sergey
Published: July 2003

We show that if

X
X

is the complement of a complex hyperplane arrangement, then the homology of

X
X

has linear free resolution as a module over the exterior algebra on the first cohomology of

X
X

. We study invariants of

X
X

that can be deduced from this resolution. A key ingredient is a result of Aramova, Avramov, and Herzog (2000) on resolutions of monomial ideals in the exterior algebra. We give a new conceptual proof of this result.
The differential Galois theory of strongly normal extensions
Authors: Kovacic Jerald
Published: July 2003

Differential Galois theory, the theory of strongly normal extensions, has unfortunately languished. This may be due to its reliance on Kolchin’s elegant, but not widely adopted, axiomatization of the theory of algebraic groups. This paper attempts to revive the theory using a differential scheme in place of those axioms. We also avoid using a universal differential field, instead relying on a certain tensor product. We identify automorphisms of a strongly normal extension with maximal differential ideals of this tensor product, thus identifying the Galois group with the closed points of an affine differential scheme. Moreover, the tensor product has a natural coring structure which translates into the Galois group operation: composition of automorphisms. This affine differential scheme splits, i.e. is obtained by base extension from a (not differential, not necessarily affine) group scheme. As a consequence, the Galois group is canonically isomorphic to the closed, or rational, points of a group scheme defined over constants. We obtain the fundamental theorem of differential Galois theory, giving a bijective correspondence between subgroup schemes and intermediate differential fields. On the way to this result we study certain aspects of differential algebraic geometry, e.g. closed immersions, products, local ringed space of constants, and split differential schemes.
Open 3-manifolds whose fundamental groups have infinite center, and a torus theorem for 3-orbifolds
Authors: Maillot Sylvain
Published: July 2003

Our main result is a characterization of open Seifert fibered

3
3

-manifolds in terms of the fundamental group and large-scale geometric properties of a triangulation. As an application, we extend the Seifert Fiber Space Theorem and the Torus Theorem to a class of

3
3

-orbifolds.
On the Diophantine equation 𝐺_{𝑛}(𝑥)=𝐺_{𝑚}(𝑃(𝑥)): Higher-order recurrences
Authors: Fuchs Clemens , Pethő Attila , Tichy Robert
Published: July 2003

Let

K

\mathbf {K}

be a field of characteristic

0
0

and let

(

G

n

(
x
)

)

n
=
0

∞

(G_{n}(x))_{n=0}^{\infty }

be a linear recurring sequence of degree

d
d

in

K

[
x
]

\mathbf {K}[x]

defined by the initial terms

G
0

,
…
,

G

d
−
1

∈

K

[
x
]

G_0,\ldots ,G_{d-1}\in \mathbf {K}[x]

and by the difference equation
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper G Subscript n plus d Baseline left-parenthesis x right-parenthesis equals upper A Subscript d minus 1 Baseline left-parenthesis x right-parenthesis upper G Subscript n plus d minus 1 Baseline left-parenthesis x right-parenthesis plus midline-horizontal-ellipsis plus upper A 0 left-parenthesis x right-parenthesis upper G Subscript n Baseline left-parenthesis x right-parenthesis comma for n greater-than-or-equal-to 0 comma">

G

n
+
d

(
x
)
=

A

d
−
1

(
x
)

G

n
+
d
−
1

(
x
)
+
⋯
+

A
0

(
x
)

G

n

(
x
)
,

for

n
≥
0
,

G_{n+d}(x)=A_{d-1}(x)G_{n+d-1}(x)+\cdots +A_0(x)G_{n}(x), \quad \mbox {for} \,\, n\geq 0,

\]
with

A
0

,
…
,

A

d
−
1

∈

K

[
x
]

A_0,\ldots ,A_{d-1}\in \mathbf {K}[x]

. Finally, let

P
(
x
)

P(x)

be an element of

K

[
x
]

\mathbf {K}[x]

. In this paper we are giving fairly general conditions depending only on

G
0

,
…
,

G

d
−
1

,

G_0,\ldots ,G_{d-1},

on

P
P

, and on

A
0

,
…
,

A

d
−
1

A_0,\ldots ,A_{d-1}

under which the Diophantine equation
\[

G

n

(
x
)
=

G

m

(
P
(
x
)
)

G_{n}(x)=G_{m}(P(x))

\]
has only finitely many solutions

(
n
,
m
)
∈

Z

2

,
n
,
m
≥
0

(n,m)\in \mathbb {Z}^{2},n,m\geq 0

. Moreover, we are giving an upper bound for the number of solutions, which depends only on

d
d

. This paper is a continuation of the work of the authors on this equation in the case of second-order linear recurring sequences.
Baxter algebras and Hopf algebras
Authors: Andrews George , Guo Li , Keigher William , Ono Ken
Published: July 2003

By applying a recent construction of free Baxter algebras, we obtain a new class of Hopf algebras that generalizes the classical divided power Hopf algebra. We also study conditions under which these Hopf algebras are isomorphic.
Compact composition operators on Besov spaces
Authors: Tjani Maria
Published: July 2003

We give a Carleson measure characterization of the compact composition operators on Besov spaces. We use this characterization to show that every compact composition operator on a Besov space is compact on the Bloch space. Finally we give conditions that guarantee that the converse holds.
A constructive Schwarz reflection principle
Authors: Clark Jeremy
Published: July 2003

We prove a constructive version of the Schwarz reflection principle. Our proof techniques are in line with Bishop’s development of constructive analysis. The principle we prove enables us to reflect analytic functions in the real line, given that the imaginary part of the function converges to zero near the real line in a uniform fashion. This form of convergence to zero is classically equivalent to pointwise convergence, but may be a stronger condition from the constructivist point of view.
Group actions on one-manifolds, II: Extensions of Hölder’s Theorem
Authors: Farb Benson , Franks John
Published: July 2003

This self-contained paper is part of a series seeking to understand groups of homeomorphisms of manifolds in analogy with the theory of Lie groups and their discrete subgroups. In this paper we consider groups which act on

R

\mathbf R

with restrictions on the fixed point set of each element. One result is a topological characterization of affine groups in

D
i
f
f

2

(

R

)

\mathrm {Diff}^2(\mathbf R)

as those groups whose elements have at most one fixed point.
Cytoplasmic N-Terminal Protein Acetylation Is Required for Efficient Photosynthesis in Arabidopsis[W]
Authors: Pesaresi Paolo , Gardner Nora A. , Masiero Simona , Dietzmann Angela , Eichacker Lutz , Wickner Reed , Salamini Francesco , Leister Dario
Published: August 2003

The Arabidopsis atmak3-1 mutant was identified on the basis of a decreased effective quantum yield of photosystem II. In atmak3-1, the synthesis of the plastome-encoded photosystem II core proteins D1 and CP47 is affected, resulting in a decrease in the abundance of thylakoid multiprotein complexes. DNA array–based mRNA analysis indicated that extraplastid functions also are altered. The mutation responsible was localized to AtMAK3, which encodes a homolog of the yeast protein Mak3p. In yeast, Mak3p, together with Mak10p and Mak31p, forms the N-terminal acetyltransferase complex C (NatC). The cytoplasmic AtMAK3 protein can functionally replace Mak3p, Mak10p, and Mak31p in acetylating N termini of endogenous proteins and the L-A virus Gag protein. This result, together with the finding that knockout of the Arabidopsis MAK10 homolog does not result in obvious physiological effects, indicates that AtMAK3 function does not require NatC complex formation, as it does in yeast. We suggest that N-acetylation of certain chloroplast precursor protein(s) is necessary for the efficient accumulation of the mature protein(s) in chloroplasts.
Contrasting Effects of Selection on Sequence Diversity and Linkage Disequilibrium at Two Phytoene Synthase Loci[W]
Authors: Palaisa Kelly A. , Morgante Michele , Williams Mark , Rafalski Antoni
Published: August 2003

We investigated the effects of human selection for yellow endosperm color, representing increased carotenoid content, on two maize genes, the Y1 phytoene synthase and PSY2, a putative second phytoene synthase. Multiple polymorphic sites were identified at Y1 and PSY2 in 75 white and yellow maize inbred lines. Many polymorphic sites showed strong association with the endosperm color phenotype at Y1, but no detectable association was found at PSY2. Nucleotide diversity was equivalent for whites and yellows at PSY2 but was 19-fold less in yellows than in whites at Y1, consistent with the white ancestral state of the gene. The strong sequence haplotype conservation within yellows at Y1 and a significant, negative Tajima's D both verified positive selection for yellow endosperm. We propose that two independent gain-of-function events associated with insertions into the promoter of the Y1 gene and upregulation of expression in endosperm have been incorporated into yellow maize.
The Arabidopsisppi1Mutant Is Specifically Defective in the Expression, Chloroplast Import, and Accumulation of Photosynthetic Proteins[W]
Authors: Kubis Sybille , Baldwin Amy , Patel Ramesh , Razzaq Azam , Dupree Paul , Lilley Kathryn , Kurth Joachim , Leister Dario , Jarvis Paul
Published: August 2003

The import of nucleus-encoded proteins into chloroplasts is mediated by translocon complexes in the envelope membranes. A component of the translocon in the outer envelope membrane, Toc34, is encoded in Arabidopsis by two homologous genes, atTOC33 and atTOC34. Whereas atTOC34 displays relatively uniform expression throughout development, atTOC33 is strongly upregulated in rapidly growing, photosynthetic tissues. To understand the reason for the existence of these two related genes, we characterized the atTOC33 knockout mutant ppi1. Immunoblotting and proteomics revealed that components of the photosynthetic apparatus are deficient in ppi1 chloroplasts and that nonphotosynthetic chloroplast proteins are unchanged or enriched slightly. Furthermore, DNA array analysis of 3292 transcripts revealed that photosynthetic genes are moderately, but specifically, downregulated in ppi1. Proteome differences in ppi1 could be correlated with protein import rates: ppi1 chloroplasts imported the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit and 33-kD oxygen-evolving complex precursors at significantly reduced rates, but the import of a 50S ribosomal subunit precursor was largely unaffected. The ppi1 import defect occurred at the level of preprotein binding, which is consistent with a role for atToc33 during preprotein recognition. The data suggest that atToc33 is involved preferentially in the import of photosynthetic proteins and, by extension, that atToc34 is involved in the import of nonphotosynthetic chloroplast proteins.
The Mitochondrial Genome of Chara vulgaris: Insights into the Mitochondrial DNA Architecture of the Last Common Ancestor of Green Algae and Land Plants[W]
Authors: Turmel Monique , Otis Christian , Lemieux Claude
Published: August 2003

Mitochondrial DNA (mtDNA) has undergone radical changes during the evolution of green plants, yet little is known about the dynamics of mtDNA evolution in this phylum. Land plant mtDNAs differ from the few green algal mtDNAs that have been analyzed to date by their expanded size, long spacers, and diversity of introns. We have determined the mtDNA sequence of Chara vulgaris (Charophyceae), a green alga belonging to the charophycean order (Charales) that is thought to be the most closely related alga to land plants. This 67,737-bp mtDNA sequence, displaying 68 conserved genes and 27 introns, was compared with those of three angiosperms, the bryophyte Marchantia polymorpha, the charophycean alga Chaetosphaeridium globosum (Coleochaetales), and the green alga Mesostigma viride. Despite important differences in size and intron composition, Chara mtDNA strikingly resembles Marchantia mtDNA; for instance, all except 9 of 68 conserved genes lie within blocks of colinear sequences. Overall, our genome comparisons and phylogenetic analyses provide unequivocal support for a sister-group relationship between the Charales and the land plants. Only four introns in land plant mtDNAs appear to have been inherited vertically from a charalean algar ancestor. We infer that the common ancestor of green algae and land plants harbored a tightly packed, gene-rich, and relatively intron-poor mitochondrial genome. The group II introns in this ancestral genome appear to have spread to new mtDNA sites during the evolution of bryophytes and charalean green algae, accounting for part of the intron diversity found in Chara and land plant mitochondria.
An Arabidopsis Mutant Resistant to Thaxtomin A, a Cellulose Synthesis Inhibitor fromStreptomycesSpecies[W]
Authors: Scheible Wolf-Rüdiger , Fry Barbara , Kochevenko Andrej , Schindelasch Dana , Zimmerli Laurent , Somerville Shauna , Loria Rosemary , Somerville Chris R.
Published: August 2003

Thaxtomin A is a phytotoxin produced by Streptomyces scabies and other Streptomyces species, the causative agents of common scab disease in potato and other taproot crops. At nanomolar concentrations, thaxtomin causes dramatic cell swelling, reduced seedling growth, and inhibition of cellulose synthesis in Arabidopsis. We identified a mutant of Arabidopsis, designated txr1, that exhibits increased resistance to thaxtomin as a result of a decrease in the rate of toxin uptake. The TXR1 gene was identified by map-based cloning and found to encode a novel, small protein with no apparent motifs or organelle-targeting signals. The protein, which has homologs in all fully sequenced eukaryotic genomes, is expressed in all tissues and during all developmental stages analyzed. Microarray transcript profiling of some 14,300 genes revealed two stomatin-like genes that were expressed differentially in the txr1 mutant and the wild type. We propose that TXR1 is a regulator of a transport mechanism.
Dry Holes in Economic Research
Authors: Laband David N. , Tollison Robert D.
Published: July 2003

Between 1974 and 1996, there was a substantial increase in the emphasis on academic research in universities located in the United States and elsewhere throughout the world. This increased emphasis was, and continues to be, reflected in a variety of increased incentives for faculty to produce research, including higher salaries, reduced teaching loads, increased money for travel, on so on. Yet, as we report in this paper, during this time period the rate of uncitedness of economics papers remained constant (at 26 percent). Clearly, universities and taxpayers/supporters of universities are obtaining no enhancement of research output (in terms of citations) from the increased subsidy to faculty research. We discuss the implications of this result for the publication and organization of economic research. In particular, we discuss the fact that resources devoted to up‐front screening of papers by authors and journals have risen substantially over this period, but to no avail with respect to reducing the incidence of dry holes.
Reputation and Relevance of Economics Journals
Authors: Bräuninger Michael , Haucap Justus
Published: July 2003

We analyse the interrelationship between economics journals' relevance and reputation. While reputation and relevance positively affect each other, relevance has a much stronger impact on reputation than reputation on relevance. Citation frequency is a key determinant for both journal reputation and relevance, but effects on journal reputation are nearly twice as strong. Specialised journals are, ceteris paribus, considered less relevant and, therefore, also less reputed, even though specialisation has a positive direct effect on reputation. German‐speaking economists find German journals more relevant, but at the same time also less reputed than foreign journals. Age and volume effects are also analysed.