bluuebunny/crossref_metadata_2025 huggingface dataset:
Measles Virus Infects Human Dendritic Cells and Blocks Their Allostimulatory Properties for CD4+ T Cells
Authors: Grosjean Isabelle , Caux Christophe , Bella Chantal , Berger Ingrid , Wild Fabian , Banchereau Jacques , Kaiserlian Dominique
Published: July 2002

Measles causes a profound immune suppression which is responsible for the high morbidity and mortality induced by secondary infections. Dendritic cells (DC) are professional antigen-presenting cells required for initiation of primary immune responses. To determine whether infection of DC by measles virus (MV) may play a role in virus-induced suppression of cell-mediated immunity, we examined the ability of CD1a+ DC derived from cord blood CD34+ progenitors and Langerhans cells isolated from human epidermis to support MV replication. Here we show that both cultured CD1a+ DC and epidermal Langerhans cells can be infected in vitro by both vaccine and wild type strains of MV. DC infection with MV resulted within 24–48 h in cell–cell fusion, cell surface expression of hemagglutinin, and virus budding associated with production of infectious virus. MV infection of DC completely abrogated the ability of the cells to stimulate the proliferation of naive allogeneic CD4+ T cell as early as day 2 of mixed leukocyte reaction (MLR) (i.e., on day 4 of DC infection). Mannose receptor–mediated endocytosis and viability studies indicated that the loss of DC stimulatory function could not be attributed to the death or apoptosis of DC. This total loss of DC stimulatory function required viral replication in the DC since ultraviolet (UV)-inactivated MV or UV-treated supernatant from MV-infected DC did not alter the allostimulatory capacity of DC. As few as 10 MV- infected DC could block the stimulatory function of 104 uninfected DC. More importantly, MV-infected DC, in which production of infectious virus was blocked by UV treatment or paraformaldehyde fixation, actively suppressed allogeneic MLR upon transfer to uninfected DC–T-cultures. Thus, the mechanisms which contribute to the loss of the allostimulatory function of DC include both virus release and active suppression mediated by MV-infected DC, independent of virus production. These data suggest that carriage of MV by DC may facilitate virus spreading to secondary lymphoid organs and that MV replication in DC may play a central role in the general immune suppression observed during measles.
Interferon Consensus Sequence Binding Protein–deficient Mice Display Impaired Resistance to Intracellular Infection Due to a Primary Defect in Interleukin 12 p40 Induction
Authors: Scharton-Kersten Tanya , Contursi Cristina , Masumi Atsuko , Sher Alan , Ozato Keiko
Published: July 2002

Mice lacking the transcription factor interferon consensus sequence binding protein (ICSBP), a member of the interferon regulatory factor family of transcription proteins, were infected with the intracellular protozoan, Toxoplasma gondii. ICSBP-deficient mice exhibited unchecked parasite replication in vivo and rapidly succumbed within 14 d after inoculation with an avirulent Toxoplasma strain. In contrast, few intracellular parasites were observed in wild-type littermates and these animals survived for at least 60 d after infection. Analysis of cytokine synthesis in vitro and in vivo revealed a major deficiency in the expression of both interferon (IFN)-γ and interleukin (IL)-12 p40 in the T. gondii exposed ICSBP−/− animals. In related experiments, macrophages from uninfected ICSBP−/− mice were shown to display a selective impairment in the mRNA expression of IL-12 p40 but not IL-1α, IL-1β, IL-1Ra, IL-6, IL-10, or TNF-α in response to live parasites, parasite antigen, lipopolysaccharide, or Staphylococcus aureus. This selective defect in IL-12 p40 production was observed regardless of whether the macrophages had been primed with IFN-γ. We hypothesize that the impaired synthesis of IL-12 p40 in ICSBP−/− animals is the primary lesion responsible for the loss in resistance to T. gondii because IFN-γ–induced parasite killing was unimpaired in vitro and, more importantly, administration of exogenous IL-12 in vivo significantly prolonged survival of the infected mice. Together these findings implicate ICSBP as a major transcription factor which directly or indirectly regulates IL-12 p40 gene activation and, as a consequence, IFN-γ–dependent host resistance.
The Transcription Factor Interferon Regulatory Factor 1 (IRF-1) Is Important during the Maturation of Natural Killer 1.1+ T Cell Receptor–α/β+ (NK1+ T) Cells, Natural Killer Cells, and Intestinal Intraepithelial T Cells
Authors: Ohteki Toshiaki , Yoshida Hiroki , Matsuyama Toshifumi , Duncan Gordon S. , Mak Tak W. , Ohashi Pamela S.
Published: July 2002

In contrast to conventional T cells, natural killer (NK) 1.1+ T cell receptor (TCR)-α/β+ (NK1+T) cells, NK cells, and intestinal intraepithelial lymphocytes (IELs) bearing CD8-α/α chains constitutively express the interleukin (IL)-2 receptor (R)β/15Rβ chain. Recent studies have indicated that IL-2Rβ/15Rβ chain is required for the development of these lymphocyte subsets, outlining the importance of IL-15. In this study, we investigated the development of these lymphocyte subsets in interferon regulatory factor 1–deficient (IRF-1−/−) mice. Surprisingly, all of these lymphocyte subsets were severely reduced in IRF-1−/− mice. Within CD8-α/α+ intestinal IEL subset, TCR-γ/δ+ cells and TCR-α/β+ cells were equally affected by IRF gene disruption. In contrast to intestinal TCR-γ/δ+ cells, thymic TCR-γ/δ+ cells developed normally in IRF-1−/− mice. Northern blot analysis further revealed that the induction of IL-15 messenger RNA was impaired in IRF-1−/− bone marrow cells, and the recovery of these lymphocyte subsets was observed when IRF-1−/− cells were cultured with IL-15 in vitro. These data indicate that IRF-1 regulates IL-15 gene expression, which may control the development of NK1+T cells, NK cells, and CD8-α/α+ IELs.
Transporters Associated with Antigen Processing (TAP)-independent Presentation of Soluble Insulin to α/β T Cells by the Class Ib Gene Product, Qa-1b
Authors: Mark Tompkins S. , Kraft Jennifer R. , Dao Chinh T. , Soloski Mark J. , Jensen Peter E.
Published: July 2002

T cell hybridomas isolated from nonresponder H-2b mice immunized with pork insulin were stimulated by insulin in the presence of major histocompatibility complex (MHC)-unmatched antigen presenting cells. The restriction element used by these CD4− T cells was mapped to an oligomorphic MHC class Ib protein encoded in the T region and identified as Qa-1b using transfectants. The antigenic determinant was localized to the insulin B chain, and experiments with truncated peptides suggested that it is unexpectedly long, comprising most or all of the 30 amino acid B chain. The antigen processing pathway used to present insulin to the Qa-1b– restricted T cells does not require transporters associated with antigen processing (TAP), and it is inhibited by chloroquine. A wide variety of cell lines from different tissues efficiently present soluble insulin to Qa-1b–restricted T cells, and insulin presentation is not enhanced by phagocytic stimuli. Our results demonstrate that Qa-1b can function to present exogenous protein to T cells in a manner similar to MHC class II molecules. Therefore, this class Ib protein may have access to a novel antigen processing pathway that is not available to class Ia molecules.
Differential Regulation and ATP Requirement for Caspase-8 and Caspase-3 Activation during CD95- and Anticancer Drug–induced Apoptosis
Authors: Ferrari Davide , Stepczynska Ania , Los Marek , Wesselborg Sebastian , Schulze-Osthoff Klaus
Published: July 2002

Apoptosis is induced by different stimuli, among them triggering of the death receptor CD95, staurosporine, and chemotherapeutic drugs. In all cases, apoptosis is mediated by caspases, although it is unclear how these diverse apoptotic stimuli cause protease activation. Two regulatory pathways have been recently identified, but it remains unknown whether they are functionally independent or linked to each other. One is mediated by recruitment of the proximal regulator caspase-8 to the death receptor complex. The other pathway is controlled by the release of cytochrome c from mitochondria and the subsequent ATP-dependent activation of the death regulator apoptotic protease-activating factor 1 (Apaf-1). Here, we report that both pathways can be dissected by depletion of intracellular ATP. Prevention of ATP production completely inhibited caspase activation and apoptosis in response to chemotherapeutic drugs and staurosporine. Interestingly, caspase-8, whose function appeared to be restricted to death receptors, was also activated by these drugs under normal conditions, but not after ATP depletion. In contrast, inhibition of ATP production did not affect caspase activation after triggering of CD95. These results suggest that chemotherapeutic drug–induced caspase activation is entirely controlled by a receptor-independent mitochondrial pathway, whereas CD95-induced apoptosis can be regulated by a separate pathway not requiring Apaf-1 function.
CD8α+ and CD8α− Subclasses of Dendritic Cells Direct the Development of Distinct T Helper Cells In Vivo
Authors: Maldonado-López Roberto , De Smedt Thibaut , Michel Patrick , Godfroid Jacques , Pajak Bernard , Heirman Carlo , Thielemans Kris , Leo Oberdan , Urbain Jacques , Moser Muriel
Published: July 2002

Cells of the dendritic family display some unique properties that confer to them the capacity to sensitize naive T cells in vitro and in vivo. In the mouse, two subclasses of dendritic cells (DCs) have been described that differ by their CD8α expression and their localization in lymphoid organs. The physiologic function of both cell populations remains obscure. Studies conducted in vitro have suggested that CD8α+ DCs could play a role in the regulation of immune responses, whereas conventional CD8α− DCs would be more stimulatory. We report here that both subclasses of DCs efficiently prime antigen-specific T cells in vivo, and direct the development of distinct T helper (Th) populations. Antigen-pulsed CD8α+ and CD8α− DCs are separated after overnight culture in recombinant granulocyte/macrophage colony-stimulating factor and injected into the footpads of syngeneic mice. Administration of CD8α− DCs induces a Th2-type response, whereas injection of CD8α+ DCs leads to Th1 differentiation. We further show that interleukin 12 plays a critical role in Th1 development by CD8α+ DCs. These findings suggest that the nature of the DC that presents the antigen to naive T cells may dictate the class selection of the adaptative immune response.
The Transmembrane Sequence of Human Histocompatibility Leukocyte Antigen (HLA)-C as a Determinant in Inhibition of a Subset of Natural Killer Cells
Authors: Davis Daniel M. , Mandelboim Ofer , Luque Isabel , Baba Eishi , Boyson Jonathan , Strominger Jack L.
Published: July 2002

Molecular interactions with the extracellular domains of class I major histocompatibility complex proteins are major determinants of immune recognition that have been extensively studied both physically and biochemically. However, no immunological function has yet been placed on the transmembrane or cytoplasmic amino acid sequences of these proteins despite strict conservation of unique features within each class I major histocompatibility complex locus. Here we report that lysis by a subset of natural killer (NK) cells inhibited by target cell expression of human histocompatibility leukocyte antigen (HLA)-Cw6 or -Cw7 was not inhibited by expression of chimeric proteins consisting of the extracellular domains of HLA-C and the COOH-terminal portion of HLA-G. Assays using transfectants expressing a variety of HLA-Cw6 mutants identified the transmembrane sequence and, in particular, cysteine at position 309 as necessary for inhibition of 68% (25/37) of NK cell lines and 23% (33/145) of NK clones tested. Moreover, these NK clones inhibited by target cell expression of HLA-Cw6 and dependent upon the transmembrane sequence were found not to express or to only dimly express NK inhibitory receptors (NKIR1) that are EB6/HP3E4-positive. Furthermore, assays using monoclonal antibody blocking suggest that an NK receptor other than NKIR1 or CD94 is responsible for recognition dependent upon the transmembrane sequence of HLA-Cw6.
Cytokine-Induced Src Homology 2 Protein (Cis) Promotes T Cell Receptor–Mediated Proliferation and Prolongs Survival of Activated T Cells
Authors: Li Suling , Chen Shangwu , Xu Xiufeng , Sundstedt Anette , Paulsson Kajsa M. , Anderson Per , Karlsson Stefan , Sjögren Hans-Olov , Wang Ping
Published: July 2002

Members of the suppressor of cytokine signaling (SOCS) family were discovered as negative regulators of cytokine signaling by inhibition of the Janus kinase–signal transducer and activator of transcription (Jak-STAT) pathway. Among them, cytokine-induced Src homology 2 (SH2) protein (CIS) was found to inhibit the interleukin 3– and erythropietin-mediated STAT5 signaling pathway. However, involvement of SOCS proteins in other signaling pathways is still unknown. This study shows that the expression of CIS is selectively induced in T cells after T cell receptor (TCR) stimulation. In transgenic mice, with selective expression of CIS in CD4 T cells, elevated CIS strongly promotes TCR-mediated proliferation and cytokine production in vitro, and superantigen-induced T cell activation in vivo. Forced expression of CIS also prolongs survival of CD4 T cells after TCR activation. Molecular events immediately downstream from the TCR are not changed in CIS-expressing CD4 T cells, but activation of mitogen-activated protein (MAP) kinase pathways by TCR stimulation is significantly enhanced. Together with the increased MAP kinase activation, a direct interaction of CIS and protein kinase Cθ was also demonstrated. These results suggest that CIS is one of the important regulators of TCR-mediated T cell activation. The functions of CIS, enhancing TCR signaling and inhibiting cytokine signaling, may be important in the regulation of immune response and homeostasis.
Binding of the Hepatitis C Virus Envelope Protein E2 to CD81 Inhibits Natural Killer Cell Functions
Authors: Tseng Chien-Te K. , Klimpel Gary R.
Published: July 2002

Infection with hepatitis C virus (HCV) is a leading cause of chronic liver disease worldwide. Little is known about how this virus is able to persist or whether this persistence might be because of its ability to alter the early innate immune response. The major HCV envelope protein E2 has been shown to bind to CD81. Thus, HCV binding to natural killer (NK) cells could result in the cross-linking of CD81. To explore this possibility, we investigated whether cross-linking CD81 on NK cells could alter NK cell function. CD81 cross-linking by monoclonal antibody (mAb) specific for CD81 or by immobilized E2 have been shown to result in costimulatory signals for human T cells. In this study, we show that CD81 cross-linking via immobilized E2 or mAbs specific for CD81 inhibits not only non major histocompatibility complex–restricted cytotoxicity mediated by NK cells but also interferon (IFN)-γ production by NK cells after exposure to interleukin (IL)-2, IL-12, IL-15, or CD16 cross-linking. These results show that CD81 cross-linking mediates completely different signals in NK cells versus T cells. Importantly, these results suggest that one mechanism whereby HCV can alter host defenses and innate immunity is via the early inhibition of IFN-γ production by NK cells.
Hematopoietic Stem Cells Are Uniquely Selective in Their Migratory Response to Chemokines
Authors: Wright Douglas E. , Bowman Edward P. , Wagers Amy J. , Butcher Eugene C. , Weissman Irving L.
Published: July 2002

Although hematopoietic stem cell (HSC) migration into and out of sites of active hematopoiesis is poorly understood, it is a critical process that underlies modern clinical stem cell transplantation and may be important for normal hematopoietic homeostasis. Given the established roles of chemotactic cytokine (chemokine)-directed migration of other leukocyte subsets, the migration of murine HSC to a large panel of CC and CXC chemokines was investigated. HSC migrated only in response to stromal derived factor-1α, the ligand for the CXC chemokine receptor 4 (CXCR4). CXCR4 expression by HSC was confirmed by reverse transcription polymerase chain reaction analysis. Surprisingly, HSC also expressed mRNA for CCR3 and CCR9, although they failed to migrate to the ligands for these receptors. The sharply restricted chemotactic responsiveness of HSC is unique among leukocytes and may be necessary for the specific homing of circulating HSC to bone marrow, as well as for the maintenance of HSC in hematopoietic microenvironments.
MAEBL Is Essential for Malarial Sporozoite Infection of the Mosquito Salivary Gland
Authors: Kariu Tohru , Yuda Masao , Yano Kazuhiko , Chinzei Yasuo
Published: July 2002

Malarial sporozoites mature in the oocysts formed in the mosquito midgut wall and then selectively invade the salivary glands, where they wait to be transmitted to the vertebrate host via mosquito bite. Invasion into the salivary gland has been thought to be mediated by specific ligand–receptor interactions, but the molecules involved in these interactions remain unknown. MAEBL is a single transmembrane-like protein that is structurally related to merozoite adhesive proteins. We found MAEBL of the rodent malaria parasite, Plasmodium berghei, to be specifically produced by the sporozoites in the oocyst and localized in their micronemes, which are secretory organelles involved in malarial parasite invasion into the host cell. A targeted disruption experiment of the P. berghei MAEBL gene revealed that it was essential for sporozoite infection of the salivary gland and was involved in the attachment to the salivary gland surface. In contrast, the disruption of the MAEBL gene did not affect sporozoite motility in vitro nor infectivity to the vertebrate host. These results suggest that P. berghei MAEBL is a sporozoite attachment protein that participates in specific binding to and infection of the mosquito salivary gland.
Deuterium Isotope Effects on Permeation and Gating of Proton Channels in Rat Alveolar Epithelium
Authors: DeCoursey Thomas E. , Cherny Vladimir V.
Published: July 2002

The voltage-activated H+ selective conductance of rat alveolar epithelial cells was studied using whole-cell and excised-patch voltage-clamp techniques. The effects of substituting deuterium oxide, D2O, for water, H2O, on both the conductance and the pH dependence of gating were explored. D+ was able to permeate proton channels, but with a conductance only about 50% that of H+. The conductance in D2O was reduced more than could be accounted for by bulk solvent isotope effects (i.e., the lower mobility of D+ than H+), suggesting that D+ interacts specifically with the channel during permeation. Evidently the H+ or D+ current is not diffusion limited, and the H+ channel does not behave like a water-filled pore. This result indirectly strengthens the hypothesis that H+ (or D+) and not OH− is the ionic species carrying current. The voltage dependence of H+ channel gating characteristically is sensitive to pHo and pHi and was regulated by pDo and pDi in an analogous manner, shifting 40 mV/U change in the pD gradient. The time constant of H+ current activation was about three times slower (τact was larger) in D2O than in H2O. The size of the isotope effect is consistent with deuterium isotope effects for proton abstraction reactions, suggesting that H+ channel activation requires deprotonation of the channel. In contrast, deactivation (τtail) was slowed only by a factor ≤1.5 in D2O. The results are interpreted within the context of a model for the regulation of H+ channel gating by mutually exclusive protonation at internal and external sites (Cherny, V.V., V.S. Markin, and T.E. DeCoursey. 1995. J. Gen. Physiol. 105:861–896). Most of the kinetic effects of D2O can be explained if the pKa of the external regulatory site is ∼0.5 pH U higher in D2O.
Temperature Dependence of Voltage-gated H+ Currents in Human Neutrophils, Rat Alveolar Epithelial Cells, and Mammalian Phagocytes
Authors: DeCoursey Thomas E. , Cherny Vladimir V.
Published: July 2002

H+ currents in human neutrophils, rat alveolar epithelial cells, and several mammalian phagocyte cell lines were studied using whole-cell and excised-patch tight-seal voltage clamp techniques at temperatures between 6 and 42°C. Effects of temperature on gating kinetics were distinguished from effects on the H+ current amplitude. The activation and deactivation of H+ currents were both highly temperature sensitive, with a Q10 of 6–9 (activation energy, Ea, ≈ 30–38 kcal/mol), greater than for most other ion channels. The similarity of Ea for channel opening and closing suggests that the same step may be rate determining. In addition, when the turn-on of H+ currents with depolarization was fitted by a delay and single exponential, both the delay and the time constant (τact) had similarly high Q10. These results could be explained if H+ channels were composed of several subunits, each of which undergoes a single rate-determining gating transition. H+ current gating in all mammalian cells studied had similarly strong temperature dependences. The H+ conductance increased markedly with temperature, with Q10 ≥ 2 in whole-cell experiments. In excised patches where depletion would affect the measurement less, the Q10 was 2.8 at >20°C and 5.3 at <20°C. This temperature sensitivity is much greater than for most other ion channels and for H+ conduction in aqueous solution, but is in the range reported for H+ transport mechanisms other than channels; e.g., carriers and pumps. Evidently, under the conditions employed, the rate-determining step in H+ permeation occurs not in the diffusional approach but during permeation through the channel itself. The large Ea of permeation intrinsically limits the conductance of this channel, and appears inconsistent with the channel being a water-filled pore. At physiological temperature, H+ channels provide mammalian cells with an enormous capacity for proton extrusion.
The Calcium Sensitivity of Individual Secretory Vesicles Is Invariant with the Rate of Calcium Delivery
Authors: Blank Paul S. , Vogel Steven S. , Cho Myoung-Soon , Kaplan Doron , Bhuva Devang , Malley James , Zimmerberg Joshua
Published: July 2002

Differences in the calcium sensitivity of individual secretory vesicles can explain a defining feature of calcium-regulated exocytosis, a graded response to calcium. The role of the time dependence of calcium delivery in defining the observed differences in the calcium sensitivity of sea urchin egg secretory vesicles in vitro was examined. The calcium sensitivity of individual secretory vesicles (i.e., the distribution of calcium thresholds) is invariant over a range of calcium delivery rates from faster than micromolar per millisecond to slower than micromolar per second. Any specific calcium concentration above threshold triggers subpopulations of vesicles to fuse, and the size of these subpopulations is independent of the time course required to reach that calcium concentration. All evidence supports the hypothesis that the magnitude of the free calcium is the single controlling variable that determines the fraction of vesicles that fuse, and that this fraction is established before the application of calcium. Submaximal responses to calcium cannot be attributed to alterations in the calcium sensitivity of individual secretory vesicles arising from the temporal properties of the calcium delivery. Models that attempt to explain the cessation of fusion using changes in the distribution of calcium thresholds arising from the rate of calcium delivery and/or adaptation are not applicable to this system, and thus cannot be general.
Shortcomings of peer review in biomedical journals
Authors: Wager Elizabeth , Jefferson Tom
Published: July 2002

Peer review is well established across most academic disciplines, and publishers, editors, and researchers devote considerable resources to it. This paper uses examples from biomedical journals to examine its shortcomings. Although mainly anecdotal, the evidence suggests that peer review is sometimes ineffective at identifying important research and even less effective at detecting fraud. Most reviewers identify only the minority of a paper's defects and they may be biased. Peer review plus other editorial processes are associated with improvements in papers between submission and publication, but published papers remain hard to read and a significant proportion contain errors or omissions. While it is hard to quantify the costs, peer review does not seem an efficient use of resources. Research into the outcomes of peer review, the establishment of sound methods for measuring the quality of the process and its outcomes, and comparisons with alternative methods are needed.
Hindman spaces
Authors: Kojman Menachem
Published: July 2002

A topological space

X
X

is Hindman if for every sequence

(

x
n

)
n

(x_n)_n

in

X
X

there exists an infinite

D
⊆

N

D\subseteq \mathbb {N}

so that the sequence

(

x
n

)

n
∈
F
S
(
D
)

(x_n)_{n\in FS(D)}

, indexed by all finite sums over

D
D

, is IP-converging in

X
X

. Not all sequentially compact spaces are Hindman. The product of two Hindman spaces is Hindman.

Furstenberg and Weiss proved that all compact metric spaces are Hindman. We show that every Hausdorff space

X
X

that satisfies the following condition is Hindman:
\[

(

∗

)\quad The closure of every countable set in 

X

 is compact and first-countable.\quad 

\text {($*$)\quad The closure of every countable set in $X$ is compact and first-countable.\quad }

\]

Consequently, there exist nonmetrizable and noncompact Hindman spaces. The following is a particular consequence of the main result: every bounded sequence of monotone (not necessarily continuous) real functions on

[
0
,
1
]

[0,1]

has an IP-converging subsequences.
Partial actions of groups and actions of inverse semigroups
Authors: Exel Ruy
Published: July 2002

Given a group

G
G

, we construct, in a canonical way, an inverse semigroup

S

(
G
)

\mathcal {S}(G)

associated to

G
G

. The actions of

S

(
G
)

\mathcal {S}(G)

are shown to be in one-to-one correspondence with the partial actions of

G
G

, both in the case of actions on a set, and that of actions as operators on a Hilbert space. In other words,

G
G

and

S

(
G
)

\mathcal {S}(G)

have the same representation theory. We show that

S

(
G
)

\mathcal S(G)

governs the subsemigroup of all closed linear subspaces of a

G
G

-graded

C

∗

{C}^*

-algebra, generated by the grading subspaces. In the special case of finite groups, the maximum number of such subspaces is computed. A “partial” version of the group

C

∗

{ C}^*

-algebra of a discrete group is introduced. While the usual group

C

∗

{ C}^*

-algebra of finite commutative groups forgets everything but the order of the group, we show that the partial group

C

∗

{ C}^*

-algebra of the two commutative groups of order four, namely

Z

/

4
Z

Z/4 Z

and

Z

/

2
Z
⊕
Z

/

2
Z

Z/2 Z \oplus Z/2 Z

, are not isomorphic.
Conjugate points and shocks in nonlinear optimal control
Authors: Caroff N. , Frankowska H.
Published: July 2002

We investigate characteristics of the Hamilton-Jacobi-Bellman equation arising in nonlinear optimal control and their relationship with weak and strong local minima. This leads to an extension of the Jacobi conjugate points theory to the Bolza control problem. Necessary and sufficient optimality conditions for weak and strong local minima are stated in terms of the existence of a solution to a corresponding matrix Riccati differential equation.
On the elliptic equation Δ𝑢+𝑘𝑢-𝐾𝑢^{𝑝}=0 on complete Riemannian manifolds and their geometric applications
Authors: Li Peter , Tam Luen-fai , Yang DaGang
Published: July 2002

We study the elliptic equation

Δ
u
+
k
u
−
K

u

p

=
0

\Delta u + ku - Ku^{p} = 0

on complete noncompact Riemannian manifolds with

K
K

nonnegative. Three fundamental theorems for this equation are proved in this paper. Complete analyses of this equation on the Euclidean space

R

n

{\mathbf {R}}^{n}

and the hyperbolic space

H

n

{\mathbf {H}}^{n}

are carried out when

k
k

is a constant. Its application to the problem of conformal deformation of nonpositive scalar curvature will be done in the second part of this paper.
The coefficients of primitive polynomials over finite fields
Authors: Han Wen Bao
Published: July 2002

For

n
≥
7

n\ge 7

, we prove that there always exists a primitive polynomial of degree

n
n

over a finite field

F
q

(
q
odd
)

F_q (q \operatorname {odd})

with the first and second coefficients prescribed in advance.
Integral cohomology and detection of 𝑤-basic 2-groups
Authors: Pearson Kimberly
Published: July 2002

In this paper we compute the cohomology

H
∗

(
G
;

Z
w

)

H^*(G;Z^w)

of all

w
w

-basic 2-groups

(
G
,
w
)

(G,w)

with integral coefficients twisted by the orientation character

w
w

. We also calculate appropriate restiction maps and thus prove that the cohomology of any

w
w

-basic group is detected by subgroups isomorphic to one of five types, and we provide a sample application of this main theorem.
Numbers whose positive divisors have small integral harmonic mean
Authors: Cohen G.
Published: July 2002

A natural number

n
n

is said to be harmonic when the harmonic mean

H
(
n
)

H(n)

of its positive divisors is an integer. These were first introduced almost fifty years ago. In this paper, all harmonic numbers less than

2
×

10

9

2\times 10^{9}

are listed, along with some other useful tables, and all harmonic numbers

n
n

with

H
(
n
)
≤
13

H(n)\le 13

are determined.
On numerical methods for discrete least-squares approximation by trigonometric polynomials
Authors: Faßbender Heike
Published: July 2002

Fast, efficient and reliable algorithms for discrete least-squares approximation of a real-valued function given at arbitrary distinct nodes in

[
0
,
2
π
)

[0,2\pi )

by trigonometric polynomials are presented. The algorithms are based on schemes for the solution of inverse unitary eigenproblems and require only O

(
m
n
)

(mn)

arithmetic operations as compared to O

(
m

n
2

)

(mn^2)

operations needed for algorithms that ignore the structure of the problem. An algorithm which solves this problem with real-valued data and real-valued solution using only real arithmetic is given. Numerical examples are presented that show that the proposed algorithms produce consistently accurate results that are often better than those obtained by general QR decomposition methods for the least-squares problem.
Universal binary Hermitian forms
Authors: Earnest A. , Khosravani Azar
Published: July 2002

We will determine (up to equivalence) all of the integral positive definite Hermitian lattices in imaginary quadratic fields of class number 1 that represent all positive integers.
Analysis of a FEM/BEM coupling method for transonic flow computations
Authors: Berger H. , Warnecke G. , Wendland W.
Published: July 2002

A sensitive issue in numerical calculations for exterior flow problems, e.g. around airfoils, is the treatment of the far field boundary conditions on a computational domain which is bounded. In this paper we investigate this problem for two–dimensional transonic potential flows with subsonic far field flow around airfoil profiles. We take the artificial far field boundary in the subsonic flow region. In the far field we approximate the subsonic potential flow by the Prandtl–Glauert linearization. The latter leads via the Green representation theorem to a boundary integral equation on the far field boundary. This defines a nonlocal boundary condition for the interior ring domain. Our approach leads naturally to a coupled finite element/boundary element method for numerical calculations. It is compared with local boundary conditions. The error analysis for the method is given and we prove convergence provided the solution to the analytic transonic flow problem around the profile exists.
Distribution of irreducible polynomials of small degrees over finite fields
Authors: Ham Kie , Mullen Gary
Published: July 2002

D. Wan very recently proved an asymptotic version of a conjecture of Hansen and Mullen concerning the distribution of irreducible polynomials over finite fields. In this note we prove that the conjecture is true in general by using machine calculation to verify the open cases remaining after Wan’s work.
Global and superlinear convergence of the smoothing Newton method and its application to general box constrained variational inequalities
Authors: Chen X. , Qi L. , Sun D.
Published: July 2002

The smoothing Newton method for solving a system of nonsmooth equations

F
(
x
)
=
0

F(x)=0

, which may arise from the nonlinear complementarity problem, the variational inequality problem or other problems, can be regarded as a variant of the smoothing method. At the

k
k

th step, the nonsmooth function

F
F

is approximated by a smooth function

f
(
⋅
,

ε
k

)

f(\cdot , \varepsilon _k)

, and the derivative of

f
(
⋅
,

ε
k

)

f(\cdot , \varepsilon _k)

at

x
k

x^k

is used as the Newton iterative matrix. The merits of smoothing methods and smoothing Newton methods are global convergence and convenience in handling. In this paper, we show that the smoothing Newton method is also superlinearly convergent if

F
F

is semismooth at the solution and

f
f

satisfies a Jacobian consistency property. We show that most common smooth functions, such as the Gabriel-Moré function, have this property. As an application, we show that for box constrained variational inequalities if the involved function is

P
P

–uniform, the iteration sequence generated by the smoothing Newton method will converge to the unique solution of the problem globally and superlinearly (quadratically).
Orbits of algebraic numbers with low heights
Authors: Dresden Gregory
Published: July 2002

We prove that the two smallest values of

h
(
α
)
+
h
(

1

1
−
α

)
+
h
(
1
−

1
α

)

h(\alpha ) + h(\frac {1}{1-\alpha }) + h(1 - \frac {1}{\alpha })

are

0
0

and

0.4218
…

0.4218\dots

, for

α
\alpha

any algebraic integer.
Computations of class numbers of real quadratic fields
Authors: Srinivasan Anitha
Published: July 2002

In this paper an unconditional probabilistic algorithm to compute the class number of a real quadratic field

Q

(

d

)

\mathbb {Q}(\sqrt {d})

is presented, which computes the class number in expected time

O
(

d

1

/

5
+
ϵ

)

O(d^{1/5+\epsilon })

. The algorithm is a random version of Shanks’ algorithm. One of the main steps in algorithms to compute the class number is the approximation of

L
(
1
,
χ
)

L(1, \chi )

. Previous algorithms with the above running time

O
(

d

1

/

5
+
ϵ

)

O(d^{1/5+\epsilon })

, obtain an approximation for

L
(
1
,
χ
)

L(1, \chi )

by assuming an appropriate extension of the Riemann Hypothesis. Our algorithm finds an appoximation for

L
(
1
,
χ
)

L(1, \chi )

without assuming the Riemann Hypothesis, by using a new technique that we call the ‘Random Summation Technique’. As a result, we are able to compute the regulator deterministically in expected time

O
(

d

1

/

5
+
ϵ

)

O(d^{1/5+\epsilon })

. However, our estimate of

O
(

d

1

/

5
+
ϵ

)

O(d^{1/5+\epsilon })

on the running time of our algorithm to compute the class number is not effective.
On two classes of simultaneous Pell equations with no solutions
Authors: Walsh P.
Published: July 2002

In this paper we describe two classes of simultaneous Pell equations of the form

x
2

−
d

y
2

=

z
2

−
e

y
2

=
1

x^2-dy^2=z^2-ey^2=1

with no solutions in positive integers

x
,
y
,
z

x,y,z

. The proof is elementary and covers the case

(
d
,
e
)
=
(
8
,
5
)

(d,e)=(8,5)

, which was solved by E. Brown using very deep methods.
Finite element approximation to a contact problem in linear thermoelasticity
Authors: Copetti M.
Published: July 2002

A finite element approximation to the solution of a one-dimensional linear thermoelastic problem with unilateral contact of the Signorini type and heat flux is proposed. An error bound is derived and some numerical experiments are performed.
On the coupling of BEM and FEM for exterior problems for the Helmholtz equation
Authors: Li Ruixia
Published: July 2002

This paper deals with the coupled procedure of the boundary element method (BEM) and the finite element method (FEM) for the exterior boundary value problems for the Helmholtz equation. A circle is selected as the common boundary on which the integral equation is set up with Fourier expansion. As a result, the exterior problems are transformed into nonlocal boundary value problems in a bounded domain which is treated with FEM, and the normal derivative of the unknown function at the common boundary does not appear. The solvability of the variational equation and the error estimate are also discussed.
Fractional Power Series and Pairings on Drinfeld Modules
Authors: Poonen Bjorn
Published: July 2002

Let

C
C

be an algebraically closed field containing

F

q

\mathbb {F}_q

which is complete with respect to an absolute value

|

|

|\;|

. We prove that under suitable constraints on the coefficients, the series

f
(
z
)
=

∑

n
∈

Z

a
n

z

q
n

f(z) = \sum _{n \in \mathbb {Z}} a_n z^{q^n}

converges to a surjective, open, continuous

F

q

\mathbb {F}_q

-linear homomorphism

C
→
C

C \rightarrow C

whose kernel is locally compact. We characterize the locally compact sub-

F

q

\mathbb {F}_q

-vector spaces

G
G

of

C
C

which occur as kernels of such series, and describe the extent to which

G
G

determines the series. We develop a theory of Newton polygons for these series which lets us compute the Haar measure of the set of zeros of

f
f

of a given valuation, given the valuations of the coefficients. The “adjoint” series
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f Superscript asterisk Baseline left-parenthesis z right-parenthesis equals sigma-summation Underscript n element-of double-struck upper Z Endscripts a Subscript n Superscript 1 slash q Super Superscript n Baseline z Superscript 1 slash q Super Superscript n">

f
∗

(
z
)
=

∑

n
∈

Z

a
n

1

/

q
n

z

1

/

q
n

f^\ast (z) = \sum _{n \in \mathbb {Z}} a_n^{1/q^n} z^{1/q^n}

converges everywhere if and only if

f
f

does, and in this case there is a natural bilinear pairing
\[

ker
⁡
f
×
ker
⁡

f
∗

→

F

q

\ker f \times \ker f^\ast \rightarrow \mathbb {F}_q

\]
which exhibits

ker
⁡

f
∗

\ker f^\ast

as the Pontryagin dual of

ker
⁡
f

\ker f

. Many of these results extend to non-linear fractional power series. We apply these results to construct a Drinfeld module analogue of the Weil pairing, and to describe the topological module structure of the kernel of the adjoint exponential of a Drinfeld module.
A deterministic displacement theorem for Poisson processes
Authors: Knill Oliver
Published: July 2002

We announce a deterministic analog of Bartlett’s displacement theorem. The result is that a Poisson property is stable with respect to deterministic Hamiltonian displacements. While the random point configurations move according to an

n
n

-body evolution, the mean measure

P
P

satisfies a nonlinear Vlasov type equation

P
˙

+
y
⋅

∇
x

P
−

∇
y

⋅
E
(
P
)
=
0

\dot {P} + y \cdot \nabla _x P - \nabla _y \cdot E(P) = 0

. Combined with Bartlett’s theorem, the result generalizes to interacting Brownian particles, where the mean measure satisfies a McKean-Vlasov type diffusion equation

P
˙

+
y
⋅

∇
x

P
−

∇
y

⋅
E
(
P
)
−
c
Δ
P
=
0

\dot {P} + y \cdot \nabla _x P-\nabla _y \cdot E(P)- c \Delta P=0

.
Tangential Hilbert problem for perturbations of hyperelliptic Hamiltonian systems
Authors: Novikov D. , Yakovenko S.
Published: July 2002

The tangential Hilbert 16th problem is to place an upper bound for the number of isolated ovals of algebraic level curves

{
H
(
x
,
y
)
=
const
}

\{H(x,y)=\operatorname {const}\}

over which the integral of a polynomial 1-form

P
(
x
,
y
)

d
x
+
Q
(
x
,
y
)

d
y

P(x,y)\,dx+Q(x,y)\,dy

(the Abelian integral) may vanish, the answer to be given in terms of the degrees

n
=
deg
⁡
H

n=\deg H

and

d
=
max
(
deg
⁡
P
,
deg
⁡
Q
)

d=\max (\deg P,\deg Q)

. We describe an algorithm producing this upper bound in the form of a primitive recursive (in fact, elementary) function of

n
n

and

d
d

for the particular case of hyperelliptic polynomials

H
(
x
,
y
)
=

y
2

+
U
(
x
)

H(x,y)=y^2+U(x)

under the additional assumption that all critical values of

U
U

are real. This is the first general result on zeros of Abelian integrals that is completely constructive (i.e., contains no existential assertions of any kind). The paper is a research announcement preceding the forthcoming complete exposition. The main ingredients of the proof are explained and the differential algebraic generalization (that is the core result) is given.
Harmonic spinors on homogeneous spaces
Authors: Landweber Gregory
Published: July 2002

Let

G
G

be a compact, semi-simple Lie group and

H
H

a maximal rank reductive subgroup. The irreducible representations of

G
G

can be constructed as spaces of harmonic spinors with respect to a Dirac operator on the homogeneous space

G

/

H

G/H

twisted by bundles associated to the irreducible, possibly projective, representations of

H
H

. Here, we give a quick proof of this result, computing the index and kernel of this twisted Dirac operator using a homogeneous version of the Weyl character formula noted by Gross, Kostant, Ramond, and Sternberg, as well as recent work of Kostant regarding an algebraic version of this Dirac operator.
Module extensions over classical Lie superalgebras
Authors: Letzter Edward
Published: July 2002

We study certain filtrations of indecomposable injective modules over classical Lie superalgebras, applying a general approach for noetherian rings developed by Brown, Jategaonkar, Lenagan, and Warfield. To indicate the consequences of our analysis, suppose that

g

\mathfrak {g}

is a complex classical simple Lie superalgebra and that

E
E

is an indecomposable injective

g

\mathfrak {g}

-module with nonzero (and so necessarily simple) socle

L
L

. (Recall that every essential extension of

L
L

, and in particular every nonsplit extension of

L
L

by a simple module, can be formed from

g

\mathfrak {g}

-subfactors of

E
E

.) A direct transposition of the Lie algebra theory to this setting is impossible. However, we are able to present a finite upper bound, easily calculated and dependent only on

g

\mathfrak {g}

, for the number of isomorphism classes of simple highest weight

g

\mathfrak {g}

-modules appearing as

g

\mathfrak {g}

-subfactors of

E
E

.
Deformation of Schottky groups in complex hyperbolic space
Authors: Aebischer Beat , Miner Robert
Published: July 2002

Let

G
=
P
U
(
1
,
d
)

G=PU(1,d)

be the group of holomorphic isometries of complex hyperbolic space

H

C

d

\mathbf {H}^d_\mathbf {C}

. The latter is a Kähler manifold with constant negative holomorphic sectional curvature. We call a finitely generated discrete group

Γ
=
⟨

g
1

,
…
,

g
n

⟩
⊂
G

\Gamma = \langle g_1,\dots , g_n \rangle \subset G

a marked classical Schottky group of rank

n
n

if there is a fundamental polyhedron for

G
G

whose sides are equidistant hypersurfaces which are disjoint and not asymptotic, and for which

g
1

,
…
,

g
n

g_1, \dots , g_n

are side-pairing transformations. We consider smooth families of such groups

Γ
t

=
⟨

g

1
,
t

,
…
,

g

n
,
t

⟩

\Gamma _t = \langle g_{1,t}, \dots , g_{n,t} \rangle

with

g

j
,
t

g_{j,t}

depending smoothly (

C
1

C^1

) on

t
t

whose fundamental polyhedra also vary smoothly. The groups

Γ
t

\Gamma _t

are all algebraically isomorphic to the free group in

n
n

generators, i.e. there are canonical isomorphisms

ϕ
t

:

Γ
0

→

Γ
t

\phi _t: \Gamma _0\to \Gamma _t

. We shall construct a homeomorphism

Ψ
t

\Psi _t

of

H

¯

C

d

=

H

C

d

∪
∂

H

C

d

\overline {\mathbf {H}}^d_\mathbf {C} = \mathbf {H}^d_\mathbf {C}\cup \partial \mathbf {H}^d_\mathbf {C}

which is equivariant with respect to these groups:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="phi Subscript t Baseline left-parenthesis g right-parenthesis ring normal upper Psi Subscript t Baseline equals normal upper Psi Subscript t Baseline ring g for-all g element-of normal upper Gamma 0 comma 0 less-than-or-equal-to t less-than-or-equal-to 1">

ϕ
t

(
g
)
∘

Ψ
t

=

Ψ
t

∘
g

∀
g
∈

Γ
0

,

0
≤
t
≤
1

\begin{equation*} \phi _t(g) \circ \Psi _t = \Psi _t \circ g \quad \; \forall g\in \Gamma _0, \quad 0\leq t\leq 1 \end{equation*}

which is quasiconformal on

∂

H

C

d

\partial \mathbf {H}^d_\mathbf {C}

with respect to the Heisenberg metric, and which is symplectic in the interior. As a corollary, the limit sets of such Schottky groups of equal rank are quasiconformally equivalent to each other. The main tool for the construction is a time-dependent Hamiltonian vector field used to define a diffeomorphism, mapping

D
0

D_0

onto

D
t

D_t

, where

D
t

D_t

is a fundamental domain of

Γ
t

\Gamma _t

. In two steps, this is extended equivariantly to

H

¯

C

d

\overline {\mathbf {H}}^d_\mathbf {C}

. The method yields similar results for real hyperbolic space, while the analog for the other rank-one symmetric spaces of noncompact type cannot hold.
Geometry of the Feigenbaum map
Authors: Buff Xavier
Published: July 2002

We show that the Cvitanović-Feigenbaum equation can be interpreted as a linearizing equation, and the domain of analyticity of the Feigenbaum fixed point of renormalization as a basin of attraction. As a consequence, we give a combinatorial description of this ramified covering, and we show the surprising result that there exist points in the boundary of this domain with three accesses from inside the domain. Besides, there is a natural decomposition of this basin which makes it possible to recover a result of local connectivity by Hu and Jiang (The Julia set of the Feigenbaum quadratic polynomial is locally connected, Preprint, 1993) for the Feigenbaum Julia set.
The co-evolution of human fertility and wealth inheritance strategies
Authors: Mace Ruth
Published: July 2002

Life history theory concerns the scheduling of births and the level of parental investment in each offspring. In most human societies the inheritance of wealth is an important part of parental investment. Patterns of wealth inheritance and other reproductive decisions, such as family size, would be expected to influence each other. Here I present an adaptive model of human reproductive decision-making, using a state-dependent dynamic model. Two decisions made by parents are considered: when to have another baby, and thus the pattern of reproduction through life; and how to allocate resources between children at the end of the parents life. Optimal decision rules are those that maximize the number of grandchildren. Decisions are assumed to depend on the state of the parent, which is described at any time by two variables: number of living sons, and wealth. The dynamics of the model are based on a traditional African pastoralist system, but it is general enough to approximate to any means of subsistence where an increase in the amount of wealth owned increases the capacity for future production of resources. The model is used to show that, in the unpredictable environment of a traditional pastoralist society, high fertility and a biasing of wealth inheritance to a small number of children are frequently optimal. Most such societies are now undergoing a transition to lower fertility, known as the demographic transition. The effects on fertility and wealth inheritance strategies of reducing mortality risks, reducing the unpredictability of the environment and increasing the costs of raising children are explored. Reducing mortality has little effect on completed family sizes of living children or on the wealth they inherit. Increasing the costs of raising children decreases optimal fertility and increases the inheritance left to each child at each level of wealth, and has the potential to reduce fertility to very low levels. The results offer an explanation for why wealthy families are frequently also those with the smallest number of children in heterogenous, post-transition societies.