bluuebunny/crossref_metadata_2025 huggingface dataset:
Dishevelled activates Ca2+ flux, PKC, and CamKII in vertebrate embryos
Authors: Sheldahl Laird C. , Slusarski Diane C. , Pandur Petra , Miller Jeffrey R. , Kühl Michael , Moon Randall T.
Published: May 2003

Wnt ligands and Frizzled (Fz) receptors have been shown to activate multiple intracellular signaling pathways. Activation of the Wnt–β-catenin pathway has been described in greatest detail, but it has been reported that Wnts and Fzs also activate vertebrate planar cell polarity (PCP) and Wnt–Ca2+ pathways. Although the intracellular protein Dishevelled (Dsh) plays a dual role in both the Wnt–β-catenin and the PCP pathways, its potential involvement in the Wnt–Ca2+ pathway has not been investigated. Here we show that a Dsh deletion construct, XDshΔDIX, which is sufficient for activation of the PCP pathway, is also sufficient for activation of three effectors of the Wnt–Ca2+ pathway: Ca2+ flux, PKC, and calcium/calmodulin-dependent protein kinase II (CamKII). Furthermore, we find that interfering with endogenous Dsh function reduces the activation of PKC by Xfz7 and interferes with normal heart development. These data suggest that the Wnt–Ca2+ pathway utilizes Dsh, thereby implicating Dsh as a component of all reported Fz signaling pathways.
Kinetic analysis of receptor-activated phosphoinositide turnover
Authors: Xu Chang , Watras James , Loew Leslie M.
Published: May 2003

We studied the bradykinin-induced changes in phosphoinositide composition of N1E-115 neuroblastoma cells using a combination of biochemistry, microscope imaging, and mathematical modeling. Phosphatidylinositol-4,5-bisphosphate (PIP2) decreased over the first 30 s, and then recovered over the following 2–3 min. However, the rate and amount of inositol-1,4,5-trisphosphate (InsP3) production were much greater than the rate or amount of PIP2 decline. A mathematical model of phosphoinositide turnover based on this data predicted that PIP2 synthesis is also stimulated by bradykinin, causing an early transient increase in its concentration. This was subsequently confirmed experimentally. Then, we used single-cell microscopy to further examine phosphoinositide turnover by following the translocation of the pleckstrin homology domain of PLCδ1 fused to green fluorescent protein (PH-GFP). The observed time course could be simulated by incorporating binding of PIP2 and InsP3 to PH-GFP into the model that had been used to analyze the biochemistry. Furthermore, this analysis could help to resolve a controversy over whether the translocation of PH-GFP from membrane to cytosol is due to a decrease in PIP2 on the membrane or an increase in InsP3 in cytosol; by computationally clamping the concentrations of each of these compounds, the model shows how both contribute to the dynamics of probe translocation.
Caveolae/raft-dependent endocytosis
Authors: Nabi Ivan R. , Le Phuong U.
Published: May 2003

Although caveolae are well-characterized subdomains of glycolipid rafts, their distinctive morphology and association with caveolins has led to their internalization being considered different from that of rafts. In this review, we propose that caveolae and rafts are internalized via a common pathway, caveolae/raft-dependent endocytosis, defined by its clathrin independence, dynamin dependence, and sensitivity to cholesterol depletion. The regulatory role of caveolin-1 and ligand sorting in this complex endocytic pathway are specifically addressed.
Custom Distinctions in the Interaction of G-protein β Subunits with N-type (CaV2.2) Versus P/Q-type (CaV2.1) Calcium Channels
Authors: Agler Heather L. , Evans Jenafer , Colecraft Henry M. , Yue David T.
Published: May 2003

Inhibition of N- (Cav2.2) and P/Q-type (Cav2.1) calcium channels by G-proteins contribute importantly to presynaptic inhibition as well as to the effects of opiates and cannabinoids. Accordingly, elucidating the molecular mechanisms underlying G-protein inhibition of voltage-gated calcium channels has been a major research focus. So far, inhibition is thought to result from the interaction of multiple proposed sites with the Gβγ complex (Gβγ). Far less is known about the important interaction sites on Gβγ itself. Here, we developed a novel electrophysiological paradigm, “compound-state willing-reluctant analysis,” to describe Gβγ interaction with N- and P/Q-type channels, and to provide a sensitive and efficient screen for changes in modulatory behavior over a broad range of potentials. The analysis confirmed that the apparent (un)binding kinetics of Gβγ with N-type are twofold slower than with P/Q-type at the voltage extremes, and emphasized that the kinetic discrepancy increases up to ten-fold in the mid-voltage range. To further investigate apparent differences in modulatory behavior, we screened both channels for the effects of single point alanine mutations within four regions of Gβ1, at residues known to interact with Gα. These residues might thereby be expected to interact with channel effectors. Of eight mutations studied, six affected G-protein modulation of both N- and P/Q-type channels to varying degrees, and one had no appreciable effect on either channel. The remaining mutation was remarkable for selective attenuation of effects on P/Q-, but not N-type channels. Surprisingly, this mutation decreased the (un)binding rates without affecting its overall affinity. The latter mutation suggests that the binding surface on Gβγ for N- and P/Q-type channels are different. Also, the manner in which this last mutation affected P/Q-type channels suggests that some residues may be important for “steering” or guiding the protein into the binding pocket, whereas others are important for simply binding to the channel.
Saxitoxin Is a Gating Modifier of hERG K+ Channels
Authors: Wang Jixin , Salata Joseph J. , Bennett Paul B.
Published: May 2003

Potassium (K+) channels mediate numerous electrical events in excitable cells, including cellular membrane potential repolarization. The hERG K+ channel plays an important role in myocardial repolarization, and inhibition of these K+ channels is associated with long QT syndromes that can cause fatal cardiac arrhythmias. In this study, we identify saxitoxin (STX) as a hERG channel modifier and investigate the mechanism using heterologous expression of the recombinant channel in HEK293 cells. In the presence of STX, channels opened slower during strong depolarizations, and they closed much faster upon repolarization, suggesting that toxin-bound channels can still open but are modified, and that STX does not simply block the ion conduction pore. STX decreased hERG K+ currents by stabilizing closed channel states visualized as shifts in the voltage dependence of channel opening to more depolarized membrane potentials. The concentration dependence for steady-state modification as well as the kinetics of onset and recovery indicate that multiple STX molecules bind to the channel. Rapid application of STX revealed an apparent “agonist-like” effect in which K+ currents were transiently increased. The mechanism of this effect was found to be an effect on the channel voltage-inactivation relationship. Because the kinetics of inactivation are rapid relative to activation for this channel, the increase in K+ current appeared quickly and could be subverted by a decrease in K+ currents due to the shift in the voltage-activation relationship at some membrane potentials. The results are consistent with a simple model in which STX binds to the hERG K+ channel at multiple sites and alters the energetics of channel gating by shifting both the voltage-inactivation and voltage-activation processes. The results suggest a novel extracellular mechanism for pharmacological manipulation of this channel through allosteric coupling to channel gating.
Degenerate parabolic equations with initial data measures
Authors: Andreucci Daniele
Published: May 2003

We address the problem of existence of solutions to degenerate (and nondegenerate) parabolic equations under optimal assumptions on the initial data, which are assumed to be measures. The requirements imposed on the initial data are connected both with the degeneracy of the principal part of the equation, and with the form of the nonlinear forcing term. The latter depends on the space gradient of a power of the solution. Applications to related problems are also outlined.
The Wills conjecture
Authors: Brannen Noah
Published: May 2003

Two strengthenings of the Wills conjecture, an extension of Bonnesen’s inradius inequality to

n
n

-dimensional space, are obtained. One is the sharpest of the known strengthenings of the conjecture in three dimensions; the other employs techniques which are fundamentally different from those utilized in the other proofs.
Four-Manifolds With Surface Fundamental Groups
Authors: Cavicchioli Alberto , Hegenbarth Friedrich , Repovš Dušan
Published: May 2003

We study the homotopy type of closed connected topological

4
4

-manifolds whose fundamental group is that of an aspherical surface

F
F

. Then we use surgery theory to show that these manifolds are

s
s

-cobordant to connected sums of simply-connected manifolds with an

S

2

\mathbb {S}^{2}

-bundle over

F
F

.
On the conjecture of Birch and Swinnerton-Dyer
Authors: Gonzalez-Avilés Cristian
Published: May 2003

In this paper we complete Rubin’s partial verification of the conjecture for a large class of elliptic curves with complex multiplication by

Q

(

−
7

)

{\mathbb {Q}}(\sqrt {-7})

.
Tame Combings of Groups
Authors: Mihalik Michael , Tschantz Steven
Published: May 2003

In this paper, we introduce the idea of tame combings for finitely presented groups. If

M
M

is a closed irreducible 3-manifold and

π

1

(
M
)

\pi _{1}(M)

is tame combable, then the universal cover of

M
M

is homeomorphic to

R

3

{\mathbb {R}}^{3}

. We show that all asynchronously automatic and all semihyperbolic groups are tame combable.
Asymptotic prime-power divisibility of binomial, generalized binomial, and multinomial coefficients
Authors: Holte John
Published: May 2003

This paper presents asymptotic formulas for the abundance of binomial, generalized binomial, multinomial, and generalized multinomial coefficients having any given degree of prime-power divisibility. In the case of binomial coefficients, for a fixed primepp, we consider the number of(x,y)(x, y)with0≤x,y>pn0 \leq x, y > p^nfor which(x+yx)\binom {x+y}{x}is divisible bypznp^{zn}(but notpzn+1p^{zn+1}) whenznznis an integer andα>z>β\alpha > z > \beta, say. By means of a classical theorem of Kummer and the probabilistic theory of large deviations, we show that this number is approximatelypnD((α,β))p^{n D((\alpha , \beta ))}, where<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper D left-parenthesis left-parenthesis alpha comma beta right-parenthesis right-parenthesis colon equals sup left-brace right-brace colon of DD left-parenthesis right-parenthesis z colon greater-than greater-than greater-than alpha z beta">D((α,β)):=sup{D(z):α>z>β}D((\alpha , \beta )) := \sup \{ D(z) : \alpha > z > \beta \}andDDis given by an explicit formula. We also develop a “pp-adic multifractal” theory and show howDDmay be interpreted as a multifractal spectrum of divisibility dimensions. We then prove that essentially the same results hold for a large class of the generalized binomial coefficients of Knuth and Wilf, including theqq-binomial coefficients of Gauss and the Fibonomial coefficients of Lucas, and finally we extend our results to multinomial coefficients and generalized multinomial coefficients.
Hamiltonian torus actions on symplectic orbifolds and toric varieties
Authors: Lerman Eugene , Tolman Susan
Published: May 2003

In the first part of the paper, we build a foundation for further work on Hamiltonian actions on symplectic orbifolds. Most importantly, we prove the orbifold versions of the abelian connectedness and convexity theorems. In the second half, we prove that compact symplectic orbifolds with completely integrable torus actions are classified by convex simple rational polytopes with a positive integer attached to each open facet and that all such orbifolds are algebraic toric varieties.
Monge-Ampère equations relative to a Riemannian metric
Authors: Atallah A. , Zuily C.
Published: May 2003

We prove that in a bounded strictly convex open set

Ω
\Omega

in

R

n

\mathbb {R}^n

, the problem
\[

{

det

∇
2

u
=
f
(
x
)
,
 
u

|

∂
Ω

=
φ
,

\begin {cases} \det \nabla ^2u=f(x),\ u|_{\partial \Omega }=\varphi , \end {cases}

\]
where
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f greater-than 0 comma f element-of upper C Superscript normal infinity Baseline left-parenthesis normal upper Omega overbar right-parenthesis comma phi element-of upper C Superscript normal infinity Baseline left-parenthesis partial-differential normal upper Omega right-parenthesis">

f
>
0
,
f
∈

C
∞

(

Ω
¯

)
,
φ
∈

C
∞

(
∂
Ω
)

f>0,f\in C^\infty (\overline \Omega ), \varphi \in C^\infty (\partial \Omega )

, has a unique strictly convex solution

u
∈

C
∞

(

Ω
¯

)

u\in C^\infty (\overline \Omega )

. This result extends to an arbitrary metric a theorem which has been proved by Caffarelli-Nirenberg-Spruck in the case of the Euclidean metric.
Equilibria of set-valued maps on nonconvex domains
Authors: Ben-El-Mechaiekh H. , Kryszewski W.
Published: May 2003

We present new theorems on the existence of equilibria (or zeros) of convex as well as nonconvex set-valued maps defined on compact neighborhood retracts of normed spaces. The maps are subject to tangency conditions expressed in terms of new concepts of normal and tangent cones to such sets. Among other things, we show that if

K
K

is a compact neighborhood retract with nontrivial Euler characteristic in a Banach space

E
E

, and

Φ
:
K
⟶

2
E

\Phi :K\longrightarrow 2^E

is an upper hemicontinuous set-valued map with nonempty closed convex values satisfying the tangency condition

Φ
(
x
)
∩

T
K
r

(
x
)
≠
∅
 for all 
x
∈
K
,

\begin{equation*} \Phi (x)\cap T_K^r(x)\neq \emptyset \text { for all }x\in K, \end{equation*}

then there exists

x
0

∈
K

x_0\in K

such that

0
∈
Φ
(

x
0

)
.

0\in \Phi (x_0).

Here,

T
K
r

(
x
)

T_K^r(x)

denotes a new concept of retraction tangent cone to

K
K

at

x
x

suited for compact neighborhood retracts. When

K
K

is locally convex at

x
,

T
K
r

(
x
)

x,T_K^r(x)

coincides with the usual tangent cone of convex analysis. Special attention is given to neighborhood retracts having “lipschitzian behavior”, called

L
−

L-

retracts below. This class of sets is very broad; it contains compact homeomorphically convex subsets of Banach spaces, epi-Lipschitz subsets of Banach spaces, as well as proximate retracts. Our results thus generalize classical theorems for convex domains, as well as recent results for nonconvex sets.
On the convergence of ∑𝑐_{𝑛}𝑓(𝑛𝑥) and the Lip 1/2 class
Authors: Berkes István
Published: May 2003

We investigate the almost everywhere convergence of

∑

c

n

f
(
n
x
)

\sum c_{n} f(nx)

, where

f
f

is a measurable function satisfying

f
(
x
+
1
)
=
f
(
x
)
,

∫

0

1

f
(
x
)

d
x
=
0.

\begin{equation*} f(x+1) = f(x), \qquad \int _{0}^{1} f(x) \, dx =0.\end{equation*}

By a known criterion, if

f
f

satisfies the above conditions and belongs to the Lip

α
\alpha

class for some

α
>
1

/

2

\alpha > 1/2

, then

∑

c

n

f
(
n
x
)

\sum c_{n} f(nx)

is a.e. convergent provided

∑

c

n

2

>
+
∞

\sum c_{n}^{2} > +\infty

. Using probabilistic methods, we prove that the above result is best possible; in fact there exist Lip 1/2 functions

f
f

and almost exponentially growing sequences

(

n

k

)

(n_{k})

such that

∑

c

k

f
(

n

k

x
)

\sum c_{k} f(n_{k} x)

is a.e. divergent for some

(

c

k

)

(c_{k})

with

∑

c

k

2

>
+
∞

\sum c_{k}^{2} > +\infty

. For functions

f
f

with Fourier series having a special structure, we also give necessary and sufficient convergence criteria. Finally we prove analogous results for the law of the iterated logarithm.
Shellable nonpure complexes and posets. II
Authors: Björner Anders , Wachs Michelle
Published: May 2003

This is a direct continuation of Shellable Nonpure Complexes and Posets. I, which appeared in Transactions of the American Mathematical Society 348 (1996), 1299-1327.
Asymptotic analysis for linear difference equations
Authors: Iwasaki Katsunori
Published: May 2003

We are concerned with asymptotic analysis for linear difference equations in a locally convex space. First we introduce the profile operator, which plays a central role in analyzing the asymptotic behaviors of the solutions. Then factorial asymptotic expansions for the solutions are given quite explicitly. Finally we obtain Gevrey estimates for the solutions. In a forthcoming paper we will develop the theory of cohomology groups for recurrence relations. The main results in this paper lay analytic foundations of such an algebraic theory, while they are of intrinsic interest in the theory of finite differences.
The Szego curve, zero distribution and weighted approximation
Authors: Pritsker Igor , Varga Richard
Published: May 2003

In 1924, Szegő showed that the zeros of the normalized partial sums,

s

n

(
n
z
)

s_{n}(nz)

, of

e

z

e^{z}

tended to what is now called the Szegő curve

S
S

, where
\[

S
:=

{
z
∈

C

:

|

z

e

1
−
z

|

=
1
 and 

|

z

|

≤
1
}

.

S:= \left \{ z \in {\mathbb {C}}:|ze^{1-z}|=1 \text { and } |z| \leq 1 \right \}.

\]
Using modern methods of weighted potential theory, these zero distribution results of Szegő can be essentially recovered, along with an asymptotic formula for the weighted partial sums

{

e

−
n
z

s

n

(
n
z
)

}

n
=
0

∞

\{e^{-nz}s_{n} (nz)\}^{\infty }_{n=0}

. We show that

G
:=

Int

S

G:= {\operatorname {Int}} S

is the largest universal domain such that the weighted polynomials

e

−
n
z

P

n

(
z
)

e^{-nz} P_{n}(z)

are dense in the set of functions analytic in

G
G

. As an example of such results, it is shown that if

f
(
z
)

f(z)

is analytic in

G
G

and continuous on

G
¯

\overline {G}

with

f
(
1
)
=
0

f(1)=0

, then there is a sequence of polynomials

{

P

n

(
z
)
}

n
=
0

∞

\left \{P_{n}(z)\right \}^{\infty }_{n=0}

, with

deg
⁡

P

n

≤
n

\deg P_{n} \leq n

, such that
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="limit Underscript n right-arrow normal infinity Endscripts double-vertical-bar e Superscript minus n z Baseline upper P Subscript n Baseline left-parenthesis z right-parenthesis minus f left-parenthesis z right-parenthesis double-vertical-bar Subscript upper G overbar Baseline equals 0 comma">

lim

n
→
∞

‖

e

−
n
z

P

n

(
z
)
−
f
(
z
)

‖

G
¯

=
0
,

\lim _{n \rightarrow \infty } \|e^{-nz} P_{n}(z)-f(z)\|_{\overline {G}} =0,

\]
where

‖
⋅

‖

G
¯

\| \cdot \|_{\overline {G}}

denotes the supremum norm on

G
¯

\overline {G}

. Similar results are also derived for disks.
Two Decompositions in Topological Combinatorics with Applications to Matroid Complexes
Authors: Chari Manoj
Published: May 2003

This paper introduces two new decomposition techniques which are related to the classical notion of shellability of simplicial complexes, and uses the existence of these decompositions to deduce certain numerical properties for an associated enumerative invariant. First, we introduce the notion of M-shellability, which is a generalization to pure posets of the property of shellability of simplicial complexes, and derive inequalities that the rank-numbers of M-shellable posets must satisfy. We also introduce a decomposition property for simplicial complexes called a convex ear-decomposition, and, using results of Kalai and Stanley on

h
h

-vectors of simplicial polytopes, we show that

h
h

-vectors of pure rank-

d
d

simplicial complexes that have this property satisfy

h

0

≤

h

1

≤
⋯
≤

h

[
d

/

2
]

h_{0} \leq h_{1} \leq \cdots \leq h_{[d/2]}

and

h

i

≤

h

d
−
i

h_{i} \leq h_{d-i}

for

0
≤
i
≤
[
d

/

2
]

0 \leq i \leq [d/2]

. We then show that the abstract simplicial complex formed by the collection of independent sets of a matroid (or matroid complex) admits a special type of convex ear-decomposition called a PS ear-decomposition. This enables us to construct an associated M-shellable poset, whose set of rank-numbers is the

h
h

-vector of the matroid complex. This results in a combinatorial proof of a conjecture of Hibi [Face numbers inequalities for matroid complexes and Cohen-Macaulay types of Stanley-Reisner rings of distributive lattices, Pacific Journal of Math. 154 (1992), 253-264] that the

h
h

-vector of a matroid complex satisfies the above two sets of inequalities.
Incompressible reacting flows
Authors: Avrin Joel
Published: May 2003

We establish steady-state convergence results for a system of reaction-convection-diffusion equations that model in particular combustion phenomena in the presence of nontrivial incompressible fluid motion. Despite the presence of the convection terms, we find that the asymptotic behavior of the system is identical to the case we have previously considered in which the velocity field was set equal to zero. In particular we are again able to establish the convergence of solutions to steady-states and to explicitly calculate the steady-states from the initial and boundary data. Key to our analysis is the establishment of high-order uniform bounds on the temperature and mass fraction components, a process significantly complicated by the presence of the convection terms.
Existence of positive solutions for some problems with nonlinear diffusion
Authors: Cañada A. , Drábek P. , Gámez J.
Published: May 2003

In this paper we study the existence of positive solutions for problems of the type
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartLayout 1st Row 1st Column minus normal upper Delta Subscript p Baseline u left-parenthesis x right-parenthesis 2nd Column a m p semicolon equals u left-parenthesis x right-parenthesis Superscript q minus 1 Baseline h left-parenthesis x comma u left-parenthesis x right-parenthesis right-parenthesis comma 3rd Column a m p semicolon 4th Column a m p semicolon x element-of normal upper Omega comma 2nd Row 1st Column u left-parenthesis x right-parenthesis 2nd Column a m p semicolon equals 0 comma 3rd Column a m p semicolon 4th Column a m p semicolon x element-of partial-differential normal upper Omega comma EndLayout">

−

Δ
p

u
(
x
)

a
m
p
;
=
u
(
x

)

q
−
1

h
(
x
,
u
(
x
)
)
,

a
m
p
;

a
m
p
;
x
∈
Ω
,

u
(
x
)

a
m
p
;
=
0
,

a
m
p
;

a
m
p
;
x
∈
∂
Ω
,

\begin{equation*} \begin {aligned} -\Delta _pu(x) &=u(x)^{q-1}h(x,u(x)), && x\in \Omega , \\ u(x)&=0, && x\in \partial \Omega , \end{aligned} \end{equation*}

where

Δ
p

\Delta _p

is the

p
p

-Laplace operator and

p
,
q
>
1

p,q>1

. If

p
=
2

p=2

, such problems arise in population dynamics. Making use of different methods (sub- and super-solutions and a variational approach), we treat the cases

p
=
q

p=q

,

p
>
q

p>q

and

p
>
q

p>q

, respectively. Also, some systems of equations are considered.
A hypergeometric function approach to the persistence problem of single sine-Gordon breathers
Authors: Denzler Jochen
Published: May 2003

It is shown that for an interesting class of perturbation functions, at most one of the continuum of sine-Gordon breathers can persist for the perturbed equation. This question is much more subtle than the question of persistence of large portions of the family, because analytic continuation arguments in the amplitude parameter are no longer available. Instead, an asymptotic analysis of the obstructions to persistence for large Fourier orders is made, and it is connected to the asymptotic behaviour of the Taylor coefficients of the perturbation function by means of an inverse Laplace transform and an integral transform whose kernel involves hypergeometric functions in a way that is degenerate in that asymptotic analysis involves a splitting monkey saddle. Only first order perturbation theory enters into the argument. The reasoning can in principle be carried over to other perturbation functions than the ones considered here.
Spherical classes and the algebraic transfer
Authors: Hu’ng Nguyẽn
Published: May 2003

We study a weak form of the classical conjecture which predicts that there are no spherical classes in

Q
0

S
0

Q_0S^0

except the elements of Hopf invariant one and those of Kervaire invariant one. The weak conjecture is obtained by restricting the Hurewicz homomorphism to the homotopy classes which are detected by the algebraic transfer. Let

P
k

=

F

2

[

x
1

,
…
,

x
k

]

P_k=\mathbb {F}_2[x_1,\ldots ,x_k]

with

|

x
i

|

=
1

|x_i|=1

. The general linear group

G
L

k

=
G
L
(
k
,

F

2

)

\mathrm {GL}_k=GL(k,\mathbb {F}_2)

and the (mod 2) Steenrod algebra

A

\mathcal {A}

act on

P
k

P_k

in the usual manner. We prove that the weak conjecture is equivalent to the following one: The canonical homomorphism
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="j Subscript k Baseline colon double-struck upper F 2 circled-times Underscript script upper A Endscripts left-parenthesis upper P Subscript k Superscript normal upper G normal upper L Super Subscript k Superscript Baseline right-parenthesis right-arrow left-parenthesis double-struck upper F 2 circled-times Underscript script upper A Endscripts upper P Subscript k Baseline right-parenthesis Superscript normal upper G normal upper L Super Subscript k Superscript">

j
k

:

F

2

⊗

A

(

P
k

G
L

k

)
→
(

F

2

⊗

A

P
k

)

G
L

k

j_k:\mathbb {F}_2 \underset {\mathcal {A}}{\otimes } (P_k^{\mathrm {GL}_k})\to (\mathbb {F}_2 \underset {\mathcal {A}}{\otimes } P_k)^{\mathrm {GL}_k}

induced by the identity map on

P
k

P_k

is zero in positive dimensions for

k
>
2

k>2

. In other words, every Dickson invariant (i.e. element of

P
k

G
L

k

P_k^{\mathrm {GL}_k}

) of positive dimension belongs to

A

+

⋅

P
k

\mathcal {A}^+ \cdot P_k

for

k
>
2

k>2

, where

A

+

\mathcal {A} ^+

denotes the augmentation ideal of

A

\mathcal {A}

. This conjecture is proved for

k
=
3

k=3

in two different ways. One of these two ways is to study the squaring operation

S

q
0

Sq^0

on

P
(

F

2

⊗

G

L
k

P
k
∗

)

P(\mathbb {F}_2 \underset {GL_k}{\otimes } P_k^*)

, the range of

j
k
∗

j_k^*

, and to show it commuting through

j
k
∗

j_k^*

with Kameko’s

S

q
0

Sq^0

on

F

2

⊗

G

L
k

P
(

P
k
∗

)

\mathbb {F}_2 \underset {GL_k}{\otimes } P(P_k^*)

, the domain of

j
k
∗

j_k^*

. We compute explicitly the action of

S

q
0

Sq^0

on

P
(

F

2

⊗

G

L
k

P
k
∗

)

P(\mathbb {F}_2 \underset {GL_k}{\otimes } P_k^*)

for

k
≤
4

k \leq 4

.
Graded Lie Algebras of Maximal Class
Authors: Caranti A. , Mattarei S. , Newman M.
Published: May 2003

We study graded Lie algebras of maximal class over a field

F

\mathbf {F}

of positive characteristic

p
p

. A.  Shalev has constructed infinitely many pairwise non-isomorphic insoluble algebras of this kind, thus showing that these algebras are more complicated than might be suggested by considering only associated Lie algebras of p-groups of maximal class. Here we construct

|

F

|

ℵ

0

| \mathbf {F}|^{\aleph _{0}}

pairwise non-isomorphic such algebras, and

max
{

|

F

|

,

ℵ

0

}

\max \{| \mathbf {F}|, \aleph _{0} \}

soluble ones. Both numbers are shown to be best possible. We also exhibit classes of examples with a non-periodic structure. As in the case of groups, two-step centralizers play an important role.
The Hironaka theorem on resolution of singularities (Or: A proof we always wanted to understand)
Authors: Hauser Herwig
Published: May 2003

This paper is a handyman’s manual for learning how to resolve the singularities of algebraic varieties defined over a field of characteristic zero by sequences of blowups.
Rotation numbers and instability sets
Authors: Franks John
Published: May 2003

Translation and rotation numbers have played an interesting and important role in the qualitative description of various dynamical systems. In this exposition we are especially interested in applications which lead to proofs of periodic motions in various kinds of dynamics on the annulus. The applications include billiards and geodesic flows.

Going beyond this simple qualitative invariant in the study of the dynamics of area preserving annulus maps, G.D. Birkhoff was led to the concept of “regions of instability” for twist maps. We discuss the closely related notion of instability sets for a generic area preserving surface diffeomorphism and develop their properties.
Measures and dimensions in conformal dynamics
Authors: Urbański Mariusz
Published: May 2003

This survey collects basic results concerning fractal and ergodic properties of Julia sets of rational functions of the Riemann sphere. Frequently these results are compared with their counterparts in the theory of Kleinian groups, and this enlarges the famous Sullivan dictionary. The topics concerning Hausdorff and packing measures and dimensions are given most attention. Then, conformal measures are constructed and their relations with Hausdorff and packing measures are discussed throughout the entire article. Also invariant measures absolutely continuous with respect to conformal measures are touched on. While the survey begins with facts concerning all rational functions, much time is devoted toward presenting the well-developed theory of hyperbolic and parabolic maps, and in Section 3 the class NCP is dealt with. This class consists of such rational functionsffthat all critical points offfwhich are contained in the Julia set offfare non-recurrent. The NCP class comprises in particular hyperbolic, parabolic and subhyperbolic maps. Our last section collects some recent results about other subclasses of rational functions, e.g. Collet-Eckmann maps and Fibonacci maps. At the end of this article two appendices are included which are only loosely related to Sections 1-4. They contain a short description of tame mappings and the theory of equilibrium states and Perron-Frobenius operators associated with Hölder continuous potentials.
In vitro propagation and transcriptional profiling of human mammary stem/progenitor cells
Authors: Dontu Gabriela , Abdallah Wissam M. , Foley Jessica M. , Jackson Kyle W. , Clarke Michael F. , Kawamura Mari J. , Wicha Max S.
Published: May 2003

Although the existence of mammary stem cells has been suggested by serial transplantation studies in mice, their identification has been hindered by the lack of specific surface markers, and by the absence of suitable in vitro assays for testing stem cell properties: self-renewal and ability to generate differentiated progeny. We have developed an in vitro cultivation system that allows for propagation of human mammary epithelial cells (HMECs) in an undifferentiated state, based on their ability to proliferate in suspension, as nonadherent mammospheres. We demonstrate that nonadherent mammospheres are enriched in early progenitor/stem cells and able to differentiate along all three mammary epithelial lineages and to clonally generate complex functional structures in reconstituted 3D culture systems. Gene expression analysis of cells isolated from nonadherent mammospheres revealed overlapping genetic programs with other stem and progenitor cells and identified new markers that may be useful in the identification of mammary stem cells. The isolation and characterization of these stem cells should help elucidate the molecular pathways that govern normal mammary development and carcinogenesis.
Transient activation of β-catenin signaling in cutaneous keratinocytes is sufficient to trigger the active growth phase of the hair cycle in mice
Authors: Van Mater David , Kolligs Frank T. , Dlugosz Andrzej A. , Fearon Eric R.
Published: May 2003

Wnts have key roles in many developmental processes, including hair follicle growth and differentiation. Stabilization of β-catenin is essential in the canonical Wnt signaling pathway. We developed transgenic mice expressing a regulated form of β-catenin in the skin. Chronic activation of β-catenin in resting (telogen) hair follicles resulted in changes consistent with induction of an exaggerated, aberrant growth phase (anagen). Transient activation of β-catenin produced a normal anagen. Our data lend strong support to the notion that a Wnt/β-catenin signal operating on hair follicle precursor cells serves as a crucial proximal signal for the telogen–anagen transition.
An intersubunit contact stimulating transcription initiation byE. coliRNA polymerase: interaction of the α C-terminal domain and ς region 4
Authors: Ross Wilma , Schneider David A. , Paul Brian J. , Mertens Aaron , Gourse Richard L.
Published: May 2003

The C-terminal domain of theEscherichia coliRNA polymerase (RNAP) alpha subunit (αCTD) stimulates transcription initiation by interacting with upstream (UP) element DNA and a variety of transcription activators. Here we identify specific substitutions in region 4.2 of sigma 70 (ς70) and in αCTD that decrease transcription initiation from promoters containing some, but not all, UP elements. This decrease in transcription derives from a decrease in the initial equilibrium constant for RNAP binding (KB). The open complexes formed by the mutant and wild-type RNAPs differ in DNAse I sensitivity at the junction of the αCTD and ς DNA binding sites, correlating with the differences in transcription. A model of the DNA–αCTD–ς region 4.2 ternary complex, constructed from the previously determined X-ray structures of theThermus aquaticusς region 4.2–DNA complex and theE. coliαCTD–DNA complex, indicates that the residues identified by mutation in ς region 4.2 and in αCTD are in very close proximity. Our results strongly suggest that αCTD, when bound to an UP element proximal subsite, contacts the RNAP ς70subunit, increasing transcription. Previous data from the literature suggest that this same ς–αCTD interaction also plays a role in transcription factor-mediated activation.
Altered localization ofDrosophilaSmoothened protein activates Hedgehog signal transduction
Authors: Zhu Alan Jian , Zheng Limin , Suyama Kaye , Scott Matthew P.
Published: May 2003

Hedgehog (Hh) signaling is critical for many developmental events and must be restrained to prevent cancer. A transmembrane protein, Smoothened (Smo), is necessary to transcriptionally activate Hh target genes. Smo activity is blocked by the Hh transmembrane receptor Patched (Ptc). The reception of a Hh signal overcomes Ptc inhibition of Smo, activating transcription of target genes. UsingDrosophilasalivary gland cells in vivo and in vitro as a new assay for Hh signal transduction, we investigated the regulation of Hh-triggered Smo stabilization and relocalization. Hh causes Smo to move from internal membranes to the cell surface. Relocalization is protein synthesis-independent and occurs within 30 min of Hh treatment. Ptc and the kinesin-related protein Costal2 (Cos2) cause internalization of Smo, a process that is dependent on both actin and microtubules. Disruption of endocytosis by dominant negative dynamin or Rab5 prevents Smo internalization. Fly versions of Smo mutants associated with human tumors are constitutively present at the cell surface. Forced localization of Smo at the plasma membrane activates Hh target gene transcription. Conversely, trapping of activated Smo mutants in the ER prevents Hh target gene activation. Control of Smo localization appears to be a crucial step in Hh signaling inDrosophila.
A complex of LIN-5 and GPR proteins regulates G protein signaling and spindle function inC. elegans
Authors: Srinivasan Dayalan G. , Fisk Ridgely M. , Xu Huihong , van den Heuvel Sander
Published: May 2003

TheCaenorhabditis eleganscoiled-coil protein LIN-5 mediates several processes in cell division that depend on spindle forces, including alignment and segregation of chromosomes and positioning of the spindle. Here, we describe two closely related proteins, GPR-1 and GPR-2 (Gproteinregulator), which associate with LIN-5 in vivo and in vitro and depend on LIN-5 for localization to the spindle and cell cortex. GPR-1/GPR-2 contain a GoLoco/GPR motif that mediates interaction with GDP-bound Gαi/o. Inactivation oflin-5,gpr-1/gpr-2, or the Gαi/ogenesgoa-1andgpa-16all cause highly similar chromosome segregation and spindle positioning defects, indicating a positive role for the LIN-5 and GPR proteins in G protein signaling. Thelin-5andgpr-1/gpr-2genes appear to act downstream of theparpolarity genes in the one- and two-cell stages and downstream of the tyrosine kinase-related genesmes-1andsrc-1at the four-cell stage. Together, these results indicate that GPR-1/GPR-2 in association with LIN-5 activate G protein signaling to affect spindle force. Polarity determinants may regulate LIN-5/GPR/Gα locally to create the asymmetric forces that drive spindle movement. Results inC. elegansand other species are consistent with a novel model for receptor-independent activation of Gαi/osignaling.
RNA polymerase mutations that impair conversion to a termination-resistant complex by Q antiterminator proteins
Authors: Santangelo Thomas J. , Mooney Rachel Anne , Landick Robert , Roberts Jeffrey W.
Published: May 2003

Bacteriophage λ Q-protein stably binds and modifies RNA polymerase (RNAP) to a termination-resistant form. We describe amino acid substitutions in RNAP that disrupt Q-mediated antitermination in vivo and in vitro. The positions of these substitutions in the modeled RNAP/DNA/RNA ternary elongation complex, and their biochemical properties, suggest that they do not define a binding site for Q in RNAP, but instead act by impairing interactions among core RNAP subunits and nucleic acids that are essential for Q modification. A specific conjecture is that Q modification stabilizes interactions of RNAP with the DNA/RNA hybrid and optimizes alignment of the nucleic acids in the catalytic site. Such changes would inhibit the activity of the RNA hairpin of an intrinsic terminator to disrupt the 5′-terminal bases of the hybrid and remove the RNA 3′ terminus from the active site.
Notch activity inducesNodalexpression and mediates the establishment of left–right asymmetry in vertebrate embryos
Authors: Raya Ángel , Kawakami Yasuhiko , Rodrı́guez-Esteban Concepción , Büscher Dirk , Koth Christopher M. , Itoh Tohru , Morita Masanobu , Raya R. Marina , Dubova Ilir , Bessa Joaquı́n Grego , de la Pompa José Luis , Belmonte Juan Carlos Izpisúa
Published: May 2003

Left-sided expression ofNodalin the lateral plate mesoderm is a conserved feature necessary for the establishment of normal left–right asymmetry during vertebrate embryogenesis. By using gain- and loss-of-function experiments in zebrafish and mouse, we show that the activity of the Notch pathway is necessary and sufficient forNodalexpression around the node, and for proper left–right determination. We identify Notch-responsive elements in theNodalpromoter, and unveil a direct relationship between Notch activity andNodalexpression around the node. Our findings provide evidence for a mechanism involving Notch activity that translates an initial symmetry-breaking event into asymmetric gene expression.
Notch signaling regulates left–right asymmetry determination by inducingNodalexpression
Authors: Krebs Luke T. , Iwai Naomi , Nonaka Shigenori , Welsh Ian C. , Lan Yu , Jiang Rulang , Saijoh Yukio , O'Brien Timothy P. , Hamada Hiroshi , Gridley Thomas
Published: May 2003

Generation of left–right asymmetry is an integral part of the establishment of the vertebrate body plan. Here we show that the Notch signaling pathway plays a primary role in the establishment of left–right asymmetry in mice by directly regulating expression of theNodalgene. Embryos mutant for the Notch ligand Dll1 or doubly mutant for the Notch1 and Notch2 receptors exhibit multiple defects in left–right asymmetry. Analysis of the enhancer regulating node-specificNodalexpression revealed the presence of binding sites for the RBP-J protein, the primary transcriptional mediator of Notch signaling. Mutation of these sites destroyed the ability of this enhancer to direct node-specific gene expression in transgenic mice. Our results demonstrate that Dll1-mediated Notch signaling is essential for generation of left–right asymmetry, and that the Notch pathway acts upstream ofNodalexpression during left–right asymmetry determination in mice.
JNK initiates a cytokine cascade that causes Pax2 expression and closure of the optic fissure
Authors: Weston Claire R. , Wong Anthony , Hall J. Perry , Goad Mary E.P. , Flavell Richard A. , Davis Roger J.
Published: May 2003

The c-Jun NH2-terminal kinase (JNK) group of mitogen-activated protein kinases is stimulated in response to a wide array of cellular stresses and proinflammatory cytokines. Mice lacking individual members of theJnkfamily (Jnk1,Jnk2, andJnk3) are viable and survive without overt structural abnormalities. Here we show that mice with a compound deficiency inJnkexpression can survive to birth, but fail to close the optic fissure (retinal coloboma). We demonstrate that JNK initiates a cytokine cascade of bone morphogenetic protein-4 (BMP4) and sonic hedgehog (Shh) that induces the expression of the paired-like homeobox transcription factor Pax2 and closure of the optic fissure. Interestingly, the role of JNK to regulate BMP4 expression during optic fissure closure is conserved inDrosophiladuring dorsal closure, a related morphogenetic process that requires JNK-regulated expression of the BMP4 ortholog Decapentaplegic (Dpp).
Mice lacking a transcriptional corepressor Tob are predisposed to cancer
Authors: Yoshida Yutaka , Nakamura Takahisa , Komoda Masato , Satoh Hitoshi , Suzuki Toru , Tsuzuku Junko K. , Miyasaka Takashi , Yoshida Eri H. , Umemori Hisashi , Kunisaki Reiko K. , Tani Kenzaburo , Ishii Shunsuke , Mori Shigeo , Suganuma Masami , Noda Tetsuo , Yamamoto Tadashi
Published: May 2003

tobis a member of antiproliferative family genes. Mice lackingtobare prone to spontaneous formation of tumors. The occurrence rate of diethylnitrosamine-induced liver tumors is higher intob−/−mice than in wild-type mice.tob−/−p53−/−mice show accelerated tumor formation in comparison with single null mice. Expression ofcyclin D1mRNA is increased in the absence of Tob and is reduced by Tob. Tob acts as a transcriptional corepressor and suppresses thecyclin D1promoter activity through an interaction with histone deacetylase. Levels oftobmRNA are often decreased in human cancers, implicatingtobin cancer development.
Collaborative, synchronous robots serving machines and cells
Authors: Ranky Paul G.
Published: May 2003

Multi‐arm, collaborative, synchronous robots are gaining acceptance in industry, because of the cycle time reduction, productivity increase, flexibility and quality gain, distributed control, layout design/simulation, and programming support robot manufacturers and system integrators can offer. On the negative side, when things go wrong such systems are more complex to recover, and maintain, than non‐networked and non‐distributed controlled individual robots. In this paper, we introduce some of the most important engineering, and technology management principles that collaborate robots and their users and should be kept in mind while developing such systems, and/or planning for such applications.
Distributed control of a track based multi‐head robot
Authors: Derby Stephen J. , Brown David
Published: May 2003

A novel closed loop track based multi‐head robot has been developed to increase the material handing throughput. This robot allows waves of autonomous robot heads to move materials in to the working path by eliminating the traditional return path. Two distributed control architectures were developed using a system comprising of desktop, embedded and single board PC's some linked by wireless communications. This paper discusses the design and impact of such control architectures, and looks at some performance boundaries.
Robotics moves onwards and upwards
Authors: Kochan Anna
Published: May 2003

The 2002 climbing and walking robots (CLAWAR) conference featured 130 papers on topics related to CLAWAR. This article reviews the conference, highlighting papers in the areas of modular design, inspection of tanks, weld inspection, sewer inspection/cleaning, window cleaning, medical robotics, hybrid locomotion and hopping robots.
ROBOVOLC: a robot for volcano exploration result of first test campaign
Authors: Muscato G. , Caltabiano D. , Guccione S. , Longo D. , Coltelli M. , Cristaldi A. , Pecora E. , Sacco V. , Sim P. , Virk G.S. , Briole P. , Semerano A. , White T.
Published: May 2003

ROBOVOLC is a new robotic system that has been designed to help scientists in the exploration of volcanoes. It is composed of three subsystems:a rover platformwith six articulated and independently actuated wheels;a manipulator armto collect rock samples, drop and pick up sensors and sample gas; anda pan‐tilt turretwith a high resolution camera, video‐camera, infrared camera and a doppler radar for gas speed measurement. This paper contains a short description of the system, following an introduction to the problem and review of the state‐of‐the‐art. Finally, results from the first test campaign on Mount Etna during September 2002 are briefly described.
Conflict definitions and mistakes in American industrial robotics standard for static performance evaluation
Authors: Zhu Zhenqi , Cui Hongliang
Published: May 2003

The ANSI/RIA R15.05‐1‐1990 is an American national industrial robotics standard that covers methods for evaluating the point‐to‐point and static performance of industrial robots. This standard introduces many important concepts for carrying out performance tests. These concepts include standard test plane, standard test path, and working space center point. Eight mistakes and two conflict definitions related to working space center point have been identified and corrected in this paper. Most of the mistakes are definition mistakes related to the base coordinate system, working space center point, standard reference plane, and standard test plane. Mistakes also result from the confusion between the reference plane and the test plane.
Re‐configurable dual‐robot assembly system design, development and future directions
Authors: Hsieh Sheng‐Jen
Published: May 2003

This paper describes the design and development of a re‐configurable dual‐robot assembly system using off‐the‐shelf re‐configurable pneumatic modules, Hall‐effect sensors, a vision system, and a programmable logic controller (PLC). Each robot arm consists of three sets of pneumatic modules and a pneumatic gripper. Each module consists of a pneumatic housing, an air cylinder, and a Hall‐effect sensor, and provides one degree of freedom. Solenoids are used to redirect airflow and thereby extend and/or retract the air cylinder. A vision system is used for fixture inspection. A conveyor and part stopper are designed to transfer and stop pallets. All these modules, the gripper, the part stopper, and the vision system are controlled and synchronized using a PLC. At the end of this paper, a framework for making the system over the Web for remote operation and diagnosis is proposed and described.
Portable robotic system for steel H‐beam welding
Authors: Moon Seungbin B. , Hwang Sung‐Ho , Shon Woong‐Hee , Lee Ho‐Gil , Taek Oh Yeon
Published: May 2003

Steel beam welding at a construction site is challenging due to the increasing thickness of steel members in today's buildings. In order to achieve high quality welding and resolve the problem caused by the shortage of skilled welders, robotic systems are in high demand. We have proposed a practical robotic system for steel beam welding, specifically designed for working on H‐shaped column structures that are known to be the most difficult structures for automation.
Facilitating shared vision in the organization
Authors: Eigeles Dan
Published: May 2003

The current paper presents a structured method helping organizational facilitators to work efficiently with their clients. Through this method it is possible to motivate and encourage top executive team efficiently to willingly generate true vision and mission and implement these in the organization for achieving both improved performance and harmony.