bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of channels reconstituted from the major intrinsic protein of lens fiber membranes.
Authors: Ehring G R , Zampighi G , Horwitz J , Bok D , Hall J E
Published: May 2004

Detergent-solubilized plasma membrane protein of either adult bovine or calf lens and high-performance liquid chromatography-purified major intrinsic protein (MIP) of the lens were reconstituted into unilamellar vesicles and planar lipid bilayers. Freeze-fracture studies showed that the density of intramembrane particles in the vesicles was proportional to the protein/lipid ratio. At high ratios, these particles crystallized into tetragonal arrays as does MIP in lens fibers. Channels induced by either purified MIP or detergent-solubilized protein had essentially identical properties. The conductance of multichannel membranes was maximal near 0 mV and decreased to 0.49 +/- 0.08 of the maximum value at voltages greater than 80 mV. The dependence of the conductance on voltage was well fit by a two-state Boltzmann distribution. Voltage steps greater than 30 mV elicited an ohmic current step followed by a slow (seconds) biexponential decrease. The amplitudes and time constants depended on the magnitude but not the sign of the voltage. Steps from 100 mV to voltages less than 30 mV caused the channels to open exponentially with a millisecond time constant. Analysis of latency to first closure after a voltage step gave nearly the same time constants as multichannel kinetics. Single-channel conductance is proportional to salt concentration from 0.1 to 1.0 M in KCl. In 0.1M KCl, the channel had two preferred conductance states with amplitudes of 380 and 160 pS, as well as three additional substates. Multi- and single-channel data suggest that the channel has two kinetically important open states. The channel is slightly anion selective. The properties of the channel do not vary appreciably from pH 7.4 to 5.8 or from pCa 7 to 2. We propose that a channel with these properties could contribute to maintenance of lens transparency and fluid balance.
Modulation of the T-type cardiac Ca channel by changes in proton concentration.
Authors: Tytgat J , Nilius B , Carmeliet E
Published: May 2004

Single-channel measurements and whole-cell experiments with the two suction electrode, voltage clamp technique were used to investigate the effects of external and internal proton concentrations on T-type Ca channels in heart muscle cells of the guinea pig. As in the L-type Ca channel, an increase in the external proton concentration decreases T-type currents, while external alkalinization enlarges the currents. In contrast to the L-type Ca channel, however, a change in the internal proton concentration does not modulate T-type Ca currents. The T-type Ca channel is much more sensitive to variations in pHo than the L-type Ca channel. By the combination of single-channel and whole-cell experiments we can conclude that the observed changes in macroscopic currents are due to (a) changes in the single-channel conductance and in the probability of the T-type Ca channel being open, and (b) the titration of the negative surface charges in the neighborhood of the T-type Ca channel with shifts of both the activation and inactivation processes of the channel. The pHo-induced changes in the maximal conductance (gmax) of the T-type Ca channel show an apparent pKa in the range of 7.1-7.5, while the titration of the negative surface charges near the channel shows an apparent pKa of 7.1 with a concomitant surface potential of -24.6 mV at 5.4 mM [Ca]o. These pKa values, less acid than the pKa values found for the pHo-induced, L-type Ca channel modulation, might imply a physiological importance of this novel type of channel modulation.
Myoplasmic calcium transients monitored with purpurate indicator dyes injected into intact frog skeletal muscle fibers.
Authors: Konishi M , Baylor S M
Published: May 2004

Intact single twitch fibers from frog muscle were studied on an optical bench apparatus after microinjection with tetramethylmurexide (TMX) or purpurate-3,3' diacetic acid (PDAA), two compounds from the purpurate family of absorbance Ca2+ indicators previously used in cut muscle fibers (Maylie, J., M. Irving, N. L. Sizto, G. Boyarsky, and W. K. Chandler. 1987. J. Gen. Physiol. 89:145-176; Hirota, A., W. K. Chandler, P. L. Southwick, and A. S. Waggoner. 1989. J. Gen. Physiol. 94:597-631.) The apparent longitudinal diffusion constant of PDAA (mol wt 380) in myoplasm was 0.99 (+/- 0.04, SEM) x 10(-6) cm2 s-1 (16-17 degrees C), a value which suggests that 24-43% of the PDAA molecules were bound to myoplasmic constituents of large molecular weight. The corresponding values for TMX (mol wt 322) were 0.98 (+/- 0.05) x 10(-6) cm2 s-1 and 44-50%, respectively. Muscle membranes (surface and/or transverse-tubular) appear to be permeable to TMX and, to a lesser extent, to PDAA, since the total amount of indicator contained within a fiber decreased with time after injection. The average time constants for disappearance of indicator were 46 (+/- 7, SEM) min for TMX and 338 (+/- 82) min for PDAA. The fraction of indicator in the Ca2(+)-bound state in resting fibers was significantly different from zero for TMX (0.070 +/- 0.008) but not for PDAA (0.026 +/- 0.009). In in vitro calibrations PDAA but not TMX appeared to react with Ca2+ with 1:1 stoichiometry. In agreement with Hirota et al. (Hirota, A., W. K. Chandler, P. L. Southwick, and A. S. Waggoner. 1989. J. Gen. Physiol. 94:597-631), we conclude that PDAA is probably a more reliable myoplasmic Ca2+ indicator than TMX. In fibers that contained PDAA and were stimulated by a single action potential, the calibrated peak value of the myoplasmic free [Ca2+] transient (delta[Ca2+]) averaged 9.4 (+/- 0.6) microM, a value about fivefold larger than that calibrated with antipyrylazo III under otherwise identical conditions (Baylor, S. M., and S. Hollingworth. 1988. J. Physiol. 403:151-192). The fivefold difference is similar to that previously reported in cut fibers with antipyrylazo III and PDAA. Since in both intact and cut fibers the percentage of PDAA bound to myoplasmic constituents is considerably smaller than that found for antipyrylazo III, the PDAA calibration of delta[Ca2+] is likely to be more accurate. Interestingly, in intact fibers the peak value of delta[Ca2+] calibrated with either PDAA or antipyrylazo III is about half that calibrated in cut fibers.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinetics of bicarbonate and chloride transport in human red cell membranes.
Authors: Gasbjerg P K , Brahm J
Published: May 2004

Unidirectional [14C]HCO3- and 36Cl- efflux from human red cells and ghosts was studied under self-exchange conditions at pH 7.8 and 0 degrees C by means of the Millipore-Swinnex filtering technique. Control bicarbonate experiments showed that 14CO2 loss from the cells to the efflux medium was insignificant. The anion flux was determined under (a) symmetric variations of the anion concentration (C(i) = C(o) = 5-700 mM), and (b) asymmetric conditions with CAn constant on one side and varied on the other side of the membrane. Simple Michaelis-Menten-like kinetics (MM fit: J(eff) = J(eff)max.C/(K1/2 + C)) was used to describe anion flux dependence on C for (a) C(i) = C(o) = 5-100 mM, (b) C(i) = 6-100 mM, C(o) = constant, and (c) C(i) = constant, C(o) = 1-25 mM. At higher cellular concentrations noncompetitive self-inhibition by anion binding (inhibition constant Ki mM) to an intracellular site was included in the model (MS fit): J(eff) = J(eff)max.C(i)/[(K1/2 + C(i)).(1 + C(i)/Ki)]. The MM fits show that the external half-saturation constant, Ko1/2 ( = C(o)An for J(eff,o) = 1/2.j(eff,o)max) at C(o) = 1-25 mM is 1.5-2.4 mM (HCO3-) and 1.8-2.6 mM (Cl-). At C(o) = 1-260 mM Ko1/2 is 1.2-1.5 mM (HCO3-) and 1.4-1.8 mM (Cl-). The respective maximum flux, J(eff,o)max (nmol/[cm2.s]), for C(o) = 1-25 mM is 0.41-0.51 (HCO3-) and 0.28-0.38 (Cl-), and for C(o) = 1-260 mM 0.39-0.44 (HCO3-) and 0.27-0.31 (Cl-). The internal half-saturation constant, Ki1/2 mM is: MM fit (C(i) = 6-100 mM, C(o) = 50 mM), 18.0 mM (HCO3-) and 23.8 mM (Cl-); MS fit (C(i) = 6-920 mM, C(o) = 50 mM), 32.0 mM (HCO3-) and 45.1 mM (Cl-). The maximum flux, J(eff,i)max (nmol/[cm2.s]) is: MM fit; 0.50 (HCO3-) and 0.34 (Cl-); MS fit, 0.70 (HCO-3) and 0.50 (Cl-). The half-inhibition constants of the MS fit, Ki, are 393 mM (HCO3-) and 544 mM (Cl-). The MM fit shows that the symmetric half-saturation constant, Ks1/2, is 20.2 (HCO-3) and 23.9 (Cl-) mM, and J(eff,s)max is 0.51 (HCO3-) and 0.32 (Cl-) nmol/(cm2.s). The MS fit shows that for C = 5-700 mM Ks1/2 is 30.4 nM (HCO3-) and 50.1 mM (Cl-), and Ki is 541 mM (HCO3-) and 392 mM (Cl-).(ABSTRACT TRUNCATED AT 400 WORDS)
Ion permeation in normal and batrachotoxin-modified Na+ channels in the squid giant axon.
Authors: Correa A M , Latorre R , Bezanilla F
Published: May 2004

Na+ permeation through normal and batrachotoxin (BTX)-modified squid axon Na+ channels was characterized. Unmodified and toxin-modified Na+ channels were studied simultaneously in outside-out membrane patches using the cut-open axon technique. Current-voltage relations for both normal and BTX-modified channels were measured over a wide range of Na+ concentrations and voltages. Channel conductance as a function of Na+ concentration curves showed that within the range 0.015-1 M Na+ the normal channel conductance is 1.7-2.5-fold larger than the BTX-modified conductance. These relations cannot be fitted by a simple Langmuir isotherm. Channel conductance at low concentrations was larger than expected from a Michaelis-Menten behavior. The deviations from the simple case were accounted for by fixed negative charges located in the vicinity of the channel entrances. Fixed negative charges near the pore mouths would have the effect of increasing the local Na+ concentration. The results are discussed in terms of energy profiles with three barriers and two sites, taking into consideration the effect of the fixed negative charges. Either single- or multi-ion pore models can account for all the permeation data obtained in both symmetric and asymmetric conditions. In a temperature range of 5-15 degrees C, the estimated Q10 for the conductance of the BTX-modified Na+ channel was 1.53. BTX appears not to change the Na+ channel ion selectively (for the conditions used) or the surface charge located near the channel entrances.
Single channel studies of the phosphorylation of K+ channels in the squid giant axon. I. Steady-state conditions.
Authors: Perozo E , Vandenberg C A , Jong D S , Bezanilla F
Published: May 2004

Phosphorylation of the delayed rectifier channel of squid potentiates the macroscopic K+ current and slows its activation kinetics. We have studied this phenomenon at the single channel level using the cut-open axon technique under steady-state conditions. In 10 mM external K+/310 mM internal K+ there are predominantly two types of channels present, a 20-pS and a 40-pS channel. In steady state at depolarized potentials, the 40-pS channel was most active, whereas the 20-pS channel tended to disappear due to a slow inactivation process. Two methods were developed to shift the population of channels toward a dephosphorylated state. One method consisted of predialyzing a whole axon with solutions containing no ATP, while recording the currents under axial-wire voltage clamp. A piece of axon was then removed and cut open, and single channel currents were recorded from the cut-open axon. A second method was based on the difference in diffusion coefficients for ATP and proteins such as the endogenous phosphatase. The axon was cut open in a solution that did not contain Ca2+ or Cl- in order to maintain the axoplasm structurally intact and permit endogenous phosphatase to act on the membrane while ATP diffused away, before removing the axoplasm and forming a membrane patch. When dephosphorylating conditions were used, the steady-state open probability of the 40-pS channel at 42 mV was very low (less than 0.0002), and the channel openings appeared as a series of infrequent, short-duration events. The channel activity was increased up to 150-fold by photoreleasing caged ATP inside the patch pipette in the presence of the catalytic subunit of protein kinase A. The sharp increase in open probability could be accounted for by a decrease of the slow component of the closed time distribution from 23 s to 170 ms with little change in the distribution of open times (1-2 ms) and no change in the single channel current amplitude. In voltage-jump experiments the contribution of the 40-pS channel to the delayed rectifier current was often small due to the large values of the latency to the first opening.
Calcium-activated potassium conductance in presynaptic terminals at the crayfish neuromuscular junction.
Authors: Sivaramakrishnan S , Bittner G D , Brodwick M S
Published: May 2004

Membrane potential changes that typically evoke transmitter release were studied by recording intracellularly from the excitor axon near presynaptic terminals of the crayfish opener neuromuscular junction. Depolarization of the presynaptic terminal with intracellular current pulses activated a conductance that caused a decrease in depolarization during the constant current pulse. This conductance was identified as a calcium-activated potassium conductance, gK(Ca), by its disappearance in a zero-calcium/EGTA medium and its block by cadmium, barium, tetraethylammonium ions, and charybdotoxin. In addition to gK(Ca), a delayed rectifier potassium conductance (gK) is present in or near the presynaptic terminal. Both these potassium conductances are involved in the repolarization of the membrane during a presynaptic action potential.
Calcium currents in the A7r5 smooth muscle-derived cell line. An allosteric model for calcium channel activation and dihydropyridine agonist action.
Authors: Marks T N , Jones S W
Published: May 2004

We have investigated the gating kinetics of calcium channels in the A7r5 cell line at the level of single channels and whole cell currents, in the absence and presence of dihydropyridine (DHP) calcium channel agonists. Although latencies to first opening and macroscopic currents are strongly voltage dependent, analysis of amplitude histograms indicates that the primary open-closed transition is voltage independent. This suggests that the molecular mechanisms for voltage sensing and channel opening are distinct, but coupled. We propose a modified Monod-Wyman-Changeux (MWC) model for channel activation, where movement of a voltage sensor is analogous to ligand binding, and the closed and open channels correspond to inactive (T) and active (R) states. This model can account for the activation kinetics of the calcium channel, and is consistent with the existence of four homologous domains in the main subunit of the calcium channel protein. DHP agonists slow deactivation kinetics, shift the activation curve to more negative potentials with an increase in slope, induce intermingled fast and slow channel openings, and reduce the latency to first opening. These effects are predicted by the MWC model if we make the simple assumption that DHP agonists act as allosteric effectors to stabilize the open states of the channel.
Skew exactness perturbation
Authors: Harte Robin , Larson David
Published: May 2004

We offer a perturbation theory for finite ascent and descent properties of bounded operators.
The s-elementary frame wavelets are path connected
Authors: Dai X. , Diao Y. , Gu Q. , Han D.
Published: May 2004

An s-elementary frame wavelet is a function

ψ
∈

L
2

(

R

)

\psi \in L^2(\mathbb {R})

which is a frame wavelet and is defined by a Lebesgue measurable set

E
⊂

R

E\subset \mathbb {R}

such that

ψ
^

=

1

2
π

χ
E

\hat {\psi }= \frac {1}{\sqrt {2\pi }}\chi _E

. In this paper we prove that the family of s-elementary frame wavelets is a path-connected set in the

L
2

(

R

)

L^2(\mathbb {R})

-norm. This result also holds for s-elementary

A
A

-dilation frame wavelets in

L
2

(

R

d

)

L^2(\mathbb {R}^d)

in general. On the other hand, we prove that the path-connectedness of s-elementary frame wavelets cannot be strengthened to uniform path-connectedness. In fact, the sets of normalized tight frame wavelets and frame wavelets are not uniformly path-connected either.
Conservativeness of diffusion processes with drift
Authors: Kuwae Kazuhiro
Published: May 2004

We show the conservativeness of the Girsanov transformed diffusion process by drift

b
∈

L
p

(

R

d

→

R

d

)

b\in L^p(\mathbb {R}^d\!\to \!\mathbb {R}^d)

with

p
≥
4

/

(
2
−

2
δ
(
|
b

|
2

)

/

λ

)

p\geq 4/(2-\sqrt {2\delta (\vert b\vert ^2)/\lambda })

or

p
>
4
d

/

(
d
+
2
)

p>4d/(d+2)

, or

p
=
2

p=2

if

|
b

|
2

\vert b\vert ^2

is of the Hardy class with sufficiently small coefficient of energy

δ
(
|
b

|
2

)
>
λ

/

2

\delta (\vert b\vert ^2)>\lambda /2

. Here

λ
>
0

\lambda >0

is the lower bound of the symmetric measurable matrix-valued function

a
(
x
)
:=
(

a

i
,
j

(
x
)

)

i
,
j

a(x):=(a_{i,j}(x))_{i,j}

appearing in the given Dirichlet form. In particular, our result improves the conservativeness of the transformed process by

b
∈

L
d

(

R

d

→

R

d

)

b\in L^d(\mathbb {R}^d\!\to \!\mathbb {R}^d)

when

d
≥
3

d\geq 3

.
A cusp singularity with no Galois cover by a complete intersection
Authors: Anderson David
Published: May 2004

With an explicit example, we confirm a conjecture by Neumann and Wahl that there exist cusps with no Galois cover by a complete intersection. Some computational techniques are reviewed, and a method for deciding whether a given cusp has a complete intersection Galois cover is developed.
Constants of derivations in polynomial rings over unique factorization domains
Authors: El Kahoui M’hammed
Published: May 2004

A well-known theorem, due to Nagata and Nowicki, states that the ring of constants of any

K

{\mathcal K}

-derivation of

K

[
x
,
y
]

{\mathcal K}[x,y]

, where

K

{\mathcal K}

is a commutative field of characteristic zero, is a polynomial ring in one variable over

K

{\mathcal K}

. In this paper we give an elementary proof of this theorem and show that it remains true if we replace

K

{\mathcal K}

by any unique factorization domain of characteristic zero.
New obstructions to the thickening of 𝐶𝑊-complexes
Authors: Cornea Octavian
Published: May 2004

In this note we use Morse theory to produce new obstructions to the existence of thickenings of

C
W

CW

-complexes in low codimension. The obstructions are expressed as nonexistence of solutions

x
x

to an equation of type

Σ

k

L
=

Σ

s

x

\Sigma ^{k}L=\Sigma ^{s}x

with

L
L

a Ganea-Hopf type invariant.
The exchange property for purely infinite simple rings
Authors: Ara Pere
Published: May 2004

It is proven that every purely infinite simple ring is an exchange ring. This result is applied to determine those Leavitt algebras that are exchange rings.
“Lebesgue measure” on ℝ^{∞}, II
Authors: Baker Richard
Published: May 2004

Let

R

\mathbb {R}

be the set of real numbers, and define

R

∞

=

∏

i
=
1

∞

R

\mathbb {R}^{\infty }=\prod \limits ^{\infty }_{i=1}\mathbb {R}

. We construct a complete measure space

(

R

∞

,

L

,
λ
)

(\mathbb {R}^{\infty },\mathcal {L},\lambda )

where the

σ
\sigma

-algebra

L

\mathcal {L}

contains the Borel subsets of

R

∞

\mathbb {R}^{\infty }

, and

λ
\lambda

is a translation-invariant measure such that for any measurable rectangle

R
=

∏

i
=
1

∞

R

i

R=\prod \limits ^{\infty }_{i=1}R_{i}

, if

0
≤

∏

i
=
1

∞

m
(

R

i

)
>
+
∞

0\le \prod \limits ^{\infty }_{i=1}m(R_{i})>+\infty

, then

λ
(
R
)
=

∏

i
=
1

∞

m
(

R

i

)

\lambda (R)=\prod \limits ^{\infty }_{i=1}m(R_{i})

, where

m
m

is Lebesgue measure on

R

\mathbb {R}

. The measure

λ
\lambda

is not

σ
\sigma

-finite. We prove three Fubini theorems, namely, the Fubini theorem, the mean Fubini-Jensen theorem, and the pointwise Fubini-Jensen theorem. Finally, as an application of the measure

λ
\lambda

, we construct, via selfadjoint operators on

L

2

(

R

∞

,

L

,
λ
)

L_{2}(\mathbb {R}^{\infty },\mathcal {L},\lambda )

, a “Schrödinger model” of the canonical commutation relations:

[

P

j

,

P

k

]
=
[

Q

j

,

Q

k

]
=
0

[P_{j},P_{k}]=[Q_{j},Q_{k}]=0

,

[

P

j

,

Q

k

]
=
i

δ

j
k

[P_{j},Q_{k}]=i\delta _{jk}

,

1
≤
j
,
k
>
+
∞

1\le j,k>+\infty

.
Entire invariant solutions to Monge-Ampère equations
Authors: Bielawski Roger
Published: May 2004

We prove existence and regularity of entire solutions to Monge-Ampère equations invariant under an irreducible action of a compact Lie group.
Mixed-mean inequalities for subsets
Authors: Leng Gangsong , Si Lin , Zhu Qingsan
Published: May 2004

For
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper A subset-of upper X equals StartSet x 1 comma period period period comma x Subscript n Baseline vertical-bar x Subscript i Baseline greater-than-or-equal-to 0 comma i equals 1 comma 2 comma period period period comma n EndSet comma">

A
⊂
X
=
{

x
1

,
.
.
.
,

x
n

 

|

 

x
i

≥
0
,
 
i
=
1
,
2
,
.
.
.
,
n
}
,

A\subset X=\{x_1,...,x_n ~|~x_i\geq 0, ~i=1,2,...,n\},

let

a
A

a_A

and

g
A

g_A

denote the arithmetic mean and geometric mean of elements of

A
A

, respectively. It is proved that if

k
k

is an integer in

(

n
2

,
n
]

(\frac {n}{2}, n]

, then
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis product Underscript StartLayout 1st Row StartAbsoluteValue upper A EndAbsoluteValue equals k 2nd Row upper A subset-of upper X EndLayout Endscripts a Subscript upper A Baseline right-parenthesis Superscript StartFraction 1 Over upper C Super Subscript n Super Superscript k Superscript EndFraction Baseline greater-than-or-equal-to StartFraction 1 Over upper C Subscript n Superscript k Baseline EndFraction left-parenthesis sigma-summation Underscript StartLayout 1st Row StartAbsoluteValue upper A EndAbsoluteValue equals k 2nd Row upper A subset-of upper X EndLayout Endscripts g Subscript upper A Baseline right-parenthesis comma">

(

∏

|

A

|

=
k

A
⊂
X

a

A

)

1

C
n
k

≥

1

C
n
k

(

∑

|

A

|

=
k

A
⊂
X

g

A

)

,

\Big (\prod _{|A|=k\atop A\subset X}a_{A}\Big )^{\frac {1}{C_n^k}} \geq \frac {1}{C_n^k}\Big (\sum _{|A|=k\atop A\subset X}g_{A}\Big ),

\]
with equality if and only if

x
1

=
.
.
.
=

x
n

x_1=...=x_n

. Furthermore, as a generalization of this inequality, a mixed power-mean inequality for subsets is established.
On 𝐷_{𝑝}-extensions in characteristic 𝑝
Authors: Ledet Arne
Published: May 2004

We study the relationship between generic polynomials and generic extensions over a finite ground field, using dihedral extensions as an example.
Indecomposables of multiplicative fibrations
Authors: Lin James
Published: May 2004

Given a multiplicative fibration

F

⟶

j

E

⟶

π

B

F \stackrel {j}{\longrightarrow } E \stackrel {\pi }{\longrightarrow } B

we study the module of indecomposables

Q

H
∗

(
E
;

Z

p

)

QH^*(E; \mathbb {Z}_p)

for

p
p

a prime.
(𝑛+1,𝑚+1)-hypergeometric functions associated to character algebras
Authors: Mizukawa Hiroshi , Tanaka Hajime
Published: May 2004

In this paper, we obtain certain discrete orthogonal polynomials expressed in terms of the

(
d
+
1
,
2
(
d
+
1
)
)

(d+1,2(d+1))

-hypergeometric functions, from the eigenmatrices of character algebras.
Locally homogeneous affine connections on compact surfaces
Authors: Opozda Barbara
Published: May 2004

Global properties of locally homogeneous and curvature homogeneous affine connections are studied. It is proved that the only locally homogeneous connections on surfaces of genus different from 1 are metric connections of constant curvature. There exist nonmetrizable nonlocally symmetric locally homogeneous affine connections on the torus of genus 1. It is proved that there is no global affine immersion of the torus endowed with a nonflat locally homogeneous connection into

R

3

{\mathbf R} ^3

.
First countable extensions of regular spaces
Authors: Simon Petr , Tironi Gino
Published: May 2004

We investigate feebly compact extensions of first countable regular locally feebly compact spaces. Solutions of problems posed by R. M. Stephenson, Jr. and G. M. Reed are given.
The number of Hall 𝜋-subgroups of a 𝜋-separable group
Authors: Turull Alexandre
Published: May 2004

We observe a simple formula to compute the number

ν
π

(
G
)

\nu _\pi (G)

of Hall

π
\pi

-subgroups of a

π
\pi

-separable finite group

G
G

in terms of only the action of a fixed Hall

π
\pi

-subgroup of

G
G

on a set of normal

π
′

\pi ’

-sections of

G
G

. As a consequence, we obtain that

ν
π

(
K
)

\nu _\pi (K)

divides

ν
π

(
G
)

\nu _\pi (G)

whenever

K
K

is a subgroup of a finite

π
\pi

-separable group

G
G

. This generalizes a recent result of Navarro. In addition, our method gives an alternative proof of Navarro’s result.
On criteria for extremality of Teichmüller mappings
Authors: Yao Guowu
Published: May 2004

Let

f
f

be a Teichmüller self-mapping of the unit disk

Δ
\Delta

corresponding to a holomorphic quadratic differential

φ
\varphi

. If

φ
\varphi

satisfies the growth condition
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper A left-parenthesis r comma phi right-parenthesis equals double-integral Underscript StartAbsoluteValue z EndAbsoluteValue greater-than r Endscripts StartAbsoluteValue phi EndAbsoluteValue d x d y equals upper O left-parenthesis left-parenthesis 1 minus r right-parenthesis Superscript negative s Baseline right-parenthesis">

A
(
r
,
φ
)
=

∬

|

z

|

>
r

|

φ

|

d
x
d
y
=
O
(
(
1
−
r

)

−
s

)

A(r,\varphi )=\iint _{|z|>r}|\varphi |dxdy=O((1-r)^{-s})

(as

r
→
1

r\to 1

), for any given

s
>
0

s>0

, then

f
f

is extremal, and for any given

a
∈
(
0
,
1
)

a\in (0,1)

, there exists a subsequence

{

n
k

}

\{n_k\}

of

N

\mathbb {N}

such that
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-brace StartFraction phi left-parenthesis a Superscript 1 slash 2 Super Superscript n Super Super Subscript k Super Superscript Superscript Baseline z right-parenthesis Over double-integral Underscript normal upper Delta Endscripts StartAbsoluteValue phi left-parenthesis a Superscript 1 slash 2 Super Superscript n Super Super Subscript k Super Superscript Superscript Baseline z right-parenthesis EndAbsoluteValue d x d y EndFraction right-brace">

{

φ
(

a

1

/

2

n
k

z
)

∬
Δ

|

φ
(

a

1

/

2

n
k

z
)

|

d
x
d
y

}

\begin{equation*} \Big \{\frac {\varphi (a^{1/2^{n_k}}z)} {\iint _\Delta |\varphi (a^{1/2^{n_k}}z)|dxdy}\Big \} \end{equation*}

is a Hamilton sequence. In addition, it is shown that there exists

φ
\varphi

with bounded Bers norm such that the corresponding Teichmüller mapping is not extremal, which gives a negative answer to a conjecture by Huang in 1995.
Sub-exponential decay of operator kernels for functions of generalized Schrödinger operators
Authors: Bouclet Jean-Marc , Germinet François , Klein Abel
Published: May 2004

We study the decay at large distances of operator kernels of functions of generalized Schrödinger operators. We prove sub-exponential decay for functions in Gevrey classes and exponential decay for real analytic functions.
Logarithmic derivatives of solutions to linear differential equations
Authors: Hillar Christopher
Published: May 2004

Given an ordinary differential field

K
K

of characteristic zero, it is known that if

y
y

and

1

/

y

1/y

satisfy linear differential equations with coefficients in

K
K

, then

y
′

/

y

y’/y

is algebraic over

K
K

. We present a new short proof of this fact using Gröbner basis techniques and give a direct method for finding a polynomial over

K
K

that

y
′

/

y

y’/y

satisfies. Moreover, we provide explicit degree bounds and extend the result to fields with positive characteristic. Finally, we give an application of our method to a class of nonlinear differential equations.
Moment generating function of the reciprocal of an integral of geometric Brownian motion
Authors: Kim Kyounghee
Published: May 2004

In this paper we obtain a simple, explicit integral form for the moment generating function of the reciprocal of the random variable defined by

A
t

(
ν
)

:=

∫
0
t

exp
⁡
(
2

B
s

+
2
ν
s
)
d
s

A^{(\nu )}_t := \int ^t _0 \exp (2B_s + 2 \nu s) ds

, where

B
s

B_s

,

s
>
0

s>0

, is a one-dimensional Brownian motion starting from 0. In case

ν
=
1

\nu = 1

, the moment generating function has a particularly simple form.
Uncountable categoricity for gross models
Authors: Laskowski Michael , Pillay Anand
Published: May 2004

A modelMMis said to be gross if all infinite definable sets inMMhave the same cardinality (asMM). We prove that if for some uncountableκ\kappa,TThas a unique gross model of cardinalityκ\kappa, then for any uncountableκ\kappa,TThas a unique gross model of cardinalityκ\kappa.
A joint theorem generalizing the criteria of Montel and Miranda for normal families
Authors: Li Bao Qin
Published: May 2004

We give a joint normality theorem, which simultaneously generalizes Montel’s criterion and Miranda’s criterion for normal families.
On rings with small Hilbert-Kunz multiplicity
Authors: Blickle Manuel , Enescu Florian
Published: May 2004

A result of Watanabe and Yoshida says that an unmixed local ring of positive characteristic is regular if and only if its Hilbert-Kunz multiplicity is one. We show that, for fixed

p
p

and

d
d

, there exists a number

ϵ
(
d
,
p
)
>
0

\epsilon (d,p) > 0

such that for any nonregular unmixed ring

R
R

its Hilbert-Kunz multiplicity is at least

1
+
ϵ
(
d
,
p
)

1+\epsilon (d,p)

. We also show that local rings with sufficiently small Hilbert-Kunz multiplicity are Cohen-Macaulay and

F
F

-rational.
A geometric inequality and a low 𝑀-estimate
Authors: Klartag Bo’az
Published: May 2004

We present an integral inequality connecting volumes and diameters of sections of a convex body. We apply this inequality to obtain some new inequalities concerning diameters of sections of convex bodies, among which is our “low

M
M

-estimate”. Also, we give novel, alternative proofs to some known results, such as the fact that a finite volume ratio body has proportional sections that are isomorphic to a Euclidean ball.
Devaney’s chaos implies existence of 𝑠-scrambled sets
Authors: Mai Jie-Hua
Published: May 2004

Let

X
X

be a complete metric space without isolated points, and let

f
:
X
→
X

f:X\to X

be a continuous map. In this paper we prove that if

f
f

is transitive and has a periodic point of period

p
p

, then

f
f

has a scrambled set

S
=

⋃

n
=
1

∞

C

n

S=\bigcup _{n=1}^{\infty }C_{n}

consisting of transitive points such that each

C

n

C_{n}

is a synchronously proximal Cantor set, and

⋃

i
=
0

p
−
1

f

i

(
S
)

\bigcup _{i=0}^{p-1}f^{i}(S)

is dense in

X
X

. Furthermore, if

f
f

is sensitive (for example, if

f
f

is chaotic in the sense of Devaney), with

2
s

2s

being a sensitivity constant, then this

S
S

is an

s
s

-scrambled set.
Eigenvalue fields of hyperbolic orbifolds
Authors: Hamilton Emily , Reid Alan
Published: May 2004

In this paper, we prove that if

Γ
\Gamma

is a non-elementary subgroup of

O

o

(
n
,
1
,

R

)

\mathrm {O}_{\mathrm {o}}(n,1,\mathbb {R})

, with

n
≥
2

n\ge 2

, then the eigenvalue field of

Γ
\Gamma

has infinite degree over

Q

\mathbb {Q}

.
On the nonvanishing of the central value of the Rankin-Selberg 𝐿-functions
Authors: Ginzburg David , Jiang Dihua , Rallis Stephen
Published: May 2004

We characterize the nonvanishing of the central value of the Rankin-Selberg

L
L

-functions in terms of periods of Fourier-Jacobi type. This characterization is based on the Langlands philosophy on functoriality and on applications of invariant theory to automorphic representations. The result is the symplectic analog of the Gross-Prasad conjecture.
Independence of ℓ of monodromy groups
Authors: Chin CheeWhye
Published: May 2004

Let

X
X

be a smooth curve over a finite field of characteristic

p
p

, let

E
E

be a number field, and let

L

=
{

L

λ

}

\mathbf {L} = \{\mathcal {L}_\lambda \}

be an

E
E

-compatible system of lisse sheaves on the curve

X
X

. For each place

λ
\lambda

of

E
E

not lying over

p
p

, the

λ
\lambda

-component of the system

L

\mathbf {L}

is a lisse

E
λ

E_\lambda

-sheaf

L

λ

\mathcal {L}_\lambda

on

X
X

, whose associated arithmetic monodromy group is an algebraic group over the local field

E
λ

E_\lambda

. We use Serre’s theory of Frobenius tori and Lafforgue’s proof of Deligne’s conjecture to show that when the

E
E

-compatible system

L

\mathbf {L}

is semisimple and pure of some integer weight, the isomorphism type of the identity component of these monodromy groups is “independent of 

λ
\lambda

”. More precisely, after replacing

E
E

by a finite extension, there exists a connected split reductive algebraic group

G
0

G_0

over the number field

E
E

such that for every place

λ
\lambda

of

E
E

not lying over 

p
p

, the identity component of the arithmetic monodromy group of

L

λ

\mathcal {L}_\lambda

is isomorphic to the group

G
0

G_0

with coefficients extended to the local field

E
λ

E_\lambda

.
Integral motives and special values of zeta functions
Authors: Milne James , Ramachandran Niranjan
Published: May 2004

For each field

k
k

, we define a category of rationally decomposed mixed motives with

Z

\mathbb {Z}

-coefficients. When

k
k

is finite, we show that the category is Tannakian, and we prove formulas relating the behaviour of zeta functions near integers to certain

Ext
\operatorname {Ext}

groups.
Phylogenetic analysis of gastric and enterohepatic Helicobacter species based on partial HSP60 gene sequences
Authors: Mikkonen Tiina P. , Kärenlampi Rauni I. , Hänninen Marja-Liisa
Published: May 2004

Analysis of 16S rRNA gene sequences has been the method generally used to study the evolution and phylogeny of bacteria. Phylogenetic analysis of the 16S rRNA gene has shown the position of the genus Helicobacter in the ε-subclass of the Proteobacteria. Because 16S rRNA-based phylogeny does not always correspond to the results of polyphasic taxonomy, and the related species cannot always be separated, new phylogenetic markers for Helicobacter species are needed. In this study, conserved partial (600 bp) 60 kDa heat-shock protein (HSP60) sequences were used to study the phylogeny of 37 strains of gastric and enterohepatic Helicobacter species, including type strains of 15 Helicobacter species with validly published names, reference strains of flexispira taxa and Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis and canine flexispira strains. The partial HSP60 gene sequence proved to be a useful phylogenetic marker for the genus Helicobacter, providing a means of differentiating all 15 Helicobacter species analysed. In the resulting phylogenetic tree, gastric Helicobacter species and enterohepatic species with flexispira morphology formed tight, separate clusters. In general, HSP60 sequence similarities between Helicobacter species were significantly lower than the corresponding 16S rRNA gene sequence similarities, indicating a better resolution for species identification. In addition, a specific PCR method for identifying H. salomonis was developed based on the partial HSP60 sequence.
A combined computational-experimental approach predicts human microRNA targets
Authors: Kiriakidou Marianthi , Nelson Peter T. , Kouranov Andrei , Fitziev Petko , Bouyioukos Costas , Mourelatos Zissimos , Hatzigeorgiou Artemis
Published: May 2004

A new paradigm of gene expression regulation has emerged recently with the discovery of microRNAs (miRNAs). Most, if not all, miRNAs are thought to control gene expression, mostly by base pairing with miRNA-recognition elements (MREs) found in their messenger RNA (mRNA) targets. Although a large number of human miRNAs have been reported, many of their mRNA targets remain unknown. Here we used a combined bioinformatics and experimental approach to identify important rules governing miRNA-MRE recognition that allow prediction of human miRNA targets. We describe a computational program, “DIANA-microT”, that identifies mRNA targets for animal miRNAs and predicts mRNA targets, bearing single MREs, for human and mouse miRNAs.
Collaboration of Brca1 and Chk2 in tumorigenesis
Authors: McPherson John Peter , Lemmers Bénédicte , Hirao Atsushi , Hakem Anne , Abraham Jacinth , Migon Eva , Matysiak-Zablocki Elzbieta , Tamblyn Laura , Sanchez-Sweatman Otto , Khokha Rama , Squire Jeremy , Hande M. Prakash , Mak Tak W. , Hakem Razqallah
Published: May 2004

Disruption of Brca1 results in cellular demise or tumorigenesis depending on cellular context. Inactivation of p53 contributes to Brca1-associated tumor susceptibility. However the activation of p53-dependent checkpoint/apoptotic signaling in the absence of Brca1 is poorly understood. Here, we show that Chk2 inactivation is partially equivalent to p53 inactivation, in that Chk2 deficiency facilitates the development, survival, and proliferation of Brca1-deficient T cells at the expense of genomic integrity. Brca1 deficiency was found to result in Chk2 phosphorylation and the Chk2-dependent accumulation and activation of p53. Furthermore, inactivation of Chk2 and Brca1 was cooperative in breast cancer. Our findings identify a critical role for Chk2 as a component of the DNA damage-signaling pathway activated in response to Brca1 deficiency.
Viral RNA silencing suppressors inhibit the microRNA pathway at an intermediate step
Authors: Chapman Elisabeth J. , Prokhnevsky Alexey I. , Gopinath Kodetham , Dolja Valerian V. , Carrington James C.
Published: May 2004

RNA silencing suppressors from different plant viruses are structurally diverse. In addition to inhibiting the antiviral silencing response to condition susceptibility, many suppressors are pathogenicity factors that cause disease or developmental abnormalities. Here, unrelated suppressors from multiple viruses were shown to inhibit microRNA (miRNA) activities and trigger an overlapping series of severe developmental defects in transgenic Arabidopsis thaliana. This suggests that interference with miRNA-directed processes may be a general feature contributing to pathogenicity of many viruses. A normally labile intermediate in the miRNA biogenesis/RNA-induced silencing complex (RISC) assembly pathway, miRNA*, accumulated specifically in the presence of suppressors (P1/HC-Pro, p21, or p19) that inhibited miRNA-guided cleavage of target mRNAs. Both p21 and p19, but not P1/HC-Pro, interacted with miRNA/miRNA* complexes and hairpin RNA-derived short interfering RNAs (siRNAs) in vivo. In addition, p21 bound to synthetic miRNA/miRNA* and siRNA duplexes in vitro. We propose that several different suppressors act by distinct mechanisms to inhibit the incorporation of small RNAs into active RISCs.
Genome-Wide Analysis of Spatial Gene Expression in Arabidopsis Flowers[W]
Authors: Wellmer Frank , Riechmann Joseé Luis , Alves-Ferreira Maércio , Meyerowitz Elliot M.
Published: May 2004

We have compared the gene expression profiles of inflorescences of the floral homeotic mutants apetala1, apetala2, apetala3, pistillata, and agamous with that of wild-type plants using a flower-specific cDNA microarray and a whole genome oligonucleotide array. By combining the data sets from the individual mutant/wild type comparisons, we were able to identify a large number of genes that are, within flowers, predicted to be specifically or at least predominantly expressed in one type of floral organ. We have analyzed the expression patterns of several of these genes by in situ hybridization and found that they match the predictions that were made based on the microarray experiments. Moreover, genes with known floral organ–specific expression patterns were correctly assigned by our analysis. The vast majority of the identified transcripts are found in stamens or carpels, whereas few genes are predicted to be expressed specifically or predominantly in sepals or petals. These findings indicate that spatially limited expression of a large number of genes is part of flower development and that its extent differs significantly between the reproductive organs and the organs of the perianth.
A probabilistic model for prediction of LCF life of PM alloys
Authors: Yan Xiao‐Jun , Li Hao‐Yue , Nie Jing‐Xu
Published: May 2004

Inclusions have been shown to be the most significant factor to decrease the low cycle fatigue (LCF) life in powder metallurgy (PM) alloys used by most of turbine discs for advanced turboengines. In this paper, effects of inclusions on PM alloys' LCF life are evaluated through the definition of initial damage value D0 based on damage mechanics. By investigating the relationship between D0 and characteristic dimension of inclusions, Bussac's probabilistic model is extended to consider surface and internal inclusions together.
An AUSM‐based high‐order compact method for solving Navier‐Stokes equations
Authors: Mawlood Mahmood K. , Basri ShahNor , Asrar Waqar , Omar Ashraf A. , Mokhtar Ahmad S. , Ahmad Megat M.H.M.
Published: May 2004

A high‐order compact upwind algorithm is developed for solving Navier‐Stokes equations in two‐space dimensions. The method is based on advection upstream splitting method and fourth‐order compact finite‐difference schemes. The convection flux terms of the Navier‐Stokes equations are discretized by a compact cell‐centered differencing scheme while the diffusion flux terms are discretized by a central fourth‐order compact scheme. The midpoint values of the flux functions required by the cell‐centered compact scheme are determined by a fourth‐order MUSCL approach. For steady‐state solutions; first‐order implicit time integration, with LU decomposition, is employed. Computed results for a laminar flow past a flat plate and the problem of shock‐wave boundary layer interaction are presented.
Experimental and numerical results obtained for a scaled RPV and a full size aircraft
Authors: Galinski Cezary , Goraj Zdobyslaw
Published: May 2004

This paper describes a series of tests of remotely piloted vehicles (RPV) and full scale aircraft from which most of the performance information and selected dynamic characteristics normally required for aircraft operation can be obtained. The main goal of the paper is to compare corresponding characteristics of RPVs and full scale aircraft and establish if RPV testing can help and influence an early stage design project in order to optimise its aerodynamic configuration and predict its static and dynamic characteristics. This paper presents basic similarity transformations, including mass scale, force scale, power scale, linear acceleration scale, Reynolds number scale etc. as functions of linear scale. It was found that tests in steady conditions are difficult to perform, time‐consuming, and do not offer significant advantages over the classical wind tunnel tests. RPV tests in unsteady conditions are much easier to perform and quite accurate.
Using the dynamic mesh method for genetically obtained wing structures
Authors: Vatandaş Ergüven , Özkol İbrahim , Kaya Metin O.
Published: May 2004

In this study, dynamic mesh method is implemented on a real coded genetic algorithm to demonstrate gain in computational time as well as in higher performance for optimized parameters. Since the differences developed at each step in geometries of new members are not significant, therefore, it is possible to use dynamic mesh methods for new members. In this work, because the population members are obtained by modifying the pervious ones, each member is considered as one step of geometry‐change of a deforming body, for examples, a wing inflating, deflating or cambering.
Hybrid problems of determining unknown shape of bladings in compressible S2‐flow in mixed‐flow turbomachinery via variational technique
Authors: He Ji‐Huan
Published: May 2004

Using the semi‐inverse method proposed by the present author, a family of variational principle for direct problem of S2‐flow in mixed‐flow turbomachinery is obtained; then, applying the functional variation with variable domain, two families of variational principles are established for the hybrid problems of determining the unknown shape of bladings, where pressure or velocity is over‐specified. The present variational models are well posed for redundant data at boundaries. The theory provides both rational ways for best contouring the hub/casing walls to meet various practical design requirements and a theoretical basis for introducing the finite element method into computational aerodynamics of turbomachinery.
Latest advances in the understanding of acid dewpoint corrosion: corrosion and stress corrosion cracking in combustion gas condensates
Authors: Huijbregts W.M.M. , Leferink R.G.I.
Published: May 2004

Corrosion failures due to condensing flue gases containing H2O, SO3, NOx and HCl still occur more often than might be expected. The corrosion failures can be of several types: general corrosion, pitting attack and stress corrosion cracking (SCC). The chemistry of condensing gases is discussed, and some examples of corrosion in large‐scale installations are presented, including blast stoves for steel production, heat recovery steam generators, and waste incineration boilers. The use of thermal insulation inside boiler casings can result in nitrate SCC when the flue gas contains high concentrations of NOx. Nitric acid from flue gas can react with carbon steel and insulation material forming ammonium nitrate and calcium nitrate. Both materials have hygroscopic properties and are very corrosive, even above the water dewpoint of the gases.
The application of “grey system theory” in a molybdate inhibitive study
Authors: Daowu Yang , Yuchun Li , Fang Zhang , Zhiping Zhu
Published: May 2004

In this study, electrochemical parameters were used to evaluate the inhibition effects of molybdate and silicate inhibitors in tap water. With the aid of “grey system” theory, we determine the inhibitive state model of such systems.
Aspects of selective and pitting corrosion in cast duplex stainless steels
Authors: Batista S.R.F. , Kuri S.E.
Published: May 2004

Duplex stainless steels are excellent materials for industrial applications and their use has increased in the oil, chemical, petroleum (offshore), and electric power industries. Pitting resistance equivalent (PRE) is the first parameter used to characterise the pitting and crevice corrosion resistance. Nevertheless, there are other aspects to be considered, such as the precise values of the PRE in the α and γ phases and the selective corrosion processes that may occur at grain boundaries. This paper indicates that α/γ and α/σ interfaces are preferential sites for the nucleation and growth of pits and for consequent selective corrosion, with increasing tendency in the ferritic phase. In addition, the selective dissolution potential is more reactive (and therefore, is of greater significance) than the pitting potential.
An investigation on the atmospheric corrosion behaviour of coatings of electrical equipment in the coast of Persian Gulf – Bandar Abbas
Authors: Rezaei Saman Kandi Masoud , Shahrabi Taghi , Reza Allahkaram Saed , Javad Geramian Mir
Published: May 2004

Electrical industry equipment in the southern parts of Iran have sustained severe damages as a result of corrosive soil containing different kinds of salt, in combination with the corrosive local atmosphere. The present paper is the result of investigations into the behaviour of coatings for various electrical insulators end‐fittings. In this research, the performance of Al‐Zn alloy coating was compared to conventional galvanized zinc coatings by means of atmospheric corrosion tests. The results demonstrated the higher corrosion resistance of the alloy coatings, compared to that of conventional galvanized coatings. Insulator end‐fittings generally are made of steel, which are coated with a hot‐dip galvanized coating. The combination of Al and Zn elements in this coating was demonstrated to possess better galvanic protection and lower corrosion rate than did pure zinc.