bluuebunny/crossref_metadata_2025 huggingface dataset:
The frequency decomposition multilevel method: A robust additive hierarchical basis preconditioner
Authors: Stevenson Rob
Published: July 2002

Hackbusch’s frequency decomposition multilevel method is characterized by the application of three additional coarse-grid corrections in parallel to the standard one. Each coarse-grid correction was designed to damp errors from a different part of the frequency spectrum. In this paper, we introduce a cheap variant of this method, partly based on semicoarsening, which demands fewer recursive calls than the original version. Using the theory of the additive Schwarz methods, we will prove robustness of our method as a preconditioner applied to anisotropic equations.
Computation of Galois groups over function fields
Authors: Mattman Thomas , McKay John
Published: July 2002

Symmetric function theory provides a basis for computing Galois groups which is largely independent of the coefficient ring. An exact algorithm has been implemented over

Q

(

t
1

,

t
2

,
…
,

t
m

)

\mathbb {Q}(t_1,t_2,\ldots ,t_m)

in Maple for degree up to 8. A table of polynomials realizing each transitive permutation group of degree 8 as a Galois group over the rationals is included.
Treatments of discontinuity and bubble functions in the multigrid method
Authors: Zhang Shangyou , Zhang Zhimin
Published: July 2002

When multilevel finite element spaces are not nested, different intergrid transfer operators would lead to different multigrid algorithms. It is proposed in this paper that discontinuous functions be averaged to continuous functions and that the bubble functions be discarded in the multigrid transferring. Applications of the techniques to various problems are presented with convergence analysis. Numerical comparisons with other existing methods are provided.
Diameters of complete sets of conjugate algebraic integers of small degree
Authors: Grandcolas Michel
Published: July 2002

We give bounds for the coefficients of a polynomial as functions of the diameter of its roots, hence we obtain polynomials with minimal diameters and small degree
A constructive theory of triple and quintuple product identities of the second degree
Authors: Blecksmith Richard , Brillhart John , Gerst Irving
Published: July 2002

The groundwork for a theory of quadratic identities involving the classical triple and quintuple products is layed. The approach is through the study and use of affine maps that act on indexing lattices associated with the terms (double sums) in the given identity. The terms of the identity are found to be connected by the invariant of a ternary quadratic form.
An algorithm for constructing a basis for 𝐶^{𝑟}-spline modules over polynomial rings
Authors: Deo Satya , Mazumdar Lipika
Published: July 2002

Let

◻

\Box

be a polyhedral complex embedded in the euclidean space

E

d

E^{d}

and

S

r

(

◻

)

S^{r}(\Box )

,

r
≥
0

r \geq 0

, denote the set of all

C

r

C^{r}

-splines on

◻

\Box

. Then

S

r

(

◻

)

S^{r}(\Box )

is an

R
R

-module where

R
=
E
[

x

1

,
…
,

x

d

]

R = E[x_{1},\ldots ,x_{d}]

is the ring of polynomials in several variables. In this paper we state and prove the existence of an algorithm to write down a free basis for the above

R
R

-module in terms of obvious linear forms defining common faces of members of

◻

\Box

. This is done for the case when

◻

\Box

consists of a finite number of parallelopipeds properly joined amongst themselves along the above linear forms.
Interpolation correction for collocation solutions of Fredholm integro-differential equations
Authors: Hu Qiya
Published: July 2002

In this paper we discuss the collocation method for a large class of Fredholm linear integro-differential equations. It will be shown that, when a certain higher order interpolation operation is added to the collocation solution of this equation, the new approximations will, under suitable assumptions, admit a multiterm error expansion in even powers of the step-size

h
h

. Based on this expansion, ideal multilevel correction results of this collocation solution are obtained.
A shadowing result with applications to finite element approximation of reaction-diffusion equations
Authors: Larsson Stig , Sanz-Serna J.-M.
Published: July 2002

A shadowing result is formulated in such a way that it applies in the context of numerical approximations of semilinear parabolic problems. The qualitative behavior of temporally and spatially discrete finite element solutions of a reaction-diffusion system near a hyperbolic equilibrium is then studied. It is shown that any continuous trajectory is approximated by an appropriate discrete trajectory, and vice versa, as long as they remain in a sufficiently small neighborhood of the equilibrium. Error bounds of optimal order in the

L
2

L_2

and

H
1

H^1

norms hold uniformly over arbitrarily long time intervals.
Proving that a genus 2 curve has complex multiplication
Authors: van Wamelen Paul
Published: July 2002

Recently examples of genus 2 curves defined over the rationals were found which, conjecturally, should have complex multiplication. We prove this conjecture. This involves computing an explicit representation of a rational map defining complex multiplication.
Voevodsky’s proof of Milnor’s conjecture
Authors: Morel F.
Published: July 2002

We give an overview of Voevodsky’s recent proof of Milnor’s conjecture on the

m
o
d

2

\mathrm {mod}\,2

Galois cohomology of fields of characteristic

≠
2

\not =2

.
The 𝐿² ∂̄-method, weak Lefschetz theorems, and the topology of Kähler manifolds
Authors: Napier Terrence , Ramachandran Mohan
Published: July 2002

A new approach to Nori’s weak Lefschetz theorem is described. The new approach, which involves the

∂
¯

\bar \partial

-method, avoids moving arguments and gives much stronger results. In particular, it is proved that if

X
X

and

Y
Y

are connected smooth projective varieties of positive dimension and

f
:
Y
→
X

f : Y \rightarrow X

is a holomorphic immersion with ample normal bundle, then the image of

π
1

(
Y
)

\pi _1(Y)

in

π
1

(
X
)

\pi _1(X)

is of finite index. This result is obtained as a consequence of a direct generalization of Nori’s theorem. The second part concerns a new approach to the theorem of Burns which states that a quotient of the unit ball in

C

n

\Bbb C ^n

(

n
≥
3

n\geq 3

) by a discrete group of automorphisms which has a strongly pseudoconvex boundary component has only finitely many ends. The following generalization is obtained. If a complete Hermitian manifold 

X
X

of dimension

n
≥
3

n\geq 3

has a strongly pseudoconvex end 

E
E

and

Ricci

(
X
)
≤
−
C

\text {Ricci}\, (X) \leq -C

for some positive constant 

C
C

, then, away from 

E
E

,

X
X

has finite volume.
A new proof of Federer’s structure theorem for 𝑘-dimensional subsets of 𝐑^{𝐍}
Authors: White Brian
Published: July 2002

We prove that Federer’s structure theorem for

k
k

-dimensional sets in

R

N

\mathbf {R}^{N}

follows from the special case of

1
1

-dimensional sets in the plane, which was proved earlier by Besicovitch.
Ergodic behavior of graph entropy
Authors: Kieffer John , Yang En-hui
Published: July 2002

For a positive integer

n
n

, let

X
n

X^n

be the vector formed by the first

n
n

samples of a stationary ergodic finite alphabet process. The vector

X
n

X^n

is hierarchically represented via a finite rooted acyclic directed graph

G
n

G_n

. Each terminal vertex of

G
n

G_n

carries a label from the process alphabet, and

X
n

X^n

can be reconstituted as the sequence of labels at the ends of the paths from root vertex to terminal vertex in

G
n

G_n

. The entropy

H
(

G
n

)

H(G_n)

of the graph

G
n

G_n

is defined as a nonnegative real number computed in terms of the number of incident edges to each vertex of

G
n

G_n

. An algorithm is given which assigns to

G
n

G_n

a binary codeword from which

G
n

G_n

can be reconstructed, such that the length of the codeword is approximately equal to

H
(

G
n

)

H(G_n)

. It is shown that if the number of edges of

G
n

G_n

is

o
(
n
)

o(n)

, then the sequence

{
H
(

G
n

)

/

n
}

\{H(G_n)/n\}

converges almost surely to the entropy of the process.
Classification of compact homogeneous spaces with invariant symplectic structures
Authors: Guan Daniel
Published: July 2002

We solve a longstanding problem of classification of compact homogeneous spaces with invariant symplectic structures. We also give a splitting conjecture on compact homogeneous spaces with symplectic structures (which are not necessarily invariant under the group action) that makes the classification of this kind of manifolds possible.
Prevalence of non-Lipschitz Anosov foliations
Authors: Hasselblatt Boris , Wilkinson Amie
Published: July 2002

We give sharp regularity results for the invariant subbundles of hyperbolic dynamical systems and give open dense sets of codimension one systems where this regularity is not exceeded as well as open dense sets of symplectic, geodesic, and codimension one systems where the analogous regularity results of Pugh, Shub, and Wilkinson are optimal. We produce open sets of symplectic Anosov diffeomorphisms and flows with low transverse Hölder regularity of the invariant foliations almost everywhere. Prevalence of low regularity of conjugacies on large sets is a corollary. We also establish a new connection between the transverse regularity of foliations and their tangent subbundles.
Quantization of Poisson structures on 𝐑²
Authors: Tamarkin Dmitry
Published: July 2002

An ‘isomorphism’ between the ‘moduli space’ of star products on

R

2

\mathbf {R}^2

and the ‘moduli space’ of all formal Poisson structures on

R

2

\mathbf {R}^2

is established.
Invariant sets with zero measure and full Hausdorff dimension
Authors: Barreira Luis , Schmeling Jörg
Published: July 2002

For a subshift of finite type and a fixed Hölder continuous function, the zero measure invariant set of points where the Birkhoff averages do not exist is either empty or carries full Hausdorff dimension. Similar statements hold for conformal repellers and two-dimensional horseshoes, and the set of points where the pointwise dimensions, local entropies, Lyapunov exponents, and Birkhoff averages do not exist simultaneously.
Invariants of twist-wise flow equivalence
Authors: Sullivan Michael
Published: July 2002

Twist-wise flow equivalence is a natural generalization of flow equivalence that takes account of twisting in the local stable manifold of the orbits of a flow. Here we announce the discovery of two new invariants in this category.
The distribution of totients
Authors: Ford Kevin
Published: July 2002

This paper is an announcement of many new results concerning the set of totients, i.e. the set of values taken by Euler’s

ϕ
\phi

-function. The main functions studied are

V
(
x
)

V(x)

, the number of totients not exceeding

x
x

,

A
(
m
)

A(m)

, the number of solutions of

ϕ
(
x
)
=
m

\phi (x)=m

(the “multiplicity” of

m
m

), and

V

k

(
x
)

V_{k}(x)

, the number of

m
≤
x

m\le x

with

A
(
m
)
=
k

A(m)=k

. The first of the main results of the paper is a determination of the true order of

V
(
x
)

V(x)

. It is also shown that for each

k
≥
1

k\ge 1

, if there is a totient with multiplicity

k
k

, then

V

k

(
x
)
≫
V
(
x
)

V_{k}(x) \gg V(x)

. We further show that every multiplicity

k
≥
2

k\ge 2

is possible, settling an old conjecture of Sierpiński. An older conjecture of Carmichael states that no totient has multiplicity 1. This remains an open problem, but some progress can be reported. In particular, the results stated above imply that if there is one counterexample, then a positive proportion of all totients are counterexamples. Determining the order of

V
(
x
)

V(x)

and

V

k

(
x
)

V_{k}(x)

also provides a description of the “normal” multiplicative structure of totients. This takes the form of bounds on the sizes of the prime factors of a pre-image of a typical totient. One corollary is that the normal number of prime factors of a totient

≤
x

\le x

is

c
log
⁡
log
⁡
x

c\log \log x

, where

c
≈
2.186

c\approx 2.186

. Lastly, similar results are proved for the set of values taken by a general multiplicative arithmetic function, such as the sum of divisors function, whose behavior is similar to that of Euler’s function.
Nonabelian Sylow subgroups of finite groups of even order
Authors: Chigira Naoki , Iiyori Nobuo , Yamaki Hiroyoshi
Published: July 2002

We have been able to prove that every nonabelian Sylow subgroup of a finite group of even order contains a nontrivial element which commutes with an involution. The proof depends upon the consequences of the classification of finite simple groups.
Thickness measures for Cantor sets
Authors: Astels S.
Published: July 2002

For a fixed

k
≥
1

k\ge 1

let

C
1

,
…
,

C
k

C_1,\dots ,C_k

be generalized Cantor sets. We examine various criteria under which

C
1

+
⋯
+

C
k

C_1+\dots + C_k

contains an interval. When these criteria do not hold, we give a lower bound for the Hausdorff dimension of

C
1

+
⋯
+

C
k

C_1+\dots +C_k

. Our work will involve the development of two different types of thickness measures.
Zeta functions and counting finite p-groups
Authors: du Sautoy Marcus
Published: July 2002

We announce proofs of a number of theorems concerning finite

p
p

-groups and nilpotent groups. These include: (1) the number of

p
p

-groups of class

c
c

on

d
d

generators of order

p
n

p^n

satisfies a linear recurrence relation in

n
n

; (2) for fixed

n
n

the number of

p
p

-groups of order

p
n

p^n

as one varies

p
p

is given by counting points on certain varieties mod

p
p

; (3) an asymptotic formula for the number of finite nilpotent groups of order

n
n

; (4) the periodicity of trees associated to finite

p
p

-groups of a fixed coclass (Conjecture P of Newman and O’Brien). The second result offers a new approach to Higman’s PORC conjecture. The results are established using zeta functions associated to infinite groups and the concept of definable

p
p

-adic integrals.
Bounds for Fourier transforms of regular orbital integrals on 𝑝-adic Lie algebras
Authors: Herb Rebecca
Published: July 2002

Let

G
G

be a connected reductive

p
p

-adic group and let

g

\mathfrak g

be its Lie algebra. Let

O

\mathcal O

be a

G
G

-orbit in

g

\mathfrak g

. Then the orbital integral

μ

O

\mu _{\mathcal O}

corresponding to

O

\mathcal O

is an invariant distribution on

g

\mathfrak g

, and Harish-Chandra proved that its Fourier transform

μ
^

O

\hat \mu _{\mathcal O }

is a locally constant function on the set

g

′

\mathfrak g’

of regular semisimple elements of

g

\mathfrak g

. Furthermore, he showed that a normalized version of the Fourier transform is locally bounded on

g

\mathfrak g

. Suppose that

O

\mathcal O

is a regular semisimple orbit. Let

γ
\gamma

be any semisimple element of

g

\mathfrak g

, and let

m

\mathfrak m

be the centralizer of

γ
\gamma

. We give a formula for

μ
^

O

(
t
H
)

\hat \mu _{\mathcal O }(tH)

(in terms of Fourier transforms of orbital integrals on

m

\mathfrak m

), for regular semisimple elements

H
H

in a small neighborhood of

γ
\gamma

in

m

\mathfrak m

and

t
∈

F

×

t\in F^{\times }

sufficiently large. We use this result to prove that Harish-Chandra’s normalized Fourier transform is globally bounded on

g

\mathfrak g

in the case that

O

\mathcal O

is a regular semisimple orbit.
Classification of admissible nilpotent orbits in simple exceptional real Lie algebras of inner type
Authors: Noël Alfred
Published: July 2002

In this paper we give a classification of admissible nilpotent orbits of the noncompact simple exceptional real Lie groups of inner type. We use a lemma of Takuya Ohta and some information from the work of Dragomir Djoković to construct a simple algorithm which allows us to decide the admissiblity of a given orbit.
Functions on the model orbit in 𝐸₈
Authors: Adams Jeffrey , Huang Jing-Song , Vogan David
Published: July 2002

We decompose the ring of regular functions on the unique coadjoint orbit for complex

E

8

E_{8}

of dimension 128, finding that every irreducible representation appears exactly once. This confirms a conjecture of McGovern. We also study the unique real form of this orbit.
A Kloosterman sum in a relative trace formula for 𝐺𝐿₄
Authors: Ye Yangbo
Published: July 2002

We study a Kloosterman sum for

G

L
4

GL_4

and prove that it is equal to an exponential sum over a quadratic number field. This identity has applications in a relative trace formula for

G

L
4

GL_4

which might be used to give a new proof of quadratic base change and characterize its image.
A generalization of Springer theory using nearby cycles
Authors: Grinberg Mikhail
Published: July 2002

Let

g

\mathfrak g

be a complex semisimple Lie algebra, and

f
:

g

→
G
∖
∖

g

f : {\mathfrak {g}} \to G \backslash \backslash {\mathfrak {g}}

the adjoint quotient map. Springer theory of Weyl group representations can be seen as the study of the singularities of

f
f

. In this paper, we give a generalization of Springer theory to visible, polar representations. It is a class of rational representations of reductive groups over

C

\mathbb C

, for which the invariant theory works by analogy with the adjoint representations. Let

G

|

V

G \, | \, V

be such a representation,

f
:
V
→
G
∖
∖
V

f : V \to G \backslash \backslash V

the quotient map, and

P
P

the sheaf of nearby cycles of

f
f

. We show that the Fourier transform of

P
P

is an intersection homology sheaf on

V
∗

V^*

. Associated to

G

|

V

G \, | \, V

, there is a finite complex reflection group

W
W

, called the Weyl group of

G

|

V

G \, | \, V

. We describe the endomorphism ring

E
n
d

(
P
)

{\mathrm {End}} (P)

as a deformation of the group algebra

C

[
W
]

{\mathbb {C}} [W]

.
Uniformly quasiregular mappings of Lattès type
Authors: Mayer Volker
Published: July 2002

Using an analogy of the Lattès’ construction of chaotic rational functions, we show that there are uniformly quasiregular mappings of the

n
n

-sphere

R

¯

n

\overline {{\Bbb R}}^n

whose Julia set is the whole sphere. Moreover there are analogues of power mappings, uniformly quasiregular mappings whose Julia set is

S

n
−
1

{\Bbb S}^{n-1}

and its complement in

S

n

{\Bbb S}^{n}

consists of two superattracting basins. In the chaotic case we study the invariant conformal structures and show that Lattès type rational mappings are either rigid or form a 1-parameter family of quasiconformal deformations.
Ergodicity of conformal measures for unimodal polynomials
Authors: Prado Eduardo
Published: July 2002

Let

f
f

be a polynomial and

μ
\mu

a conformal measure for

f
f

, i.e., a Borel probability measure

μ
\mu

with Jacobian equal to

|

D
f
(
z
)

|

δ

|Df(z)|^{\delta }

. We show that if

f
f

is a real unimodal polynomial (a polynomial with just one critical point), then

μ
\mu

is ergodic. We also show that

μ
\mu

is ergodic if

f
f

is a complex unimodal polynomial with one parabolic periodic point or a quadratic polynomial in the

S
L

\mathcal {SL}

class with a priori bounds (as defined in Lyubich (1997)).
Families of Baker domains II
Authors: Rippon P. , Stallard G.
Published: July 2002

Let

f
f

be a transcendental meromorphic function and

U
U

be an invariant Baker domain of

f
f

. We use estimates for the hyperbolic metric to show that there is a relationship between the size of

U
U

and the proximity of

f
f

in

U
U

to the identity function, and illustrate this by discussing how the dynamics of transcendental entire functions of the following form vary with the parameter

a
a

:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f left-parenthesis z right-parenthesis equals a z plus b z Superscript k Baseline e Superscript negative z Baseline left-parenthesis 1 plus o left-parenthesis 1 right-parenthesis right-parenthesis as normal fraktur upper R left-parenthesis z right-parenthesis right-arrow normal infinity comma">

f
(
z
)
=
a
z
+
b

z
k

e

−
z

(
1
+
o
(
1
)
)

 as 
ℜ
(
z
)
→
∞
,

\begin{equation*} f(z) = az + bz^ke^{-z}(1+o(1)) \; \text { as } \Re (z) \rightarrow \infty , \end{equation*}

where

k
∈

N

k \in \mathbf N

,

a
≥
1

a \geq 1

and

b
>
0

b > 0

.
Nonlinear automorphisms of plane domains
Authors: Erkama Timo
Published: July 2002

We prove that the number of holomorphic nonlinear polynomials mapping a plane domain one-to-one onto itself is at most countable.
Evolution of amino acid biosynthesis and enzymes with broad
substrate specificity
Authors: Nishida Hiromi
Published: July 2002

Summary: I selected 82 proteins that were related to amino acid biosynthesis in the genome of Escherichia coli. I then searched the extensive sequence homology for each of the selected proteins from among the proteins of E.coli. The result showed that 30 proteins of the selected proteins had extensive sequence homology within the selected proteins, and 21 proteins had extensive sequence homology to proteins outside the selected proteins. In addition, the enzymes with broad substrate specificity play an important role in the amino acid biosynthesis. I demonstrate here that some substrate-specific enzymes evolved from an ancestor enzyme with broad substrate specificity.

Contact: hnishida@iam.u-tokyo.ac.jp
The novel peptide HEADY specifies apical fate in a simple radially symmetric metazoan
Authors: Lohmann Jan U. , Bosch Thomas C.G.
Published: July 2002

One of the first steps in animal development is axis formation, during which an uneven distribution of signals and/or transcription factors results in the establishment of polarity in the embryo.Hydra, one of the simplest metazoan animals, shows characteristics of a permanent embryo. Even adult polyps have a striking capacity to regenerate, suggesting that molecular mechanisms underlying de novo pattern formation are permanently active and self regulatory. Here we show that HEADY, a short, amidated peptide, plays a central role in the specification of apical fate in this simple metazoan. The HEADY gene, whose transcripts accumulate at the apical organizing center, is required for specification of apical fate, as disruption of HEADY function by dsRNA mediated interference (RNAi) results in severe defects in head formation. Conversely, an instructive role of HEADY in head specification is demonstrated by the application of synthetic HEADY peptide, which induces formation of secondary axes with head morphology. Thus, the HEADY peptide acts as developmental switch to pattern the apical-basal axis of Hydra, providing a first insight into how initial asymmetry is specified in lower metazoan animals.
Accommodating practical constraints for intensity modulated radiation therapy by means of compensators
Authors: Meyer Juergen
Published: July 2002

The thesis deals with the practical implementation of intensity modulated radiation therapy (IMRT) generated by means of patient specific metal compensators. An elaborate comparison between several compensator‐machining techniques, with respect to their suitability for production within a hospital workshop, is presented. The limitations associated with the selected compensator manufacturing technique are identified and implemented as constraints in an existing inverse treatment‐planning algorithm. In order to obtain the profile of a compensator, which produces a desired intensity distribution, inverse modeling of the radiation attenuation within the compensator is required. Two novel and independent approaches, based on deconvolution and system identification, are proposed to accomplish this. To compare the approach with the “rival” state of the art beam modulation technique, a theoretical and experimental examination of the modulated fields generated by manufactured compensators and multileaf collimators is presented. This comparison focused on the achievable resolution of the intensity modulated beams in lateral and longitudinal directions. To take into account the characteristics of a clinical environment the suitability of the most common commercially available treatment couch systems for IMRT treatments is studied. An original rule based advisory system is developed to alert the operator of any potential collision of the beam with the movable supporting structures of the treatment couch. The system is capable of finding alternative positions for the supporting frames and, if necessary, can suggest alternative beam directions. Finally, a head and neck phantom is designed for gel dosimetry to assess IMRT treatment delivery techniques. The phantom is based on a simplistic but realistic design and contains the main anatomical features.
Favorable noise uniformity properties of Fourier‐based interpolation and reconstruction approaches in single‐slice helical computed tomography
Authors: La Rivière Patrick J. , Pan Xiaochuan
Published: July 2002

Volumes reconstructed by standard methods from single‐slice helical computed tomography (CT) data have been shown to have noise levels that are highly nonuniform relative to those in conventional CT. These noise nonuniformities can affect low‐contrast object detectability and have also been identified as the cause of the zebra artifacts that plague maximum intensity projection (MIP) images of such volumes. While these spatially variant noise levels have their root in the peculiarities of the helical scan geometry, there is also a strong dependence on the interpolation and reconstruction algorithms employed. In this paper, we seek to develop image reconstruction strategies that eliminate or reduce, at its source, the nonuniformity of noise levels in helical CT relative to that in conventional CT. We pursue two approaches, independently and in concert. We argue, and verify, that Fourier‐based longitudinal interpolation approaches lead to more uniform noise ratios than do the standard 360LI and 180LI approaches. We also demonstrate that a Fourier‐based fan‐to‐parallel rebinning algorithm, used as an alternative to fanbeam filtered backprojection for slice reconstruction, also leads to more uniform noise ratios, even when making use of the 180LI and 360LI interpolation approaches.
Considerations of anthropometric, tissue volume, and tissue mass scaling for improved patient specificity of skeletal S values
Authors: Bolch W. E. , Patton P. W. , Shah A. P. , Rajon D. A. , Jokisch D. W.
Published: July 2002

It is generally acknowledged that reference man (70 kg in mass and 170 cm in height) does not adequately represent the stature and physical dimensions of many patients undergoing radionuclide therapy, and thus scaling of radionuclide S values is required for patient specificity. For electron and beta sources uniformly distributed within internal organs, the mean dose from self‐irradiation is noted to scale inversely with organ mass, provided no escape of electron energy occurs at the organ boundaries. In the skeleton, this same scaling approach is further assumed to be correct for marrow dosimetry; nevertheless, difficulties in quantitative assessments of marrow mass in specific skeletal regions of the patient make this approach difficult to implement clinically. Instead, scaling of marrow dose is achieved using various anthropometric parameters that presumably scale in the same proportion. In this study, recently developed three‐dimensional macrostructural transport models of the femoral head and humeral epiphysis in three individuals (51‐year male, 82‐year female, and 86‐year female) are used to test the abilities of different anthropometric parameters (total body mass, body surface area, etc.) to properly scale radionuclide S values from reference man models. The radionuclides considered are and localized in either the active marrow or endosteal tissues of the bone trabeculae. S value scaling is additionally conducted in which the 51‐year male subject is assigned as the reference individual; scaling parameters are then expanded to include tissue volumes and masses for both active marrow and skeletal spongiosa. The study concludes that, while no single anthropometric parameter emerges as a consistent scaler of reference man S values, lean body mass is indicated as an optimal scaler when the reference S values are based on 3D transport techniques. Furthermore, very exact patient‐specific scaling of radionuclide S values can be achieved if measurements of spongiosa volume and marrow volume fraction (high‐resolution CT with image segmentation) are known in both the patient and the reference individual at skeletal sites for which dose estimates are sought. However, the study indicates that measurements of the spongiosa volume alone may be sufficient for reasonable patient‐specific scaling of S values for the majority of radionuclides of interest in internal‐emitter therapy.
Absorbed dose conversion factors for therapeutic kilovoltage and megavoltage x‐ray beams calculated by the Monte Carlo method
Authors: Knight Richard T.
Published: July 2002

This thesis describes techniques for performing calculations of the backscatter factor, B, and the ratio of mean mass energy absorption coefficients water‐to‐air, for kilovoltage x‐ray beams, and the ratio of mean stopping powers water‐to‐air, for megavoltage x‐ray beams, through application of the Monte Carlo method. Consistent theoretical expressions for absorbed dose to water, in low‐ and medium‐energy x‐rays have been proposed. Bremsstrahlung spectra were calculated by detailed Monte Carlo simulations of the U.K. National Physical Laboratory (NPL)standard accelerator, a Philips SL series accelerator and a Siemens Stabilipan x‐ray unit. Values of polyenergetic were calculated by a kerma‐weighted averaging technique which utilizes precalculated monoenergetic values and primary fluence spectra. Comprehensive sets of data for and are presented, appropriate for insertion into the proposed expressions for Values of the Spencer–Attix were calculated for the accelerator beams by a dose‐weighted averaging technique which utilizes precalculated monoenergetic dose distributions and primary fluence spectra. Accurate values of accounting for spectrum quality shift off‐axis, were acquired by convolving water terma distributions with point‐energy‐deposition kernels. The beam quality dependence of the NPL absorbed dose‐to‐water calibration factor, was subsequently investigated.
Use of asymmetric fan‐beam transmission computed tomography for attenuation correction of cardiac SPECT imaging
Authors: Hollinger Edward F.
Published: July 2002

Photon attenuation is often the largest source of infidelity in cardiac single photon emission computed tomography (SPECT). This investigation evaluates the feasibility of using an asymmetric fan‐beam transmission CT (AsF–TCT), acquired immediately before or after the emission computed tomogram (ECT), to correct for photon attenuation in cardiac SPECT. AsF–TCTs are reconstructed to generate patient‐specific attenuation maps. The maps are used with an iterative maximum‐likelihood algorithm to reconstruct attenuation‐corrected (AC) SPECT images. AsF attenuation correction significantly improves the accuracy of images of a cardiac‐thorax phantom modeling a large patient with a normal myocardial perfusion study. Similar improvements in image uniformity are obtained for patient studies. Using a high‐activity line source and rapid camera rotation, a suitable attenuation map is obtained with a four minute transmission acquisition; shorter acquisitions could be used for SPECT systems with higher count‐rate performance. Misregistration between the ECT and TCT can create artifacts in the reconstructed AC images, with lateral patient shifts as small as 2–3 cm causing severe artifacts. Axial, anterior‐posterior, and rotational misregistrations require larger shifts before artifacts become significant. Finally, applying AC improves assessments of both defect size and severity. Without AC, cardiac SPECT can significantly over‐estimate the size of perfusion defects, particularly in the septum and inferior wall of the left ventricle. AC improves estimates of lesion severity and results in better contrast between adjacent normal and defect regions. This investigation demonstrates that AsF–TCT is a viable technique for attenuation correction for cardiac SPECT, and may improve the diagnostic accuracy of this modality.
The analysis and interpretation of some special properties of higher order symmetric Lamb waves: The case for plates
Authors: Werby M. F. , Überall H.
Published: July 2002

Results derived from exact linear homogeneous elastodynamic theory are used for two-dimensional unloaded plates in order to understand certain features generated by proper symmetric Lamb modes. It is shown that S1 modes for all elastic materials have a phase velocity defined below the usual critical frequency and which initially exhibits anomalous dispersion (has a negative slope with respect to frequency). Over a certain range, it has a phase velocity that is double valued. In addition, there are an infinite number of proper symmetric Lamb modes that have this characteristic for materials with a Poisson ratio equal to 1/3. It also appears that all A3n modes are anomalous when VL⩽2VT. The cause and implication of these effects are examined, including an associated negative group velocity over a small frequency zone for these modes. Further, it is noted that all proper symmetric Lamb modes have a plateau region in phase velocity with respect to wave number. It is shown that this always occurs for a phase velocity corresponding to the longitudinal bulk velocity of the elastic material. These issues are examined along with how one may obtain material parameters and possibly plate thickness from their dispersion curves.
Temporal and spatio-temporal vibrotactile displays for voice fundamental frequency: An initial evaluation of a new vibrotactile speech perception aid with normal-hearing and hearing-impaired individuals
Authors: Auer Edward T. , Bernstein Lynne E. , Coulter David C.
Published: July 2002

Four experiments were performed to evaluate a new wearable vibrotactile speech perception aid that extracts fundamental frequency (F0) and displays the extracted F0 as a single-channel temporal or an eight-channel spatio-temporal stimulus. Specifically, we investigated the perception of intonation (i.e., question versus statement) and emphatic stress (i.e., stress on the first, second, or third word) under Visual-Alone (VA), Visual-Tactile (VT), and Tactile-Alone (TA) conditions and compared performance using the temporal and spatio-temporal vibrotactile display. Subjects were adults with normal hearing in experiments I–III and adults with severe to profound hearing impairments in experiment IV. Both versions of the vibrotactile speech perception aid successfully conveyed intonation. Vibrotactile stress information was successfully conveyed, but vibrotactile stress information did not enhance performance in VT conditions beyond performance in VA conditions. In experiment III, which involved only intonation identification, a reliable advantage for the spatio-temporal display was obtained. Differences between subject groups were obtained for intonation identification, with more accurate VT performance by those with normal hearing. Possible effects of long-term hearing status are discussed.
Cortical representation of spatiotemporal pattern of firing evoked by echolocation signals: Population encoding of target features in real time
Authors: Palakal Mathew J. , Wong Donald
Published: July 2002

Target perception in echolocating bats entails the generation of an acoustic image of the target in the auditory cortex. By integrating information conveyed in the sequence of acoustic echoes, the population of cortical neurons in hypothesized to encode different target features based on its spatiotemporal pattern of neural-spike firing during the course of echolocation. A biologically plausible approach to the cortical representation of target features is employed by using electrophysiological data recorded from the auditory cortex of the FM bat, Myotis lucifugus. A single-neuron model of delay-sensitive neurons is first approximated by the formulation of a Gaussian function with different variables to represent the delay-tuning properties of individual cortical neurons. A cortical region consisting of delay-sensitive neurons organized topographically according to best frequency (i.e., tontopically organized) is then modeled with multiple layers of the single-neuron model. A mechanism is developed to represent and encode the responses of these neurons based on time-dependent, incoming echo signals. The time-varying responses of the population of neurons are mapped spatially on the auditory-cortical surface as a cortical response map (CORMAP). The model is tested using phantom targets with single and multiple glints. These simulation results provide further validation of the current auditory framework as a biomimetic mechanism for capturing time-varying, acoustic stimuli impinging in the bat's ears, and the neural representation of acoustic stimulus features by saptiotemporal-firing patterns in the cortical population.
Direct Measurement of Hole Error for Viscoelastic Fluids in Flow Between Infinite Parallel Plates
Authors: Novotny E. J. , Eckert Roger E.
Published: July 2002

For viscoelastic fluids the use of a “pressure tap” to measure the normal stress on a channel wall can lead to large errors. In previous studies the true normal stress on the wall was theoretically predicted or indirectly measured and compared to the erroneous measurements. Here pressure transducers are flush mounted on a rectangular channel approximating infinite parallel plates so that the true stress on the wall can be measured experimentally. A transducer is recessed to create a hole; the reading thus obtained is compared with the true stress to determine the hole error. Solutions of 0.9, 2, and 3% Polyox (polyethylene oxide, MW=4,000,000) in water were studied. Shear rates reached 17,000 sec−1 and hole errors up to 6000 dynes/cm3 were found. In the region of creeping flow, the hole error is equal to −0.16 of the primary normal stress difference. Hole errors have been determined at Reynolds numbers from 10−4 to 103 and at the higher values cross zero and become positive, as they are for Newtonian fluids. A mechanism is presented which explains this behavior of viscoelastic fluids over the seven cycle range of Reynolds number.
The application of the multipass rheometer to time-dependent capillary flow measurements of a polyethylene melt
Authors: Ranganathan M. , Mackley M. R. , Spitteler P. H. J.
Published: July 2002

This communication presents experimental data on the time-dependent capillary flow measurements for a high-density polyethylene using a newly developed multipass rheometer (MPR). The experimental data consist of precision pressure measurements on the MPR, which has well-defined fully constrained boundary conditions. A model developed previously by Molenaar and Koopmans [Molenaar, J. and R. J. Koopmans, J. Rheol. 38, 99–109 (1994)] and incorporating melt compressibility has been adapted to suit the MPR boundary conditions and is shown to give good agreement with the experimental data without necessitating the use of any arbitrary adjustable parameters. The results, in particular, show that the experimentally observed pressure relaxation on cessation of the piston movement can be almost entirely attributed to the compressibility of the melt alone and this conclusion is consistent with the findings reported by Hatzikiriakos and Dealy [Hatzikiriakos, S. G. and J. M. Dealy, Polym. Eng. Sci. 34, 493–499 (1994)] for related time- dependent extrusion experimental observations using a conventional capillary rheometer.
Nanoconfinement Synthesis of Ultrasmall Bismuth Oxyhalide Nanocrystals with Size‐Induced Fully Reversible Potassium‐Ion Storage and Ultrahigh Volumetric Capacity
Authors: Hao Guolin , Zhang Chan , Chen Zhonghui , Xu Yuxi
Published: March 2022

Bismuth oxyhalide (BiOX, X = Cl, Br, I) nanomaterials have attracted enormous attention because their unique layered structure and nano‐size effect endows them with fascinating physicochemical properties and wide application potential. However, synthesis of ultrasmall BiOX nanocrystals with sizes down to sub‐10 nm remains a considerable challenge and the investigation of such ultrasmall BiOX nanocrystals in alkali‐metal ion batteries have not yet been explored so far. The fabrication of ultrasmall BiOX nanocrystals with an average size of 6 nm on reduced graphene oxide by a versatile nanoconfinement strategy is reported here. The obtained ultrasmall BiOCl nanocrystals‐based monolithic composites are evaluated as free‐standing anodes for potassium‐ion batteries (PIBs) and exhibit the highest reversible capacity of 521 mAh g−1 at 0.05 A g−1 among all reported Bi‐based PIB anodes and ultrahigh volumetric capacity of 1148 mAh cm‐3, along with excellent rate capability (205 mAh g−1 at 5 A g−1 ) and extraordinary cycling stability with 94.7% capacity retention after 3000 cycles. More importantly, a fully reversible potassium storage mechanism of BiOCl (BiOCl ↔ Bi ↔ K3Bi) induced by the ultrasmall nano‐size effect is revealed for the first time by detailed characterizations, providing new fundamental insights for boosting the electrochemical performance of nanostructured materials.
Influence of Dimensionality on the Charge Density Wave Phase of 2H‐TaSe2
Authors: Chowdhury Sugata , Rigosi Albert F. , Hill Heather M. , Briggs Andrew , Newell David B. , Berger Helmuth , Hight Walker Angela R. , Tavazza Francesca
Published: March 2022

Metallic transition metal dichalcogenides like tantalum diselenide (TaSe2) exhibit exciting behaviors at low temperatures, including the emergence of charge density wave (CDW) states. In this work, density functional theory (DFT) is used to catalog influences of van der Waals interactions and reduced dimensionality on the CDW atomic structures as a function of thickness, with the former effect being most strongly present between the layers of bulk TaSe2, slightly reduced in few‐layer TaSe2, and effectively absent in monolayer (1L) TaSe2. To support the validity of the DFT models, experimental Raman data are provided for monolayer, bilayer, and bulk TaSe2 in the spectral range 165–215 cm−1. The phonons seen in the experimental Raman spectra are compared with the results calculated from the DFT models as a function of temperature and layer number. The matching of data and calculations substantiates the model's description of the CDW structural formation as a function of thickness, which is shown in depth for 1L through 6L systems. These results highlight the importance of understanding interlayer interactions, which are pervasive in many quantum phenomena involving 2D confinement.
Optimal Discrimination of Two Nonorthogonal States by Continuous Probing and Feedback Operation
Authors: Xu Peng , Zhao Peng , Zhao Shengmei
Published: March 2022

For a quantum system prepared probabilistically on two or more non‐orthogonal states, the observer cannot discriminate the initial preparation perfectly. Kurt Jacobs [Quantum Inf. Comput. 2007, 7, 127] introduced a measurement operator that could increase the rate of information obtained using a continuous measurement scheme. However, the better effect happens at the expense of reducing the total information from the quantum system. To address this problem, an optimal operator that could yield the maximal value of mutual information for a long‐time measurement is found. Particularly, it turns out that the error probability is minimized for any measurement moment by measuring the optimal operator. Furthermore, for a given finite measurement time, a measurement scheme to maximize the obtained mutual information is presented. It is shown that while the Jacobs' operator should be used for a short‐time case, for a long‐time limit, the proposed optimal operator should be employed. For a given finite duration, the proposal could determine the optimal measurement operator that maximizes the final value of mutual information.
Surface disinfection influences the antioxidant capacity and GABA content of saline‐treated brown rice (Oryza sativa L.)
Authors: Toyoizumi Tomoyasu , Ikegaya Atsushi , Kosugi Toru
Published: March 2022

Background and Objective

Saline‐induced osmotic stress can help enhance the functionality of brown rice (BR; Oryza sativa L.); moreover, it can increase the antioxidant capacity and gamma‐aminobutyric acid (GABA) content in BR. Therefore, the aim of this study was to examine the effect of surface disinfection on the antioxidant capacity and GABA content of saline‐treated BR.

Findings

GABA content of nondisinfected BR decreased significantly with increasing salinity. In contrast, GABA content and hydrophilic antioxidant capacity of disinfected BR increased with increasing salinity up to 1.0% w/v, as evidenced by the increase in 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and oxygen radical absorbance capacity values, and total phenolic content of disinfected BR. Additionally, the amino acid and protein contents of both disinfected and nondisinfected BR were significantly affected by saline treatments.

Conclusions

Overall, the findings of this study showed that soaking disinfected BR in saline solutions (0.5%–1% w/v) can increase hydrophilic antioxidant capacity and GABA content without negatively affecting metabolic processes.

Significance and Novelty

Our findings provide the validation of basic food processing steps for the enhancement of BR functionality via saline treatment.
Minimized feature overhead malware detection machine learning model employing MRMR‐based ranking
Authors: Singh Priyanka , Borgohain Samir Kumar , Sharma Lakhan Dev , Kumar Jayendra
Published: March 2022

To deal with the huge amount of data, minimizing the overhead will play a key role in speedy and efficient malware detection. We propose a machine learning (ML) malware detection model with preprocessing to limit the feature overhead. The portable‐executable (PE) header information that retains meaningful and distinctive information has been considered to classify benign and malware files. The dataset is preprocessed by applying transformation, outlier detection and filling, and smoothing techniques. A maximum relevance minimum redundancy‐based feature selection method is deployed to assign the rank and score to each feature retaining the maximum relevant and minimal redundant information. Based on the obtained rank, many subsets of features have been created and investigated against support vector machine (SVM) and k‐nearest neighbors (k‐NN) with parametric tuning. The proposed ML model integrated with data preprocessing, feature selection, and SVM‐polynomial classifier has superior performance. This model is eliminating 63.8% feature overhead with accuracy above 99.1% for the benchmark datasets. To examine the robustness of the proposed model, new balanced and imbalanced datasets are created using new malware. The test results are encouraging with accuracy and specificity above 96.68%, 97.65%, and 91.57%, respectively. Interestingly, the proposed model is not trained using the newly created dataset.
Predicting required and voluntary employee green behavior using the theory of planned behavior
Authors: Khalid Bilal , Shahzad Khurram , Shafi Muhammad Qaiser , Paille Pascal
Published: March 2022

Employee green behavior research has not focused on its holistic examination from the perspective of the environmental theory of planned behavior and bridging of green intention–behavior gap. This study examines the impact of employee green attitude, green subjective norms, and green perceived behavioral control on both required (in‐role) and voluntary (extra‐role) employee green behavior through green behavioral intention. The moderating role of perceived organizational support toward the environment has also been examined in the intention–behavior relationship. Multisource data was collected from 720 employees and their 72 supervisors in three time‐lags and was analyzed through structural equation modeling. Results show that employee green attitude, green subjective norm, and green perceived behavioral control positively influence employees' both required and voluntary green behavior indirectly through their green behavioral intention. Also, perceived organizational support toward the environment strengthens the positive effect of employee green behavioral intention on their required and voluntary green behavior.