bluuebunny/crossref_metadata_2025 huggingface dataset:
Zeros of Dedekind zeta functions in the critical strip
Authors: Tollis Emmanuel
Published: July 2002

In this paper, we describe a computation which established the GRH to height

92
92

(resp.

40
40

) for cubic number fields (resp. quartic number fields) with small discriminant. We use a method due to E. Friedman for computing values of Dedekind zeta functions, we take care of accumulated roundoff error to obtain results which are mathematically rigorous, and we generalize Turing’s criterion to prove that there is no zero off the critical line. We finally give results concerning the GRH for cubic and quartic fields, tables of low zeros for number fields of degree

5
5

and

6
6

, and statistics about the smallest zero of a number field.
Existence and uniqueness of traveling waves and error estimates for Godunov schemes of conservation laws
Authors: Fan Haitao
Published: July 2002

The existence and uniqueness of the Lipschitz continuous traveling wave of Godunov’s scheme for scalar conservation laws are proved. The structure of the traveling waves is studied. The approximation error of Godunov’s scheme on single shock solutions is shown to be

O
(
1
)
Δ
x

O(1)\Delta x

.
Numerical evaluation of a symmetric potential function
Authors: Carmack Lori
Published: July 2002

We discuss the numerical evaluation of a symmetric potential function which arises naturally in applications. We present a method designed to accurately and efficiently compute this integral, and compare the performance of this method with two other popular techniques. This method requires considerably fewer function evaluations than all other techniques we tested, and is applicable to any integral which can be expressed in terms of complete elliptic integrals.
Detecting perfect powers in essentially linear time
Authors: Bernstein Daniel
Published: July 2002

This paper (1) gives complete details of an algorithm to compute approximate

k
k

th roots; (2) uses this in an algorithm that, given an integer

n
>
1

n>1

, either writes

n
n

as a perfect power or proves that

n
n

is not a perfect power; (3) proves, using Loxton’s theorem on multiple linear forms in logarithms, that this perfect-power decomposition algorithm runs in time

(
log
⁡
n

)

1
+
o
(
1
)

(\log n)^{1+o(1)}

.
The translation planes of order 49 and their automorphism groups
Authors: Charnes C. , Dempwolff U.
Published: July 2002

Using isomorphism invariants, we enumerate the translation planes of order 49 and determine their automorphism groups.
Asymptotic upper bounds for the coefficients in the Chebyshev series expansion for a general order integral of a function
Authors: Flyer Natasha
Published: July 2002

The usual way to determine the asymptotic behavior of the Chebyshev coefficients for a function is to apply the method of steepest descent to the integral representation of the coefficients. However, the procedure is usually laborious. We prove an asymptotic upper bound on the Chebyshev coefficients for the

k

t
h

k^{th}

integral of a function. The tightness of this upper bound is then analyzed for the case

k
=
1

k=1

, the first integral of a function. It is shown that for geometrically converging Chebyshev series the theorem gives the tightest upper bound possible as

n
→
∞

n\rightarrow \infty

. For functions that are singular at the endpoints of the Chebyshev interval,

x
=
±
1

x=\pm 1

, the theorem is weakened. Two examples are given. In the first example, we apply the method of steepest descent to directly determine (laboriously!) the asymptotic Chebyshev coefficients for a function whose asymptotics have not been given previously in the literature: a Gaussian with a maximum at an endpoint of the expansion interval. We then easily obtain the asymptotic behavior of its first integral, the error function, through the application of the theorem. The second example shows the theorem is weakened for functions that are regular except at

x
=
±
1

x=\pm 1

. We conjecture that it is only for this class of functions that the theorem gives a poor upper bound.
Gaps between integers with the same prime factors
Authors: Cochrane Todd , Dressler Robert
Published: July 2002

We give numerical and theoretical evidence in support of the conjecture of Dressler that between any two positive integers having the same prime factors there is a prime. In particular, it is shown that the abc conjecture implies that the gap between two consecutive such numbers

a
>
c

a >c

is

≫

a

1

/

2
−
ϵ

\gg a^{1/2 - \epsilon }

, and it is shown that this lower bound is best possible. Dressler’s conjecture is verified for values of

a
a

and

c
c

up to

7
⋅

10

13

7\cdot 10^{13}

.
Tight closure
Authors: Bruns Winfried
Published: July 2002

The theory of tight closure was created by Mel Hochster and Craig Huneke about ten years ago. Assisted by numerous contributions of others, they have continuously developed the theory since then. ‘Tight closure’ can now be regarded as a synonym for ‘characteristic

p
p

methods in commutative algebra’. It ties several strands of commutative algebra and algebraic geometry together: invariant theory, rational singularities, the Briançon–Skoda theorem, the ‘homological conjectures’, big Cohen–Macaulay modules and algebras, and various other topics.
Factorization and approximation problems for matrix functions
Authors: Peller V.
Published: July 2002

We study maximizing vectors of Hankel operators with matrix-valued symbols. This study leads to a solution of the so-called recovery problem for unitary-valued functions and to a new approach to Wiener–Hopf factorizations for functions in a function space

X
X

satisfying natural conditions. Finally, we improve earlier results of Peller and Young on hereditary properties of the operator of superoptimal approximation by analytic matrix functions.
The Nash conjecture for threefolds
Authors: Kollár János
Published: July 2002

Nash conjectured in 1952 that every compact differentiable manifold can be realized as the set of real points of a real algebraic variety which is birational to projective space. This paper announces the negative solution of this conjecture in dimension 3. The proof shows that in fact very few 3-manifolds can be realized this way.
On quantum de Rham cohomology theory
Authors: Cao Huai-Dong , Zhou Jian
Published: July 2002

We define the quantum exterior product

∧
h

\wedge _h

and quantum exterior differential

d
h

d_h

on Poisson manifolds. The quantum de Rham cohomology, which is a deformation quantization of the de Rham cohomology, is defined as the cohomology of

d
h

d_h

. We also define the quantum Dolbeault cohomology. A version of quantum integral on symplectic manifolds is considered and the corresponding quantum Stokes theorem is stated. We also derive the quantum hard Lefschetz theorem. By replacing

d
d

by

d
h

d_h

and

∧
\wedge

by

∧
h

\wedge _h

in the usual definitions, we define many quantum analogues of important objects in differential geometry, e.g. quantum curvature. The quantum characteristic classes are then studied along the lines of the classical Chern-Weil theory. The quantum equivariant de Rham cohomology is defined in the similar fashion.
On Bojarski’s index formula for nonsmooth interfaces
Authors: Mitrea Marius
Published: July 2002

Let

D
D

be a Dirac type operator on a compact manifold

M

{\mathcal {M}}

and let

Σ
\Sigma

be a Lipschitz submanifold of codimension one partitioning

M

{\mathcal {M}}

into two Lipschitz domains

Ω

±

\Omega _{\pm }

. Also, let

H

±

p

(
Σ
,
D
)

{\mathcal {H}}^{p}_{\pm }(\Sigma ,D)

be the traces on

Σ
\Sigma

of the (

L

p

L^{p}

-style) Hardy spaces associated with

D
D

in

Ω

±

\Omega _{\pm }

. Then
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis script upper H Subscript minus Superscript p Baseline left-parenthesis normal upper Sigma comma upper D right-parenthesis comma script upper H Subscript plus Superscript p Baseline left-parenthesis normal upper Sigma comma upper D right-parenthesis right-parenthesis">

(

H

−

p

(
Σ
,
D
)
,

H

+

p

(
Σ
,
D
)
)

({\mathcal {H}}^{p}_{-}(\Sigma ,D),{\mathcal {H}}^{p}_{+}(\Sigma ,D))

is a Fredholm pair of subspaces for

L

p

(
Σ
)

L^{p}(\Sigma )

(in Kato’s sense) whose index is the same as the index of the Dirac operator

D
D

considered on the whole manifold

M

{\mathcal {M}}

.
Powers of positive polynomials and codings of Markov chains onto Bernoulli shifts
Authors: Marcus Brian , Tuncel Selim
Published: July 2002

We give necessary and sufficient conditions for a Markov chain to factor onto a Bernoulli shift (i) as an eventual right-closing factor, (ii) by a right-closing factor map, (iii) by a one-to-one a.e. right-closing factor map, and (iv) by a regular isomorphism. We pass to the setting of polynomials in several variables to represent the Bernoulli shift by a nonnegative polynomial

p
p

in several variables and the Markov chain by a matrix

A
A

of such polynomials. The necessary and sufficient conditions for each of (i)–(iv) involve only an eigenvector

r
r

of

A
A

and basic invariants obtained from weights of periodic orbits. The characterizations of (ii)–(iv) are deduced from (i). We formulate (i) as a combinatorial problem, reducing it to certain state-splittings (partitions) of paths of length

n
n

. In terms of positive polynomial masses associated with paths, the aim then becomes the construction of partitions so that the masses of the paths in each partition element sum to a multiple of

p
n

p^n

, the multiple being prescribed by

r
r

. The construction, which we sketch, relies on a description of the terms of

p
n

p^n

and on estimates of the relative sizes of the coefficients of

p
n

p^n

.
Exponential sums with multiplicative coefficients
Authors: Bachman Gennady
Published: July 2002

We provide estimates for the exponential sum

F
(
x
,
α
)
=

∑

n
≤
x

f
(
n
)

e

2
π
i
α
n

,

\begin{equation*}F(x,\alpha )=\sum _{n\le x} f(n)e^{2\pi i\alpha n}, \end{equation*}

where

x
x

and

α
\alpha

are real numbers and

f
f

is a multiplicative function satisfying

|

f

|

≤
1

|f|\le 1

. Our main focus is the class of functions

f
f

which are supported on the positive proportion of primes up to

x
x

in the sense that

∑

p
≤
x

|

f
(
p
)

|

/

p
≫
log
⁡
log
⁡
x

\sum _{p\le x}|f(p)|/p\gg \log \log x

. For such

f
f

we obtain rather sharp estimates for

F
(
x
,
α
)

F(x,\alpha )

by extending earlier results of H. L. Montgomery and R. C. Vaughan. Our results provide a partial answer to a question posed by G. Tenenbaum concerning such estimates.
The Dynkin diagram 𝑅-group
Authors: Pascovici Dana
Published: July 2002

We define an abelian group from the Dynkin diagram of a split real linear Lie group with abelian Cartan subgroups,

G
G

, and show that the

R

δ
,
0

R_{\delta , 0}

-groups defined by Knapp and Stein are subgroups of it. The proof relies on Vogan’s approach to the

R
R

-groups. The

R
R

-group of a Dynkin diagram is easily computed just by looking at the diagram, and so it gives, for instance, quick proofs of the fact that the principal series with zero infinitesimal character of the split groups

E
6

E_6

,

E
8

E_8

,

G
2

G_2

or

F
4

F_4

are irreducible. The Dynkin diagram subgroup also implicitly describes a small Levi subgroup, which we hope might play a role in computing regular functions on principal nilpotent orbits. We present in the end a conjecture and some evidence in this direction.
On the 𝔫-cohomology of limits of discrete series representations
Authors: Soergel Wolfgang
Published: July 2002

Using localization we translate the problem of computing the

n

\mathfrak {n}

-cohomology of limits of discrete series representations into a problem about the combinatorics of Weyl groups.
Nilpotent orbits and theta-stable parabolic subalgebras
Authors: Noël Alfred
Published: July 2002

In this work, we present a new classification of nilpotent orbits in a real reductive Lie algebra

g

{\mathfrak {g}}

under the action of its adjoint group. Our classification generalizes the Bala-Carter classification of the nilpotent orbits of complex semisimple Lie algebras. Our theory takes full advantage of the work of Kostant and Rallis on

p

C

{\mathfrak {p}}_{{}_{\mathbb {C}}}

, the “complex symmetric space associated with

g

{\mathfrak {g}}

”. The Kostant-Sekiguchi correspondence, a bijection between nilpotent orbits in

g

{\mathfrak {g}}

and nilpotent orbits in

p

C

{\mathfrak {p}}_{{}_{\mathbb {C}}}

, is also used. We identify a fundamental set of noticed nilpotents in

p

C

{\mathfrak {p}}_{{}_{\mathbb {C}}}

and show that they allow us to recover all other nilpotents. Finally, we study the behaviour of a principal orbit, that is an orbit of maximal dimension, under our classification. This is not done in the other classification schemes currently available in the literature.
Thirty-three yes or no questions about mappings, measures, and metrics
Authors: Heinonen Juha , Semmes Stephen
Published: July 2002

We display thirty-three questions of geometric nature. Most of the problems are of fairly recent origin, and the formulation of each problem is such that it can be answered by one word only.
Branch sets of uniformly quasiregular maps
Authors: Martin G.
Published: July 2002

Let

n
≥
2

n\geq 2

and

f
:

S

n

→

S

n

f: {\Bbb S}^n\to {\Bbb S}^n

be a quasiregular mapping with branch set

B
f

B_f

, the set where

f
f

fails to be locally injective. We show that there is a quasiregular mapping

g
:

S

n

→

S

n

g: {\Bbb S}^n\to {\Bbb S}^n

with

B
g

=

B
f

B_g = B_f

and such that

g
g

can be chosen to be conformal (rational) with respect to some measurable Riemannian structure on

S

n

{\Bbb S}^n

. Hence

g
g

is uniformly quasiregular. That is,

g
g

and all its iterates are quasiregular with a uniform bound on the dilatation.
The localization and interactions of huntingtin
Authors: Jones A. Lesley
Published: July 2002

Huntingtin was localized by using a series of antibodies that detected different areas of the protein from the immediate N–terminus to the C–terminal region of the protein. The more C–terminal antibodies gave a cytoplasmic localization in neurons of the brain in controls and cases of Huntington'sdisease (HD). The N–terminal antibody, however, gave a distinctive pattern of immunoreactivity in the HD brain, with marked staining of axon tracts and white matter and the detection of densely staining intranuclear inclusions. This implies some processing differences between mutated and normal huntingtin. We have also localized two interacting proteins, cystathionine β–synthase and the nuclear receptor co–repressor (N–CoR), in brain. Cystathionine beta–synthase was not relocalized in HD brain, but the N–CoR was excluded from neuronal nuclei in HD brain, and a further protein that exists in the same repression complex, mSin3, was similarly excluded. We conclude that the co–repressor might have a part in HD pathology.
Can wave–particle duality be based on the uncertainty relation?
Authors: Dürr Stephan , Rempe Gerhard
Published: July 2002

Wave and particle properties of a quantum object cannot be observed simultaneously. In particular, the fringe visibility in an interferometer is limited by the amount of which-way information which can be obtained. This limit is set by the recently discovered duality relation. So far, all derivations of the duality relation are independent of Heisenberg’s uncertainty relation. Here we demonstrate that it is alternatively possible to derive the duality relation in the form of an uncertainty relation for some suitably chosen observables.
Multiple representations of work–energy processes
Authors: Van Heuvelen Alan , Zou Xueli
Published: July 2002

An energy process can be represented by verbal, pictorial, bar chart, and mathematical representations. This multiple-representation method for work–energy processes has been introduced and used in the work–energy part of introductory college physics courses. Assessment indicates that the method, especially the qualitative work–energy bar charts, serves as a useful visual tool to help students understand work–energy concepts and to solve related problems. This paper reports how the method has been used to teach work–energy concepts, student attitudes toward this approach, and their performance on work–energy problems.
A numerical model for the low frequency diffuse field sound transmission loss of double-wall sound barriers with elastic porous linings
Authors: Sgard F. C. , Atalla N. , Nicolas J.
Published: July 2002

This paper discusses the prediction of the low frequency diffuse field transmission loss through double-wall sound barriers with elastic porous linings. The studied sound barriers are made up from a porous-elastic decoupling material sandwiched between an elastic skin and a septum. The prediction approach is based on a finite element model for the different layers of the sound barrier coupled to a variational boundary element method to account for fluid loading. The diffuse field is modeled as a combination of uncorrelated freely propagating plane waves with equal amplitude, no two of which are traveling in the same direction. The corresponding vibroacoustic indicators are calculated efficiently using a Gauss integration scheme. Also, a power balance is presented to explain the dissipation mechanisms in the different layers. Typical results showing the effects on the transmission loss of several parameters such as the septum mass, the decoupling porous layer properties and the multi-layer mounting conditions are presented.
The influence of substructure modeling on the structural-acoustic response of a plate system
Authors: Shepard W. Steve , Cunefare Kenneth A.
Published: July 2002

Changes in the vibro-acoustic response of a fluid-loaded plate due to variations in some of the modeling details associated with an attached substructure are examined. The attached substructure consists of a smaller plate supported by springs along each edge. To examine the important modeling issues, three studies are performed. In the first study, discrete changes in the system response due to discrete changes in the size of the region over which the spring elasticity is distributed are examined. In the second study, substructure modeling issues are examined by varying the number of degrees-of-freedom included in the substructure model. Finally, sensitivity relationships that express changes in the system response to changes in the scale of the spring elements are developed. These relationships are used to examine changes in the system response due to small variations in the scale of the distributed elasticity. Both the combined system response and acoustic radiation are computed using the Acoustic Surface Variational Principle and Hamilton’s Principle. For the example cases considered, it is shown that details associated with the scale of the spring are only important for frequencies near or below the resonances of the isolated subsystem. Furthermore, only the dynamics of the substructure including rigid-body type motions are important.
Adaptive tuning of an electrodynamically driven thermoacoustic cooler
Authors: Li Yaoyu , Minner Brian L. , Chiu George T.-C. , Mongeau Luc , Braun James E.
Published: July 2002

The commercial development of thermoacoustic coolers has been hampered in part by their low efficiencies compared to vapor compression systems. A key component of electrodynamically driven coolers is the electromechanical transducer, or driver. The driver’s electroacoustic transduction efficiency, defined as the ratio of the acoustic power delivered to the working gas by the moving piston and the electrical power supplied, must be maintained near its maximum value if a high overall system efficiency is to be achieved. Modeling and experiments have shown that the electroacoustic efficiency peaks sharply near the resonance frequency of the electro-mechano-acoustic system. The optimal operating frequency changes as the loading condition changes, and as the properties of the working gas vary. The driver efficiency may thus drop significantly during continuous operation at a fixed frequency. In this study, an on-line driver efficiency measurement scheme was implemented. It was found that the frequency for maximum electroacoustic efficiency does not precisely match any particular resonance frequency, and that the efficiency at resonance can be significantly lower than the highest achievable efficiency. Therefore, a direct efficiency measurement scheme was implemented and validated using a functional thermoacoustic cooler. An adaptive frequency-tuning scheme was then implemented. Experiments were performed to investigate the effectiveness of the control scheme to maintain the maximum achievable driver efficiency for varying operating conditions.
Near-field localization in echoic rooms
Authors: Santarelli Scott , Kopco Norbert , Shinn-Cunningham Barbara G. , Brungart Douglas
Published: July 2002

The current study examines the ability of subjects to indicate the distance and direction of sources within 1 m of the head in a medium-sized, echoic classroom. Two conditions were tested in the same group of subjects. In the first, subjects were seated in the center of the room, relatively far from any hard reflective surfaces. In the second condition, subjects were located at the same position in the room, but a 12×4 enamel-covered wallboard was positioned next to the listener to create an additional artificial wall approximately 6 in. from the left ear of the listeners. The initial hypothesis was that previous localization results from tests in anechoic space would be nearly indistinguishable from the results in the first condition, since for sources near the head, the direct-to-reverberant energy ratio in this first condition would be very large. However, it was believed that the addition of a single, short-latency echo might bias some localization judgments, particularly judgments of distance and elevation. Instead the results indicate that localization accuracy and variability are comparable for the two echoic conditions, but that both measures of localization ability are worse in echoic conditions than in anechoic conditions.
Ultrasound-induced cell lysis and sonoporation enhanced by contrast agents
Authors: Ward Mark , Wu Junru , Chiu Jen-Fu
Published: July 2002

The enhancement of ultrasound-induced cell destruction, lysis, and sonoporation in low cell concentration suspensions (2×105/mL) by the presence of contrast agents (gas bubble to cell ratio=230) was demonstrated using cervical cancer cells (HeLa S3) suspensions containing micron-size denatured albumin microspheres filled with air (Albunex®) or octafluoropropane (Optison™). The suspensions were insonificated by 2-MHz continuous or tone burst ultrasound in near field. The spatial peak-pressure amplitude was 0.2 MPa. The enhancement of cell destruction due to Optison™ was shown to be much higher than that due to Albunex® for similar bubble concentration and ultrasound conditions. For tone burst exposures, significant lysis and sonoporation only occurred in the presence of a contrast agent. The majority of the bioeffects observed occured in the first 5 min of exposure. The relationship between the enhancement of bioeffects and duty cycle of tone burst ultrasound appears to indicate that both stable gas spheres of contrast agents and cavitation nuclei created by the disruption of the gas spheres play a significant role in causing the bioeffects.
Biharmonic Solutions of Certain Integro-Differential Equations of Linear Viscoelasticity
Authors: Elder Alexander S.
Published: July 2002

A stress function theory for linearly viscoelastic solids is developed in this paper. If body forces and inertial forces are neglected, the stresses, strains, and displacements are biharmonic functions of the space variables. The displacements are expressed in terms of harmonic functions by an extension of the Neuber-Papkovitch theory. Axially symmetric stresses and strains are given in terms of a single biharmonic function. As the analysis does not involve boundary conditions, it is valid for problems involving moving leads and moving boundaries. The theory may be used to formulate stress analysis problems in terms of Volterra integral equations, using creep or relaxation functions as the kernel. The integral equations governing the stresses in a viscoelastic propellant grain subjected to the combined effects of internal pressure and erosion are derived.
Velocity Profiles in Tube Flow
Authors: Gerrard J. E.
Published: July 2002

The terminal velocity profile of a liquid flowing in a capillary (tube) can be determined quite accurately from a simultaneous measurement of the mass flux (throughput) and momentum flux (thrust). The flow may be of almost any type, i.e., laminar, transitional, turbulent, most shear-sensitive, and most non-isothermal cases. The assumptions embodied appear to be quite logical and exclude very few types of flow systems.
Dielectric Constants, Permeabilities, and Conductivities of Random Media
Authors: Brown William Fuller
Published: July 2002

A material property is often described by a proportionality factor between a solenoidal vector (electric or magnetic induction, electric current density) and an irrotational vector (field intensity); in an isotropic dielectric, for example, D=εE. Often one wishes to calculate the effective ε for a random mixture of two homogeneous materials A and B, with constants εA and εB, filling volume fractions p and q. There are exact formulas for the cases of boundaries all parallel or all perpendicular to the field, and an approximate formula for spheres A in a matrix B with p≪1. For a statistically isotropic random mixture with arbitrary p, many approximations of unknown reliability have been proposed. Recently two rigorous results have been derived. (1) A series expansion in εA−εB requires, besides p, additional statistical information, dependent on the probabilities p12...n(n) of finding n points r1,r2,...,rn all simultaneously in material A. (2) Given only εA, εB, and p1(1)(=p=1−q), we can state that ε*⩽ε⩽ε where ε* and ε* are calculable and attainable. The present paper reviews these rigorous theories and presents closer bounds, based on additional information dependent on p12(2) and p123(3).
A Thermodynamic Analysis of Deformable Media
Authors: Tsai Stephen W.
Published: July 2002

A constitutive equation of deformable media subjected to infinitesimal deformation is derived from the principles of thermodynamics. An explicit equation, which contains physical nonlinearity, is formulated by using the invariant properties of isotropic media. It is found that the equation provides a consistent description of creep and stress relaxation.
Thermistor Analog Study of Dynamic Shear in an Ideal Viscous Material
Authors: Gruntfest I. J. , Mueller G. E.
Published: July 2002

As part of a continuing study of the mechanical behavior of materials with temperature-dependent properties, dynamic responses of an ideal viscous material are considered. An electric analog circuit containing thermistors and ideal inductors is presented. The characteristics of this circuit simulate the highly nonlinear characteristics of the model of the material. The experiments show how the conversion of mechanical work to heat can lead to stress and time-dependent apparent viscosities and to thermal instability in velocity-driven Couette flow. When the boundary velocity is sinusoidal, the heating can lead to the appearance of a pseudo elasticity as well as to thermal instability. The thermal stability of the system is shown to depend on the frequency as well as the amplitude of the excitation. A group of similarity parameters are described which are ratios of characteristic times for heating, velocity diffusion, thermal diffusion, and loading. These provide a description of the model mechanical experiment and make the connection with the electrical analog.
Generalizations of Some Elastic-Viscoplastic Stress-Strain Relations
Authors: Kelly James M.
Published: July 2002

Extensions of the Sokolovsky-Malvern theory of strain-rate-dependent plasticity are proposed. These extensions are based on concepts of strain-dependent viscosity and of hereditary integral viscosity, and are based on both the linearly viscoplastic constitutive equation and on the exponentially viscoplastic one. The basic tests, creep, relaxation, and constant strain rate, are examined and the application of the theories to wave propagation is discussed.
Comparison of Complex Moduli Obtained from Forced and Free Damped Oscillations
Authors: Heller R. A. , Nederveen C. J.
Published: July 2002

While the concept of the complex modulus is based on a forced vibration experiment it is a frequent practice to perform instead a much simpler free damped oscillation test from which an approximate value of the modulus is then evaluated. The validity of this approach and the ensuing errors are discussed and illustrated on a multielement generalized Maxwell body. It is shown that with modifications the method is applicable even for highly damped materials.
Responses of Model Viscoelastic Materials to Impact
Authors: Gruntfest I. J. , Mueller G. E.
Published: July 2002

As part of a continuing exploration of the mechanical behavior of materials which have temperature-dependent properties, the effect of a hammer blow on a small sample of model viscoelastic material is considered. In this situation, the duration of the experiment is long compared with the time required for stress equilibrium to develop and short in comparison with the thermal relaxation time of the sample. The analysis shows how a material which responds in an almost perfectly elastic manner to a light blow can respond in a viscous manner to a heavy blow. It also suggests that a homogeneous continuum with properties that would make it acceptable as a structural material must be brittle. This result may contribute to the understanding of the important relationship between microstructure and ductility. The hammer experiment involves relatively high strain rates which vary continuously during the deformation. In earlier work, the constant deformation rate case was studied. The latter situation is difficult to produce in the laboratory in the range of rates of interest here and is less likely to arise in practice.
Deformation Mechanism of Nonlinear Viscoelasticity
Authors: Mack Charles
Published: July 2002

The description of the flow mechanism of nonlinear viscoelasticity is based on what is known and on what can be measured by experiment. Such materials harden or soften under stress. These processes cannot go on indefinitely, but must result finally in failure. Their deformations are both reversible and irreversible, hence stresses and entropy changes at constant temperature consist also of reversible and irreversible parts. Experiments are generally carried out by applying an external force and measuring the resulting deformation. For the nonlinear case, these quantities are not known a priori in terms of stress and strain components, but the problem can be simplified by treating nonlinear behavior as a special case of linear behavior. It is shown that, where the normal stress-strain or strain rate relationships are constant for the linear case, they are also constant for the nonlinear case if the strain or stress rate consists of the sum of reversible and irreversible parts. The upper limit of this constant relationship coincides with the stress at which a nonlinear material has its ultimate strength. At greater stresses, the material is in a region of instability. The validity of this approach is demonstrated by data on a bituminous paving mixture (typical of hardening) and on several molten polyethylenes.
Application of The Valanis-Landel Theory to Small Deformations Superposed on a Finite Stretch
Authors: Peng T. J. , Tschoegl N. W.
Published: July 2002

Expressions were obtained for the Young's modulus, E, and the shear modulus, G, of an elastic material, resulting from a small extension, twist, or shear, respectively, superposed on a finite uniaxial stretch. The expressions are given in terms of the stretch ratio, λ, and the partial derivatives of the strain-energy function with respect to λ. The predictions of the theory arising from several proposed forms of the strain-energy function are calculated and compared. If the small deformation is imposed after the stress resulting from the finite stretch in a viscoelastic material has relaxed, substitution of the time- or frequency-dependent viscoelastic functions for the elastic constants describes viscoelastic behavior in the small deformation when the finite stretch is within the region in which strain and time effects can be factored.
Hydrorheology of Clay Soils
Authors: Krizek Raymond J. , Achenbach Jan D. , Adeyeri Joseph B.
Published: July 2002

A multiple integral theory is advanced to describe the influence of water content on the mechanical behavior of clay soils. Experimental data from three series of creep tests and one set of relaxation tests over a wide range from a few seconds to beyond 10,000 minutes are reported and analyzed. In the range of experimental observations the theoretical results show good agreement with the experimental data.
Flow of a Nonlinear Heat-Conducting Viscoelastic Fluid
Authors: Cook Richard D. , Koh Severino L.
Published: July 2002

The Koh-Eringen formulation of nonlinear thermoviscoelasticity is used to study the behavior of a heat-conducting Rivlin-Ericksen fluid characterized by a set of constitutive equations involving the coupled dependence of stress and heat flux on temperature gradient and the first two Rivlin-Ericksen tensors. Slow steady-state flow of the fluid under a small temperature gradient is considered. With the use of a perturbation technique, the basic equations and boundary conditions are derived for each increasing order of approximation. The first order equations are precisely those of a Newtonian fluid. Succeeding higher order corrections involve linear equations also although the results of preceding lower order approximations are used. The given boundary conditions are satisfied in the first order analysis. Homogeneous boundary conditions are then applicable for higher order corrections. Two specific problems are considered: (1) pressure flow of the fluid between two parallel plates in relative motion and at different constant temperatures; and (2) Couette-helical flow in the annular region between two coaxial circular cylinders in relative translational velocity parallel to the axis and at two different constant temperatures. Numerical results are plotted for several Eckert numbers and other thermomechanical parameters.
On Intrinsic Pressure-Hole Errors for Viscoelastic Fluids
Authors: Salathe Eric P. , Sawyers Kenneth N.
Published: July 2002

Expressions previously derived for the intrinsic error associated with pressure-tap measurements under the assumption of steady symmetrical flow of a second order fluid are found to be applicable under more general conditions.
Shear Flow Behavior of Complex Asbestos Fibril Dispersions
Authors: Rosinger Eva L. J. , Woodhams Raymond T. , Chaffey Charles E.
Published: July 2002

The viscosity behavior of colloidal asbestos fibril dispersions, in the presence of a polystyrene copolymer latex, was investigated over a range of shear rates using a Ferranti-Shirely cone-and-plate viscometer. Flow of the asbestos suspensions was highly dependent on shear rate and time; the apparent viscosity was reduced when aluminum trichloride, an effective agent for separating the fibrils, was added. This effect was not seen when poly(acrylic acid) (PAA) was added instead. The complex dispersions containing a relatively low fraction of latex had a high apparent viscosity and were markedly thixotropic. As the fraction of latex increased, the behavior approached that of the unmodified latex. This had a small yield stress, but was otherwise nearly Newtonian. At high shear rates, the increase in viscosity due to addition of asbestos fibrils to the latex was relatively small.
Osmotically Driven Flow in Narrow Channels
Authors: Frisch H. L.
Published: July 2002

Osmotically driven flow in a narrow, long channel whose walls are a rigid, ideal semipermeable membrane leads to a convective velocity field satisfying Burger's equation. A particular boundary value problem is solved exactly.
Viscoelastic Properties of Water-in-Oil Cream
Authors: Komatsu Hideo , Takahashi Motoji , Fukushima Shoji
Published: July 2002

A number of series of water-in-oil creams were prepared in which the oil phase consisted of liquid paraffin and microcrystalline wax. The emulsifying agent employed was polyoxyethylenel oleyl ether. The dynamic viscoelastic properties of the creams, and also of the oil phases, were measured at 25°C with a Weissenberg rheogoniometer at frequencies ranging from 5×10−3 to 1.582 Hz. The frequency dependence of viscoelastic functions was influenced much by the change in the weight fractions of water, but little by the change in the ratios of microcrystalline wax to liquid paraffin. The gradient of curves in logarithmic plots of the viscoelastic functions of the creams against the weight fraction of water changed drastically at a certain weight fraction of water. These results of viscoelastic measurements were compatible with the microscopic appearance of the creams that large particles of microcrystalline wax were dispersed through the liquid paraffin medium, together with emulsified water drops of much smaller size. The observed dependence of the viscoelastic functions on the weight fraction of water was explained qualitatively by the theory of viscoelastic properties of disperse system proposed by Okano.
Effects of Weight Change on Knee and Hip Radiographic Measurements and Pain Over Four Years: Data From the Osteoarthritis Initiative
Authors: Joseph Gabby B. , McCulloch Charles E. , Nevitt Michael C. , Lynch John , Lane Nancy E. , Link Thomas M.
Published: March 2022

Objective

To assess the effects of weight loss and weight gain on hip and knee radiographic changes, pain, and joint replacement over 4 years.

Methods

Participants (n = 2,752) from the Osteoarthritis Initiative were classified as those with weight gain (more than 5% gain), weight loss (more than –5% loss), or as controls (–3% to 3% change) over 4 years. Generalized estimating equations (adjusted for age, sex, and body mass index) were used to assess the relationship between the weight‐change group and 4‐year changes in knee radiographic osteoarthritis (OA) (Kellgren/Lawrence [K/L] grade), hip OA (Croft summary grade), joint space narrowing (JSN), and joint pain.

Results

For radiographic knee OA, weight loss was associated with significantly lower odds of K/L grade worsening over 4 years (odds ratio [OR] 0.69 [95% confidence interval (95% CI) 0.53–0.91], P = 0.009), and weight gain was significantly associated with higher odds of medial knee JSN (OR 1.29 [95% CI 1.01–1.64], P = 0.038) compared to controls. For knee pain, weight loss was significantly associated with knee pain resolution over 4 years (OR 1.40 [95% CI 1.06–1.86], P = 0.019) while weight gain was associated with knee pain development (OR 1.34 [95% CI 1.08–1.67], P = 0.009) compared to controls. For all hip outcomes, no significant associations (P > 0.05) were found with weight‐change groups. The associations between the weight‐change group and total hip or total knee replacement were not significant (P > 0.05).

Conclusion

This large, longitudinal study (n = 2,752 with 4‐year follow‐up) suggests that weight loss may protect against, and weight gain may exacerbate, radiographic and symptomatic knee OA, while weight change (at a 5% threshold) does not have significant effects on hip OA.
Proton‐Pump Inhibitors and Risk of Calcium Pyrophosphate Deposition in a Population‐Based Study
Authors: Liew Jean W. , Peloquin Christine , Tedeschi Sara K. , Felson David T. , Zhang Yuqing , Choi Hyon K. , Terkeltaub Robert , Neogi Tuhina
Published: March 2022

Objective

There are no proven effective medical treatments to prevent calcium pyrophosphate crystal deposition (CPPD). Hypomagnesemia is a known CPPD risk factor. The present study was undertaken to carry out a real‐world epidemiologic study on proton‐pump inhibitor (PPI) use, which can cause hypomagnesemia, and CPPD risk.

Methods

We conducted a time‐stratified, propensity score (PS)–matched cohort study using the UK‐based IQVIA Medical Research Data. We compared risk of incident CPPD among PPI users versus H2 blocker users using Cox proportional hazards models. We used greedy matching of incident PPI users 1:1 to incident histamine receptor 2 (H2) blocker users in 1‐year cohort accrual blocks. Subjects were censored at time of drug switch. We evaluated incident use of PPI and H2 blockers prior to incident CPPD using a nested case–control study within the same cohort, matched 1:4 by age and sex using risk‐set sampling.

Results

We identified 81,102 PPI and H2 blocker initiators, with 113 and 63 incident cases of CPPD, respectively. In the case–control study when compared with nonusers, both PPI and H2B users had higher risk of incident CPPD, with odds ratios (ORs) of 1.79 (95% confidence interval [95% CI] 1.55–2.07) and 1.52 (95% CI 1.14–2.03), respectively. Incident PPI use was nonsignificantly associated with incident CPPD (hazard ratio 1.03 [95% CI 0.75–1.41]) compared with H2 blocker use.

Conclusion

In this study using real‐world data, incident use of PPIs was not associated with a higher risk of CPPD compared with incident H2 blocker use, although use of PPI and H2 blockers had higher risk compared with nonuse.
OIG for first time endorses more than $75 a year for contingency management
Authors: Knopf Alison
Published: March 2022

Last month, the Office of the Inspector General (OIG) of the Department of Health and Human Services (HHS) moved forward on showing that it does not oppose sums larger than $75 a year for contingency management (CM), a form of treatment for substance use disorders (SUDs) in which patients are given material rewards for negative drug tests. And while many think of CM as only for stimulant use disorders, the Feb. 25 OIG opinion to DynamiCare Health, a copy of which was obtained by ADAW, shows that HHS is balking unnecessarily by not allowing more liberalized CM policies to go forward (see “HHS OIG doubles down on constraints against contingency management,” ADAW Aug. 24, 2020; https://onlinelibrary.wiley.com/doi/10.1002/adaw.32812, “CM for stimulant use disorder: No limit imposed by OIG,” Nov. 8, 2021; https://onlinelibrary.wiley.com/doi/10.1002/adaw.33255; “SAMHSA keeps $75/$15 CM limits despite methamphetamine epidemic, OIG ruling,” Nov. 14, 2021; https://onlinelibrary.wiley.com/doi/10.1002/adaw.33258).
Efficient Non‐Doped Blue Electro‐fluorescence with Boosted and Balanced Carrier Mobilities
Authors: Wang Runze , Li Tengyue , Liu Chaoke , Xie Mingliang , Zhou Huayi , Sun Qikun , Yang Bing , Zhang Shi‐Tong , Xue Shanfeng , Yang Wenjun
Published: March 2022

One of the most important issues of the organic light‐emitting diode (OLED) is the highly efficient blue‐emissive material, which demands both excellent photoluminescent quantum yield (PLQY) and balanced carrier mobilities. Herein, a series of blue‐emissive donor–π–acceptor (D–π–A) materials with fluorene π‐bridge and their D–A analogues are synthesized and discovered with a theoretical combined experimental method. Based on the excellent electron mobility of the oxadiazole (OXZ) acceptor, it is further proven that the insertion of the fluorene π‐bridge can not only contribute to the formation of hybrid local and charge‐transfer excited state with high PLQY, but also give rise to the hole mobilities by enhanced intermolecular face‐to‐face stacking. As a result, the non‐doped OLED of TPACFOXZ exhibits a high maximum external quantum efficiency approaching 10% with boosted and balanced hole and electron mobilities of 5.60 × 10−5 and 6.60 × 10−5 cm2 V−1 s−1, respectively, which are among the best results of the non‐doped blue fluorescent OLEDs.
Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes
Authors: Liang Shenghua , Sun Wenhong
Published: March 2022

AlGaN‐based deep ultraviolet light‐emitting diodes (UV LEDs) have gained rapidly growing attention due to their wide applications in water purification, air disinfection, and sensing as well as optical communication. Moreover, deep UV radiation has been verified as one of effective way to inactivate COVID‐19. However, although numerous efforts have been made in deep UV LED chips, the reported highest external quantum efficiency (EQE) of them is 20.3%, which is far lower than that of visible LEDs. The EQE of commercial packaged AlGaN‐based deep UV LEDs is usually lower than 5%, which will cause serious reliability problems as well. Therefore, it is very urgent to improve EQE and reliability of the devices from packaging level. In this review, a systematical summarization about the packaging technologies of AlGaN‐based deep UV LEDs has been analyzed and future prospects have been made as well. Firstly, this work provides a brief overview of the devices and analyzes why the packaging level reduces EQE and reliability in theory. Then, systematically reviews the recent advances in packaging technologies and deep UV micro‐LEDs. Finally, conclusions and outlooks are given as well. This review is of great significance for promoting the development of the packaging technologies for AlGaN‐based deep UV LEDs.
Wavelength‐Selective Light Trapping with Nanometer‐Thick Metallic Coating
Authors: Yang Chenying , Wen Junren , Chen Xiao , Luo Hao , Zhu Yining , Wang Hailan , Zheng Tingting , Zhang Yueguang , Shen Weidong
Published: March 2022

Wavelength‐selective light trapping has been widely applied in fields such as energy utilization, optical sensing, optical imaging, and so forth. Though metasurfaces have exhibited to efficiently trap the light for diverse optical responses with specific configurations, the manufacturing costs and processing precision both limit the extensive applications. Here, a compact optical coating to trap light either at a single wavelength or across a broadband within a nanometer‐thick single‐layer metallic coating based on mirror|phase tuning layer|absorptive (MPA) and MPA|anti‐reflection coating stacks is proposed. The intermediate phase‐tuning dielectric provides a specific phase shift for the cavity to achieve destructive or constructive interference for ≈100% absorption or reflection correspondingly by switching from ultrahigh‐index dielectric behavior to epsilon‐near‐zero material behavior. And the additional dielectric is introduced to reduce the increasing reflection for the final broadband absorption with a thicker absorptive metal. Furthermore, the efficient color‐preserving solar–thermal conversion based on this compact coating (4‐layer) with the entire thickness of ≈300 nm is demosntrated experimentally. Various perceived colors are produced by simply changing the thickness of the top dielectric layer with the efficient solar–thermal conversion remained, verified by the temperature difference between the fabricated device and the dye‐based plastic exceeding 13 °C with the solar irradiance ≈850 W m−2.
Exome and RNA‐Seq analyses of an incomplete penetrance variant in USP9X in female‐specific syndromic intellectual disability
Authors: Li Dong , March Michael E. , Wang Tiancheng , Merengwa Victoria , Sertori Finoti Livia , Schrier Vergano Samantha A. , Hakonarson Hakon , Bhoj Elizabeth J.
Published: March 2022

Pathogenic variants in USP9X, on X chromosome, have been implicated in syndromic intellectual disability (ID) in both males and females with distinct craniofacial features. We report a truncating variant, c.885_889delAAAAG, p.(Lys296Serfs*4), in the USP9X gene with incomplete penetrance in two nontwin female siblings with phenotypic resemblance to female‐specific syndromic ID (MIM 300969, also known as MRX99F). To investigate the possible genetic etiology of the reduced penetrance, X‐inactivation, RNA‐Seq, and full quad exome analyses were attempted, but failed to identify a promising candidate modifier. While the penetrance of pathogenic variants in USP9X in female appears to be high (95%) and the variants frequently occur de novo, incomplete penetrance should be considered.