bluuebunny/crossref_metadata_2025_split huggingface dataset:
Netted or tangled? hydrophobic or hydrophilic? stiff or flexible? a review of some polyelectrolyte chemistry
Authors: Hatch Melvin J. 
Published: June 2010

AbstractIn this talk, highlights and an interconnected thread of ideas will be presented in relation to the following specific areas of polyelectrolyte research: (1) the development of ion retardation resins, which are “snake‐cage” or semi‐interpenetrating polyelectrolyte systems that absorb ionic species reversibly; (2) the synthesis of specially and chelating ion exchange resins, by overcoming barriers to polymer reactivity; (3) reactive sulfonium monomers and polymers, in relation to coatings; (4) the enhancement, by chain stiffening, of the viscosifying effect of high molecular weight polyelectrolytes, in relation to improved water‐flooding of oil wells. In the talk, the qualitative importance of the factors given in the title will be emphasized, and the influence of the work of Turner Alfrey will be illustrated.
Sorption and diffusion in multicomponent polymers
Authors: Rogers C. E. 
Published: June 2010

AbstractThe solution, diffusion, and permeation of low molecular weight substances in polymeric materials are governed by the relative chemical compositions and physical structures of the penetrant molecule and the polymer. Those factors determine the chain segmental mobility, defect structures, and interactions which control the sorption magnitude and penetrant molecular mobility within the polymer. The transport of relatively noninteracting penetrant molecules in a polymer almost always follows the classical behavior predicted by Fick's law relationships with a constant (or nearly so) diffusion coefficient. An increase in generalized interactions (van der Waals, etc.) leads to increased sorption of the penetrant, with consequent increase in plasticization of the polymer, such that the diffusion process often becomes concentration‐dependent. Then, depending upon the relative rates of polymer relaxation processes concurrent with the sorption‐diffusion process, the overall transport process may exhibit Fickian behavior with a simple concentration‐dependent diffusion coefficient or it may deviate significantly from that behavior due to complicating relaxation effects. Systems in which there may be more specific interactions (hydrogen‐bonding, polar, ionic) often show a pronounced dependence of transport behavior on compositional, temporal, and spatial parameters which relate to changes in sorption modes. In these present investigations, we have used copolymer systems, prepared under controlled conditions, to gain some further insight into the dependence of polymer structure on variations in composition and how these variations affect or are reflected by transport and relaxation properties.
Correlations between polymer matrix and composite mechanical properties
Authors: Adams Donald F. 
Published: June 2010

AbstractDuring the past decade or more, the composite materials community has restricted itself primarily to the use of only a few structural epoxy matrix materials. Very recently, whole new families of polymer matrices have become of practical interest. In order to select from this wide range of new polymers for each specific structural application, the relation between the various polymer mechanical and physical properties, e.g., modulus, strength, strain to failure, thermal and moisture expansion coefficients, moisture absorption rate, etc., and resulting composite properties must be known. Correlations of finite element analysis predictions with actual experimental data will be presented, using measured mechanical and physical response properties of various toughened epoxy, bismaleimide, polyimide, and thermoplastic matrix systems as inputs to the analyses. Results will include fracture mechanics evaluations, the role of matrix nonlinear response, crack initiation and propagation, thermally induced damage, and the influence of the interface. Matrix properties to be modeled have been generated in the author's own laboratories, as part of several current and ongoing funded research studies for various government and industry groups. Several types of finite element analyses have been used, including 2‐dimensional generalized plane strain with longitudinal shear loading, 2‐dimensional axisymmetric, and fully 3‐dimensional formulations. All of these analyses permit the input of actual matrix nonlinear stress‐strain response, and how it varies as a function of temperature and moisture content. Fibers having anisotropic properties in a composite of arbitrary fiber volume are included. Time‐dependent response, e.g., creep, recovery, and relaxation, and crack propagation are also possible response modes. Results will be presented in the form of composite stress‐strain curves, plots of stress contours in the matrix, and at the fiber‐matrix interface.
Some criteria for the design of polyurethaneurea elastomers
Authors: Spell H. L. , Macdonald C. E. , Turner R. B. 
Published: June 2010

AbstractGiven the numerous variables in composition, reaction conditions, and processing, the design of a polyurethane elastomer with a specified set of properties is indeed a challenging task. The control of characteristics such as heat stability, toughness, fatigue, and other key qualities requires a compendium of theoretical and experimental knowledge. Optimizing a single property, e.g., low temperature resiliency, can necessitate changes in composition that may compromise other important properties. Thus, to balance the entire system in order to meet the specification limits, much more than an empirical approach is needed to achieve the goal in a reasonable time. In this presentation, we will demonstrate that, by use of an array of sophisticated testing methods and carefully designed experiments combined with computer modeling, the tailoring of a segmented elastomer can be placed on a scientific basis. Key methods of characterization are dynamic mechanical spectroscopy, small angle X‐ray scattering, electron microscopy, Fourier transform infrared, and differential scanning calorimetry. Special experiments included the systematic synthesis and testing of a wide range of model compounds. Optimum soft segment properties such as chain length and mobility were defined. Hard segments that are properly segregated and have high thermal and mechanical integrity were synthesized and characterized. These and related experiments have led us to a better understanding of the molecular mechanisms underlying the mechanical and thermal behavior of an elastomer. With this knowledge we can select molecular components and control phase relationships in building elastomers to meet end use requirements that demand maximum static and dynamic polymer properties.
Modern design data for short‐fiber thermoplastic composites
Authors: Turner S. 
Published: June 2010

AbstractItems fabricated from thermoplastics containing short glass fibers are anisotropic and the anisotropy varies from point to point. Guidance as to how such materials should be evaluated and what data are required for the design of end products molded from them is provided by a combination of the theories of viscoelasticity and anisotropic elasticity, whereby the stiffness and compliance coefficients of the latter are functions of time, temperature, and strain. A methodology then emerges, similar in overall nature to that pertaining to thermosetting resins containing long aligned fibers, but rather more complex because of the variations in fiber alignment. However, an adequately comprehensive evaluation in accordance with the formal rationale tends to be prohibitively expensive and, on the other hand, a curtailed evaluation can yield misleading data. Recent work aimed at resolving that impasse seems promising. The central principle is the use of special test specimens chosen because their flow geometries and possible flow irregularities are similar to those commonly found in commercial end products. The data that can be derived from such specimens can be related quantitatively to those derived from the conventional tests, and therefore the presentation and use of the new class of data entail no interpretation difficulties. Examples of what has been achieved and speculations about what might further be achieved are presented in the paper.
The thinking injection molding machine: A followup to systematic process analyses
Authors: Menges G. , Janke W. , Matzke A. 
Published: June 2010

AbstractLatest injection molding machines are often equipped with process control computers monitoring and controlling operating sequence, injection speed, holding pressure, clamping motion, clamping force, and all temperatures. This provides for the possibility to overlay process‐related optimization programs for adaptation of the machine to the respective material condition and programs for the machine control. The following pages inform about such optimization programs.
Recent developments in sheet molding compound technology
Authors: Newman Seymour , Fesko Donald G. 
Published: June 2010

AbstractThe molding of fiber‐reinforced thermoset components is a complex process involving a highly exothermic chemical reaction which takes place in the presence of flow and thermal gradients. The flow in turn is complicated by time and temperature‐dependent rheological characteristics. The industry has grown largely on the basis of empirical developments. However, numerous problems do remain which required increased understanding for solution. This report reviews work underway in numerous laboratories to characterize the flow and cure of SMC and phenomena associated with these processes such as orientation, mechanical properties, residual internal stresses, mold fill, and surface defects.
Mean field theory for the rheological properties of moderately concentrated polymer solutions in transversal shear flow
Authors: Hess Walter 
Published: June 2010

AbstractModerately concentrated polymer solutions are described as a suspension of interacting harmonic dumbbells. The interaction is treated in a mean field approximation. In the framework of this model the exact conformational distribution function for transversal shear flow is obtained. The shear viscosity and the first normal stress coefficient show the typical non‐Newtonian form with a distinct power law behavior after the onset of shear rate dependence.
Extended Occupational and Positional Disorder in Pavonite Homologous Copper Bismuth Chalcogenide Halogenides
Authors: Heerwig Andreas , Thybaut Cyril Louis Jaques , Ruck Michael 
Published: June 2010

AbstractMelting reactions of CuBr, BiBr3 and Bi2Q3 (Q = S or Se) resulted in black needles of quaternary chalcogenide bromides. Cu1.5Bi2.64S3.42Br2.58 has a melting point of 708(5) K and crystallizes in the monoclinic space group C2/m with a = 1315.1(3) pm, b = 410.28(5) pm, c = 937.2(2) pm, β = 90.33(2)° at T = 293(2) K. The isostructural selenide Cu1.57Bi2.37Se2.68Br3.32, which melts at 724(5) K, has the lattice parameters a = 1353.9(3) pm, b = 417.54(5) pm, c = 960.4(2) pm, β = 91.13(2)°. Black needles of the selenide iodides Cu1.57Bi4.69Se7.64I0.36 and Cu2.31Bi5Se8.31I0.69 were obtained by chemical vapor transport of CuI and Bi2Se3. They also crystallize in space group type C2/m with a = 1373.9(4) pm, b = 417.4(1) pm, c = 1464.6(4) pm, β = 115.57(2)°, and a = 1369.1(3) pm, b = 416.6(1) pm, c = 1526.4(3) pm, β = 99.81(3)°, respectively. All four compounds belong to pavonite homologous series. Their structures are built up of two alternating types of layered modules parallel (001), denoted A and B. Composition and shape of module A are almost the same in all structures. They consist of paired rods $\rm ^1_\infty[BiQ_{3/3}X_{2/2}Z_{2/2}]$ = Br, I) running along [010] and copper(I) cations that are distributed over various voids between the rods. Modules of type B are composed of [MZ6] octahedra (M = Bi/Cu), which are arranged in NaCl‐type fragments of thickness N = 1, 3 or 4. The Joint Probability Density Function (JPDF) reveals a continuous pathway for copper ion transport along [010] in the case of the sulfide bromide. The pseudo‐potential for hopping of copper ions was calculated as 47 meV only. The electrical and thermal conductivities as well as the Seebeck coefficient were determined to evaluate the thermoelectric properties.
Surgical correction of equinus deformity in children with cerebral palsy: A systematic review
Authors: Shore Benjamin J. , White Nathan , Kerr Graham H. 
Published: June 2010

Purpose Equinus is the most common deformity in cerebral palsy. However, despite the large volume of published studies, there are poor levels of evidence to support surgical intervention. This study was undertaken to examine the current evidence base for the surgical management of equinus deformity in cerebral palsy. Methods A systematic review of the literature using “equinus deformity”, “cerebral palsy” and “orthopaedic surgery” generated 49 articles. After applying inclusion and exclusion criteria, 35 articles remained. The Oxford Centre for Evidence-Based Medicine (CEBM) levels of evidence and the Methodological Index for Non-Randomized Studies (MINORS) were used to grade the articles. Results Studies ranged in sample size from 9 to 156 subjects, with an average of 38 subjects. The mean age of subjects at index surgery ranged from 5 to 19 years. Nineteen studies used instrumented gait analysis, with an average follow-up of 2.8 years. Seven studies reported that a younger age at index surgery was associated with an increased risk of recurrent equinus. The average rate of calcaneus in hemiplegic children was 1% and it was 15% in those with spastic diplegia. Most studies were level 4 quality of evidence, leading to, at best, only grade C recommendation. Conclusions Cerebral palsy subtype (hemiplegia versus diplegia) and age at index surgery were the two most important variables for determining the outcome of surgery for equinus deformity in cerebral palsy. Despite the great emphasis on differences in surgical procedures, there was less evidence to support the type of operation in relation to outcome.
DIVERGENT STREAMS
Authors: Massey Douglas S. , Probasco LiErin 
Published: June 2010

AbstractIn this paper, we extend previous research on racial performance gaps at twenty-eight selective U.S. colleges and universities by examining differences in grade achievement and graduate rates across race-gender categories. Using data from the National Longitudinal Survey of Freshmen (NLSF), we show that Black males, Black females, and Hispanic males attain significantly lower grades than other race-gender groups, and that Black males are thirty-five percent less likely to graduate on-time than other race-gender groups. Analyses consider an array of personal and institutional indicators of academic performance. Grades and graduation rates are improved by academic preparation (particularly high school grade point average), scholarly effort, and, for graduation rates, membership in career-oriented or majority-White campus groups. Grade performance and graduation rates are undermined by a hostile racial climate on campus, family stress, and stereotype threat, all of which disproportionately affect minority students. We conclude with recommendations to college administrators for ways of selecting and supporting minority students to reduce differentials in academic achievement across race-gender groups.
DRIVING WHILE BLACK IN SUBURBAN DETROIT
Authors: Bates Timothy 
Published: June 2010

AbstractOne objective of this study is to investigate whether Black drivers are more likely than White motorists to receive traffic tickets and to be arrested following routine traffic stops in the Detroit suburb of Eastpointe, Michigan. Compared to White drivers, Blacks were more likely to be arrested and ticketed when police officer discretion was most pronounced. My broader objective is to explore police enforcement of racialized space in suburban Detroit. Outcomes of routine traffic stops were analyzed to determine whether enforcement of racialized space could be detected by comparing how drivers were treated on Eastpointe streets that were more, opposed to less, White. Black motorists driving on internal streets were more likely to attract police attention than those driving along Eastpointe's border street with Detroit, Eight Mile Road, which is interpreted as evidence that Black drivers are more likely to be ticketed, searched, and arrested when they were “out of place”.
Operator-valued Feynman integrals of certain finite-dimensional functionals
Authors: Johnson G. W. , Skoug D. L. 
Published: June 2010

Let

C
0

[
a
,
b
]

{C_0}[a,b]

denote the space of continuous functions

x
x

on

[
a
,
b
]

[a,b]

such that

x
(
a
)
=
0

x(a) = 0

. Let

F
(
x
)
=

f
1

(
x
(

t
1

)
)
⋯

f
n

(
x
(

t
n

)
)

F(x) = {f_1}(x({t_1})) \cdots {f_n}(x({t_n}))

where

a
=

t
0

>

t
1

>
⋯
>

t
n

=
b

a = {t_0} > {t_1} > \cdots > {t_n} = b

. Recently, Cameron and Storvick defined an operator-valued “Feynman Integral.” In their setting, we give a strong existence theorem as well as an explicit formula for the “Feynman Integral” of functionals

F
F

as above under weak restrictions on the

f
i

{f_i}

’s. We also give necessary and sufficient conditions for the operator to be invertible and an explicit formula for the inverse.
On differentiability of minimal surfaces at a boundary point
Authors: Geveci Tunc 
Published: June 2010

Let

F
(
z
)
=
{
u
(
z
)
,
v
(
z
)
,
w
(
z
)
}
,

|

z

|

>
1

F(z) = \{ u(z),v(z),w(z)\} ,|z| > 1

, represent a minimal surface spanning the curve

Γ
:
{
U
(
s
)
,
V
(
s
)
,
W
(
s
)
}
,
s

\Gamma :\{ U(s),V(s),W(s)\} ,s

being the arc length. Suppose

Γ
\Gamma

has a tangent at a point

P
P

. Then

F
(
z
)

F(z)

is differentiable at this point if

U
′

(
s
)
,

V
′

(
s
)
,

W
′

(
s
)

U’(s),V’(s),W’(s)

satisfy a Dini condition at

P
P

.
On idempotent, commutative, and nonassociative groupoids
Authors: Grätzer G. , Padmanabhan R. 
Published: June 2010

For an algebra

A

=

⟨

A
;
F

⟩

\mathfrak {A} = \left \langle {A;F} \right \rangle

and for

n
≧
2

n \geqq 2

, let

p
n

(

A

)

{p_n}(\mathfrak {A})

denote the number of essentially

n
n

-ary polynomials of

A

\mathfrak {A}

. J. Dudek has shown that if

A

\mathfrak {A}

is an idempotent and nonassociative groupoid then

p
n

(

A

)
≧
n

{p_n}(\mathfrak {A}) \geqq n

for all

n
>
2

n > 2

. In this paper this result is improved for the commutative case to show that for such groupoids

A

,

p
n

(

A

)
≧

1
3

(

2
n

−

(
−
1

)
n

)

\mathfrak {A},{p_n}(\mathfrak {A}) \geqq \frac {1}{3}({2^n} - {( - 1)^n})

for all

n
≧
2

n \geqq 2

(Theorem 1) and that this is the best possible result. Those groupoids for which this lower bound is attained are completely characterized. In fact, the relevant result proved below is much stronger (Theorem 3). From these and other known results it is deduced that the sequence

⟨

0
,
0
,
1
,
3

⟩

\left \langle {0,0,1,3} \right \rangle

has the minimal extension property.
Quasilinear systems with several periodic solutions
Authors: Cronin Jane 
Published: June 2010

By using topological degree, it is proved that for a certain class of quasilinear systems of ordinary differential equations of the form
\[

x
˙

=
A
(
t
)
x
+
ϵ
μ
f
(
x
,
t
,
μ
)
+
μ
g
(
x
,
t
,
μ
)
+
h
(
t
)

\dot x = A(t)x + \epsilon \mu f(x,t,\mu ) + \mu g(x,t,\mu ) + h(t)

\]
where

ϵ
,
μ

\epsilon ,\mu

are small parameters and A, f, g, h are periodic in t, there exist at least two periodic solutions.
The Hardy class of a Bazilevič function and its derivative
Authors: Miller Sanford S. 
Published: June 2010

The Bazilevič function

f
(
z
)

f(z)

defined in

Δ
:

|

z

|

>
1

\Delta :|z| > 1

by

f
(
z
)
≡

[
α

∫
0
z

P
(
ζ
)
g

(
ζ

)
α

ζ

−
1

d
ζ

]

1

/

α

f(z) \equiv {[\alpha \smallint _0^zP(\zeta )g{(\zeta )^\alpha }{\zeta ^{ - 1}}d\zeta ]^{1/\alpha }}

where

g
(
ζ
)

g(\zeta )

is starlike in

Δ
\Delta

,

P
(
ζ
)

P(\zeta )

is regular with Re

P
(
ζ
)
>
0

P(\zeta ) > 0

in

Δ
\Delta

and

α
>
0

\alpha > 0

is univalent. The class of such functions contains many of the special classes of univalent functions. The author determines the Hardy classes to which

f
(
z
)

f(z)

and

f
′

(
z
)

f’(z)

belong. In addition if

f
(
z
)
=

∑
0
∞

a
n

z
n

f(z) = \sum \nolimits _0^\infty {{a_n}{z^n}}

the limiting value of

|

a
n

|

/

n

|{a_n}|/n

is obtained.
An eigenvalue problem for the Stieltjes mean sigma-integral related to Gronwall’s inequality
Authors: Kroll Jeffrey R. , Smith Keith P. 
Published: June 2010

This paper is concerned with the solution of the eigenvalue problem

λ
f
(
t
)
=

∫
0
t

f
(
s
)

d
g
(
s
)
,
0
≦
t
≦
T

\lambda f(t) = \smallint _0^t {f(s)\;dg(s),0 \leqq t \leqq T}

, where g is nondecreasing and right continuous on [0, T] and the integral is the Stieltjes mean sigma-integral. In addition to the solution of the general problem, the solution of the problem with positive eigenfunctions is given. The relationship of the eigenvalue problem to the failure of the Gronwall inequality for g is also established. Furthermore, the techniques used to solve this eigenvalue problem are readily adapted to solve the extended problem in which the function g is merely of bounded variation and right continuous.
Operators associated with a pair of nonnegative matrices
Authors: Suchan Gerald E. 
Published: June 2010

Let

A

m
×
n

,

B

m
×
n

,

X

n
×
1

{A_{m \times n}},{B_{m \times n}},{X_{n \times 1}}

, and

Y

m
×
1

{Y_{m \times 1}}

be matrices whose entries are nonnegative real numbers and suppose that no row of A and no column of B consists entirely of zeroes. Define the operators U, T and T’ by

(
U
X

)
i

=

X
i

−
1

[

or

(
U
Y

)
i

=

Y
i

−
1

]

{(UX)_i} = X_i^{ - 1}[{\text {or}}{(UY)_i} = Y_i^{ - 1}]

,

T
=
U

B
t

U
A

T = U{B^t}UA

and

T
′

=
U
A
U

B
t

T’ = UAU{B^t}

. T is called irreducible if for no nonempty proper subset S of

{
1
,
⋯
,
n
}

\{ 1, \cdots ,n\}

it is true that

X
i

=
0
,
i
∈
S
;

X
i

≠
0
,
i
∉
S

{X_i} = 0,i \in S;{X_i} \ne 0,i \notin S

, implies

(
T
X

)
i

=
0
,
i
∈
S
;

(
T
X

)
i

≠
0
,
i
∉
S

{(TX)_i} = 0,i \in S;{(TX)_i} \ne 0,i \notin S

. M. V. Menon proved the following Theorem. If T is irreducible, there exist row-stochastic matrices

A
1

{A_1}

and

A
2

{A_2}

, a positive number

θ
\theta

, and two diagonal matrices D and E with positive main diagonal entries such that

D
A
E
=

A
1

DAE = {A_1}

and

θ
D
B
E
=

A
2
t

\theta DBE = A_2^t

. Since an analogous theorem holds for T’, it is natural to ask if it is possible that T’ be irreducible if T is not. It is the intent of this paper to show that T’ is irreducible if and only if T is irreducible.
On oscillations for solutions of 𝑛th order differential equations
Authors: Onose H. 
Published: June 2010

Necessary and sufficient conditions are given that all solutions of

x

(
n
)

+
f
(
t
,
x
,

x
′

,
⋯
,

x

(
n
−
2
)

)
=
0

{x^{(n)}} + f(t,x,x’, \cdots ,{x^{(n - 2)}}) = 0

are oscillatory for n even and are oscillatory or tend monotonically to zero as

t
→
∞

t \to \infty

for n odd. The results generalize recent results of J. S. W. Wong and G. H. Ryder and D. V. V. Wend.
The growth of hypoelliptic polynomials and Gevrey classes
Authors: Newberger E. , Zieleźny Z. 
Published: June 2010

For given hypoelliptic polynomials

P
P

and

Q
Q

, classes

Γ
P
ρ

(
Ω
)

\Gamma _P^\rho (\Omega )

and

Γ
Q
ρ

(
Ω
)

\Gamma _Q^\rho (\Omega )

involving Gevrey type estimates on the successive iterates of the corresponding differential operators are defined. The equivalence of the inequality

|

Q
(
ξ
)

|

2

≦
C

(
1
+

|

P
(
ξ
)

|

2

)
h

,
ξ
∈

R
n

|Q(\xi ){|^2} \leqq C{(1 + |P(\xi ){|^2})^h},\xi \in {R^n}

, and the inclusion

Γ
P
ρ

(
Ω
)
⊂

Γ
Q

ρ
h

(
Ω
)

\Gamma _P^\rho (\Omega ) \subset \Gamma _Q^{\rho h}(\Omega )

is proved.